Pedicle screw stabilization systems and instruments

Abstract

To provide bone fastener assemblies for spine surgery, and instruments for installing the same.SOLUTION: The invention provides orthopedic fixation devices, assemblies, instruments, and methods relating to the same. The orthopedic fixation device may include a tulip head with one or more internal components configured to secure a bone fastener, such as a saddle, a retaining clip, and a friction ring. A spinal rod may be secured into the tulip head, e.g., with a locking cap, thereby securing the bone fastener. One or more instruments, such as screwdrivers and correction instruments, may be used for reduction, derotation, compression and / or distraction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application generally relates to orthopedic fixation devices and instruments, and more particularly, for example, to bone fixation assemblies for spinal surgery and instruments for installing the same.

Background Art

[0002] Many types of spinal irregularities cause pain, limit range of motion, or damage the nervous system within the spine. These irregularities can result from, but are not limited to, trauma, tumors, disc degeneration, and disease. In many cases, these irregularities are treated by fixing a portion of the spine. This treatment typically involves attaching a bone fixation device to one or more vertebrae and connecting the bone fixation device to an elongate spinal rod that stabilizes the spinal member.

[0003] The bone fixation device may include a tulip-shaped head for coupling the bone fixation device to an elongate spinal rod. A locking cap may be used to secure the elongate spinal rod within the tulip-shaped head. One or more instruments may also be used to correct deformities and spinal irregularities. There is a need for an improved pedicle screw system with various implant options that are adapted to the condition, with increased strength, reduced spread, and improved instrument connection.

Summary of the Invention

[0004] To meet this and other needs, bone fixation devices, assemblies, systems, instruments, and methods for treating spinal irregularities are provided. The bone fixation device may include a tulip-shaped head having a locking cap for securing a spinal rod therein. The bone fixation device may be configured to be used with various screws such as multi-axis, one-plane, single-axis, reduced, modular, etc. The bone fixation device may be implanted, for example, via an open approach to the posterior spine, a semi-open approach, or a percutaneous approach.

[0005] According to one embodiment, the orthopedic fixation assembly includes a tulip-type assembly including a tulip head, a saddle, a retaining clip, and a friction ring. The tulip head has two arms defining a rod slot therebetween and a bore extending therethrough. The saddle is receivable within the bore of the tulip head. The saddle has an upper surface defining a rod seat aligned with the rod slot. The retaining clip is positioned at the bottom of the tulip head, and the friction ring is positioned between the saddle and the retaining clip. The bone fixture includes a screw head receivable within the tulip head and a shaft configured to engage the bone.

[0006] The orthopedic fixation assembly may include one or more of the following features. The retaining clip may include a split ring configured to be seated within a corresponding groove within the tulip-shaped head. The retaining clip may include an upper radial neck configured to be seated on a ledge within a groove within the tulip-shaped head. The friction ring may include a split ring configured to be seated within a corresponding groove within the tulip-shaped head. The friction ring may have a smooth circular outer profile, and the groove may have a semi-circular cross-section to accommodate the friction ring. The screw head may include a helical groove, and the friction ring may be positioned around the screw head and engage the helical groove to assist in holding its angular position relative to the bone fixture when the tulip-shaped head is positioned by the user. The orthopedic fixation assembly may include a locking cap having an outer body defining threads. The locking cap may be threadable between two arms of the tulip-shaped head to secure a rod therein. The locking cap may include a circular groove on an upper surface surrounding a drive recess. The circular groove may be configured to receive one or more protrusions from a driver to hold the locking cap. When the locking cap is threaded downwardly onto the rod, the rod presses against a rod seat of the saddle, and the saddle locks the bone fixture in a locked position.

[0007] According to one embodiment, an orthopedic fixation system includes an implant having a tulip-shaped head and a bone fixture, a tower body, and a tower removal tool. The tulip-shaped head has two arms that define a rod slot therebetween. The arms define a circumferential groove. The bone fixture includes a screw head receivable within the tulip-shaped head and a threaded shaft for engaging the bone. The tower body includes a proximal base and two distal arms, with a rod slot defined therebetween. The distal arms include retaining tabs having inner hooks configured to grip the circumferential groove of the tulip-shaped head. When connected thereto, the rod slot of the tower body is configured to be aligned with the rod slot of the tulip-shaped head. Below each retaining tab, there is a protrusion passing through the slot of the distal arm. The tower removal tool is configured to be inserted through the tower body. The tower removal tool includes an outer sleeve having an elongated opening and a spreader sized and dimensioned to fit through the elongated opening and engage the protrusion below each retaining tab to release the retaining tab from the tulip-shaped head.

[0008] The orthopedic fixation system may include one or more of the following features. The elongated opening and the spreader may have an oval shape. The spreader may define an angled slot that moves along a pin connected to the outer sleeve of the tower removal tool. The angled slot may include a pair of parallel slots on each spreader. The first spreader may have a first pair of angled slots with a lower distal portion inclined with respect to an upper proximal portion, and the second spreader may have a second pair of angled slots with an upper distal portion inclined with respect to a lower proximal portion. The tower removal tool may include an inner shaft that, when translated distally, extends the spreader outwardly to engage the retaining tab. The proximal end of the outer sleeve may include guiding portions in the form of axial tabs on both sides of the outer sleeve, and the guiding portions are configured to fit into corresponding slots within the tower.

[0009] According to one embodiment, a method of installing an orthopedic fixation device includes, in any suitable order, (1) providing an implant including a tulip-shaped head having two arms that define a rod slot therebetween, wherein a saddle, a retaining clip, and a friction ring are received within the tulip-shaped head, and a bone fixture including a screw head having a helical groove and a threaded shaft, wherein the friction ring is positioned around the screw head and engages the helical groove such that the screw head is receivable within the tulip-shaped head to assist the tulip-shaped head in maintaining its angular position relative to the bone fixture when positioned by a user; (2) inserting the shaft of the bone fixture into the bone; (3) positioning a spinal rod between the two arms and within the rod slot of the tulip-shaped head; (4) threading a locking cap downwardly between the two arms of the tulip-shaped head, wherein the rod presses against a rod seat of the saddle and the saddle presses against the screw head of the bone fixture, thereby locking the spinal rod and the bone fixture; (5) attaching a tower having tulip-shaped retaining tabs to the tulip-shaped head to provide a guide portion and a working channel in a percutaneous approach; (6) removing the tower using a tower removal tool having a spreader, wherein the spreader interacts with the underside of each retaining tab to spread and open the retaining tabs and release the tulip-shaped head from the tower when actuated; (7) attaching a reducer assembly to the proximal end of the tower and pressing the spinal rod into the tulip-shaped head; and (8) attaching a compression device and / or an extension device to the tower, wherein the tower attached to the tulip-shaped head compresses or extends the attached bone, and may include one or more of the above.

