Implants for spinal fixation and or fusion

Abstract

To provide bone implants, and methods of use and assembly thereof.SOLUTION: The bone implants, which are optionally composite implants, generally include a distal anchoring region and a growth region that is proximal to the distal anchoring region. The distal anchoring region can have one or more distal surface features that adapt the distal anchoring region for anchoring into iliac bone. The growth region can have one or more growth features that adapt the growth region to facilitate at least one of bony on-growth, in-growth, or through-growth. The implants may be positioned along a posterior sacral alar-iliac ("SAI") trajectory. The implants may be coupled to one or more bone stabilizing constructs, such as rod elements.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Patent Application No. 16 / 276,430, filed February 14, 2019, U.S. Provisional Patent Application No. 62 / 859,646, filed June 10, 2019, and U.S. Provisional Patent Application No. 62 / 933,250, filed November 9, 2019, the entire contents of which are incorporated herein by reference.

[0002] All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. For example, the entire contents of U.S. Patent Publication Nos. 2011 / 0087294, 2011 / 0087296, 2011 / 0118785, and 2011 / 0125268 are incorporated by reference into this application.

[0003] The present disclosure relates generally to bone implants, and more particularly to bone implants used for stabilizing, fixating, and / or fusing the sacroiliac joint and / or vertebrae. [Background technology]

[0004] Many types of hardware are available for fixation of fractured bones and fixation of bones that are to be fused (arthrodesed).

[0005] For example, the human hip girdle is made up of three large bones joined by three relatively immobile joints. One bone is called the "sacrum," which is at the bottom of the lumbar spine and connects to the L5 vertebra. The other two bones are commonly called the "hip bones," technically the "right ilium" and "left ilium." The sacrum connects to both hip bones at the sacroiliac joints (abbreviated SI joints).

[0006] The SI joint functions in the transmission of force from the spine to the lower extremities and vice versa. The SI joint is said to be the source of up to 22% of low back pain. Summary of the Invention [Problem to be solved by the invention]

[0007] To relieve pain arising from the SI joint, sacroiliac joint fusion is typically indicated as a surgical treatment for, for example, degenerative sacroiliitis, inflammatory sacroiliitis, paroxysmal instability of the sacroiliac joint, sclerosing osteitis of the ilium, or traumatic fracture-dislocation of the pelvis. Currently, screws and screws with plates are used for sacroiliac joint fusion. At the same time, cartilage is typically removed from the "synovial" portion of the sacroiliac joint. This requires a large incision to access the damaged, subluxated, dislocated, fractured, or degenerated joint.

[0008] Additionally, elongated structures can be used to join, fuse, and / or stabilize multiple vertebrae in the thoracic, lumbar, and sacral portions of the spine. These elongated structures may include one or more rods. For example, the implant and rod system described herein can be used to fuse the L5 vertebra to the S1 vertebra to treat spinal disorders such as degenerative scoliosis. [Means for solving the problem]

[0009] The present disclosure generally relates to one or more bone implants, methods of their use, or methods of assembly. The implants herein can be used for the treatment of SI joints and / or as fixation components of constructs that join, fuse, and / or stabilize vertebrae.

[0010] One aspect of the present disclosure is an implant for use in at least one of bone fusion or stabilization of multiple bones, the implant including a distal fixation region and a growth region proximal to the distal fixation region, the distal fixation region having one or more distal surface features that adapt the distal fixation region for fixation within an ilium bone, the growth region including one or more growth features that adapt the growth region to facilitate at least one of bone on-growth, bone in-growth, or bone through-growth.

[0011] Optionally, the implant is a composite implant. The composite implant may include an elongated member, such as an inner shank, and an elongated member, such as an outer sleeve. The inner shank may have a distal end region with one or more threads sized and configured for fixation within the ilium. The outer sleeve may be sized and configured to be disposed over at least a portion of the inner shank. The sleeve may be positioned relative to the inner member to form a composite implant with interfacing inner member and sleeve interface features to resist relative movement between the sleeve and inner member in at least one direction.

[0012] The distal fixation region can have one or more distal surface features that better adapt the distal fixation region for fixation within the ilium than the growth region. The growth region can have one or more growth features that better adapt the growth region to facilitate at least one of bone overgrowth, bone ingrowth, or bone through-growth than the fixation region.

[0013] The inner member (eg, inner shank) may have better resistance to fatigue than the outer member (eg, outer sleeve).

[0014] Optionally, the implants herein are not composite implants.

[0015] One aspect of the disclosure herein includes a method of implanting an implant, optionally a composite implant, for use in at least one of fusing or stabilizing bone tissue. The method includes positioning a distal fixation region within the ilium and advancing the implant along the posterior sacral alar iliac ("SAI") tract until an in-growth region is positioned across the SI joint. The method can include coupling a tulip or other coupling member to the implant and, optionally, coupling a structural member (e.g., a rod) to the tulip.

[0016] One aspect of the present disclosure is a method of assembling a composite bone implant for use in fusing or stabilizing one or more bones. The method includes positioning an outer member (e.g., a sleeve) such that the outer member is positioned over an inner member (e.g., an inner shank). Forming the composite implant can include forming the composite implant such that features of the inner member (e.g., shank) interface with features of the sleeve interface with one another to resist relative movement between the sleeve and inner member in at least one direction. The composite implant can have a distal fixation region and an in-growth region proximal to the distal fixation region, the distal fixation region optionally having one or more distal surface features that better adapt the distal fixation region for fixation within the ilium than the in-growth region, and the in-growth region having one or more in-growth features that better adapt the in-growth region to facilitate at least one of bone over-growth, bone ingrowth, or bone through-growth than the fixation region.

[0017] One aspect of the present disclosure is an inner shank that can be used as part of a composite bone implant, the inner shank can include any of the features described herein or in the claims.

[0018] One aspect of the present disclosure is an outer sleeve that can be used as part of a composite bone implant, the outer sleeve can include any of the features described herein or in the claims.

[0019] In some merely exemplary embodiments, an implant for use in fusing and / or stabilizing multiple bones includes a shank portion, a body portion, and a head portion. The shank portion has a proximal end and a distal end. The body portion is coupled to the shank portion and configured to be positioned through a first bone segment, across a bone joint or fracture, and into a second bone segment. The body portion is configured to allow bone overgrowth, bone ingrowth, or bone through-growth. The head portion is coupled to the proximal end of the shank portion and configured to couple the shank portion to a stabilization rod.

[0020] Body portion as used in this context may include any of the sleeves described herein.

[0021] In some embodiments of the implant, the distal end of the shank portion comprises a thread for securing the implant to a second bone segment. In some embodiments, the first bone segment is a sacrum and the second bone segment is an ilium. The body portion may be integral with the shank portion. The body portion may include at least one straight side to prevent rotation. In some embodiments, the body portion is triangular in shape and has a cross section transverse to the longitudinal axis to prevent rotation. The body portion may include at least one vertex to prevent rotation. In some embodiments, the body portion includes a plurality of fenestrations, each of the plurality of fenestrations communicating with a central lumen of the body portion. The shank portion may include at least one spline that mates with a slot in the body portion to prevent relative rotation between the shank portion and the body portion.

[0022] In some embodiments, an implant for use in fusing and / or stabilizing multiple bones comprises a shank portion, a body portion, and a head portion. The shank portion has a proximal end and a distal end. The body portion is coupled to the shank portion and configured for placement within a first bone segment. The body portion is configured to allow bone overgrowth, ingrowth, and through-growth. The head portion is coupled to the proximal end of the shank portion and configured to couple the shank portion to a stabilization rod.

[0023] In some embodiments, the first bone segment is a vertebra, a sacrum, or an ilium. The distal end of the shank portion can be provided with threads for securing the implant to the second bone segment. In some embodiments, the body portion is integral with the shank portion. In some embodiments, the body portion includes at least one straight side to prevent rotation. The body portion may be triangular in shape and have a cross section transverse to the longitudinal axis to prevent rotation. In some embodiments, the body portion includes at least one vertex to prevent rotation. The body portion includes a plurality of fenestrations, each of which communicates with a central lumen of the body portion. In some embodiments, the shank portion includes at least one spline that mates with a slot in the body portion to prevent relative rotation between the shank portion and the body portion. The distal end of the shank portion can include a plurality of bristles to allow the shank portion to be inserted distally into the bone but prevent it from being withdrawn proximally from the bone.

[0024] One aspect of the present disclosure is an implant for use in at least one of fusing or stabilizing bone tissue, comprising: an elongate body sized and configured to be implanted across a sacroiliac ("SI") joint and extend into the sacrum and ilium (optionally into or beyond a teardrop-shaped region); a distal fixation region of the elongate body having one or more distal surface features configured to secure the distal fixation region within the ilium; and a proximal region of the elongate body disposed proximal to the distal region, the proximal region having one or more proximal surface features adapted to allow at least one of bone overgrowth, ingrowth, or through-growth.

[0025] One aspect of the present disclosure is a bone stabilization implant including an elongate implant body and one or more deployable members, each having a non-deployed position and a deployed position relative to the elongate implant body. The elongate implant body can include one or more screws and, optionally, multiple regions having different numbers of leads. The elongate implant body can include multiple rows of openings (optionally linear rows), each row including multiple openings separated by a portion of the elongate implant body. The portion of the elongate implant body separating the multiple openings can include one or more screws. Any of the deployable members can include multiple protrusions extending from a spine. The protrusions extend radially outward further than the barbs and, optionally, are integrally formed with the barbs. The one or more deployable members can be positioned relative to the elongate implant body such that they are deployed upon actuation of the internal deployment member. The one or more deployable members move radially outward when the internal deployment member is rotated and can include a plurality of radially protruding cam surfaces. One or more threads on the elongate implant body provide a radial mechanical stop for the one or more deployable members and optionally prevent the opening from bending under load. Any openings can be tapered to limit play between the elongate implant body and the one or more deployable members. The elongate implant body can also include one or more lattice sections. [Brief explanation of the drawings]

[0026] [Figure 1] 1A-1C illustrate an embodiment of an implant structure. [Figure 2A] 1A-1C are side cross-sectional views illustrating the formation of a broached bore in bone according to one embodiment of the present invention. [Figure 2B] 10A-10C are side cross-sectional views illustrating the formation of a broach bore in bone according to one embodiment of the present invention. [Figure 2C] 10A-10C are side cross-sectional views illustrating the formation of a broach bore in bone according to one embodiment of the present invention. [Figure 2D] 10A-10C are side cross-sectional views illustrating the formation of a broach bore in bone according to one embodiment of the present invention. [Figure 2E] 10A-10C illustrate assembly of the soft tissue protection device for placement over a guidewire. [Figure 2F] 10A-10C illustrate assembly of the soft tissue protection device for placement over a guidewire. [Figure 3] FIG. 1 is an anatomical diagram of the anterior portion of the human hip girdle, including the sacrum and hip bones (right and left ilium), showing how the sacrum connects to both hip bones at the sacroiliac joints (abbreviated SI joints). [Figure 4] FIG. 1 shows an anatomical diagram of the posterior portion of the human hip girdle, including the sacrum and hip bones (right and left ilium), where the sacrum is connected to both hip bones at the sacroiliac joints (abbreviated SI joints). [Figure 5] FIG. 1 is an anatomical diagram showing the implantation of three implant structures for SI joint fixation using a lateral approach through the ilium and sacroiliac joint into the sacrum, in a perspective view prior to implantation. [Figure 6] FIG. 1 is an anatomical diagram showing implantation of three implant structures for SI joint fixation using a lateral approach through the ilium and sacroiliac joint into the sacrum, in a perspective view after implantation. [Figure 7A] FIG. 1 is an anatomical diagram showing the implantation of three implant structures for SI joint fixation using a lateral approach through the ilium and sacroiliac joint into the sacrum, in a frontal view after implantation. [Figure 7B] FIG. 1 is an anatomical diagram showing the implantation of three implant structures for SI joint fixation using a lateral approach through the ilium and sacroiliac joint into the sacrum, with a craniocaudal cross-sectional view after implantation. [Figure 8A] 1A-1C illustrate an embodiment of an implant design with head portions joined using a Morse taper. [Figure 8B]1A-1C illustrate an embodiment of an implant design with head portions joined using a Morse taper. [Figure 8C] 1A-1C illustrate an embodiment of an implant design with head portions joined using a Morse taper. [Figure 9] 1A-1C illustrate an embodiment of an implant structure with a head portion joined using a screw-type attachment. [Figure 10A] 1A-1C illustrate an embodiment of an implant structure with an integral head portion. [Figure 10B] 1A-1C illustrate an embodiment of an implant structure with an integral head portion. [Figure 11A] 1A-1C illustrate an embodiment of an implant design suitable for pedicle screw salvage. [Figure 11B] 1A-1C illustrate an embodiment of an implant design suitable for pedicle screw salvage. [Figure 12] 1A-1C illustrate an embodiment of an implant structure with a fixation device. [Figure 13A] 13A-13D show the attachment of the tulip structure to the implant structure and the fixation of the rod to the tulip structure. [Figure 13B] 13A-13D show the attachment of the tulip structure to the implant structure and the fixation of the rod to the tulip structure. [Figure 14] 11A-11C show alternative embodiments of a head portion having deployable attachment features. [Figure 15] 11A-11C show alternative embodiments of a head portion having deployable attachment features. [Figure 16] 1A-1C illustrate an embodiment of an implant structure with a threaded head portion that passes completely through the stem portion of the implant structure. [Figure 17] 10A-10C illustrate an embodiment in which a ball and socket joint is used to attach the head portion to the stem portion of the implant structure. [Figure 18A] FIG. 10 shows the head portion of the implant structure relative to the tulip structure. [Figure 18B] FIG. 10 shows the head portion of the implant structure relative to the tulip structure. [Figure 18C] FIG. 10 shows the head portion of the implant structure relative to the tulip structure. [Figure 18D] FIG. 10 shows the head portion of the implant structure relative to the tulip structure. [Figure 18E] FIG. 10 shows the head portion of the implant structure relative to the tulip structure. [Figure 19A] FIG. 12 is a side view of an embodiment of an implant structure crossing the sacroiliac joint using a posterolateral approach, entering through the posterior iliac spine of the ilium, angling through the sacroiliac joint, and terminating at the ala of the sacrum. [Figure 19B] FIG. 12 is an axial view of an embodiment of an implant structure crossing the sacroiliac joint using a posterolateral approach, entering through the posterior iliac spine of the ilium, angling through the sacroiliac joint, and terminating at the ala of the sacrum. [Figure 20A] FIG. 1 illustrates a disassembled, anatomical, posterior perspective view of a representative configuration of one or more implant structural assemblies sized and configured to achieve non-invasive translaminar lumbar fusion without disc removal, prior to implantation. [Figure 20B] FIG. 20B is an anatomical subsection showing the assembly of FIG. 20A after implantation. [Figure 21A] FIG. 1 illustrates a disassembled, anatomical, posterior perspective view of a representative configuration of one or more implant structural assemblies sized and configured to achieve atraumatic lumbar facet joint fusion prior to implantation. [Figure 21B] FIG. 21B is an anatomical subsection showing the assembly of FIG. 21A after implantation. [Figure 21C] FIG. 21B is an anatomical side view showing the assembly of FIG. 21A after implantation. [Figure 22A]FIG. 12 is an exploded anatomical posterior view prior to implantation of a representative configuration of one or more implant structural assemblies sized and configured to achieve fusion between the lumbar L5 and sacral S1 vertebrae non-invasively without disc removal using a posterolateral approach, entering through the posterior iliac spine of the ilium, angling through the sacroiliac joint, and terminating at the ala of the sacrum. [Figure 22B] FIG. 22B is a posterior anatomical view showing the assembly of FIG. 22A after implantation. [Figure 23A] FIG. 1 is a disassembled anatomic anterior perspective view of a representative configuration of an assembly of one or more implant structures sized and configured to stabilize spondylolisthesis at the L5 / S1 joint prior to implantation. [Figure 23B] FIG. 23B is an anatomic anterior perspective view showing the assembly of FIG. 23A after implantation. [Figure 23C] FIG. 23B is an anatomical side view showing the assembly of FIG. 23A after implantation. [Figure 24] FIG. 1 is an axial view showing the implant inserted via the posteromedial approach. [Figure 25A] 1A and 1B are perspective views of an exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end. [Figure 25B] FIG. 25B is an exploded view showing the components of the bone implant of FIG. 25A. [Figure 25C] FIG. 25B is a side view of the bone implant of FIG. 25A. [Figure 25D] FIG. 25B is a top plan view of the bone implant of FIG. 25A. [Figure 25E] FIG. 25B shows the distal end of the bone implant of FIG. 25A. [Figure 25F] 25B is a schematic side cross-sectional view of a portion of the bone implant of FIG. 25A. FIG. [Figure 25G] 25B is a schematic cross-sectional side view of a variation of a portion of the bone implant of FIG. 25A. FIG. [Figure 26A]1A and 1B are perspective views of an exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end. [Figure 26B] FIG. 26B is an exploded view showing the components of the bone implant of FIG. 26A. [Figure 26C] FIG. 26B is a side view of the bone implant of FIG. 26A. [Figure 26D] FIG. 26B is a top plan view of the bone implant of FIG. 26A. [Figure 26E] FIG. 26B shows the distal end of the bone implant of FIG. 26A. [Figure 27A] 1A and 1B are perspective views of an exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end. [Figure 27B] FIG. 27B is a side cross-sectional view of the bone implant of FIG. 27A. [Figure 28A] 1A and 1B are perspective views of an exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end. [Figure 28B] FIG. 28B is a side cross-sectional view of the bone implant of FIG. 28A. [Figure 29A] 1A and 1B are perspective views of an exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end. [Figure 29B] FIG. 29B is a side cross-sectional view of the bone implant of FIG. 29A. [Figure 30A] 1A and 1B are perspective views of an exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end. [Figure 30B] FIG. 30B is a side cross-sectional view of the bone implant of FIG. 30A. [Figure 31] FIG. 1 illustrates an example of a composite implant. [Figure 32A] 1 is an image showing an exemplary SAI trajectory for implanting an SI joint stabilization implant across the SI joint, with an arrow indicating the trajectory. [Figure 32B]1 is an image showing an exemplary SAI trajectory for implanting an SI joint stabilization implant across the SI joint, with an arrow indicating the trajectory. [Figure 33A] 1 illustrates an exemplary composite implant. [Figure 33B] 1A-1C illustrate an exemplary elongated inner member. [Figure 33C] 1 illustrates an exemplary outer member. [Figure 34A] 1 illustrates an exemplary composite implant. [Figure 34B] 1 illustrates an exemplary composite implant. [Figure 35] 1 illustrates an exemplary internal member. [Figure 36A] 1 illustrates an exemplary composite implant. [Figure 36B] 1 illustrates an exemplary composite implant. [Figure 36C] 1 illustrates an exemplary composite implant. [Figure 37] 1 illustrates an exemplary internal member. [Figure 38] 1 illustrates an exemplary internal member. [Figure 39] 1A-1C illustrate a portion of an exemplary composite implant. [Figure 40] 1A-1C illustrate a portion of an exemplary composite implant. [Figure 41A] 1A-1C illustrate a portion of an exemplary composite implant. [Figure 41B] 1A-1C illustrate a portion of an exemplary composite implant. [Figure 42] 1A-1C illustrate a portion of an exemplary composite implant. [Figure 43] 1A-1C illustrate a portion of an exemplary composite implant. [Figure 44A] 1 illustrates an exemplary composite implant. [Figure 44B] 1 illustrates an exemplary composite implant. [Figure 44C] 1 illustrates an exemplary internal member. [Figure 45A] 1 illustrates an exemplary composite implant. [Figure 45B] 1 illustrates an exemplary composite implant. [Figure 46A] 1 illustrates an exemplary composite implant. [Figure 46B] 1 illustrates an exemplary composite implant. [Figure 46C] 1 illustrates an exemplary composite implant. [Figure 46D] 1 illustrates an exemplary composite implant. [Figure 46E] 1 illustrates an exemplary internal member. [Figure 47] 1 illustrates an exemplary composite implant. [Figure 48A] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48B] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48C] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48D] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48E] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48F] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48G] 1A-1C illustrate an exemplary implant comprising one or more deployable members. [Figure 48H] 1A-1C illustrate an exemplary implant comprising one or more deployable members. DETAILED DESCRIPTION OF THE INVENTION