[0010] According to one embodiment, the reducer instrument includes a tower body and a reducer assembly. The tower body includes a proximal base and two distal arms, with a rod slot defined therebetween, and releasably secures pedicle connectors configured to be attached to respective vertebrae. The reducer assembly has an outer housing, an inner pusher, and a locking cap driver aligned along a central tool axis. The outer housing is attached to a cutout on the proximal end of the tower body via a releasable spring clip. The inner pusher has a tubular body with an outer threaded portion sized and dimensioned to receive the locking cap driver. A pair of half nuts are fixed within the outer housing on pins that move along inclined slots within the outer housing. The half nuts are externally threaded to interact with the outer threaded portion of the inner pusher. When an axial force is applied distally to the inner pusher, the half nuts are opened by translating within the inclined slots, allowing the inner pusher to bypass the male threads of the half nuts. When an axial force is applied proximally to the inner pusher, the half nuts are locked by translating within the inclined slots, allowing the half nuts to engage the inner pusher.

[0011] The reducer device may include one or more of the following features. When in the open state, the pin may translate within the inclined slot away from the central tool axis, and when in the locked state, the pin may translate within the inclined slot towards the central tool axis. The inclined slot may include a pair of inclined slots that are inclined towards the central tool axis at the proximal end of the slot and away from the central tool axis at the distal end of the slot. The spring clip may be pivotally coupled to the outer housing via a pivot pin. The distal end of the spring clip may include an outwardly facing keying projection that interacts with a corresponding slot on the tower body to prevent rotation during use. The spring clip may be spring loaded via an inner spring to bias the projection outwardly, thereby securing the reducer assembly to the tower body. The half nut may be spring loaded to ensure engagement with the inner pusher.

[0012] According to one embodiment, a reducer system includes a tulip-type assembly, a tower body, and a reducer assembly. The tulip-type assembly includes a tulip-type head having a rod slot for receiving a spinal rod, and bone screws attached to the tulip-type head using threaded shafts attachable to vertebrae. The tower body includes a proximal base and two distal arms, with a rod slot defined therebetween. When connected thereto, the rod slot of the tower body is configured to be aligned with the rod slot of the tulip-type head. The reducer assembly has an outer housing and an inner pusher. The outer housing is attached to the proximal base of the tower body. The inner pusher has a tubular body with an outer threaded portion. A pair of half nuts is fixed within the outer housing on pins that move along inclined slots within the outer housing. The half nuts are externally threaded to interact with the outer threaded portion of the inner pusher. The inner pusher is configured to push a spinal rod along the rod slot of the tower body and into the rod slot within the tulip-type head, thereby enabling precise positioning and alignment of the spinal rod within the tulip-type head. When a reduced load is applied to the inner pusher by the spinal rod, the half nuts may translate toward the centerline of the reducer assembly within the inclined slots, enabling the half nuts to engage the inner pusher. When an axial force is applied onto the inner pusher in the distal direction, the half nuts may translate outwardly and away from the centerline of the reducer assembly within the inclined slots, enabling the half nuts to disengage from the inner pusher.

[0013] According to one embodiment, a spinal manipulation instrument includes a first arm and a second arm configured to releasably secure pedicle connectors configured to be attached to respective vertebrae, and a drive rod having a threaded portion defining a rod axis therethrough. The first arm and the second arm are threadedly coupled to the drive rod such that in response to rotation of the drive rod about the rod axis, one of the arms translates along the drive rod. A separate removable fulcrum device is positionable through the first arm and the second arm in two different orientations to provide a forward bend or translation of the first arm and the second arm.

[0014] The spinal manipulation instrument may include one or more of the following features. The first arm may be a movable arm and the second arm may be a fixed arm. The first arm and the second arm may have a nested configuration in which the proximal ends of the arms fit together. One arm may have a male contact surface with a prominent rounded shape at the proximal end, and this male contact surface nests within a corresponding rounded female contact surface on the other arm to provide a pivotal movement between the first arm and the second arm in the forward bend orientation. The first arm and the second arm may define a first set of bores along a first axis parallel to the rod axis. The first arm and the second arm may define a second set of bores along a second axis perpendicular to the rod axis. When a removable fulcrum is inserted through the first set of bores, the fulcrum may act as a guide rail for the first arm and the second arm to translate over a translation. When a removable fulcrum is inserted through the second set of bores, the fulcrum may act as a pivot point for the first arm and the second arm for a forward bend movement. A modular connector tip for fixing the tower may be coupled to each arm. The distal end of each arm may include a connector post extending from the attachment end to the free end for receiving the modular connector tip. The connector post may define a circumferential groove configured to interact with a button on the modular connector tip having a protrusion that automatically engages the groove.

[0015] Also provided are kits including implants, rods, bone fixation devices, fixtures, various instruments, guiding parts, tools, guide wires, and other components for performing procedures, of various types and sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more complete understanding of the present invention, as well as the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0017] Embodiments of the present disclosure generally relate to bone fixation devices, assemblies, systems, instruments, and methods for fixing bone fixtures and / or spinal rods. Specifically, embodiments relate to tulip-type assemblies and systems configured to fix a spinal rod to a bone fixture. In some embodiments, the system includes various types of heads such as multi-axis, modular, reduced, single-plane, uniaxial, sacrum-ilium-acetabulum (S2AI), closed head, and various types of screws such as solid, cannula-inserted, fenestrated, one-piece, cortical, double outer diameter, cortical cancellous, and hydroxyapatite (HA) coated pedicle screw systems. A locking cap mates with the head of the screw, locks the spinal rod to the screw head, and forms a rigid structure for spinal stabilization. Additional implants may include hooks and other connectors.

[0018] The system can be used in both open and percutaneous approaches, including minimally invasive surgical (MIS) procedures for various conditions including degenerative conditions, deformities, tumors, trauma, and infections. The fitting instrument interacts with connection features on the screw head and screw for insertion, manipulation, correction, and locking of the implant. The MIS tower can be attached to the screw head to provide a guide and working channel for a percutaneous approach.

[0019] A screwdriver or other instrument can be used for the placement of screws into the vertebra under fluoroscopy, image guidance, and robotic guidance approaches. A screw extender can be used, for example, with a robotic navigation system for alignment and tracking of the anatomical structure of the bone. Examples of surgical robotic systems and / or navigation systems can be found, for example, in U.S. Patent Nos. 10,675,094 and 9,782,229, which are hereby incorporated by reference in their entirety for all purposes. The correction instrument can be used for reduction, segmental derotation, mass derotation, global derotation, compression, and distraction. Although generally described with reference to the spine, it will be understood that the devices and systems described herein may be applicable to other orthopedic sites and applications such as trauma applications.