[0027] Elongated, stemmed implant structures 20, such as those shown in FIG. 1, allow for minimally invasive fixation of the SI joint (shown in anterior and posterior views in FIGS. 3 and 4, respectively). These implant structures 20 can be effectively implanted by utilizing a lateral surgical approach. This procedure is desirably assisted by conventional lateral, entry, and exit visualization techniques, e.g., using an x-ray image intensifier such as a C-arm or fluoroscope to generate a live image feed that is displayed on a television screen.

[0028] In one embodiment of a lateral approach (see FIGS. 5, 6, and 7A / B), one or more implant structures 20 are introduced laterally through the ilium, the SI joint, and into the sacrum. This path and the resulting placement of the implant structures 20 are best shown in FIGS. 6 and 7A / B. In the illustrated embodiment, three implant structures 20 are so positioned. Also, in the illustrated embodiment, the implant structures 20 are rectilinear in cross-section, in this case triangular, although it should be understood that implant structures 20 with other rectilinear cross-sections may also be used.

[0029] Before performing a lateral implantation procedure, the physician will identify the sacroiliac joint segments to be fixed or fused (articulated) using, for example, the Fortin finger test, femoral thrust, FABER, Gaenslen's, compression, distraction, and diagnostic SI-Joint injection.

[0030] With the patient lying prone, aided by lateral, inlet, and outlet C-arm imaging, the physician aligns the greater sciatic hiatus and then the ala of the sacrum (using the lateral view) to provide a true lateral position. A 3 cm incision is initiated in line with the posterior cortex of the sacral canal, followed by blunt tissue separation to the ilium. From the lateral view, a guide pin 38 (with sleeve (not shown)) (e.g., a Steinmann pin) is placed resting on the ilium, inferior to the sacral endplate and just anterior to the sacral canal. From the outlet view, the guide pin 38 should be parallel to the sacral endplate; from the inlet view, the guide pin 38 should be at a shallow angle anteriorly (e.g., 15 to 20 degrees from the base, as shown in Figure 7B). From the lateral view, the guide pin 38 should be posterior to the anterior sacral wall. From the exit point, the guide pin 38 should be superior to the first sacral foramen and lateral to the midline. This generally corresponds to the sequence shown in Figures 2A and 2B. A soft tissue protector (not shown) is desirably slid over the guide pin 38 and rests firmly against the ilium before removing the guide pin sleeve (not shown).

[0031] Above the guide pin 38 (through the soft tissue protector), a pilot bore 42 is drilled in the manner previously described, as shown in Figure 2C. The pilot bore 42 extends through the ilium, past the S1 joint, and into S1. The drill bit 40 is removed.

[0032] A shaped broach 44 is threaded over the guide pin 38 (through the soft tissue protector) and into the pilot bore 42 to form a broach bore 48 having the desired profile for the triangular implant structure 20 of the illustrated embodiment. This generally corresponds to the sequence shown in Figure 2D. The triangular profile of the broach bore 48 is also shown in Figure 5.

[0033] 2E and 2F show an embodiment of an assembly of a soft tissue protector, or dilator, or delivery sleeve 200, a drill sleeve 202, a guide pin sleeve 204, and a handle 206. In some embodiments, the drill sleeve 202 and the guide pin sleeve 204 can be inserted into the soft tissue protector 200 to form a soft tissue protector assembly 210 that can slide over a guide pin 208 until bone contact is achieved. The soft tissue protector 200 can be any one of the soft tissue protectors, dilators, or delivery sleeves disclosed herein. In some embodiments, a deployable dilator or delivery sleeve 200 as disclosed herein can be used in place of a conventional soft tissue dilator. In the case of an expandable dilator, in some embodiments, the expandable dilator can be slid over the guide pin and then expanded before the drill sleeve 202 and / or guide pin sleeve 204 are inserted into the expandable dilator. In other embodiments, the insertion of a drill sleeve 202 and / or a guide pin sleeve 204 into the expandable dilator can be used to deploy the expandable dilator.

[0034] In some embodiments, a dilator can be used to open a channel through the tissue before sliding the soft tissue protector assembly 210 over the guide pin. The dilator can be placed over the guide pin, for example, using multiple successively larger dilators or using an expandable dilator. After the channel is formed through the tissue, the dilator can be removed and the soft tissue protector assembly can be slid over the guide pin. In some embodiments, the expandable dilator can function as a soft tissue protector after being deployed. For example, after deployment, a drill sleeve and a guide pin sleeve can be inserted into the expandable dilator.

[0035] As shown in FIGS. 5 and 6 , the triangular implant structure 20 can be threaded over the guide pin 38, through the soft tissue protector, through the ilium, past the S1 joint, and into the S1 bone until the proximal end of the implant structure 20 abuts the lateral wall of the ilium (see FIGS. 7A and 7B ). The guide pin 38 and soft tissue protector are then withdrawn, leaving the implant structure 20 in the broached passage against the lateral wall of the ilium (see FIGS. 7A and 7B ). In the illustrated embodiment, two additional implant structures 20 are implanted in this manner, as best shown in FIG. 6 . In other embodiments, the proximal end of the implant structure 20 is left proximally against the lateral wall of the ilium, extending 1, 2, 3, or 4 mm beyond the ilium. This ensures that the implant 20 engages the harder cortical portion of the ilium as well as the softer cancellous bone. Without structural support from the hard cortical bone, the implant may move in the soft cancellous bone. Hard cortical bone is also able to withstand the loads or forces typically applied to bone by implants 20 .

[0036] The implant structure 20 is sized according to the local anatomy. For the S1 joint, a typical implant structure 20 may have a length of about 35 mm to about 60 mm and an inscribed circle diameter of about 7 mm (i.e., a triangle with a height of about 10.5 mm and a base of about 12 mm), depending on the local anatomy. The morphology of the local structure can generally be understood by a medical professional using an anatomy textbook on the human skeleton, along with knowledge of the site and its disease or injury. A physician can also ascertain the dimensions of the implant structure 20 based on a preliminary analysis of the morphology of the target bone, using, for example, plain film x-rays, fluoroscopic x-rays, or MRI or CT scans.

[0037] As previously described, using a lateral approach, one or more implant structures 20 can be individually inserted minimally invasively through the SI joint. Conventional tissue access tools, obturators, cannulas, and / or drills can be used for this purpose. Alternatively, the novel tissue access tools described in previously described and co-pending U.S. Application No. 61 / 609,043, entitled "Tissue Expander and Protector," filed March 9, 2012, and incorporated herein by reference in its entirety, can also be used. Because no joint preparation, cartilage removal, or abrasion is required before creation of the insertion path or before the implant structure 20 is inserted, a minimally invasive insertion path can be created that is sized to be at or near the maximum outer diameter of the implant structure 20.

[0038] The implant structure 20 may obviate the need for autogenous bone graft material, additional pedicle screws and / or rods, hollow modular fixation screws, cannulated compression screws, intra-articular threaded cages, or fracture fixation screws. Additionally, bone graft material and other fixation devices may be used in combination with the implant structure 20 at the physician's discretion.

[0039] A typical procedure may use one to six, or perhaps up to eight, implant structures 20, depending on the size of the patient and the size of the implant structures 20. After placement, the patient is advised to prevent or deload the sacroiliac joint while fusion occurs, which may be approximately six to twelve weeks or longer, depending on the patient's health and compliance with post-operative protocols.

[0040] The implant structure 20 allows for a less invasive surgical technique than traditional open surgery because it does not involve extensive soft tissue dissection. A lateral approach to the SI joint provides a simple surgical approach that complements minimally invasive surgical techniques. The profile and design of the implant structure 20 minimize or reduce rotation and micromotion. The rigid titanium implant structure 20 provides immediate postoperative stability of the sacroiliac joint. The bone ingrowth region 24, including a porous plasma-sprayed coating with an irregular surface, supports stable bone fixation / fusion. The implant structure 20 and surgical approach allow for the placement of a larger fusion surface area designed to maximize postoperative load-bearing capacity, providing a biomechanically precise implant specifically designed to stabilize the heavily loaded sacroiliac joint.

[0041] To improve the implant's stability and load-bearing capacity, the implant can be inserted across three or more cortical walls. For example, after insertion, the implant can traverse two cortical walls of the ilium and at least one cortical wall of the sacrum. Cortical bone is much denser and stronger than cancellous bone, allowing it to withstand the high stresses found in the sacroiliac joint. By traversing three or more cortical walls, the implant can distribute the load across more load-bearing structures, thereby reducing the load each structure must bear. Furthermore, providing structural support at three locations around the implant rather than just two reduces implant movement within the bone after implantation.

[0042] In some embodiments, the implant structure can function like a pedicle screw, allowing fixation and / or fusion of bones, such as the spine and / or sacroiliac joint. For example, a long structure can be used to connect, fuse, and / or stabilize multiple vertebrae in the thoracic, lumbar, and sacral portions of the spine. For example, the implant and rod system described herein can be used to fuse the L5 vertebra to the S1 vertebra to treat spinal disorders such as degenerative scoliosis. As shown in FIGS. 8A through 18E, the implant structure can include a stem portion and a head portion. The stem portion can be formed similarly to those described herein and in co-pending U.S. Patent Application Publication No. 2013 / 0296953, filed May 6, 2013, entitled "Fenestrated Implant," and U.S. Patent No. 8,202,305, entitled "System and Method for Bone Fixation or Fusion." A tulip or saddle structure can be attached to the head portion, and rods can be inserted and secured into multiple tulip structures attached to the implanted implant structure. Thereby fusing and / or stabilizing the spine and / or other bones. In some embodiments, the stem portion, head portion, and tulip or saddle structure can all be cannulated and have lumens extending longitudinally through the assembled structure so that the assembled structure can be placed over a guide wire or guide pin.

[0043] In some embodiments, as shown in Figures 8A through 8C, the head portion 804 can be separate from the stem portion 802. For example, Figures 8A through 8C illustrate an embodiment of an implant structure 800 that includes a mechanical taper, such as a Morse taper. In some embodiments, as shown in Figure 8A, the head portion 804 can have a ball portion 806 and a tapered shank 808. The tapered shank 808 can fit into a corresponding tapered cavity 810 in the stem portion 802, forming a taper lock that is held together by friction. The length of the tapered shank 808 can be varied, thereby allowing for a variable distance between the ball portion 806 and the proximal end of the stem portion 802.

[0044] 8B, the head portion 804 can have a tapered cavity 810, while the stem portion 802 can have a tapered shank 808 extending from the proximal end of the stem portion 802. The length of the tapered shank 808 can be varied so that the distance between the head portion 804 and the stem portion 802 can be adjusted as needed. In some embodiments, the tapered shank 808 of the stem portion 802 can be angled or curved relative to the longitudinal axis of the stem portion 802. A curved tapered shank 808 can be useful as described below for the embodiment shown in FIG.

[0045] 8C , the head portion 804 can have a ball portion 806 and a tapered shank 808 that may be curved or angled such that its distal portion is offset or angled relative to the ball portion 806 and the proximal portion of the tapered shank. A curved tapered shank 808 may be useful when the appropriate implant implant locations in one or more bones do not align with other implant locations. To align the implant structure 800 with stabilization rods, the curved tapered shank 808 can be used to ensure that the head portion 806 aligns with all stabilization rods, even when the implant locations are misaligned.

[0046] 9 shows another embodiment of an implant structure 900 having a stem portion 902 and a head portion 904. The head portion 904 can have a ball portion 906 and a shank 908. The shank 908 can have threads 910 that can be threaded into a complementary internally threaded cavity 912, like a screw. The ball portion 904 can have a screw drive 914 that facilitates rotation of the head portion 904. The screw drive 914 can be a slot, a socket (square, hexagonal, star-shaped, etc.), or other typical screw drive mechanism 914.

[0047] 10A and 10B illustrate an embodiment of an integrated implant structure 1000 having a stem portion 1002 and a head portion 1004 that is integral with the stem portion 1002. As shown in FIGS. 10A and 10B, the head portion 1004 is integral with or fixed to the stem portion 1002, and thus has a fixed length relative to the stem portion 1002. As shown in FIG. 10A, the head portion 1004 can have a ball portion 1006 that can be attached to a tulip portion, for example, as described in more detail below in FIGS. 13A and 18A-18C. Alternatively, as shown in FIG. 10B, the head portion 1004 can have a tulip portion 1007 that is directly integrated with the stem portion 1002. Having an integrated implant structure 1000 can be useful when it is known in advance that the implant structure 1000 will be used in a fixation or stabilization procedure that requires the use of an implant structure with a head portion 1004, for example. The integrated implant 1000 can reduce procedure time by eliminating the need to attach the head portion 1004 to the stem portion 1002. Additionally, because the head portion 1004 is integral with the stem portion 1002, the integrated implant 1000 can have greater structural integrity or strength than an implant assembled from separate pieces.