[0020] Additional aspects, advantages, and / or other features of exemplary embodiments of the present invention will become apparent in view of the following detailed description. It will be apparent to those skilled in the art that the described embodiments provided herein are merely exemplary and illustrative and not limiting. Numerous embodiments of modifications thereof are contemplated as falling within the scope of the present disclosure and equivalents thereto.

[0021] Referring now to the drawings, like reference numerals refer to like elements, and FIGS. 1 - 5 illustrate an orthopedic fixation device, implant, or bone fixture assembly 10 according to one embodiment. The implant or bone fixture assembly 10 may include a screw head or tulip - type head 12 attachable to a bone fixture 14. The assembly 10 may have various mechanisms to achieve different amounts of angular formation. As best seen in FIG. 2, the screw head or tulip - type head 12 is configured to receive a locking cap 16 and secure a spinal rod 18 therein. In the case of a multi - axis bone fixture 14, when the locking cap 16 is tightened, the rod 18 is compressed into the tulip - type head 12, thereby restricting the movement of the bone fixture 14 and forming a rigid structure.

[0022] The tulip - type head 12 extends along a longitudinal central axis from an upper surface or top 20 to a lower surface or bottom 22. The tulip - type head 12 may include a base or body 24 and an arm 26 extending upwardly from the body 24. The arms 26 may be positioned substantially parallel to each other. A central bore 28 may extend through the body 24 of the tulip - type head 12. The opposing arms 26 may define a U - shaped channel or rounded rod slot 30 that traverses the bore 28. The rod slot 30 is sized and configured to receive the rod 18 perpendicular to the threads of the locking cap 16. The rod slot 30 may be sized to receive rods of various diameters and curvatures. Each of the arms 26 has an inner surface 32 with a threaded portion 34 for engaging the locking cap 16. These threads 34 intersect the rod slot 30 to receive the locking cap 16, lock the rod 18 to the tulip - type head 12, and restrict the movement of the angular formation mechanism of the head.

[0023] As best seen in FIG. 3A, the rod 18 can be fixed within the tulip-shaped head 12 using the locking cap 16. The locking cap 16 can include a body having an upper surface 50, a lower surface 52, and an outer body defining a threaded portion 56. The locking cap 16 can be in the form of a set screw having a drive feature or recess 58 defined in the upper surface 50 that is configured to be engaged by a drive tool capable of inserting and tightening the locking cap 16 into the tulip-shaped head 12. The recess 58 can be a hex lobe, slot, cross, or other suitable shape that can engage a tool or device having a corresponding tip. The recess 58 can extend partially within the body of the locking cap 16 or can pass completely through the locking cap 16. A circular groove 59 can be provided in the top surface 50 of the locking cap 16 to interact with the tool (as shown in more detail by FIGS. 13A-13B). The bottom 52 of the locking cap 16 can be flat or otherwise configured to ensure a desired contact with the rod 18.

[0024] The male threaded portion 56 of the locking cap 16 can have a threaded shape configured to secure the locking cap 16 to the tulip-shaped head 12. The male threaded portion 56 of the locking cap 16 can extend between the upper surface 50 and the lower surface 52. The female thread 34 within the tulip-shaped head 12 mates with the male thread 56 of the locking cap 16. Tightening the locking cap 16 compresses the rod 18 into the head 12 and internal components, thereby restricting the movement of the screw 14 and forming a rigid structure.

[0025] In one embodiment shown in FIG. 3A, the threads 34, 56 of the locking cap 16 and the tulip head 12 can be configured to mesh with each other to prevent or reduce the spread of the arm 26 of the tulip portion 12. In one embodiment, the locking cap thread 56 is a reverse buttress design having an inward-facing top surface 60 and an outward-facing ramp 62. The inward-facing top surface 60 resists the outwardly spreading force, and the outward-facing ramp 62 provides structural strength across the root of the thread 56. It will be appreciated that other suitable thread connections or threadless connections may also be used.

[0026] As best seen in FIGS. 3B - 3C, each of the arms 26 can include an outer surface 36 having one or more features for engaging a fitting instrument. One or more instrument contact surfaces can be used to engage one or more instruments such as an insertion, positioning, reduction, untwisting, compression, extension, and / or other holding instrument. The instrument interface allows one or more instruments to be fully or partially constrained or attached to the implant, increases the holding strength, reduces the spreading force that can cause disengagement of the instrument, reduces and presses the rod in place, and / or simplifies manufacture. In some embodiments, the instrument engagement features 38, 40, 42 are attached to the fitting instrument to resist tension and rotational loads.

[0027] Emphasizing FIG. 3B, each of the arms 26 may include a tool engagement groove 38, which may be used to hold the tulip-shaped head 12 with a suitable tool. In one embodiment, the tool engagement groove 38 is an annular or cylindrical groove defined within the outer surface 36 of the tulip-shaped head 12, providing engagement for an insertion, reduction, untwisting, or other holding device. The groove 38 may include a circumferential groove cut into the tulip-shaped head 12 having an inward-facing top surface 46 and an outward-facing bottom surface 48. The inward-facing top surface 46 may be low toward the outer surface 36 and have an inclined surface that slopes such that it becomes higher as the inclined surface 46 extends inwardly. The outward-facing bottom surface 48 faces toward the inward-facing top surface 46. The outward-facing bottom surface 48 may also be inclined or tilted. For example, the outward-facing bottom surface 48 may have the same or a similar inclination as the inward-facing top surface 46. The annular groove 38 may form an upper double tail configured to engage with the instrument. The inward-facing top surface 46 of the circumferential groove 38 prevents the mating instrument from being disengaged when under tension.

[0028] As best seen in FIG. 3C, each of the arms 26 may include a tower pocket 40 configured to engage with a mating instrument to restrain rotation of the instrument relative to the tulip-shaped head 12. The tower pocket 40 may include a slot along a run-on-rod adjacent to the rod slot 30. For example, vertical slots may be provided along the upper portion of each side of the arm 26. The inward-facing surface 41 of the slot 40 prevents the mating instrument from spreading and disengaging from the circumferential groove 38. The outer surface of the pocket 40 is configured to contact a corresponding surface on the instrument, thereby preventing spreading and disengagement of the instrument from the tulip-shaped head 12. In this way, the inward-facing top surface 46 of the groove 38 and the inward-facing surface 41 of the slot 40 prevent disengagement of the mating instrument under tension and spreading loads. The circumferential groove 38 and the tower pocket 40 may be combined to completely restrain the instrument to the tulip-shaped head 12.

[0029] The outer surface 36 of each arm 26 may also define a ball hole or a locker hole 42. The locker hole 42 may interrupt the engagement groove 38, for example, at the central position of each arm 26. The locker hole 42 may be a cylindrical or oval pocket that enables engagement of a locker-type instrument with a pin mechanism and allows rotation of the instrument within the hole 42. By rotating about the locker hole 42, the user can push the rod 18 and retract it into the head 12.