[0048] In some embodiments, as shown in FIGS. 11A and 11B , which may be particularly suited for pedicle screw salvage, the implant structure 1100 can have a stem portion 1102 with ridges or fenestrations 1003 to promote bone ingrowth. Examples of fenestrations that can be incorporated into the implant structure 1100 are described in co-pending U.S. Patent Application Publication No. 2013 / 0296953, filed May 6, 2013, and entitled “Fenestrated Implant.” In some embodiments, the exterior surface and / or structure of the stem portion 1102 can be twisted. In some embodiments, the stem portion 1102 can have a circular cross-section to better fit into the cavity in the bone after the old pedicle screw is removed. In some embodiments, the stem portion 1102 can be oval, circular, square, triangular, or straight. In some embodiments, a head portion 1104 can be attached to the stem portion 1102, as described above. For example, the head portion 1104 can be attached to the stem portion 1102 using a Morse taper or screw attachment, or the head portion 1104 can be integral with the stem portion. Pedicle screw salvage can be performed when an implant, such as a pedicle screw, becomes loose within the bone due to winshield wiping or butterflying effects caused by stresses applied to the bone by the implant. The loosened implant can be removed and replaced with one of the implants described herein.

[0049] FIG. 12 illustrates an implant structure 1200 including a stem portion 1202, a head portion 1204 attached to the proximal end of the stem portion 1202, and a fixation device 1210 distally disposed at the distal end of the stem portion 1202. The fixation device 1210 can be folded into a collapsed configuration during insertion of the implant structure 1200 into bone and then deployed and / or expanded to an deployed configuration after insertion. In some embodiments, the fixation device 1210 can have one or more arm portions 1212 that are foldable and / or deployable. In some embodiments, the fixation device 1210 can be mechanically actuated from the collapsed configuration to the deployed configuration. In some embodiments, the arm portions 1212 can be joined by a hinge or hub 1214. In some embodiments, the arm portions 1212 can be deployed like the frame of an umbrella. In other embodiments, the fixation device 1210 can be self-expanding and made of a shape memory material, such as a nickel-titanium alloy. In some embodiments, the fixation device 1210 can be constrained by a sheath or other restraining element when in the collapsed configuration. In some embodiments, the fixation device 1210 can be attached to and / or extend from the distal end of the stem portion 1202. The fixation device 1210 can reduce or prevent migration of the implant structure 1200 after implantation.

[0050] 13A and 13B show an implant structure 1300 and a corresponding tulip or saddle structure 1350 that can be attached to the head portion 1304 of the implant structure 1300. The tulip structure 1350 can have a slot 1352 for receiving a rod 1380 that can be used to stabilize the spine. In some embodiments, the tulip structure 1350 can have internal threads 1354 on two wall portions 1356 that form the slot 1352. In some embodiments, a locking screw 1390 can be used to lock and secure the rod 1380 in position within the tulip structure 1350. The locking screw 1390 can have threads 1392 that correspond to the internal threads 1354 on the two wall portions 1356. The locking screw can simply be threaded into position on the rod 1380 to lock and secure the rod in position. The locking screw 1390 can have a screw drive similar to the screw drive 914 described above with respect to FIG. 9. In other embodiments, other securing mechanisms can be used instead of locking screw 1390 to hold the rod in place. In some embodiments, the top of wall portion 1356 can snap off along break line 1358. In some embodiments, break line 1358 can be formed by scoring or thinning wall portion 1356 along break line 1358. In some embodiments, tulip structure 1350 does not have a break line 1358 or extra wall portion 1356 that can be cut away, but instead can have wall portion 1356 sized to accept rod 1380 and locking screw 1390 without having extra material that passes through locking screw 1390.

[0051] 14 illustrates another embodiment of an implant structure 1400. The implant structure 1400 has a stem portion 1402 with a cavity 1412 for receiving a deployable attachment 1410 on a shank 1408 of a head portion 1404. The deployable attachment 1410 on the shank 1408 can have a collapsed configuration and a deployed configuration. The entrance to the cavity 1412 can be a narrowed opening 1414 having a diameter smaller than the diameter of the cavity 1412. The shank 1408 can be inserted into the cavity 1412 through the narrowed opening 1414 with the deployable attachment 1410 in the collapsed configuration. Once within the cavity 1412, the deployable attachment 1410 can expand to the deployed configuration, thereby securing the head portion 1404 to the stem portion 1402. The head portion 1404 can have a ball portion 1406 for connecting to the tulip structure.

[0052] 15 shows another embodiment of a head portion 1504 that can be secured in a cavity 1412 in a stem portion 1402 similar to that shown in FIG. 14. The head portion 1504 can have a ball portion 1506 and a shank 1508 with a narrowed or undercut portion 1508 and a tapered distal portion 1510. The tapered distal portion 1510 has an end that is narrow enough to be inserted into the narrowed opening 1414. As the tapered distal portion 1510 is inserted further through the narrowed opening 1414, the tapered distal portion 1510 forces the narrowed opening to open wider until the narrowed opening fits into the undercut portion 1508 of the shank 1508. The undercut portion 1508 of the shank 1508 , in combination with the tapered distal portion 1510 within the cavity, serves to secure the head portion 1504 to the stem portion 1402 .

[0053] FIG. 16 illustrates another embodiment of a head portion 1604 that can be threaded into an implant structure 1600 in a manner similar to that described in connection with FIG. 9 . However, in this embodiment, the shank 1608 can have a length that allows the shank 1608 to extend completely through the implant structure 1600. Similar to the embodiment described in FIG. 9 , the shank 1608 can be threaded 1610, and the screw drive of the head portion 1604 can be utilized to drive the screw, as can the shank 1608. In some embodiments, the threads 1610 on the proximal portion of the shank 1608 can be mechanical threads for engaging with corresponding threads in the implant structure 1600. The threads 1610 on the distal portion of the shank 1608 can be deeper than mechanical threads, allowing the threads to better engage cancellous bone. In some embodiments, the pitch of the threads 1610 can be constant along the length of the shank 1608. In other embodiments, the pitch of the threads 1610 can vary between different thread types.

[0054] 17 illustrates another embodiment of the attachment of a stem portion 1702 of an implant structure 1700 to a head portion 1704. In this embodiment, the stem portion 1702 has a socket 1708 for receiving a ball 1706 corresponding to the distal end of the head portion 1704. The ball 1706 can reside within the socket 1708 to form a ball-and-socket joint such that the head portion 1704 can be rotated through a predetermined rotational angle. In some embodiments, the rotational angle can be approximately 60 degrees or less. In other embodiments, the rotational angle can be approximately 30 degrees to 90 degrees or less.

[0055] 18A through 18E illustrate embodiments of a snap-on tulip or saddle structure 1850. In some embodiments, the tulip structure 1850 can have a slot 1852 for receiving a rod that can be used to stabilize the spine or other bones. In some embodiments, the tulip structure 1850 can have internal threads on two wall portions 1856 that form the slot 1852. In some embodiments, the wall portions 1856 can have extension tabs that can be broken off and removed. In some embodiments, the tulip structure 1850 can have a head portion receiving slot 1858 formed to receive the head portion 1804 attached to the implant structure 1800. The head portion receiving slot 1858 can be located at the distal end of the tulip structure 1850 and provide access to the internal cavity of the tulip structure 1850. The distal end of the tulip structure can have an opening 1860 that allows a portion of the implant structure 1800 to pass through. The diameter or size of the opening 1860 is smaller than the diameter or size of the head portion 1804, which allows the tulip structure 1850 to receive and retain the head portion within the cavity of the tulip structure 1850. The stabilization rod can then be secured in place within the slot 1852 of the tulip structure 1850, thereby securing the head portion 1804 to the tulip structure 1850.

[0056] In some embodiments, the head portion receiving slot 1858 includes both a portion of one sidewall and a portion along the bottom up to the opening 1860. In some embodiments, the top of the head portion receiving slot 1858 may be circular in shape to accommodate the ball portion of the head portion 1804. The circular portion of the head portion receiving slot 1858 may be positioned a sufficient distance from the bottom of the tulip structure 1850 so that after the ball portion of the head portion 1804 enters the cavity of the tulip structure 1850, the ball portion falls against the bottom, preventing the ball portion from inadvertently sliding off the tulip structure 1850. To remove the ball portion of the head portion 1804 from the tulip structure 1850, the ball portion must be lifted off the bottom of the tulip structure 1850 until it aligns with the circular portion of the head portion receiving slot. The head portion 1804 can then be removed from the tulip structure. In some embodiments, the portion of the head portion receiving slot 1858 at the bottom of the tulip structure may be a straight slot. In other embodiments, the portion of the head portion receiving slot 1858 at the bottom of the tulip structure may be a curved slot.

[0057] The shape and configuration of the cavity and opening 1860 of the tulip structure 1850 allows the tulip structure 1850 to have an angle of translation and rotation of approximately 60 degrees after being attached to the head portion 1804. Such a tulip structure 1850 and head portion 1804 can be referred to as polyaxial, meaning that the tulip structure 1850 can move freely within the conical region. In other embodiments, the angle of translation and rotation can be approximately 30 degrees to 90 degrees or less. Having a substantial angle of translation and rotation allows the implant structure 1800 to be inserted at a wider variety of angles and still align the tulip structure 1850 with the rod for fixation.

[0058] Any of the implants described herein can be used in various surgical procedures, such as stabilization, fixation, or fusion of the spine, including the sacroiliac joint and / or vertebrae and facet joints. Furthermore, surgical procedures utilizing a posterior or posterolateral approach are particularly well-suited for use with the implant structures described herein, since the tulip structure of the implant aligns with other implants along the spine after implantation. As described herein, these implant structures can be connected together using rods that can be secured to each tulip structure. For simplicity, the following procedures are illustrated and described using a generic implant structure 20, but it should be understood that any of the implant structures described herein can be used in place of the generic implant structure 20.

[0059] For example, Figures 19A and 19B show lateral and axial views of an embodiment of an implant structure that crosses the SI joint using a posterolateral approach, entering through the posterior iliac spine of the ilium, angling through the SI joint, and terminating at the ala of the sacrum.

[0060] The posterolateral approach involves less soft tissue disruption than the lateral approach because less soft tissue covers the entry point at the posterior iliac spine of the ilium. Therefore, introduction of the implant structure 20 from this area allows for a smaller, more maneuverable incision. Furthermore, because the implant structure 20 passes through more bone along the posterolateral route than a strictly lateral route, it can touch more surfaces of the SI joint, resulting in more fusion and better fixation of the SI joint. Using the posterolateral approach also allows for bypassing all nerve roots, including the L5 nerve root.

[0061] The setup for the posterolateral approach is generally the same as for the lateral approach. It preferably involves identifying the SI joint segments to be fixed or fused (articulated), using, for example, a Faber test, CT-guided injection, or X-ray / MRI of the SI joint. This is preferably performed with the patient lying prone (stomach down) and assisted by a lateral and anterior-posterior (AP) C-arm. Using the same surgical instruments, a pilot bore 42 is formed on the guide pin 38, but in this case, the path of the pilot bore 42 begins at the posterior iliac spine of the ilium, angles through the SI joint, and terminates at the ala of the sacrum. The pilot bore 42 is shaped to the desired profile using a broach, as previously described, and the implant structure 20 is inserted into the broach bore 48. The implant structure 20 passes from the posterior iliac spine of the ilium on the guide pin 38 through the soft tissue protector, angled through the SI joint, and terminates at the ala of the sacrum until the proximal end of the implant structure 20 abuts against the posterior iliac spine of the ilium. Depending on the bony anatomy along the posterolateral pathway, it may be advisable to introduce implant structures of different sizes, with the most superior being the longest and others being shorter.

[0062] Figure 20A shows a representative configuration of an assembly of one or more implant structures sized and configured to achieve translaminar lumbar fusion non-invasively without disc removal in an exploded view prior to implantation, and Figure 20B shows the corresponding assembly in an inferior cross-sectional view after implantation.

[0063] As shown in Figures 20A and 20B, the assembly includes two implant structures 20. The first implant structure 20 extends from the left superior articular process of vertebra L5, through the adjacent facet joint capsule, to the left inferior articular process of vertebra L4, and from there through the lamina L4 into the medial right posterolateral region of vertebra L4 adjacent the spinous process. The second implant structure 20 extends from the right superior articular process of vertebra L5, through the adjacent facet joint capsule, to the right inferior articular process of vertebra L4, and from there through the lamina L4 into the medial left posterolateral region of vertebra L4 adjacent the spinous process. The first and second implant structures 20 intersect within the medial lamina of vertebra L4.

[0064] The first and second implant structures 20 are sized and configured according to the local anatomy. If the facet joints are aligned with the sagittal plane, a translaminar lumbar fusion (posterior approach) is indicated. There is no need to remove the disc unless the condition of the disc indicates its removal is warranted.

[0065] The posterior procedure for implanting an assembly of implant structures 20 is shown in Figures 20A and 20B. Figures 20A and 20B illustrate a procedure that includes (1) identifying the vertebrae in the lumbar region to be fused, (2) making an incision, for example, a 3 mm posterior incision with the patient lying in a prone (stomach down) position, and (3) using a guide pin to establish the desired implant path through the bone for the first (e.g., left) implant structure 20. In Figures 20A and 20B, the implant path passes across the left superior articular process of vertebra L5, through the adjacent facet joint capsule, into the left inferior articular process of vertebra L4, and then through the L4 lamina into the medial-right posterolateral region of vertebra L4 adjacent the spinous process. The method further includes (iv) increasing the cross-sectional area of ​​the passageway, guided by the guide pin; (v) shaping the passageway cross-section to correspond to the cross-section of the implant structure, guided by the guide pin; (vi) inserting the implant structure 20 through the passageway on the guide pin; (vii) withdrawing the guide pin; and (viii) using the guide pin to establish the desired implant passageway through the bone for a second (e.g., right) implant structure 20. In Figures 20A and 20B, the implant passageway passes across the right superior articular process of vertebra L5, through the adjacent facet joint capsule, into the right inferior articular process of vertebra L4, through the lamina L4, and into the medial left posterolateral region of vertebra L4 adjacent to the spinous process. The surgeon sequentially repeats the remainder of the above procedure for the right implant structure 20, withdrawing the guide pin, and then closes the incision.

[0066] The intimate contact created between the bone ingrowth or through-growth region 24 along the surface of the implant structure 20 across the facet joint accelerates bone ingrowth or through-growth onto, into, or through the implant structure 20, accelerating fusion of the facet joint between L4 and L5. Of course, translaminar lumbar fusion between L5 and S1 can be achieved using first and second implant structures in the same manner.

[0067] Figure 21A shows a representative configuration of an assembly of one or more implant structures sized and configured for lumbar facet joint fusion in a non-invasive manner without disc removal in an exploded view prior to implantation, while Figures 21B and 21C show the assembly after implantation in an inferior cross-sectional view and a side view, respectively.

[0068] As seen in the representative embodiment shown in Figures 21A to 21C, the assembly includes two implant structures 20. The first implant structure 20 extends from the left inferior articular process of vertebra L4, through the adjacent facet joint, to the left superior articular process of vertebra L5, and into the pedicle of vertebra L5. The second implant structure 20 extends from the right inferior articular process of vertebra L5, through the adjacent facet joint capsule, to the right superior articular process of vertebra L5, and into the pedicle of vertebra L5. In this arrangement, the first and second implant structures 20 extend in parallel directions on the left and right pedicles of vertebra L5. The first and second implant structures 20 are sized and configured according to the local anatomy. The option of lumbar facet joint fusion (posterior approach) is indicated when the facet joint is coronally oblique. Disc removal is not required unless the condition of the disc indicates its appropriate removal.

[0069] The posterior procedure for implanting an assembly of implant structures 20 is shown in Figures 21A and 21B. Figures 21A through 21C illustrate a procedure that includes (1) identifying the vertebrae in the lumbar region to be fused, (2) making an incision, e.g., a 3 mm posterior incision, with the patient lying in a prone (stomach down) position, and (3) using a guide pin to establish the desired implant path through the bone for the first (e.g., left) implant structure 20. In Figures 21A through 21C, the implant path passes across the left inferior articular process of vertebra L4, through the adjacent facet joint capsule, into the left inferior articular process of vertebra L5, and then into the pedicle of vertebra L5. The method further includes (iv) increasing the cross-sectional area of ​​the passageway, guided by the guide pin; (v) shaping the passageway cross-section to correspond to the cross-section of the implant structure 20, guided by the guide pin; (vi) inserting the implant structure 20 through the passageway on the guide pin; (vii) withdrawing the guide pin; and (viii) using the guide pin to establish the desired implant passageway through the bone for a second (e.g., right-side) implant structure 20. In Figures 21A through 21C, the implant passageway passes across the right inferior articular process of vertebra L4, through the adjacent facet joint capsule, into the right superior articular process of vertebra L5, and then into the pedicle of vertebra L5. The surgeon then repeats the remainder of the above procedure sequentially for the right-side implant structure 20, withdraws the guide pin, and closes the incision.

[0070] The intimate contact created between the bone ingrowth or through-growth region 24 along the surface of the implant structure 20 across the facet joint accelerates bone ingrowth or through-growth onto, into, or through the implant structure 20, accelerating fusion of the facet joint between L4 and L5.

[0071] Of course, intervertebral lumbar fusion between L5 and S1 can be achieved using the first and second implant structures in the same manner.

[0072] Figure 22A shows another exemplary configuration of an assembly of one or more implant structures 20 sized and configured to achieve fusion of the lumbar L5 and sacral SI vertebrae in a non-invasive manner without disc removal, in an exploded view prior to implantation, while Figures 22B and 22C show the assembly after implantation.

[0073] As shown in Figures 22A and 22B, one or more implant structures are introduced via a posterolateral approach, entering through the posterior iliac spine of the ilium, angulating past the sacroiliac joint S1, through the sacral vertebra S1, and terminating at the lumbar vertebra L5. This path and resulting placement of the implant structures 20 are also shown in Figure 22C. In the illustrated embodiment, two implant structures 20 are positioned in this manner, although there may be more or fewer implant structures 20. Also, in the illustrated embodiment, the implant structures 20 are triangular in cross section, but it should be understood that implant structures 20 having other cross sections may be used, as previously discussed.

[0074] The posterolateral approach involves less soft tissue disruption than the lateral approach because there is less soft tissue overlying the entry point at the posterior iliac spine of the ilium. Therefore, introduction of the implant structure 20 from this area allows for a smaller, more maneuverable incision.

[0075] The setup for the posterolateral approach is generally the same as for the lateral approach. It preferably involves identifying the lumbar region to be fixed or fused (articulated), for example, using a Faber test, CT-guided injection, or an X-ray / MRI at the L5-S1 level. This is preferably performed with the patient lying prone (stomach down) and assisted by a lateral and anterior-posterior (AP) C-arm. Using the same surgical instruments, a pilot bore is created for the guide pin (e.g., on the right side), but in this case, the pilot bore path begins at the posterior iliac spine of the ilium, angles through the SI joint, and terminates at lumbar vertebra L5. A broach bore is created, and the right implant 20 structure is inserted. The guide pin is withdrawn, and the procedure is repeated for the left implant 20 structure, and vice versa. The incision is then closed.

[0076] The described assembly allows for the achievement of transiliac lumbar fusion utilizing a posterolateral approach in an atraumatic manner, with minimal incision and without necessarily removing the intervertebral disc between L5 and S1.

[0077] Figure 23A shows a representative configuration of an assembly of one or more implant structures sized and configured to stabilize spondylolisthesis at the L5 / S1 joint in an exploded view prior to implantation, while Figures 23B and 23C show the assembly after implantation.

[0078] As shown, the implant structure 20 extends from the posterior-lateral region of the sacral vertebra S1 across the intervertebral disc into the opposite anterior-lateral region of the lumbar vertebra L5. The implant structure 20 extends in an angled path (e.g., from about 20 degrees to about 40 degrees from horizontal) superiorly through the sacral vertebra S1, through the adjacent intervertebral disc, and terminates at the lumbar vertebra L5.

[0079] A physician can employ a posterior approach to implant the implant structure 20 shown in Figures 23A, 23B, and 23C. This involves creating a pilot bore on a guide pin inserted in an angled path from the posterior portion of the sacral vertebra S1 through the intervertebral disc to the opposite anterior-lateral region of the lumbar vertebra L5, creating a broach bore to insert the implant structure 20, and then withdrawing the guide pin. The incision is then closed. As previously mentioned, multiple implant structures 20 can be placed in the same manner to stabilize spondylolisthesis.

[0080] As shown in Figures 23A / B / C, the physician can optionally combine spondylolisthesis stabilization with L5 and S-1 reduction and realignment. The physician can also optionally combine spondylolisthesis stabilization with lumbar facet fusion (with or without spondylolisthesis reduction) as shown in Figures 23A / B / C. The physician can also optionally combine spondylolisthesis stabilization with decompression, for example, by posterior removal of the spinous process and bilateral lamina, as shown in Figures 23A / B / C.

[0081] Additionally, in some embodiments, the implant 2400 can be inserted using a posteromedial approach, as shown in FIG. 24 . For example, the implant 2400 can be inserted through the posterolateral sacrum, across the alar, through the SI joint, and into the ilium, where it terminates. As shown, the implant 2400 can have a stem portion 2402 that is inserted into the bone and a tulip portion 2404 (which may be a separate component coupled to the implant in any of the examples herein) that remains outside the bone. In some specific implementations, a specific posteromedial approach known as the S2 alar-iliac (S2AI) approach can be utilized. The entrance for the S2AI approach is midway between the S1 and S2 foramina, 2 mm medial to the lateral sacral crest. The guidewire and / or implant should be placed across the sacroiliac joint above the superior border of the sciatic notch.

[0082] Any of the implants herein, including any of the composite implants herein, can generally be implanted according to the illustration of FIG.

[0083] In some embodiments, only one implant is placed across each SI joint utilizing an S2AI trajectory, as shown in Figure 24. In other implementations, implants can be added above or below each S2AI implant utilizing a lateral approach through the ilium, SI joint, and into the sacrum, as shown in Figures 6A-7B.

[0084] It should be noted that, according to aspects of the present disclosure, a tulip, saddle structure, polyaxial joint, fastening mechanism, or other coupling device (such as those shown in FIGS. 13A and 13B ) can be coupled to the proximal end of any number of bone fixation devices. For example, a coupling device can be attached to the proximal end of any of the implants previously described in this disclosure, as shown in FIGS. 1 and 8A-18E, to couple the implant to a spinal rod or structure, such as rod 1380 shown in FIG. 13B . In a similar manner, a coupling device may be positioned at the proximal end of the implant shown in FIGS. 1-2 or an implant according to U.S. Patent Application Publication No. 8,734,462, as shown in FIGS. 31-34 . In some embodiments, a coupling device can be attached to the proximal end of any of the implants according to U.S. Patent Application Publication No. 2013 / 0245763, as shown in FIGS. 1B-2B , 9A-9B , and 10A-10B . In some embodiments, the coupling device can be attached to the proximal end of any of the implants according to U.S. Patent Application Publication No. 2017 / 0007409, as shown in Figures 47-49. In some embodiments, the coupling device can be attached to the proximal end of any of the implants according to U.S. Patent Application Publication No. 9,662,157, as shown in Figure 12. In some embodiments, the coupling device can be attached to the proximal end of any of the implants according to U.S. Patent Application Publication No. 2016 / 0081810, as shown in Figures 7A-9B. In some embodiments, the coupling device can be attached to the proximal end of any of the implants according to U.S. Patent Application Publication No. 62 / 649,466, as shown in Figures 11-27. In some embodiments, the proximal ends of two or more implants can be joined together with a bridging structure that includes a coupling device for attachment to a spinal rod. In some embodiments, the implant can resemble a staple with two or more prongs for insertion into bone, with the implant having a coupling device disposed at its proximal end.

[0085] 25A-25G illustrate another exemplary embodiment of a bone implant having a tulip or coupling device at its proximal end (which may be a separate component secured to the implant in a separate tulip coupling step). As best seen in FIG. 25B , implant 2500 includes a shank portion 2502, a body portion 2504 (also referred to herein as a sleeve), and a head portion 2506. Any of the head portions herein, commonly referred to as tulips, may be separate components from the implant and secured to the implant after the implant is in place. In this embodiment, the distal end of shank portion 2502 includes threads 2508 for threading shank portion 2502 into a bone segment. Threads 2508 may include one or more self-tapping cutouts 2510, as best seen in FIG. 25E . The proximal end of shank portion 2502 may include a hexagonal recess (not shown) or other suitable feature for mating with a driver for screwing shank portion 2502 into a bone segment. A central lumen 2512 is provided along the longitudinal axis of shank portion 2502, allowing it to be positioned over a guidewire or guide pin when implanted.

[0086] In this embodiment, the body portion 2504 includes a central lumen 2514 configured to slide over the proximal end of the shank portion 2502. Radially outwardly extending splines 2516, best seen in FIG. 25B , may be provided at one or more locations on the shank portion 2502 to mate with corresponding grooves along the inner surface of the central lumen 2514. The splines 2516 and / or other anti-rotation features may be provided on the shank portion 2502 and the body portion 2504 to prevent the two portions from rotating relative to one another. The splines 2516 and / or their corresponding grooves may be tapered to create a tight fit when the body portion 2504 is tapped into place on the shank portion 2502. Splines may be omitted in the center of the illustrated shank portion 2502 to reduce stress concentrations and improve the fatigue resistance of the implant. In other embodiments (not shown), these anti-rotation features may be omitted to allow body portion 2504 to rotate relative to shank portion 2502.

[0087] In this embodiment, the body portion 2504 has a triangular cross-section to prevent it from rotating relative to the surrounding bone. When the body portion 2504 is placed across a joint or fracture between two bone segments, as described above, the body portion 2504 restrains the two bone segments from rotating or translating relative to one another. In other embodiments (not shown), the body portion may have a square, rectangular, oval, or other cross-sectional shape with at least one straight side and / or at least one vertex to similarly prevent rotation. When the body portion 2504 is prevented from rotating relative to the surrounding bone by its non-rotational cross-section, the shank portion 2502 is prevented from rotating relative to the surrounding bone when the splines 2516 prevent the shank portion 2502 from rotating relative to the body portion 2504. This arrangement prevents the shank portion 2502 from undesirably backing out or moving further within the bone.

[0088] The body portion 2504 may include fenestrations 2518 to allow for bone overgrowth, ingrowth, and through-growth. In this exemplary embodiment, a repeating pattern of spars and cross-struts creates multiple triangular fenestrations on each face of the body portion 2504. Each fenestration 2518 opens into the central lumen 2514 of the body portion 2504. In some embodiments, the body portion 2504 is manufactured using an additive manufacturing process, such as 3D printing. Details regarding the design and manufacture of fenestrated implants are described in commonly-assigned U.S. Pat. No. 9,662,157, entitled "Matrix Implant," filed September 18, 2015. The distal end of the body portion 2504 may also include a tapered, rounded leading edge 2520, as shown, to facilitate insertion of the body portion 2504 into one or more bone segments. If desired, to facilitate removal of body portion 2504 from bone, the proximal end of body portion 2504 can be provided with a trailing edge 2522 having a smaller angle of taper, as shown. The less tapered trailing edge 2522 allows for better engagement between the proximal end and the surrounding cortical bone surface.

[0089] The head portion 2506 may include a coupler 2524 and a body 2526, as well as a nut (not shown), as shown in FIGS. 25A-25E. The nut has external threads that mate with internal threads disposed in a proximal recess of the body 2526 to secure a spinal rod (not shown) to the bottom of the channel 2528 in the body 2526. As shown in FIG. 25B, the proximal end of the shank portion 2502 may include a circumferential rib or barb 2530 for securing the head portion 2506 to the shank portion 2502 in a snap-fit ​​manner. In some embodiments, the body 2526 is configured to pivot polyaxially or spherically relative to the coupler 2524 and the shank portion 2502. In some embodiments, the body 2526 is configured to rotate about its major axis relative to the coupler 2524 and the shank portion 2502. In some embodiments, the body 2526 is configured to be stationary relative to the coupler 2524 and / or the shank portion 2502.

[0090] 25F and 25G, the central lumen 2514 of the body portion 2504 and / or the shank portion 2502 are configured to reduce stress concentrations in the shank portion 2502, ensuring it will not fail during use after implantation. In some prior art implants, repeated large load cycles at the proximal end of the shank portion 2502 from a spinal rod connected to the head portion can cause the shank portion to fracture. A typical failure point is where the shank portion 2502 exits the proximal end of the body portion 2504. According to aspects of the present disclosure, stress concentrations can be reduced in this area, allowing the implant to tolerate large load cycles without failure.

[0091] In some embodiments, as shown in FIG. 25F , the proximal end of the central lumen 2514 of the body portion 2504 can include a curved profile 2532 to more evenly distribute forces between the shank portion 2502 and the body portion 2504, thereby reducing stress concentrations. Referring to FIG. 25F , the proximal end of the shank portion 2502 is shown in solid lines in an unloaded state and in dashed lines in a biased state. The degree of bias is exaggerated in FIG. 25F for ease of understanding. The curved profile 2532 can be on only one side of the central lumen 2514 in the direction of maximum force, on the opposite side of the central lumen 2514, or around the entire circumference of the central lumen 2514. In some embodiments, the curved profile 2532 can reflect the natural bending profile of the shank portion 2502. In particular, the profile can be defined by the following beam deflection equation:

[0092]

number

[0093]

number

[0094] where: x is the horizontal distance in FIG. 25F, y is the vertical distance in FIG. 25F; F is the force applied to the proximal end of the shank portion 2502; E is the elastic modulus of the shank portion 2502, I is the moment of inertia of the shank portion 2502; l is the length between where the shank portion 2502 is fully supported and the point of application of the force; D is the outer diameter of the shank portion 2502; d is the inner diameter of the shank portion 2502;

[0095] In some embodiments, as shown in FIG. 25G, the shank portion 2502' can include a spherical portion 2534, and the body portion 2504' can include a mating spherical socket. The body portion 2504' can also include a central lumen 2514' that tapers outward toward both its proximal and distal ends, as shown. This arrangement allows the shank portion 2502' to pivot within the body portion 2504' when a force is applied to its proximal end. The tapered section can be on only one side of the central lumen 2514' in the direction of maximum force, on the opposite side of the central lumen 2514', or around the entire circumference of the central lumen 2514'. Once the shank portion 2502' has completed its pivoting movement, it is supported by the large surface area of ​​the body portion 2504' at both its proximal and distal ends, and also by the spherical portion 2534. These large support areas significantly reduce the stress concentrations found in prior art implants, allowing the implant to withstand greater forces and / or more load cycles without failure. In the embodiment of Figures 25F and 25G, the outer surface of shank portion 2502 / 2502' and / or the inner surface of body portion 2504 / 2504' can be highly polished to further reduce stress concentrations. In some embodiments, the surfaces can have a roughness Ra of 0.01 to 0.04 microns.

[0096] The implant 2500 / 2500′ can be placed into the bone (i.e., in the S2AI trajectory) across a bone joint or fracture in a manner similar to that described above in connection with FIGS. 2A-2F and 24 . In particular, the bone can be prepared by inserting a guide pin into the bone segment, rotating a cannulated drill over the guide pin to drill a pilot hole in the bone, and tapping a cannulated broach over the guide pin to create a bore shaped to receive the body portion 2504. In some embodiments, any or all of these steps may be omitted. The shank portion 2502 may then be threaded into the tapped pilot hole using a tool attached to the proximal end of the shank portion 2502, as described above. The body portion 2504 can then be tapped into the bone beyond the proximal end of the shank portion 2502. As the body portion 2504 engages the splines 2516 located on the proximal end of the shank portion 2502, a small rotational adjustment (e.g., 15 degrees or less) may be required to rotationally align the body portion 2504 with the molded bore. This adjustment can be made manually, or in some circumstances, automatically when the tapered, rounded leading edge 2520 of the body portion 2504 engages the molded bore opening in the bone, allowing the implant to be automatically rotated as needed while tapping the body portion 2504 into place. Once the body portion 2504 is in place, the head portion 2506 can snap into place on the proximal end of the shank portion 2502. The head portion 2506 includes a proximally extending tab, as previously described, which may then be snapped off. Once the rest of the spinal structure (not shown) is also in place, a rod can be placed into the channel 2528 and secured in place with a nut, as previously described.

[0097] As previously mentioned, in embodiments having separate head portions disposed on the shank portion being implanted, a variety of different head portions can be provided in a kit, rather than having to provide an entire implant for each head type. For example, head portions can be provided that couple to rods with diameters of 5.0, 5.5, 6.0, or 6.35 mm. The shank and body portions can also be provided in a variety of lengths, widths, and / or shapes. This modular approach allows specific head types to be placed on specific shank and body portions, creating more combinations without having to stock individual implants for each combination.

[0098] In some embodiments, the shank portion 2502 can be attached to the bone, and then a broach can be inserted into the proximal end of the attached shank portion 2502 to create a bore of a predetermined shape. After the broach is removed, the body portion 2504 can be attached over the shank portion 2502. In some embodiments, the body portion can include an integral broach so that the body portion can be attached without first preparing a preformed hole in the bone. In some embodiments, the body portion 2504 can be attached to the bone first, and then the shank portion 2502 can be attached to the bone via the body portion 2504, with or without the head portion 2506 attached to the shank portion 2502 during attachment.

[0099] According to aspects of the present disclosure, the configuration of this embodiment allows one portion of the implant to be threaded into place, another portion to be tapped into place, and the two portions to be locked together, utilizing the anti-rotational aspects of the tapped-in portion. In embodiments without splines or other locking features, the various portions can be implanted separately as described above, or the assembled implant can be installed as a single unit, in which case the body portion rotates within a bore molded into the bone as the shank portion is threaded into place. In other embodiments with a releasable locking feature (not shown), the assembled implant can be installed as a single unit with the locking feature released, in which case the shank portion can rotate relative to the body portion. After the implant is installed, the locking feature can be used to prevent rotation.