[0030] The front outer surface and the rear outer surface 44 of the tulip-shaped base 24 may be flat or planar, and one or more rounded diameters 45 may be provided along the outside of the tulip-shaped head 12. The flat portion 44 may be positioned on both sides of the tulip-shaped base 24, for example, below the rod slot 30. The flat portion 44 may function as an additional reverse rotation feature when engaged with an instrument. The rounded diameter 45 may be provided along the outer arms 26 of the tulip-shaped head 12. The rounded outer diameter 45 may have various diameters that fit with a corresponding instrument.

[0031] In one embodiment, the retraction features are combined to include a circumferential groove 38 having an inward-facing top surface 46 and an outward-facing bottom surface 48, a slot 40 along the run-on rod, and an oval pocket 42. Instrument engagement features such as the circumferential groove 38, the vertical slot 40, and the oval pocket 42 are attached to the mating instrument to resist tension and rotational loads. The external flat surface 44 and the diameter 45 may also fit with the instrument to provide a secure instrument connection.

[0032] The bone fixture 14 may be included in an assembly having various styles of tulip-shaped heads 12, or may be included as a modular component to which a modular head assembly is attached during surgery. The bone fixture 14 can include bone screws, fixation devices, clamps, etc. configured to engage the bone. In one embodiment shown in FIG. 4A, the bone fixture 14 is a bone screw such as a pedicle screw having a screw head 70 connected to a threaded shaft 72 by a neck 74. The threaded shaft 72 includes one or more bone threads configured to engage the bone. Various bone thread configurations such as cortical cancellous bone, Dual Outer Diameter (DOD), or cortical (MCS) can be used. Cannula insertion and fenestration may also be employed for placement over a guidewire or k-wire and delivery of bone cement. The threaded shaft 72 may have several different features such as, for example, thread pitch, shaft diameter to thread diameter, overall shaft shape, etc., depending on the particular application. The threaded shaft 72 terminates at the distal end as a distal tip 76. As shown in FIG. 4A, the tip 76 can generally be blunt to prevent damage to soft tissue. Alternatively, as shown in FIG. 4B, the tip 76A may be pointed, for example, having a three-sided trocar tip, or as shown in FIG. 4C, the tip 76B may include a cutting edge around the cannula to assist in starting the screw. It will be understood that the various tip shapes can be adjusted to suit particular applications.

[0033] The screw head 70 may have any general shape, but in the case of the multi-axis fixture 14, at least a portion of the screw head 70 may have a curved surface to enable rotational movement and / or angular adjustment of the bone fixture 14 relative to the tulip-shaped head 12. For example, at least a portion of the screw head 70 may be shaped to form a part of a ball or at least a portion of a sphere. The screw head 70 may be smooth, threaded, may have a roughened or textured surface, or may be otherwise configured to interact with the tulip-shaped head assembly. In one embodiment, the bone fixture 14 has a spherical head 70 with a groove 78, such as a helical groove, configured to increase gripping within the mating head assembly.

[0034] The screw head 70 may have, for example, a tool engagement surface or drive recess 80 that can be engaged by a screw driving instrument or other device. The drive recess 80 is housed at the top of the head 70. In one embodiment, the drive recess 80 has a hexalobe shape for driving the screw 14 into bone. It will be understood that tool engagement surface of any suitable shape may be provided. Examples of bone fixtures, other implants, and rod structures are described in more detail, for example, in U.S. Patent No. 10,368,917, which is hereby incorporated by reference in its entirety for all purposes.

[0035] To further emphasize FIG. 5, an exploded view of a tulip-shaped assembly 10 according to one embodiment is shown. The assembly 10 includes a tulip-shaped head 12, a bone fixture 14, a saddle 90, a clip 92, and a ring 94. The tulip-shaped head 12 houses all of the components 90, 92, 94. The multi-axis screw 14 allows angular formation of the tulip-shaped head 12 around the bone screw 14 in each of three rotations before firmly locking its angular formation when tightened by the locking cap 16. The spinal rod 18 may also be fixed to the tulip-shaped head 12 using the locking cap 16.

[0036] The saddle 90 applies a compressive force to the bone screw 14 and limits the angular formation of the bone screw 14 when the rod 18 is tightened to the implant 10 using the locking cap 16. The saddle 90 may have an upper surface 102, a lower surface 104, an outer surface 106 that may be curved or rounded, and a bore 108 defined therethrough. As best seen in FIG. 2, the lower portion of the bore 108 may be rounded as a spherical pocket 109 sized and dimensioned to receive, for example, the upper portion of the spherical screw head 70. A rod slot or seat 110 may be defined in the upper surface 102 of the saddle 90. The rod seat 110 may be configured to receive the bottom of the rod 18 therein. The rod seat 110 may be substantially aligned with the rod slot 30 passing through the tulip head 12. The saddle 90 may include a bottom rim 112 and two opposing elliptical outer shapes 114. The elliptical outer shapes 114 are configured to fit into corresponding elliptical bores 116 defined within the tulip portion 12. The elliptical bore 116 and the corresponding outer shape 114 are each sized such that when the saddle 90 is assembled to the tulip head 12, it cannot rotate out of alignment. When fully seated, the saddle 90 provides a collar around the upper portion of the screw head 80. The multi-axial movement of the screw 14 is locked when the locking cap 16 is screwed downwardly, compressing the rod 18 onto the saddle 90, thereby compressing the saddle 90 against the spherical head 80 of the bone screw 14.

[0037] Clip 92 holds the head 70 of bone screw 14 and seats at the bottom of the tulip portion 12. The retaining clip 92 can be received in the internal groove 120 of the tulip portion 12. The clip 92 can include a loop, ring, split ring, snap ring, or other suitable retaining ring. In one embodiment, the retaining clip 92 can include a split ring 122 having a central through-opening with a gap in fluid communication with the central through-opening. The screw head 70 can be positioned through the split ring 122, surround the bottom of the screw head 70, and apply compression to the bottom of the screw head 70. The inner surface of the split ring 122 can engage the groove 78 along the head 70 of the screw 14 to increase friction and enhance the grip between the split ring 122 and the screw head 70. The retaining clip 92 can include an upper radial neck 124 that projects outwardly from the split ring 116. As best seen in FIG. 2, the radial neck 124 forms a shelf or ledge that is seated within a corresponding groove 120 within the tulip portion 12, thereby holding the bone screw 14 within the tulip portion 12 and preventing disassembly.