[0100] 26A-26E show another exemplary embodiment of a bone implant having a tulip or coupling device provided at its proximal end. The implant 2600 includes a shank portion 2602, a body portion 2604, and a head portion 2606. The shank portion 2602 and the body portion 2604 may be separate components, similar to the previously described implant 2500, or they may be integrally formed as a single component. In this embodiment, the distal end of the shank portion 2602 includes bristles 2608 for securing the shank portion 2602 within the bone segment. The bristles 2608 may be angled proximally and are flexible so that they offer little resistance when introduced distally into a bore within the bone, but lock the shank portion 2602 relative to the bone and prevent it from being withdrawn proximally from the bone. In some embodiments, the bristles 2608 are disposed at a 45-degree angle relative to the longitudinal axis of the implant 2600. The bristles 2608 can be integrally formed with the shank portion 2602, for example, using an additive manufacturing process. Alternatively, the bristles 2608 are separate elements of the same or different material as the shank portion 2602 and are inserted into holes formed in the shank portion 2602. In some embodiments, the head portion 2606 functions to contact the outer surface of the bone to prevent the implant 2600 from migrating further into the bone. In other embodiments (not shown), a separate element, larger in size than the implant bore in the bone, can be positioned at or adjacent the proximal end of the body portion 2604 to allow the head portion 2606 to maintain a full range of motion relative to the shank portion 2602 while preventing the implant 2600 from migrating further into the bone. In other embodiments (not shown), the bristles 2608 can be replaced or augmented by rigid barbed elements. Details regarding the manufacture and use of bristles and barbs with orthopedic implants are described in U.S. Patent No. 5,716,358 to Ochoa et al.

[0101] The proximal end of body portion 2604 may have a flat surface (not shown) to allow shank portion 2602 and body portion 2604 to be tapped into place together within the bone segment. Alternatively, internal threads (not shown) may be provided to allow a slap hammer or other insertion tool to be temporarily attached to the proximal end of body portion 2604 to aid in insertion of implant 2600. A central lumen 2612 is provided along the longitudinal axis of shank portion 2602 and body portion 2604 to allow them to be placed over a guide wire or guide pin when implanted.

[0102] In this embodiment, body portion 2604 has a triangular cross-section to prevent it from rotating relative to the surrounding bone. As previously described, when body portion 2604 is placed across a joint or fracture between two bone segments, body portion 2604 prevents the two bone segments from rotating relative to one another. In other embodiments (not shown), body portion can have a square, rectangular, oval, or other cross-sectional shape with at least one straight side and / or at least one vertex to also prevent rotation.

[0103] The body portion 2604 may include fenestrations 2618 to allow for bone overgrowth, ingrowth, and through-growth. In this exemplary embodiment, a repeating pattern of alternating triangular fenestrations may be provided on each side of the body portion 2604. Each of the fenestrations 2618 opens into a central lumen of the body portion 2604. In some embodiments, the body portion 2604 is manufactured using an additive manufacturing process, such as 3D printing. Details regarding the design and manufacture of fenestrated implants are described in the applicant's U.S. Patent No. 9,662,157, entitled "Matrix Implant," filed September 18, 2015. The distal end of the body portion 2604 may also include a tapered leading edge 2620, as shown, to facilitate insertion of the body portion 2604 into one or more bone segments. Optionally, the proximal end of the body portion 2604 may include a trailing edge 2622 having a smaller angle of taper, as shown, to facilitate removal of the body portion 2604 from the bone. The less tapered trailing edge 2622 allows for better engagement between the proximal end and the surrounding cortical bone surface.

[0104] The head portion 2606 may include a coupler 2624 and a body 2626, as well as a nut (not shown), as shown in FIGS. 26A-26E. The nut has external threads that mate with internal threads disposed in a proximal recess of the body 2626 to secure a spinal rod (not shown) to the bottom of the channel 2628 in the body 2626. As shown in FIG. 26B, the proximal end of the body portion 2604 may include a circumferential rib or barb 2630 for securing the head portion 2606 to the body portion 2604 in a snap-fit ​​manner. In some embodiments, the body 2626 is configured to pivot polyaxially or spherically relative to the coupler 2624 and the shank portion 2602. In some embodiments, the body 2626 is configured to rotate about its major axis relative to the coupler 2624 and the shank portion 2602. In some embodiments, the body 2626 is configured to be stationary relative to the coupler 2624 and / or the body portion 2604.

[0105] The implant 2600 can be installed within the bone, across a bone joint or fracture, in a manner similar to that described above in connection with FIGS. 2A-2F . In particular, the bone can be prepared by inserting a guide pin into the bone segment, rotating a cannulated drill over the guide pin to drill a pilot hole in the bone, and tapping a cannulated broach over the guide pin to create a bore shaped to receive the body portion 2504. In some embodiments, any or all of these steps may be omitted. The shank portion 2602 can then be tapped into the pilot hole and formed bore, as described above, with or without a tool attached to the proximal end of the body portion 2604. Once the shank portion 2602 and body portion 2604 are in place, the head portion 2606 can be snapped into place at the proximal end of the body portion 2604. In some implementations, the shank portion 2602 and body portion 2604 can be tapped into place with the head portion 2606 already attached to the proximal end of the body portion 2604. Head portion 2606 includes a proximally extending tab, as previously described, which may then be snapped off. With the rest of the spinal structure (not shown) also in place, a rod may be placed into channel 2628 and secured in place with a nut, as previously described.

[0106] 27A and 27B show another exemplary embodiment of a bone implant having a tulip or coupling device disposed at its proximal end. Implant 2700 is in the form of a sacral alar iliac (SAI) screw and includes a threaded shank portion 2702, a body portion 2704, and a head portion 2706. The threaded shank portion 2702 and head portion 2706 of implant 2700 are similar to those of implant 2500 described above with reference to FIGS. 25A-25G.

[0107] The body portion 2704 includes a porous outer surface configured to traverse the bone joint and / or proximal bone segment when implanted. In this embodiment, the body portion 2704 includes a solid radial inner portion 2708 and a porous bone ingrowth region radial outer portion 2710, as shown in FIG. 27B. The radial outer portion 2710 can be formed from a porous plasma spray coating with an irregular surface, which supports stable bone fixation / fusion. This implant structure and the surgical approach disclosed herein allow for the placement of a larger fusion surface area designed to maximize postoperative weight-bearing capacity, providing a biomechanically precise implant specifically designed to stabilize the heavily loaded sacroiliac joint. In other embodiments, the entire shank and body portions may be porous.

[0108] The implant 2700 can be made of a variety of materials. For example, the implant can be made of a metal or metal alloy, such as titanium or steel, or a non-metallic material, such as a ceramic or polymer. In some embodiments, the implant material can have a lattice microstructure formed from particulates. For example, the lattice microstructure can be textured using surface finishing techniques, such as polishing or applying a metal plasma spray, to create a rough or smooth surface texture. A 3D printing process can be used to manufacture part or all of the implant 2700, thereby controlling the porosity of the implant or printed portion. For example, the implant can have a volumetric porosity of between about 30 and 70 percent, with an average pore size of between 100 and 1000 microns. The pores can be predominantly interconnected, predominantly disconnected, or a mixture of interconnected and disconnected pores. In some embodiments, the pores can be distributed throughout the implant material, including the interior and exterior surfaces of the implant. For example, the fusion of microparticles forming the implant can result in a porous, semi-porous, or non-porous structure, depending on the degree of fusion between the microparticles. In other embodiments, the pores can be located within a porous coating that can be applied to the implant. For example, the porous coating can be applied using a titanium plasma spray process or other metal plasma spray process. The coating can be applied to the exterior surface of the implant, the interior surface of the implant, or both the exterior and interior surfaces of the implant. For example, the coating can be preferentially applied to the exterior surface of a matrixed implant to provide bone ingrowth and overgrowth, but not to the interior surface of the implant to maximize bone penetration into the implant. The coating can also be preferentially applied from proximal to distal, or vice versa. The thickness of the porous coating can be between approximately 500 and 1,500 microns.In addition to, or instead of, a porous metal coating, a hydroxyapatite coating can also be applied to the implant. In some embodiments, the porosity can vary along the length of the implant. In some embodiments, the thickness of the coating can vary along the length of the implant. In some embodiments, the thickness of the coating applied to the exterior surface can be different from the thickness of the inner coating. For example, in some embodiments, the outer coating can be thicker than the inner coating. In other embodiments, the inner and outer coatings can be the same thickness.

[0109] 28A and 28B show another exemplary embodiment of a bone implant having a tulip or coupling device disposed at its proximal end. Implant 2800 is in the form of a sacral alar iliac (SAI) screw and includes a threaded shank portion 2802, a body portion 2804, and a head portion 2806. Threaded shank portion 2802 and head portion 2806 of implant 2800 are similar to those of implant 2500 described above with reference to FIGS. 25A-25G.

[0110] Body portion 2804 includes a porous outer surface configured to traverse the bone joint and / or proximal bone segment when implanted and may be similar to body portion 2704 described above with reference to Figures 27A and 27B. In this embodiment, body portion 2804 includes fenestrations 2808 communicating between the outer surface and a central lumen 2810. Fenestrations 2808 may be circular in shape, as shown, or may be formed in other shapes. Fenestrations 2808 may be configured to promote bone overgrowth, ingrowth, and / or through-growth for faster implant and / or bone joint fusion.

[0111] 29A and 29B show another exemplary embodiment of a bone implant having a tulip or coupling device provided at its proximal end. Implant 2900 is in the form of a sacral alar iliac (SAI) screw and includes a threaded shank portion 2902, a body portion 2904, and a head portion 2906. Threaded shank portion 2902 and head portion 2906 of implant 2900 are similar to those of implant 2500 described above with reference to FIGS. 25A-25G.

[0112] The body portion 2904 includes a porous outer surface configured to traverse the bone joint and / or proximal bone segment when implanted, and may be similar to the body portion 2704 described above with reference to FIGS. 27A and 27B . In this embodiment, the body portion 2904 includes fenestrations 2908 communicating between the outer surface and the central lumen 2910. The fenestrations 2908 may be elongated, as shown, or may be angled. In this exemplary embodiment, the fenestrations 2908 are all aligned in the same direction as the threads disposed in the shank portion 2902, but form a more acute angle with respect to the longitudinal axis of the implant 2900. Additionally, the fenestrations 2908 may include sharp tips along their proximal and / or posterior edges. These tips can scrape bone material from the surrounding bone and cut it toward the central lumen 2910 as the implant 2900 is threaded into place, forming a self-grafting screw SAI. This bone material can then promote faster bone growth in and / or around the implant 2900. The fenestrations 2908 themselves can also promote bone overgrowth, ingrowth, and / or through-growth for faster implant and / or bone joint fusion.

[0113] 30A and 30B show another exemplary embodiment of a bone implant having a tulip or coupling device provided at its proximal end. Implant 3000 is in the form of a sacral alar iliac (SAI) screw and includes a threaded shank portion 3002, a body portion 3004, and a head portion 3006. The threaded shank portion 3002 and head portion 3006 of implant 3000 are similar to those of implant 2500 described above with reference to FIGS. 25A-25G.

[0114] The body portion 3004 may be similar to the body portion 2704 described above with reference to FIGS. 27A and 27B , including a porous outer surface configured to traverse the bone joint and / or proximal bone segment when implanted. In this embodiment, a set of threads 3008 extends continuously across the shank portion 3002 and the body portion 3004. On the body portion 3004, the minor diameter or root of the threads 3008 may be filled with or formed by the porous material 3010. The major diameter or crest of the threads 3008 may be formed on top of a sleeve of porous material 3010, as shown in FIG. 30B . Alternatively, the major diameter or crest of the threads 3008 may be integrally formed with the minor diameter or root, and the porous material 3010 may simply reside within the root (not shown). The porous material 3010 may then promote surface growth into the body portion 3004 and ingrowth into the threads 3008.

[0115] FIG. 31 illustrates another exemplary implant for use in at least one of bony fusion and stabilization. In this case, the elongated body is sized and configured such that when implanted through the posterior sacroiliac ("SAI") joint (e.g., S2AI), the bone entry point is between the S1 foramina, the distal region of the elongated body is distal to the sacroiliac ("SI") joint, within the outer surface of the ilium, and the proximal region of the elongated body is positioned across the SI joint. The implant includes a distal fixation region having one or more distal surface features adapted to secure the distal fixation region to the ilium. The implant also includes a proximal region positioned proximal to the distal region, the proximal region having one or more proximal surface features adapted to promote at least one of bone overgrowth, ingrowth, or through-growth. The implant of FIG. 31 is an example of a composite implant, or an implant comprised of two or more components.

[0116] The embodiment of Figure 31 is similar in several respects to the embodiment of Figures 25A-30B herein. Any suitable feature described with respect to the embodiment of Figures 25A-30B may be included in the following embodiments, and vice versa, unless indicated to the contrary. The implant 3100 includes a distal region 3102 configured for anchoring to bone, such as relatively dense cortical bone, and a proximal region 3104 adapted to promote at least one of bone overgrowth, ingrowth, or through-growth. The distal region 3102 includes at least one thread 3110, and the proximal region 3104 includes at least one thread 3112.

[0117] As in the previous embodiment, the proximal region 3104 is adapted to promote at least one of bone overgrowth, ingrowth, or through-growth. In this example, the adaptation includes a porous surface 3114 formed between one or more threads. The threads 3112 in the central region of the proximal region are discontinuous but have an overall helical configuration. As shown, the proximal region 3104 includes a plurality of fenestrations 3113 (larger than the pores 3114), subsets of which are arranged together in at least a partial helical configuration. In this embodiment, multiple subsets of the plurality of fenestrations 3113 are each arranged in a partial helical configuration. As shown, at least some of the fenestrations are located at the locations of the discontinuous portions of the threads.

[0118] The implant 3100 includes an inner elongate body 3108 and an outer elongate body 3106. The inner and outer elongate bodies are adapted to stably interface with one another to resist relative movement in at least one direction. The inner elongate body 3108 includes threads 3110 on a distal region 3102 of the implant. The outer elongate body 3106 includes threads 3112 on a proximal region 3104 of the implant. The inner elongate body 3108 has an unthreaded proximal region 3111, which may optionally include threads that interface with optional threads on the outer body 3106. The outer body includes a distal region 3107 including dual lead threads, a central region with a single lead thread, and a proximal dual-threaded region 3109. One of the threads from the distal region 3107 does not continue into the central region with a single lead thread. The outer body 3106 also includes relatively large fenestrations 3113 and relatively small slots 3114 between the threads. The outer elongate body 3106 has a larger outer diameter than the inner elongate member 3108. The outer elongate body 3106 can have an inner diameter that is radially spaced from the outer diameter of the inner elongate body 3108, thereby forming a volume of space radially between the inner elongate body 3108 and the outer elongate body 3106.

[0119] In this exemplary embodiment, the inner and outer bodies each have one or more features that allow them to engage such that relative movement between the two bodies is resisted in at least one direction, optionally rotationally. The outer body 3106 includes one or more surface features 3121 disposed at its distal end region that are sized and configured to interface with (optionally linear) protruding features on the inner elongate body 3108, the interface preventing rotation between the outer and inner elongate bodies. In this embodiment, the interface features prevent rotation at the distal end of the outer elongate body. As described with reference to FIG. 25B herein, a wide variety of features can be incorporated into the inner and outer elongate bodies to provide this functionality.

[0120] When the implants herein are implanted in an SAI trajectory (e.g., S2AI) for placement across the SI joint (as described in detail elsewhere herein), at least a portion of the implant, having one or more surface features specifically adapted to facilitate any one of bone overgrowth, ingrowth, or through-growth, must be positioned at the sacroiliac joint. Figures 32A and 32B are images showing an SAI trajectory for implanting an SI joint stabilization implant across the SI joint, with the arrow indicating the trajectory. "Joint length" refers to the distance from the sacral entry point to the subject's SI joint. "Total length" refers to the distance from the sacral entry point to the outer border of the subject's iliac cortex. Furthermore, the distal portion of the implant, which is positioned distal to the SI joint, preferably has one or more surface features (e.g., a threaded region) that adapt the distal region for effective fixation to the relatively dense iliac cortical bone. An important consideration for implantable devices implanted across the SI in an SAI trajectory is to design and configure different regions of the implant based on the tissue adjacent to those regions when implanted.

[0121] For example, with reference to FIG. 31 , the implant 3100 includes length-spanning pores 3114 such that, when implanted across the SI joint in the S2AI trajectory, the pores 3114 are positioned at the SI joint to facilitate at least one of bone overgrowth, ingrowth, or through-growth. Note that the pores can also extend into the distal region 3102. In this embodiment, the single lead thread in the proximal region 3104 allows more space for pore formation within the proximal region 3104 of the implant, in this case at least some area between the threads. Furthermore, the distal region 3102, which is implanted distal to the sacroiliac joint in the relatively denser iliac cortical bone, has one or more surface features (e.g., threads) adapted to effectively and better anchor the distal region 3102 to the denser bone. In this example, the distal region 3102 includes dual lead threads (which may be more than dual) to provide better fixation than a single lead thread in the central region of the proximal region 3104. It should be noted that the threads in the central region of the proximal region 3104 may have a smaller pitch and still be adapted (e.g., have pores) to facilitate in-growth. Thus, it should be understood that one or more characteristics (e.g., pitch) of the surface features may be similar in both the proximal and distal regions. In this embodiment, the pitch is the same, but the distal region has multiple (in this case, dual) lead threads. In the embodiment of FIG. 31, one or more surface features in the proximal and distal regions have different characteristics.

[0122] 33A-33C illustrate an exemplary embodiment of a composite implant that can be sized and configured for implantation across the SI joint via the SAI trajectory (e.g., S2AI). While implant 3300 has been described as a composite implant comprised of multiple pieces (two pieces in this embodiment) assembled prior to implantation, implant 3300 can be modified to be a single, integral unit and manufactured from a single piece. Implant 3300 includes an ingrowth region 3304 similar to the "proximal regions" of other implants herein. Implant 3300 also includes a fixation region 3302 similar to the "distal regions" of other implants herein. Implant 3300 is similar to implant 3100 of FIG. 31. Any of the features of implant 3100 may be incorporated into implant 3300, and vice versa, unless otherwise indicated herein. Distal fixation region 3302 includes double lead threads 3301 and 3301′, and distal region 3302 is distally tapered. The proximal ingrowth region 3304, as shown, includes a plurality of larger fenestrations 3306, a subset of which have a partial helical configuration. In this embodiment, the threads 3303 are continuous (unlike threads 3112), with the fenestrations 3306 disposed between the threads. The proximal region 3304 also includes pores 3305 disposed between the threads 3303. In variations, the threads 3303 can have one or more discontinuities (like threads 3112), but can also have sections that rotate fully (at least 360 degrees) between the thread discontinuities.

[0123] The ingrowth region 3304 of the implant includes a plurality of fenestrations 3306 and smaller pores 3305, both of which extend through the exterior and interior surfaces of the proximal region and provide passageways from the interior implant volume (though not the "innermost" volume in this embodiment) to locations outside the implant. The fenestrations 3306 and pores 3305 serve to adapt the proximal fixation region to promote ingrowth.

[0124] In this embodiment, the implant 3300 includes an inner member 3320 (e.g., a screw or threaded component) and an outer member 3340 (e.g., an outer sleeve), which are adapted to be secured together before the implant is fully implanted (e.g., secured before a portion of the implant is implanted or secured at some point during the procedure), and which are not integrally formed from the same piece. An example of an inner member is an inner shank, and an example of an outer member is a sleeve. The inner member 3320 and outer member 3340 are shown individually and not secured together in FIGS. 33B and 33C , respectively. In this embodiment, when the inner and outer members are secured together, they interface such that relative movement between the two is limited in at least one direction (e.g., rotational and / or axial). The inner member can have an outer member interface 3321, shown in FIG. 33B , which in this embodiment is a threaded region that can mate with the internal threads of the outer member 3340, and once interfaced, the distal end of the outer member 3340 is secured to the inner member 3320. The proximal end of the outer member can also be secured to the inner member, for example, with a threaded connection (which can include, for example, a proximal threaded region 3323 on the inner member). In this embodiment, the inner component includes an unthreaded region 3322, which can be a shaft, for example, a smooth shaft. The unthreaded region can be the interior surface of an internal volume disposed between the inner and outer members. The unthreaded region 3322 can have any number of surface features intended to facilitate ingrowth, for example, a roughened or other similarly non-smooth surface. In this embodiment, it is the inner component 3320 that includes the distal fixation region 3302 of the implant 3300, which in this embodiment includes threads 3301 and 3301′.

[0125] FIG. 33C shows the outer member 3340, in this embodiment an outer sleeve sized and configured to be advanced over the inner member 3320, the outer member 3340 and inner member 3320 adapted to be secured relative to one another to resist relative movement therebetween in at least one direction. The outer member 3340 has an internal bore extending therethrough, and a fenestration 3306 is formed through the inner member 3340, providing communication between the internal bore and the exterior of the implant. The proximal end region of the outer member 3340 has a second thread 3308, forming a dual-threaded region at the proximal end region. The threads 3303 extend to the end of the threaded region and, in this exemplary embodiment, have a constant pitch along its length, although in other embodiments, the pitch can vary to a certain extent. Although not shown in FIG. 33C, a slot 3305 may be present in the outer member between the threads, as in the embodiment shown in FIG. 31. The optional porous regions 3305 are labeled (only two are labeled), but the pores are not shown in FIG. 33 for clarity. While the fenestrations are viewed as individual fenestrations, multiple individual fenestrations 3306 can extend together in a partial spiral configuration. In this embodiment, there are three fenestration regions, each extending in a partial spiral configuration, as shown. The fenestrations 3306 do not extend into the double-threaded region at the proximal end of the outer member 3340, nor do they extend all the way to the distal end of the outer member. As shown, any number of the fenestrations 3306 can be tapered (larger outer dimension). The optional fenestrations, like the optional fenestrations, can promote at least one of bone overgrowth, ingrowth, or through-growth.

[0126] The set of multiple fenestrations 3306 in this embodiment are configured and oriented to allow a physician to view through the outer member from one side to the other using radiographic imaging to monitor bone ingrowth and fusion over time.

[0127] An exemplary advantage of having a composite implant with two (or more) pieces is that the more fatigue-resistant first component (e.g., inner shank) can be manufactured using several common techniques, including several common screw manufacturing techniques. The first component (e.g., inner component) may be made of a relatively more fatigue-resistant material, such as, but not limited to, titanium or stainless steel. For example, the inner member 3320 shown in FIG. 33B can be made of a relatively fatigue-resistant material, such as titanium, which provides strength to the implant 3300. Furthermore, the distal fixation region 3302 can be manufactured using, for example, common screw manufacturing techniques. By selecting a material for the inner member that is stronger and provides strength to the implant, the second component, such as the outer member 3340 (e.g., outer sleeve) shown in FIG. 33C, does not need to be fatigue-resistant. This provides more options for selecting the design and / or material of the second component, allowing for more design options for the second component and facilitating the process of using design features of the second component to provide additional functionality to the implant. For example, the outer member 3340 (e.g., sleeve) can be designed with certain features (e.g., porosity and / or a rough surface) that make it less fatigue-resistant, optionally significantly less fatigue-resistant than the inner member. The outer member (e.g., 3340) can be made from a variety of materials, such as titanium alloys, polymers, or ceramics. In this embodiment, the outer member, referred to as the outer sleeve, provides several features to the implant. By having an axially extending central bore with an inner diameter larger than the outer diameter of the inner member, the implant has an empty volume between the inner and outer members, which promotes tissue ingrowth and helps stabilize the implant after implantation. The empty volume can also be used to deliver one or more drugs to the recipient after the implant is placed in the recipient. Additionally, the outer sleeve includes openings and / or fenestrations that can also promote tissue ingrowth into the volume.The outer sleeve also includes one or more screws that, in this embodiment, help secure the implant at the screw location, including at the SI joint.

[0128] Thus, any of the composite implants of the present disclosure can benefit from the exemplary advantages of the composite implants described herein.

[0129] As described herein, the implants of FIGS. 25-47 can be implanted across the SI joint and advanced utilizing an SAI trajectory (e.g., S2AI) as generally shown in FIG. 24 herein. As described herein, different regions of the implant can be configured to provide one or more functions, which can depend on the type of tissue adjacent to a particular region during or after implantation. For example, an SAI implant preferably has a region, such as proximal region 3304, that can promote at least one of bone overgrowth, ingrowth, or through-growth when implanted and extending across the SI joint. As can be seen in FIGS. 32A and 32B, the proximal region should have a length such that it extends across the SI joint when implanted. In some embodiments, the proximal ingrowth region (e.g., region 3304) has a distal end that extends at least 20 mm from the proximal end of the implant. The proximal end here does not necessarily extend all the way to the proximal end of the implant. The proximal region only has a distal end at least 20 mm from the proximal end of the implant. In some embodiments, the distal end is 20 mm-100 mm, optionally 30 mm-75 mm, and optionally 30 mm-60 mm from the proximal end of the implant. The term "proximal region" herein generally refers to a region of the implant that has at least one structural difference with respect to the distal fixation region, which is closer to the distal end of the implant than the proximal growth region. In the exemplary embodiment of Figures 33A-33C, one structural difference between the proximal and distal regions is that the proximal region includes a thread region with a lower percentage (of its length) of dual-lead or multi-lead threads. Further differences in this embodiment include fenestrations and pores present in the proximal fixation region. The exemplary length of the proximal growth region in this embodiment can be incorporated into other SAI implants herein, for example, as shown in Figures 25-30. Any length of the proximal region herein ("proximal region" in these contexts may also refer to "proximal growth region") may be the length of the shank or shaft region 3322 of the inner member.

[0130] Other types of implants having similar structures and dimensions may not necessarily provide the benefits described above. For example, the relative lengths of the different sections of those other implants may not necessarily be sized to provide the benefits described herein, in combination with the overall length of those implants, when implanted by the methods described herein. For example, other types of implants may not include a distal fixation section sized (including length) and configured for internal fixation in the ilium and a proximal section sized (including length) and configured for placement across the sacroiliac joint, with the distal fixation region positioned within the ilium and the proximal region adapted to promote tissue ingrowth.

[0131] The distal fixation region (e.g., region 3302 shown in FIG. 33A ) herein generally refers to a distal region of an implant that does not extend completely to the proximal end of the implant and has one or more structural differences than more proximally disposed regions. The distal region has one or more structural features that make it better adapted to anchor in tissue than more proximally disposed regions. For example, the distal region 3302 may have a higher proportion of dual-lead or multi-lead threads, be made of a stronger material or structure than the proximal region 3304, and be better adapted for anchoring than more proximally disposed regions. The distal region may or may not extend completely to the distal end of the implant. For example, in the embodiment of FIGS. 33A-C , the distal region is considered to extend completely to the distal end of the implant. The distal end of the distal fixation region extends distally at least 40 mm from the proximal end of the implant. At least this distal extension securely anchors the distal region of the implant to the denser cortical ilium, which will be adjacent to the distal region when the implant is implanted in the SAI orbit. The distal end of the distal region may be 40 mm to 120 mm, optionally 40 mm to 100 mm, and optionally 40 mm to 80 mm from the proximal end of the implant. The distal end of the implant must not extend beyond the ilium.

[0132] In some embodiments, the length of the distal region is from 10 mm to 80 mm, such as from 10 mm to 60 mm, for example, from 10 mm to 50 mm, for example, from 10 mm to 40 mm, for example, from 10 mm to 40 mm, for example, from 15 mm to 35 mm, for example, from 20 mm to 30 mm.

[0133] The proximal region may be longer than the distal region, as in the embodiment shown in Figures 25-33, and in other embodiments, the distal region may have a length equal to that of the proximal region. And, as noted above, the "proximal growth region" (e.g., 3304 in Figure 33A) may not extend proximally as in the embodiment of Figures 25-33 (although even in this case, the implant may be adapted to fully promote ingrowth, including when intra-articular). Thus, in some alternative embodiments, the proximal growth region may be the same length as the distal fixation region, or may be shorter.

[0134] In some embodiments, the proximal growth region is longer than the distal fixation region, and in some embodiments, is 1-3 times the length of the distal fixation region, e.g., 1.1-2.9 times the length of the distal fixation region. For example, in the embodiment of Figures 33A-C, the proximal growth region is 1-3 times the length of the distal fixation region and 1-2 times the length of the distal fixation region. The relative lengths and length ratios depend on where the implant regions will be placed after implantation and the functionality required from the different implant regions based on the adjacent tissue.

[0135] The distal fixation region (e.g., regions 3302, 3102) may be a dual lead thread region, as in the embodiment of FIGS. 33A-33C. For example, without limitation, the thread pitch may be 4 mm-8 mm, e.g., 5 mm-7 mm (e.g., 6 mm), and the thread region has a 3 mm lead. The dual lead thread region helps adapt the distal fixation region for enhanced fixation in harder cortical bone. The implant 3100 shown in FIG. 31 also has a distal fixation region with a dual lead thread region.

[0136] 33A-33C, the inner member 3320 includes a shaft region 3322. The outer diameter ("OD") of the shaft is smaller than the inner diameter ("ID") of the outer sleeve 3340. In some embodiments, the distance (i.e., spacing) between the OD and ID may be between 0.1 mm and 5 mm, e.g., between 0.5 mm and 3 mm. As described herein, this spacing defines a volume that facilitates growth therein.

[0137] In some merely exemplary embodiments, the outer member 3340 (e.g., outer sleeve) can have threads (e.g., 3103) with a constant pitch along most of its length, as in the case shown in FIGS. 33A-33C. Even if the threads have one or more discontinuities along their length (e.g., as in the embodiment shown in FIG. 31), the pitch can be, for example, 3 mm to 9 mm (e.g., 4 mm to 8 mm, e.g., 5 mm to 7 mm, e.g., 6 mm). As in FIGS. 31 and 33A-33C, the threaded region can be single-lead along at least 50% or more of its length; in these embodiments, the threaded region is single-lead along at least 75% of its length. The pitch of the threaded region of the outer member can be designed to maintain sufficient surface area on the body of the outer member to create sufficient fenestrations (e.g., fenestrations 3114 or 3305) that can facilitate in-growth.

[0138] The outer members of Figures 31 and 33A-33C include a proximal region that is dual-lead (e.g., 3303 and 3308 in Figure 33C). Dual-lead and dual-thread are terms used interchangeably in this disclosure. The dual (or double) lead region serves to anchor this region of the implant to the denser cortex of the sacrum, as well as making the dual-lead fixation region of the implant dual-lead to improve fixation within the cortical ilium. Any of the implants herein can have this proximal dual-lead region.

[0139] As described herein, the inner surface of the outer member 3340 can have an internally threaded region configured to interface with an externally threaded region 3321 (see FIG. 33B) on the inner member 3320. This helps to stabilize the inner and outer members.

[0140] In some embodiments, the outer and inner members are adapted, when assembled, such that the outer member is placed under compression for secure engagement between the two components. Because a bent component may fail at the surface exposed to tension, prestressing one or more components under compression can provide the advantage of a higher working load range. However, prestressing the outer member is optional. Any of the implants herein can be prestressed in this manner to provide the advantage of a higher working load range.

[0141] With any of the implants herein, the distal (or proximal) end of the outer member can be secured to the inner member, but the proximal (or distal) end is not secured to resist relative movement in at least one direction. Allowing the proximal (or distal) end to move freely relative to the inner member has the advantage of reducing forces acting on the implant, thereby reducing fatigue of the implant.

[0142] In alternative embodiments, the shaft region of the inner member (e.g., 3322 in FIG. 33B) can include one or more openings or fenestrations therein of a wide variety of sizes and configurations. The opening or openings in the inner member can allow a substance (e.g., a therapeutic agent) to be delivered into the interior channel or bore of the inner member and then exit through openings (e.g., apertures, smaller fenestrations) in the outer member to interact with tissue.

[0143] It will be understood that any suitable feature described with respect to any of the implants of Figures 25-33 can be incorporated into any of the other embodiments of Figures 25-33, particularly if the feature can be clearly and easily incorporated.

[0144] Unless otherwise noted, the implants disclosed in Figures 31-47 include a proximal end region configured to couple to a tulip, similar to the tulip or coupling device or member at the proximal end of the implants shown in Figures 25-30. Any tulip or coupling device described in the context of Figures 25-30 herein is expressly incorporated by reference into the embodiment of Figures 31-33. The tulip coupling member is configured to allow the implant to be coupled to other bone stabilization systems described elsewhere herein.

[0145] Any of the exemplary features of any of the composite implants herein can be integrated or incorporated into other composite implant examples herein, unless specifically indicated to the contrary.