[0038] Ring 94 can be a friction ring for further securing the bone fixture 14 within the tulip-shaped head 12. The friction ring 94 can be positioned within an internal groove 132 at the bottom of the tulip-shaped head 12 and can be located around the head 70 of the fixture 14. The friction ring 94 can be positioned under the saddle 90 and above the retaining clip 92. The friction ring 94 can include a split ring 130 having a central through-opening and a gap in fluid communication with the central through-opening. The split ring 130 can have a smooth circular outer shape such that when viewed across its diameter, the ring 130 has a circular cross-section. The circular cross-section ensures uniform strength and flexibility around the circumference of the ring. The groove 132 can also have a semi-circular or rounded cross-section for receiving the ring 94. The friction ring 94 can be sized to have a slight interference fit with the tulip-shaped head 12 such that the head assembly can hold its angle against gravity when positioned by the user.

[0039] The components of the pre-assembled implant 10 can be assembled together as follows. First, the saddle 90 can be inserted into the bottom of the tulip-shaped head 12. The saddle 90 is seated within the bore 28 such that the elliptical contact surfaces 114, 116 are aligned, thereby preventing the saddle 90 from rotating out of alignment with the tulip portion 12. Next, the friction ring 94 can be inserted and seated within the groove 132. The bone screw 14 is disposed at the bottom of the tulip-shaped head 12, and the clip 92 is snap-fitted into the groove 120 of the head component to hold the bone screw 14. The friction ring 94 can assist the tulip-shaped head 12 in maintaining its angular position relative to the bone fixture 14 when positioned by the user. When implanted in a patient, the spinal rod 18 is positioned into the rod slot 30 of the tulip portion 12 and into the rod seat 110 at the top of the saddle 90. The locking cap 16 is threaded 34, 56 onto the top of the tulip portion 12. Tightening of the locking cap 16 compresses the spinal rod 18 into the rod seat 110 of the saddle 90, preventing rotation and translation about the rod 18. Force is transmitted through the saddle 90, compressing the spherical head 70 of the bone screw 14 between the spherical pocket 109 of the saddle 90 and the clip 92. This locks the multi-axial movement of the tulip-shaped head 12 relative to the bone fixture 14.

[0040] Referring now to FIGS. 6A - 7D, a modular tulip-shaped or head assembly 140 according to one embodiment is shown. The modular tulip-shaped assembly 140 functions similarly to the pre-assembled multi-axial assembly 10, but allows for intraoperative assembly of the tulip-shaped head 142 onto the bone screw 14. The clip 92 of the pre-assembled multi-axial screw assembly 10 is replaced with a modular assembly that allows the tulip-shaped head 142 to be loaded onto the bone screw 14 from the top during surgery. The friction ring 94 is also omitted so that the head 142 does not remember relative to the screw 14.

[0041] As best seen in FIGS. 6A-6B, the modular screw head assembly 140 includes a tulip head 142, a saddle 144, and a modular clip 146. The tulip head 142 includes the same features as the tulip head 12, except that the inner bore 28 is modified to accommodate the saddle 144 and the modular clip 146. The saddle 144 may be the same as or similar to the saddle 90. The tulip head 142 and the saddle 144 each have an elliptical bore 116 and an outer profile 114 sized such that the saddle 144 is assembled to the tulip head 142 and cannot rotate out of alignment. The grooves 148, 150 within the tulip head 142 are sized to receive the modular clip 146. The grooves 148, 150 may have a tapered or partially spherical outer profile to accommodate the outer profile of the modular clip 146. The modular clip 146 may include a smooth split ring 152 having a gap or cut 154 that allows the clip 146 to expand and slide over the head 70 of the bone fixture 14. The cut 154 may be angled or tapered to form a cut at an angle not perpendicular to the clip 146. The angled cut 154 allows the clip 146 to expand and facilitates assembly. The clip 146 is receivable within the lower groove 148, which may be a spherical recess to allow the clip 146 to be angled. The larger upper groove 150 is larger in diameter than the lower groove 148 and is sized such that when inserted over the bone screw 14, it allows the clip 146 to expand. The clip 146 may include an upper ridge 156 or ridge lip around the upper edge of the clip 146. The upper ridge 156 on the modular clip 146 limits the corner formation of the clip 146 within the tulip head 12. Assembly of the modular head 140 may be performed by first inserting the saddle 144 into the tulip head 142 and subsequently inserting the modular clip 146. The modular clip 146 serves to hold the saddle 144 within the tulip head 142.

[0042] As best seen in FIGS. 7A - 7D, the assembly of the modular head assembly 140 to the bone screw 14 can be accomplished by positioning the modular head assembly 140 over the bone screw 14 and applying a downward force to the bone screw 14. In the first step shown in FIG. 7A, the modular clip 146 is positioned within the lower groove 148 and the saddle 144 is seated in a low position within the bore 28. The modular head 140 is positioned over the bone screw 14. In the second step shown in FIG. 7B, a downward force is applied over the modular head 140 and the head 70 of the bone fixture 14, thereby pushing the clip 146 and the saddle 144 upward. The clip 146 is aligned with the upper groove 150 and the saddle 144 is seated in a higher position within the bore 28. In the third step shown in FIG. 7C, due to the continued downward force on the bone fixture 14, the modular clip 146 expands within the groove 150, enabling the head 70 of the bone screw 14 to pass through the modular clip 146. In the fourth step shown in FIG. 7D, the modular clip 146 is snap - fastened around the head 70 of the bone screw 14, returns to the lower groove 148, and holds the bone screw 14 within the modular head 140.

[0043] When installed on a patient, the spinal rod 18 is positioned into the rod slot 30 of the tulip portion 142 and into the rod seat 110 at the top of the saddle 144. The locking cap 16 is threaded 34, 56 onto the top of the tulip portion 142. Tightening of the locking cap 16 compresses the spinal rod 18 into the rod seat 110 of the saddle 144, preventing rotation and translation about the rod 18. The force is transmitted through the saddle 144, compressing the spherical head 70 of the bone screw 14 into the spherical pocket 109 of the saddle 144. This locks the multi - axial movement of the tulip - type head 142 relative to the bone fixture 14.

[0044] Referring now to FIGS. 8A - 8B, a uniplanar screw head assembly 160 according to one embodiment is shown. A uniplanar tulip - type assembly 160 functions similarly to the multi - axis assembly 10, but restricts lateral angulation of the tulip - type head 162 and rotation about the axis of the bone screw 14. In this embodiment, a uniplanar pedicle screw assembly 160 allows angulation in one direction but not in other directions. Uniplanar movement enables the firm application of force through the screw for the correction of spinal deformities. Similar to the multi - axis screw assembly 10, a uniplanar tulip - type assembly 160 includes a tulip - type head 162, a saddle 164, and a clip 166, but the friction ring 94 is omitted. A uniplanar tulip - type assembly 160 allows the user to manipulate the tulip - type head 162 and apply a corrective force to the bone screw 14.