[0146] 34A and 34B show side views of an exemplary (assembled) composite implant that can be sized and configured for implantation across the sacroiliac (SI) joint via a posterior sacral alar iliac ("SAI") trajectory, e.g., a posterior second sacroiliac ("S2AI") trajectory. FIG. 34A is a side view of the assembly (with the tulip coupled thereto not shown), and FIG. 34B is a cross-sectional view of the assembly. The implant 3400 includes a sleeve 3410 and a shank 3430, the sleeve being sized and configured to be positioned over at least a portion of the shank. The sleeve herein has an internal lumen that is sized and configured to receive an inner member therethrough. The sleeve further includes one or more overgrowth features adapted to promote at least one of bone overgrowth, bone ingrowth, or bone through-growth. The sleeve is positioned relative to the shank to form a composite implant with interfacing shank and sleeve interface features to resist relative movement between the sleeve and shank in at least one direction. The sleeve is positioned relative to the shank to form a composite implant having shank interface features and sleeve interface features that resist relative movement between the sleeve and shank in at least one direction. A shank herein may be referred to as an inner shank when the sleeve is positioned around at least a portion of the shank. In this context, inner and outer refer to relative radial positions with respect to the optional long axis of the implant.

[0147] In this embodiment, the sleeve 3410 is configured so that it can be front loaded onto the shank 3430. That is, the distal end of the shank can be advanced (in relative motion) into the proximal end of the sleeve to assemble the shank and sleeve into the assembled configuration shown in FIGS.

[0148] The sleeve 3410 includes a tapered distal thread region 3411, any portion of which may be textured. In this embodiment, the tapered distal thread region 3411 is a dual-lead thread. The sleeve 3410 also includes a central region 3412, which includes a single lead, a plurality of fenestrations 3413, and a plurality of separate lattice sections 3414 (only one is labeled), as shown. In this example, each of the plurality of fenestrations 3413 (in other embodiments, at least some) is positioned between axially adjacent thread regions, as shown. In this example, each of the plurality of lattice sections 3413 (in other embodiments, at least some) is positioned between axially adjacent thread regions, as shown. In this example, multiple subsets of the plurality of fenestrations are each arranged in a partial helical configuration, as shown. In this example, multiple subsets of the plurality of lattice sections are each arranged in a partial helical configuration, as shown.

[0149] The implant 3400 includes a distal fixation region ("DAR" in FIG. 34B) and an in-growth region ("GR" in FIG. 34B). The distal fixation region includes one or more distal surface features (threads in this embodiment) that make the distal fixation region better suited for fixation to the ilium than the in-growth region. The in-growth region includes one or more in-growth features (e.g., more fenestrations 3413, more lattice sections 3414, and single and double threads) that make the in-growth region better suited to promote at least one of bone over-growth, bone ingrowth, or bone through-growth than the fixation region.

[0150] FIGS. 36A-36C illustrate an exemplary composite implant 3600, which may include any relevant feature of any composite implant (multiple components) herein. Any features not specifically described may be incorporated into this embodiment by reference from other examples herein. Similar features may be numbered identically in the figures. The implant 3600 includes a sleeve 3610 and a shank 3630. In the embodiment of FIGS. 36A-C, the sleeve 3610 includes a distal tapered thread region, as shown. The distal tapered thread region has an optional textured surface 3616 on the minor diameter of the threads. A cross section B-B of FIG. 36A is shown in FIG. 36B. As shown in FIG. 36B, a lattice section 3614 is disposed in the sleeve flutes 3615 and the lattice section 3614. In a cross section CC of FIG. 36A, the sleeve also includes a lattice section 3614' that fills the cutting fluid void, as shown in FIG. 36C. In this proximal region of the sleeve, the lattice sections 3614' essentially fill or replace the openings 3613. These lattice sections 3614' can increase the amount of tissue ingrowth through the sections 3614'. Also shown in Figure 36C is a defined volume (or void) between the outer dimension of the shank and the inner diameter of the sleeve where tissue ingrowth can occur.

[0151] The sleeves in Figures 36A-36C are adapted to be front loaded onto the shank. Front loading of the sleeve allows for easy thread alignment of the sleeve and shank.

[0152] In any of the composite implant examples herein, the sleeve can be manufactured by printing.

[0153] 35 shows an exemplary shank 3530. Any of the shanks herein may also be referred to as inner members. The shank 3530 includes a distal region 3540, which in this embodiment is threaded and has double threads. The distal region 3540 is tapered.

[0154] The shank includes a section 3551 and a section 3552 with an axial section 3553 therebetween. One or both of sections 3551 and 3552 may be textured, for example, but not limited to, with TPS, grit blast, HA, or the like, to promote one or more of surface growth, ingrowth, or through-growth. Section 3553 may include a central thread, as shown. The threads in the central section 3553 may be created using the same thread path as the threads in the distal shank section. An advantage of the threads in the central section 3553 is that they can create volume between the sleeve and the shank, increasing graft volume while supporting the sleeve.

[0155] Any of the inner members herein, e.g., the shanks herein, can be manufactured by machining the inner member. In some embodiments, the inner member can be machined from a solid material, such as titanium. The central rib in section 3553 is an example of a central rib that can be configured to reduce the bending moment of the shank. This can be useful for relatively long shanks, e.g., 80-120 mm in length.

[0156] Figure 37 shows a shank 3700 that includes a central rib 3731. The central rib 3731 is a region that has a larger radial dimension than adjacent sections of the shank, as shown in Figure 37. The rib can increase graft volume and optionally help stabilize the sleeve.

[0157] Any of the shanks herein (any one of its sections) may have one or more holes therethrough, thereby facilitating the administration of one or more agents (e.g., PMMA to the ilium) after implantation.

[0158] In any of the embodiments herein, the sleeve opening herein may have one angled edge, as shown in the embodiments of Figures 34A-47, which aids in cutting the bone while screwing the implant into place, and the other edge may be straight, which aids in self-introduction of bone and filling the fenestration with bone.

[0159] 40 shows a portion of a composite implant 4000 including a sleeve 4010 and a shank 4030. An optional aperture 4013 is also shown. Other optional features according to other embodiments herein may be incorporated into the implant 4000. The implant 4000 includes a shank 4030 having optional holes 4023 adapted to serve as post-fill graft ports. The holes 4023 may communicate with the inner shank volume to facilitate post-filling of the implant. In this embodiment, the apertures 4023 are optionally aligned with the holes 4023.

[0160] 41A and 41B show an exemplary composite implant 4100 including a sleeve 4110 and a shank 4130. In this embodiment (or other embodiments herein), the sleeve 4110 includes cutting flutes in a distal region. In this exemplary embodiment, the cutting flutes have cutting surfaces 4128 that are 15 to 25 degrees, as shown in FIG. 41B. The cutting surfaces can be angled at other angles. The implant 4100 includes other features of the other composite implants herein.

[0161] The implant may have one or more ways in which the sleeve interacts with the shank to help stabilize the sleeve relative to the shank when assembled. For example, the shank can have shank interface features and the sleeve can have sleeve interface features, where the shank interface and sleeve interface are configured to interface with each other to resist relative movement in at least one direction (e.g., axial, radial, rotational) between the sleeve and inner shank. For example, the sleeve and shank can interface at one or both of the distal fixation region and the proximal region of the implant to help stabilize the sleeve relative to the shank. In some examples, the shank and sleeve do not interface in the central region of the implant.

[0162] For example, the shank 4230 may include a detent, recess, or thread barb 4239 in the distal threaded region, as shown in FIG. 42. The barb 4239 may be configured to interface with the sleeve 4210 to prevent the sleeve from advancing too far distally relative to the shank. This may act as a backup or second stop feature in the event that the primary locking mechanism fails.

[0163] Alternatively, or additionally, the sleeve and shank can resist relative movement therebetween in at least one direction by interfacing with the proximal end region of the composite implant. FIG. 43 illustrates an exemplary proximal end region locking mechanism that can be incorporated into any of the composite implants herein. The side cross-sectional view of FIG. 34B also includes a proximal end region locking mechanism the same as or similar to that shown in FIG. 43. The composite implant 4300 is shown with a schematic sleeve in which the lattice regions 4314 and 4314 are shown as solid regions. The locking ring 4316 (which can be the same as or similar to the locking ring 3416 in FIG. 34B) is a separate component configured to fit into grooves in the shank and sleeve when the shank and sleeve are assembled. The optional annular locking ring functions to prevent potential movement of a loose sleeve.

[0164] 44A-C are side views of an exemplary composite implant 4400 (FIG. 44C shows the shank 4410). FIG. 44B is a side cross-sectional view. FIGS. 44A-44C illustrate additional or alternative ways in which the sleeve and shank can interface to resist relative movement therebetween in at least one direction. As shown in the cross-sectional view of FIG. 44B, the shank and sleeve can have interference-fit threads at the thread interface region 4450, which can help resist relative movement between the shank and sleeve. There may be no clearance in any portion of the threads. In these embodiments, the sleeve includes internal threads at its distal end region configured to interface with the external threads of the shank.

[0165] Alternatively, or additionally, the shank / sleeve interface can include a tapered lock connection at tapered lock connection region 4460. At this interface region, the shank and sleeve can include distal tapers, as shown, that together form a tapered lock.

[0166] Alternatively, or in addition, the shank / sleeve interface can include a proximal end region interface in region 4470, which in this embodiment includes a tight sliding fit between the optionally smooth surfaces of the sleeve and shank. The surface 4419 of the shank that interfaces with the sleeve is shown in Figure 44C. Figures 44A-44C are examples of composite implants in which the sleeve and shaft interface at the distal and proximal end regions, but not in a central region between the distal and proximal end regions.

[0167] In any of the embodiments herein, the sleeve and shank may interface in a distal region, e.g., one or both of regions 4450 and / or 4460 in FIG. 44B, but may not interface in a proximal region (e.g., optionally not interface in region 4470 in FIG. 44B).

[0168] Furthermore, when the sleeve and shank interface at a proximal region, the proximal interface region can provide for relative movement between the sleeve and shank, yet still provide some overall resistance to movement between them in at least one direction.

[0169] 45A and 45B show an exemplary composite implant 4500 (in a side view and a cross-sectional side view, respectively) including a sleeve 4510 and a shank 4530. The implant 4500 may alternatively or additionally include any of the features of any other composite implant described herein. The shank 4530 illustrates an example in which the distal thread region 4541 and the proximal thread region 4542 may be cut from a blank starting material in the same step, such that the threads share the same start. The proximal threads 4542 may be dual-lead threads, as shown, as in other embodiments shown herein. As in other embodiments shown herein, the outer sleeve region 4519 is dual-lead.

[0170] 45B illustrates an exemplary shank / sleeve distal interface, including a threaded interface between the sleeve 4510 and the shank 4530. As shown, in the interface region 4538, the apex of the shank threads optionally flattens out proximally as shown, i.e., the apex becomes less flat further distally and flatter proximally in region 4538, as shown in FIG.

[0171] The implant 4500 is an example of a composite implant in which the sleeve can be placed under compression when the shank is assembled, as described above for exemplary advantages. For example, because bending members can fail at surfaces exposed to tension, prestressing one or more components to compress them can provide the advantage of a higher working load range. However, prestressing the outer member is optional. Any of the implants herein can be prestressed in this manner to provide the advantage of a higher working load range. The implant 4500 includes a shank 4530 having a stop 4539 in a shoulder configuration, as shown. The stop 4339 provides a mechanical stop for the sleeve 4510 and helps to compress (prestrain) the sleeve, as described above for advantages. Another aspect of the present disclosure is a composite implant in which the outer member (e.g., sleeve) is placed under compression when interfaced with the inner member (e.g., shank). One optional benefit of pre-straining / pre-compressing the sleeve is when the material properties of the sleeve, compared to the shank, make it likely or likely to fail before the shank.

[0172] FIG. 46A illustrates an exemplary composite implant 4600 including a sleeve 4610 and a shank 4630. The implant 4600 may alternatively or additionally include other features of the other composite implants described herein. Other composite implants described herein may include any of the features of the implant 4600. FIGS. 46B-46D illustrate exemplary features of an exemplary sleeve 4610. Any of the sleeves described herein may be 3D printed, for example. In the distal thread region of the sleeve shown in FIG. 46B, the threads may have a backflank angle of, for example, 5° to 15°. FIG. 46C illustrates a central region of an exemplary sleeve 4610 in a more centrally located in-growth region of the implant. In this thread region, the threads may have a backflank angle of, for example, 0° to 3°. FIG. 46D illustrates a proximal region of a sleeve 4610 having dual lead threads. As shown, the sleeve's minor diameter surface 4617 tapers radially outward from the distal end to the proximal end, as shown in both FIGS. 46A and 46D. The major diameter can remain constant or substantially constant. The threads may have a backflank angle of, for example, 0° to 3°. FIG. 46E shows the distal end region of an exemplary shank 4630. Any of the shanks herein can be machined using various known machining processes. The threads 4637, as shown, have a small flat at the top and gradually increase in length proximally, as also shown. The distal shank threads may optionally include multiple cutting flutes in this region, optionally with the first and second flutes at 180 degrees from each other. The distal shank threads may optionally have a backflank angle of, for example, 10° to 15°.

[0173] FIG. 47 is a side view illustrating an exemplary composite implant 4700 including an outer member 4710 (e.g., sleeve) and an inner member 4730 (e.g., shank). The inner member, like any inner member herein, can include a proximal end 4760 configured to be coupled to a tulip, to which a reinforcing rod can be secured (discussed in more detail below). As described herein, different regions of the implant (e.g., distal fixation region, growth region, proximal fixation region, etc.) can be configured to facilitate one or more functions when implanted. These regions have a certain length so that when implanted based on a trajectory (or a range of common trajectories, e.g., a posterior sacral-iliac ("SAI") trajectory), their proximity to a given anatomical region allows them to be better adapted to perform their functions than other regions of the implant.

[0174] In some embodiments, the distal fixation region ("DAR" in FIG. 47) of the implant (e.g., a composite implant) may be 15 mm to 40 mm in length, e.g., 15 mm to 35 mm, e.g., 15 mm to 30 mm, e.g., 20 mm to 35 mm, e.g., 25 mm.

[0175] In some embodiments, the growth region (e.g., "GR" in FIG. 47) of an implant (e.g., a composite implant) may be 25 mm to 65 mm in length, e.g., 30 mm to 60 mm, e.g., 30 mm to 55 mm, e.g., 35 mm to 55 mm, e.g., 45 mm.

[0176] In some embodiments, the proximal fixation region (eg, "PAR" in FIG. 47) of the implant (eg, composite implant) may be 3 mm to 20 mm, for example, 5 mm to 15 mm.

[0177] In some embodiments, the overall screw length of the implant (e.g., a composite implant) may be a combination of DAR, GR, and PAR, and in some embodiments may be 60 mm to 100 mm, such as 65 mm to 95 mm, such as 70 mm to 90 mm, such as 75 mm to 85 mm, such as 80 mm.

[0178] In some embodiments, the overall length of the implant (e.g., composite implant) may be the combination of the DAR, GR, optionally PAR, and proximal bond region 4760, and in some embodiments may be 65 mm to 110 mm, for example, 70 mm to 105 mm, for example, 75 mm to 100 mm, for example, 80 mm to 95 mm, for example, 85 mm.

[0179] Referring to FIG. 47, in a method of use, a distal fixation region DAR may be implanted in the ilium. A growth region GR may be implanted across the SI joint, and a proximal fixation region PAR may be implanted in the sacrum. A tulip may be attached to the proximal attachment region 4760, and a stabilization rod may be secured to the tulip. Multiple composite implants may be placed across the sacroiliac joint in a trajectory as described herein. One or more stabilization rods may be secured to any number of the implanted composite implants herein.

[0180] One aspect of the present disclosure relates to a bone stabilization implant including one or more deployable members, the one or more deployable members having an undeployed configuration and a deployed configuration. FIGS. 48A-48H illustrate an exemplary embodiment of a bone stabilization implant including one or more deployable members. FIG. 48A is a perspective view of an exemplary bone stabilization implant 4800 including an elongated implant body 4802 and multiple deployable members 4804 and 4804′ (some or all of which are labeled for clarity). The deployable members in this embodiment may be referred to as protrusions or fins and are illustrated in FIG. 48A in their deployed configuration. When the terms “fin” or “multiple fins” are used in text or figures, it should be understood that the more general term “deployable member” also applies. FIG. 48B illustrates the deployable members in a deployed configuration / position, and FIG. 48C illustrates the deployable members in an undeployed (e.g., recessed) configuration / position.

[0181] Figure 48D shows a side view of the implant 4800. Figure 48D shows the threads of the elongated implant body 4802 passing through the openings between adjacent deployable members 4804. The threads then provide a mechanical stop for the deployable members 4804 by limiting their upward travel, preventing the openings from buckling under load. The deployable members are deployed.