[0045] The tulip - type head 162 includes opposing arms 26 that define a U - shaped rod slot 30 configured to receive the rod 18, an internally threaded portion 34 for engaging the locking cap 16, and one or more outer engagement features 38, 40, 42, 44 for interacting with a fitting tool, and has many of the same features as the tulip portions 12, 142. The tulip - type head 162 provides similar advantages as the multi - axis screw assemblies 10, 140, allowing for the reuse of existing tools and a less complex manufacturing process. A uniplanar tulip - type assembly 160 allows movement or adjustment of the bone fixture 14 relative to the tulip - type head 162 along a single plane. The bone fixture 14 can be oriented along one plane of motion for the accurate alignment of the uniplanar tulip - type assembly 160.

[0046] The head component 142 houses the saddle 164 and the clip 166. The saddle 164 includes an upper seat portion 110 for receiving the rod 18 and a bottom surface for receiving the top of the screw head 70. Both sides of the saddle 164 have flat surfaces 168 configured to fit with corresponding flat surfaces 170 inside the tulip-shaped head 162. The flat portion 170 of the tulip-shaped head 162 can be positioned below the threaded portion 34 inside each arm 26. The outer flat surface 168 on the saddle 164 engages with the inner flat surface 170 inside the tulip-shaped head 162 to prevent rotation. The flat surfaces 168, 170 that fit onto the outer and inner heads 162 of the saddle 164 limit the rotation and tilting of the saddle 164 within the tulip portion 162.

[0047] In this embodiment, the screw head 70 includes a spherical surface 172 in the direction of movement (e.g., aligned with the rod 18) and a flat opposing surface 174 parallel to the angular direction that limits angular formation in the perpendicular direction. The flat surface 174 of the head 70 is aligned with a corresponding flat surface 176 inside the saddle 164. The flat portion 174 on the spherical head 70 of the bone screw 14 engages with the inner flat surface 176 inside the saddle 164 to prevent rotation between these components. These flat surfaces 174, 176 limit the rotation of the bone screw 14 about the central axis of the tulip portion 162. In particular, the flat portions 174, 176 can limit the inner-outer angular formation for a planar function.

[0048] The clip 166 may be the same as or similar to the clip 92. The clip 166 can include a loop, ring, split ring, snap ring, or other suitable retaining ring. In an exemplary embodiment, the clip 166 is a split retaining clip. The clip 166 is placed in a groove 120 within the base of the tulip portion 162 and is configured to fit around the bottom of the screw head 70. The clip component 166 holds the bone screw 14 within the assembly 160 and resists the compressive force exerted downward on the bone screw 14.

[0049] The tulip-shaped head 162 pivots in one direction (e.g., medial-lateral angulation) on the screw head 70. It will be appreciated that the tulip-shaped head 162 can pivot along or perpendicular to the rod slot 30 depending on the configuration of the components. The orientation of the flat surfaces 174, 176 parallel to the rod slot 30 results in a uniplanar screw capable of controlling coronal and axial correction. The orientation of these surfaces 174, 176 perpendicular to the rod slot 30 results in a uniplanar fracture screw capable of controlling the sagittal correction commonly used when correcting traumatic fractures.

[0050] When the saddle 164 is in the upper position, the saddle 164 can receive the screw head 70. As shown in FIG. 8A, when the saddle 164 is translated downward within the tulip-shaped head 162, the screw head 70 cannot be released. The saddle 164 compresses the head 70 of the screw 14 when the threaded locking cap 16 is screwed downward onto the spinal rod 18, thereby pressing the saddle 164. The saddle 164 applies a compressive force to the bone screw 14 and limits the angulation of the bone screw 14 when the rod 18 is tightened to the implant 160 using the locking cap 16. In this locked position, the uniplanar screw assembly 160 is locked in place, thereby restricting movement and locking the uniplanar movement of the tulip-shaped head 162 relative to the bone fixture 14.

[0051] Referring now to FIGS. 9A-9B, a sacroiliac - talus - ilium (S2AI) screw head assembly 180 according to one embodiment is shown. Similar to the multi - axis screw assembly 10, the S2AI assembly 180 includes a tulip - type head 182, a saddle 184, and a clip 186, but the friction ring 94 is omitted. The S2AI assembly 180 is configured to enter the second sacrum (S2), pass through the alar region of the sacrum, and extend into the ilium (a part of the hip bone) to provide pelvic fixation. The S2AI tulip - type assembly 180 functions similarly to the multi - axis screw assembly 10 but is configured such that angular formation in one direction is preferred. To achieve this, the bottom surfaces 22 of the tulip portion 182 and the clip 186 can be provided at an angle in the inner / outer direction with respect to the central axis of the tulip portion 182. The purpose of the preferred angle is to accommodate the S2AI trajectory in the pelvis, which is generally a more extreme and predictable angle when compared to the standard pedicle screw trajectory. Since this screw assembly 180 can be used in the pelvis which necessarily involves stronger intraoperative and postoperative forces, the outer diameter 188 of the tulip portion can be enlarged in the middle portion to reduce spreading. The screw shank 72 can also be equipped with a larger diameter 190 and a larger drive recess 80 by the neck 74 to reinforce strength.

[0052] The tulip-shaped head 182 has many of the same features as the tulip portion 12, including opposing arms 26 that define a U-shaped rod slot 30 configured to receive the spinal rod 18, an internally threaded portion 34 for engaging the locking cap 16, and one or more outer engagement features 38, 40, 42, 44 for interacting with a fitting instrument. In this embodiment, the base 24 of the tulip-shaped head 182 is offset or angled relative to the arms 26. The bottom surface 22 of the tulip-shaped head 182 is the site of contact with bone and may be inclined or angled to align with the patient's natural anatomical structure. Due to the extreme angulation of the S2AI trajectory, the inclined bottom surface 22 provides a flush fit with the bone surface and may minimize any potential for soft tissue irritation. The internal groove 120 is also defined at an angle or inclination that reflects the bottom surface 22. The internal groove 120 is configured to receive the clip 186 at the same angle or inclination around the head 70 of the bone fixture 14. The clip 186 and the saddle 184 may be the same or similar to those found in the multi-axis assembly 10.

[0053] When the saddle 184 is in the upper position, the saddle 184 can receive the screw head 70, and the screw 14 can be rotated or angled, for example, in the medial / lateral direction. When the threaded locking cap 16 is screwed downward onto the spinal rod 18, the saddle 184 is pushed downward and compresses the head 70 of the screw 14. Next, the screw head 70 is held and locked in a fixed position within the tulip-shaped assembly 180. In this locked position, the S2AI assembly 180 is fixed in place, thereby firmly fixing the structure.

[0054] Referring now to FIG. 10, a closure head connector 200 according to one embodiment is shown. In some cases, it may be desirable to replace one of the tulip type heads 12, 142, 162, 182 with the closure head connector 200. The closure head connector 200 includes a closure head 202, a saddle 204, an optional retaining clip such as clip 92, and an optional friction ring such as ring 94. The closure head connector 200 may be suitable for other applications where a closure rod slot 206 is desired instead of the S2AI screw or release rod slot 30. The enclosed rod slot 206 prevents the outward spread of the screw head for additional stability and strength. The instrument engagement features 38, 40, 42 from the tulip type head 12 may be omitted, although notches 208 may be provided on both sides of the head 202 for connection to the instrument. Otherwise, this embodiment may be equivalent to, for example, the S2AI assembly 180.

[0055] The closure head connector 200 may include a closure head body 202 for receiving a spinal rod 18 with a threaded locking cap 16 and a saddle 204 mounted therein. The closure head body 202 may have a generally cylindrical or conical body that is flared or tapered outwardly towards its base. The body 202 of the closure head connector 200 may define a through passage or rod slot 206 therethrough, which is sized and shaped to receive the spinal rod 18. The enclosed rod slot 206 may be vertically elongated such that it has a length greater than its width to allow some translation of the rod 18 within the passage 206 before the locking cap 16 is tightened. Similar to the S2AI assembly 180, the bone fixture 14 may be inserted into the bottom of the connector body 202 and angled with respect to the closure head 200. When the threaded locking cap 16 is tightened, the cap 16 presses down to fix the spinal rod 18 within the closure head connector 200, pressing the saddle 204 and thereby firmly locking the position of the bone fixture 14 with respect to the closure head connector 200.

[0056] Referring now to FIG. 11, a uniaxial bone screw 210 according to one embodiment is shown. The uniaxial screw 210 can be a unitary structure in which a tulip-shaped head 212 and a bone screw shaft 214 form one integral component. This provides complete rigidity between the screw head 212 and the screw 214, allowing the user to better control spinal correction at the expense of angulation of the screw head. The uniaxial screw 210 includes a tulip-shaped head 212 having two arms 216 that define a rod slot 218 therebetween. The tulip-shaped head 212 connects to the threaded shaft 214 at the neck 220 and extends to the distal tip 222. The distal tip 222 may be blunt or otherwise configured to engage the bone. The uniaxial bone screw 210 allows movement or attachment along a single axis. When the screw 210 is fixed to the bone, the spinal rod 18 can be positioned in one direction perpendicular to the screw. When the spinal rod 18 seats within the rod slot 218, the rod 18 can be secured with a threaded locking cap 16.

[0057] Referring now to FIG. 12, the tulip head 12 may include a removable extension 230, which provides a path for secure implantation of the spinal rod 18 while minimizing tissue dissection. The extension 230 to the tulip head 12 may be included such that tightening of the locking cap 16 causes the rod 18 to be reduced into the screw head. Once fully reduced, the extension 230 may be folded away from the screw head 12 with the tulip head 12 remaining behind. The extension 230 may extend vertically from the top 46 of each arm 26, thereby forming an integral extension tab by extending the arm 26. The inner surface of each extension 230 may include a threaded portion 232 followed by a threaded portion 34 for engaging the locking cap 16. In this way, the locking cap 16 may be screwed down into the tulip head 12 over the extension 230. Circumferential grooves 234, straight grooves 236, and / or internal grooves 238 may be included to allow the extension 230 to be cleanly folded at a desired height. The circumferential grooves 234 may extend around the outer periphery defining the boundary between the extension 230 and the tulip arms 26. The internal grooves 238 may follow the circumferential grooves 232 along the inner 32 of each arm 26. The straight grooves 236 may connect the inner grooves 232 and the outer grooves 238 along the sides of each arm 26 and the extension 230. After the rod 18 is seated between the extensions 230, the threaded locking cap 16 may be tightened down into the tulip head 12 over the extensions 230. Once the rod 18 is fully seated within the tulip head 12, the extensions 230 may be removed. The breakaway extensions 230 may serve to simplify the procedure and reduce surgical time.

[0058] Referring now to FIGS. 13A - 13C, the locking cap 16 is shown in more detail. The locking cap 16 has one or more external helical threads 56 that mate with a thread 34 defined within the arm 26 of the screw head 12 (or other heads 142, 162, 182). The thread 56 has a thread start point 57 that begins at the bottom 52 of the cap 16 and subsequently ascends helically up the cap 16. As best seen in FIG. 13B, the drive recess 58 is configured to mate with an insertion and tightening instrument such as a driver 240. The drive recess 58 is a recess or slot (e.g., a hexalobular Torx recess) within the top 50 of the locking cap 16 that is shaped to receive a mating end of the driver 240. The driver 240 includes a driver tip 242 corresponding to the drive recess 58 for applying torque to the locking cap 16 to tighten or loosen the locking cap 16 as needed.

[0059] As best seen in FIG. 13A, a circular groove 59 may be provided in the top surface 50 of the locking cap 16. The groove 59 may be a channel that surrounds and encloses the drive recess 58 at a depth shallower than the depth of the drive recess 58. The driver 240 includes one or more protrusions 244 configured to engage the groove 59 to hold the cap 16. The protrusions 244 may form part of a sleeve around the driver shaft. The protrusions 244 may include a distal tip 246 that projects distally into the groove 59 to secure the driver 240 to the implant 10. Depending on the configuration of the driver assembly 240, the driver shaft may be rotatable when the protrusions 244 are engaged, or the protrusions 244 may be engaged to prevent rotation. The bottom 52 of the locking cap 16 may include a shoulder 64 that acts as a contact surface for the rod 18 to prevent the rod 18 from contacting the threads 56 of the locking cap 16. When the locking cap 16 is fully seated within the tulip - type head 12, the locking cap 16 secures the spinal rod 18 therein and locks the implant.

[0060] As best seen in FIG. 13C, one or more markings 66 may be provided on the top 50 of the locking cap 16, and one or more markings 68 may be provided on the top 20 of the arm 26 of the tulip-shaped head 12. The markings 66, 68 may include indicators such as a pair of immersion lines or etchings, or other suitable markings. The markings 66 on the locking cap 16 and the markings 68 on the screw head 10 can be timed with respect to the thread start point 57 so that the user can visually position the locking cap 16 and easily capture the thread 56 when inserted into the tulip-shaped head 12. The locking cap 16 may be made of a titanium alloy (e.g., titanium-aluminum-vanadium) hardened to prevent the hard tulip portion 12 (e.g., cobalt-chromium) from cutting the surface of the locking cap 16 and generating debris. However, it will be understood that any suitable material may be used for the components.