[0182] FIG. 48E shows a perspective cross-sectional view of the implant in the area indicated in FIG. 48D. FIG. 48E shows an internal deployment member 4810, which may be part of the implant or may not be part of the implant and may be a deployment tool that is removed from the patient after the deployment step. The internal deployment member can function as a camming member, having camming surfaces that, when rotated, urge the deployable members radially outward into their deployed position / configuration. The internal deployment member 4810 can remain in place with the implant and can help the deployable members remain in their deployed configuration. Openings 4820 in the elongate body 4802 (through which the deployable members extend, one of which is labeled in FIG. 48G) can be tapered to limit play between the deployable members and the elongate implant body 4802. In some embodiments, the internal deployment member 4810 can be made of (for example, without limitation) titanium and can be manufactured using subtractive manufacturing techniques. The deployable members, in some embodiments, may be (for example, without limitation) titanium and may be manufactured using subtractive manufacturing techniques.

[0183] FIG. 48F shows an exemplary exploded view of an implant 4800. The implant 4800 includes an elongate body or sleeve 4802 that is threaded and includes a set of multiple linear openings 4820 separated by threads, as shown. The implant includes deployable or deployable members 4804, which in this embodiment are each coupled to a spine from which each deployable member 4804 extends, as shown in FIG. 48F. The spines and deployable members are integrally formed and may or may not be the same material. The linear spines and deployable members are disposed within the body 4802 and are pushed radially outward by an actuation member 4810, details of which are shown in FIG. 48E. A threaded tip 4820 can be coupled to the distal end region of the body 4802 using a variety of coupling techniques.

[0184] Figures 48G and 48H show perspective cross-sectional views of implant 4800 in undeployed (Figure 48G) and deployed (Figure 48H) configurations. Further details are shown in the other figures of Figures 48A-48F.

[0185] An exemplary method of implanting the implant 4800 may include one or more of the following steps, which may not necessarily be in the following order: During implant insertion, the deployable members 4804, 4804′, 4804″ are in a non-deployed (e.g., retracted) position relative to the implant body 4802. The implant can be screwed into bone like a screw. After the implant is positioned at a target location, the deployable members can be deployed by actuating an inner actuating member, such as by rotating an inner actuating member that includes one or more cam surfaces. When deployed, the deployed members (e.g., 4804) are configured to function to prevent rotation of the joint, thereby increasing joint stability. The elongate body 4804, which can include any feature of any sleeve herein, can include one or more growth features (e.g., fenestrations, lattice sections) to facilitate at least one of one or more bone overgrowth, bone ingrowth, or bone through-growth.

[0186] Implant 4800 is an example of an implant with an elongated implant body that includes one or more screws, optionally multiple regions with different numbers of leads.

[0187] Implant 4800 is an example of an implant with an elongate body (e.g., 4802) that includes multiple rows (optionally linear rows) of openings, each row including multiple openings separated by a portion of the elongate implant.

[0188] Implant 4800 is an example of an implant with an elongated implant body separating multiple openings, the separating portions including one or more threads.

[0189] Implant 4800 is an example of an implant with deployable members, any of which includes a plurality of protrusions extending from a spine, the plurality of protrusions extending radially outward from the spine and, optionally, being integrally formed with the spine.

[0190] Implant 4800 is an example of an implant with one or more deployable members disposed relative to elongate implant body 4802 to be deployed upon actuation of an internal deployment member.

[0191] Implant 4800 is an example of an implant in which an internal deployment member includes a plurality of radially protruding cam surfaces that, when rotated, move one or more deployable members radially outward.

[0192] Implant 4800 is an example of an implant having one or more threads on an elongated implant body that provide a radial mechanical stop for one or more deployable members, optionally preventing the opening from bending under load.

[0193] Implant 4800 is an example of an implant with an implant body having an opening that can be tapered to limit play between the elongated implant body and one or more deployable members.

[0194] Implant 4800 is an example of an implant with an elongated implant body that may have one or more porous surfaces.

[0195] Implant 4800 is an example of an implant with multiple deployable members that can be actuated and deployed by an internal actuatable member.

[0196] Any of the composite implants herein can include a volume defined by the inner surface of the sleeve and the outer surface of the shank, i.e., there can be a gap between the outer surface of the shank and the inner surface of the sleeve, which volume can promote bone ingrowth.

[0197] As noted above, when a composite implant herein is advanced through the posterior sacroiliac ("SAI") trajectory and positioned across the SI joint, it may be advantageous for certain regions of the implant to abut certain bone or tissue when fully implanted. As previously mentioned, the distal region of the implant is generally configured to better secure to relatively dense cortical bone, for example, using a dual-threaded distal region. In some of the composite implants described above (e.g., the example shown in FIG. 34A ), the sleeve is tapered in the distal region and includes a dual-threaded region. The central region of the sleeve proximal to the distal tapered region (which may be part of the implant's growth region) may be single-threaded (e.g., FIG. 34A ) and may include one or more growth features configured to facilitate at least one of bone overgrowth, bone ingrowth, or bone through-growth more readily than the distal fixation region. For example, in some examples herein (e.g., FIGS. 34-47 ), the central growth region includes at least one of one or more fenestrations or one or more lattice sections, examples of each of which are provided herein. Some sleeves herein may also optionally include a dual-lead proximal end region, e.g., of Figures 31, 33C, 34A, 36A, 41A, 44A, which may better configure the proximal region of the composite implant to anchor to the denser cortex of the sacrum. In some embodiments, a sleeve may have a central region with a single lead, a proximal region with multiple leads (e.g., dual-lead), and, optionally, a distal region with multiple leads (e.g., dual-lead).

[0198] In some methods of use, the implants (e.g., composite implants) herein are delivered in a posterior sacral alar iliac ("SAI") trajectory. Without intending to be limiting, it is advantageous to implant any of the composite implants herein so that, in the final implant position, at least 15 mm of the implant extends distal to the SI joint. In some methods of use, the implant extends at least 15 mm-20 mm beyond the SI joint. Thus, the distal fixation region can have a length that accommodates the distal fixation region of the implant extending at least 15 mm beyond the joint. This helps ensure that the distal fixation region of the implant extends into the dense cortical iliac bone and secures the implant.

[0199] Any of the sleeves herein include an inner lumen sized and configured to receive at least a portion of an inner member (eg, an inner shank).

[0200] Variations and modifications of the devices and methods disclosed herein will be readily apparent to those skilled in the art. It is therefore to be understood that the foregoing detailed description and accompanying figures have been designed for purposes of clarity and understanding, and are not intended to limit the scope of the invention as defined by the claims appended hereto. Any feature described in any one embodiment described herein may be combined with any other feature of any of the other embodiments, whether preferred or not.

[0201] It should be understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or changes in light thereof will be apparent to those skilled in the art and are to be included within the spirit and scope of this application and the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference for all purposes.

Claims

1. 1. A composite implant ("implant") for use in at least one of bone fusion or stabilization of multiple bones, comprising: an inner shank having a distal end region with one or more threads sized and configured for fixation within the ilium; a sleeve sized and configured to be disposed over at least a portion of the inner shank; Equipped with the sleeve is positioned relative to the inner shank to form a composite implant having an inner shank interface feature and a sleeve interface feature, the inner shank interface feature and the sleeve interface feature interfacing with each other to resist relative movement between the sleeve and the inner shank in at least one direction; the composite implant having a distal fixation region and an in-growth region proximal to the distal fixation region; the distal fixation region has one or more distal surface features that better adapt the distal fixation region for fixation within the ilium than the in-growth region; the growth region has one or more growth features that make the growth region better adapted to facilitate at least one of bone overgrowth, ingrowth, or through-growth than the distal fixation region; Implant.

2. the inner shank is more fatigue resistant than the sleeve in a region between the distal end and the proximal end of the sleeve; The implant of claim 1 .

3. The sleeve is made of a different material than the inner shank. The implant of claim 2.

4. the inner shank is made of one or more of titanium or stainless steel; The implant of claim 3.

5. the one or more distal surface features include one or more threads in the distal fixation region; The implant of claim 1 .

6. the distal fixation region has a tapered configuration that tapers radially inward in a distal direction; The implant of claim 5.

7. the one or more threads include a dual lead thread region; The implant of claim 5.

8. The inner shank includes a smooth shank region proximal to the distal fixation region, and the sleeve is disposed around at least a portion of the smooth shank region. The implant of claim 1 .

9. the inner shank interface feature is located in a proximal region of the inner shank; The implant of claim 1 .

10. the sleeve interface features are located in a proximal region of the sleeve; 10. The implant of claim 9.

11. the inner shank interface includes a threaded region.

10. The implant of claim 9.

12. the inner shank interface includes an annular groove recessed into the inner shank; 10. The implant of claim 9.

13. the inner shank interface includes a smooth surface; 10. The implant of claim 9.

14. the inner shank interface features are located in the distal fixation region. The implant of claim 1 .

15. the sleeve interface feature is located in a sleeve distal region; 15. The implant of claim 14.

16. the internal shank interface includes internal shank threads; 15. The implant of claim 14.

17. Features of the sleeve interface include sleeve internal threads, and optionally, the sleeve internal threads and inner member threads resist movement by an interference fit; 17. The implant of claim 16.

18. the internal shank thread includes a flattened top portion, the flattened top portion increasing in length along a proximal direction; 18. The implant of claim 17.

19. Features of the inner shank include a tapered section of the inner shank; 16. The implant of claim 15.

20. Features of the inner shank interface include a threaded barb having a surface indentation configured to act as a stop to prevent distal advancement of the sleeve.

16. The implant of claim 15.

21. the inner shank has a proximal end, the proximal end having a surface configured to securely interface with a tulip; The implant of claim 1 .

22. the one or more distal surface features include a distal thread region; The internal shank further includes a proximal thread region at a proximal end region of the internal shank, the proximal thread region being axially spaced from and proximal to the distal thread region. The implant of claim 1 .

23. the distal thread region and the proximal thread region are multi-lead thread regions; 23. The implant of claim 22.

24. the sleeve including a plurality of fenestrations extending therethrough; The implant of claim 1 .

25. at least half of the plurality of fenestrations are axially disposed between the one or more sleeve threads.

25. The implant of claim 24.

26. each of the plurality of fenestrations is axially disposed between the one or more sleeve threads; 26. The implant of claim 25.

27. a subset of the plurality of fenestrations arranged in at least a partial spiral configuration.

25. The implant of claim 24.

28. a second subset of the plurality of fenestrations arranged in at least a partial spiral configuration.

28. The implant of claim 27.

29. one or more, optionally all, of said plurality of fenestrations are tapered and have an outer dimension that is greater than an inner dimension; 25. The implant of claim 24.

30. the growth surface features include a plurality of lattice sections extending through at least the outer surface of the inner member, optionally each of the plurality of lattice sections including a plurality of pores having a size smaller than each of the plurality of fenestrations of the sleeve, and optionally a set of lattice sections arranged in a partial spiral configuration along the implant. The implant of claim 1 .

31. a first group of the lattice sections extending through the entire thickness of the sleeve, and a second group of the lattice sections extending only through the outer surface of the sleeve but not through the entire thickness of the sleeve; 31. The implant of claim 30.

32. each of the second groups is disposed within a fluted section of the sleeve; 32. The implant of claim 31.

33. the sleeve includes a plurality of lattice sections, at least a subset of the plurality of lattice sections not extending through the entire thickness of the sleeve; The implant of claim 1 .

34. the subset of the plurality of lattice sections is disposed within a longitudinal groove of a sleeve.

34. The implant of claim 33.

35. a second subset of the plurality of lattice sections extending entirely through the sleeve; 34. The implant of claim 33.

36. the second subset is disposed in a sleeve proximal region that is a multi-lead screw region; 36. The implant of claim 35.

37. the plurality of lattice sections are disposed axially adjacent to at least one sleeve thread; 34. The implant of claim 33.

38. a subset of the plurality of pores arranged in at least a partial helical configuration; 34. The implant of claim 33.

39. the sleeve includes a multi-lead distal thread region and a single-thread central thread region, the distal thread region being within the distal fixation region and the central thread region being within the growth region; The implant of claim 1 .

40. The sleeve further includes a proximal thread region that is multi-lead.

40. The implant of claim 39.

41. the sleeve does not extend as distally as the inner shank; The implant of claim 1 .

42. the sleeve does not extend proximally as far as the inner shank; The implant of claim 1 .

43. the inner shank includes a lumen extending between an inner shank proximal end and an inner shank distal end; The implant of claim 1 .

44. the inner shank being harder than the sleeve; The implant of claim 1 .

45. The sleeve and the inner shank define a radial spatial volume therebetween. The implant of claim 1 .

46. The inner shank and the sleeve do not have exactly the same chemical composition. The implant of claim 1 .

47. The sleeve has a length that is shorter than the length of the inner shank. The implant of claim 1 .

48. The sleeve is compressed when the composite implant is formed. The implant of claim 1 .

49. the sleeve has a distal interface location that interfaces with the inner shank at a distal half of the implant; the sleeve does not interface with the inner shank in a region proximal to the distal interface location; Optionally, the sleeve is free to move relative to the inner shank in a region proximal to the distal interface location. The implant of claim 1 .

50. 1. A composite implant ("implant") for use in at least one of bone fusion or stabilization of multiple bones, comprising: an inner shank having a distal end region with one or more threads configured for fixation within the ilium; a sleeve sized and configured to be disposed over at least a portion of the inner shank, the sleeve having one or more growth surface features adapted to facilitate at least one of bone overgrowth, ingrowth, or through-growth; Equipped with the sleeve is positioned relative to the inner shank to form a composite implant having an inner shank interface feature and a sleeve interface feature, the inner shank interface feature and the sleeve interface feature interfacing with each other to resist relative movement between the sleeve and the inner shank in at least one direction; the inner shank alone is more resistant to fatigue than the sleeve alone; Implant.

51. 50. The method of claim 1, further comprising the features or limitations of any one of claims 1 to 49.

51. The implant of claim 50.

52. 1. A method of implanting a composite implant for use in at least one of fusing or stabilizing bone tissue, comprising: and advancing the composite implant along a posterior sacral alar ilium ("SAI") trajectory, the composite implant including a sleeve and a medial shank, the sleeve being disposed over at least a portion of the medial shank and having one or more growth surface features adapted to facilitate at least one of bone overgrowth, ingrowth, or through-growth across the S-I joint, the medial shank having a distal end region with one or more threads configured for fixation within the ilium, the sleeve being disposed relative to the medial shank to form a composite implant having a medial shank interface feature and a sleeve interface feature, the medial shank interface feature and advancing the composite implant along the posterior sacral alar ilium ("SAI") trajectory, wherein the sleeve interface features interface with one another to resist relative movement between the sleeve and the inner shank in at least one direction, the composite implant having a distal fixation region and an in-growth region proximal to the distal fixation region, the distal fixation region having one or more distal surface features that better adapt the distal fixation region for fixation within the ilium than the in-growth region, and the in-growth region having one or more growth features that better adapt the in-growth region to facilitate at least one of bone overgrowth, ingrowth, or through-growth than the distal fixation region; disposing one or more distal surface features within the ilium (e.g., in a teardrop-shaped region of the ilium) such that the one or more distal surface features aid in anchoring the distal fixation region within the ilium; positioning the growth region across the sacroiliac joint such that the one or more growth features are positioned to facilitate at least one of overgrowth, ingrowth, or through-growth of bone at the location of the sacroiliac joint; Including, method.

53. further comprising coupling a tulip to a proximal end region of the inner shank.

53. The method of claim 52.

54. further comprising coupling a stabilizing rod to the tulip.

54. The method of claim 53.

55. Advancing the composite implant along the posterior sacral alar iliac ("SAI") trajectory includes advancing the composite implant along a posterior second sacral alar iliac ("S2AI") trajectory having a bony entry point between the S1 and S2 foramina.

53. The method of claim 52.

56. advancing the composite implant along the posterior sacral alar iliac ("SAI") trajectory includes rotating the composite implant.

53. The method of claim 52.

57. 1. A method of implanting a composite implant for use in at least one of fusing or stabilizing bone tissue, comprising: placing a sleeve having an internal bore such that the sleeve is positioned over the inner shank; forming a composite implant including the sleeve and the inner shank such that inner shank interface features and sleeve interface features interface with each other to resist relative movement between the sleeve and the inner shank in at least one direction; Including, The composite implant has a distal fixation region and an in-growth region proximal to the distal fixation region, the distal fixation region having one or more distal surface features that better adapt the distal fixation region for fixation within the ilium than the in-growth region, and the in-growth region having one or more in-growth features that better adapt the in-growth region to facilitate at least one of bone over-growth, ingrowth, or through-growth than the distal fixation region. method.

58. The sleeve includes any of the features described herein or in the claims.

58. The method of claim 57.

59. The inner shank includes any of the features described herein or in the claims.

58. The method of claim 57.

60. 1. An inner shank for use as part of a composite bone implant, comprising: Including any of the features described herein or in the claims, Inner shank.

61. 1. A sleeve for use as part of a composite bone implant, comprising: Including any of the features described herein or in the claims, sleeve.

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