[0061] Referring now to FIGS. 14A-14B, the spinal rod 18 may be provided in various types and sizes. The rod 18 may be straight or may be curved to conform to the curvature of the spine. The surgeon may also be able to shape the rod 18 during the surgery to be aligned with the patient. Various smaller diameter tapered rods may be provided for connection to small thoracolumbar (e.g., 4.75 mm) or cervical (e.g., 3.5 mm) screw systems. The shape of the rod 18 may be substantially circular or cylindrical along its length, or may be otherwise configured.

[0062] In some cases, minimally invasive surgery (MIS) rods 18 may be used in the procedure, which enable minimally invasive rod delivery without the need for an additional incision. Each MIS spinal rod 18 may have a body that extends along its length from a first end 250 to a second end 252. The rod 18 may include various ends 250, 252 for attaching an operating instrument, such as the rod holding instrument 540 shown in FIGS. 34A - 34D, which can insert and manipulate the MIS rod to a desired position. As best shown in FIG. 14A, a hexagonal end rod having a hexagonal contact surface 254 at one end 250 may be provided. The hexagonal contact surface 254 may include a six - sided hexagonal cross - section having six flat surfaces that ensure a secure grip and efficient transmission of rotational force, reducing the risk of slippage. The hexagonal contact surface 254 may be used, for example, for attaching a wrench, whereby the user can rotate the rod 18 to perform correction by overall derotation. Although the hexagonal contact surface 254 is shown, it will be understood that other suitable cross - sections may also be used. The MIS rod 18 may also include a tapered tip 256 for passing through soft tissue. The tapered tip 256 may taper or narrow, for example, in a conical shape from the hexagonal contact surface 254, resulting in a blunt or rounded end 250. Longer MIS rods 18 may include a hexagon 254 adjacent to the tip to enable the user to engage a wrench for correction. Shorter MIS rods 18 may omit the hexagonal feature.

[0063] The rod gripping contact surface 258 may be located on the opposite end portion 252 of the rod 18 configured to fit with a rod holding instrument such as the rod holder instrument 540. For example, the rod gripping contact surface 258 may include an elliptical or oval cross-section. In one embodiment, the oval contact surface 258 includes opposing flat portions 260 having rounded ends 262. The flat portions 260 enable the rod 18 to engage with the instrument and prevent rotation about the rod axis. One or more pivot pins 264 may be provided on the rounded ends 262 of the oval contact surface 258. For example, the spherical pivot pins 264 may be defined at the top and bottom of the MIS rod gripping contact surface 258 to prevent disengagement from the rod holder 540.

[0064] Referring now to FIG. 15, an example of a connector 270 for attaching one spinal rod 18 to another spinal rod 18 in a structure is shown. The rod 18 may be interconnected with one or more connectors 270, for example, in a single given procedure such as a scoliosis surgery or, for example, in a subsequent procedure such as a replacement surgery. In some cases, the connector 270 may be used to replace and extend the thoracolumbar structure using a minimally invasive approach.

[0065] Any of the features of the tulip-shaped head 12 may be included in any of these types of connectors 270. These connectors 270 include: (a) a tulip-shaped head 12 having a laterally extending rod portion 272; (b) a pair of tulip-shaped heads 12 having a row of rod slots 30; (c) a pair of tulip-shaped heads 12 having offset or parallel rod slots 30; (d) a tulip-shaped head 12 having an integral top-loading connector portion 274; (e) a tulip-shaped head 12 having an integral open connector portion 276; (f) a tulip-shaped head 12 having a closed connector portion 278; or (g) a pair of tulip-shaped heads 12 connected by a bridging element 282, wherein one of the tulip portions 12 functions as a modular head 280 for integrating the second head into a modular screw and eliminating separate components. The bridging element 282 separates the head portions 12 such that an instrument that fits around the screw head can engage the instrument engagement feature. The dual-head screw connector 270 can provide strength and stability in procedures that require an additional rod 18 for rigidity.

[0066] Referring now to FIGS. 16-20B, a screwdriver 300 or other instrument may be used for placement of the screw 14 into the vertebra under fluoroscopy, image guidance, or a robotic guidance approach. The screwdriver 300 may be used to drive the bone screw 14 into the bone. The screw 14 may be placed alone or in combination with the tulip type assembly 10. The screwdriver 300 may be provided in a plurality of variant forms, for example, for conventional, minimally invasive, modular, sacroiliac joint type, robotically guided type, freehand navigate type, and robotic navigate type workflows. As shown in FIG. 16, the screwdriver 300 may have a modular design that includes an inner shaft assembly 302 and an outer sleeve assembly 304 that, when combined, form a complete screwdriver 300. The inner shaft assembly 302 is used to transmit torque to the bone screw 14, while the outer sleeve assembly 304 provides a system for firmly holding the bone screw 14 to the inner shaft assembly 302.

[0067] As best seen in FIGS. 17A-17B, the inner shaft assembly 302 includes an inner shaft 306, an outer sleeve rotation lock 308, and a lock button 310. The inner shaft 306 extends from a proximal end 312 to a distal end 314 along a central tool axis. The proximal end 312 includes an attachment contact surface 316 configured to firmly couple the inner shaft 306 to a handle or power driver. The attachment contact surface 316 may include a handle contact surface having a circumferential groove 317 configured to secure a quick connect handle, such as the quick connect assembly 406 shown in FIGS. 26A-26B. The distal end 314 includes a driver contact surface 318 or driver tip configured to mate with the drive recess 80 of the bone screw 14. The inner shaft 306 may be a cannula 320, which may be aligned with the cannula insert screw 14 for receiving a guide wire or K-wire (as shown, for example, in FIG. 19B).

[0068] The rotation lock 308 includes a body having a through opening 320 defined along a central tool axis. The inner shaft 306 can be positioned through the opening 320. The rotation lock 308 includes a distal opposing surface within which radial teeth 322 are defined. The teeth 322 can include serrated teeth that engage similar-shaped teeth 338 on the outer sleeve 330. The shape of the teeth 322 allows rotation in the clockwise (tightening) direction but not in the counterclockwise (loosening) direction, preventing unintentional loosening of the outer sleeve 330 during use. The rotation lock 308 can be spring-loaded 324 to maintain tooth engagement.

[0069] The lock button 310 is positioned through a lateral hole that intersects the through opening 320. The lock button 310 can be aligned perpendicular to the inner shaft 306. The lock button 310 can also be spring-loaded 328. The base of the button 310 is receivable within a notch 326 in the shaft 306 when pulled back to hold the rotation lock 308 in the unlocked position. Pushing the lock button 310 causes the rotation lock 308 to re-engage, thereby returning the rotation lock 308 to the locked position.

[0070] As best seen in FIGS. 18A-18B, the outer sleeve assembly 304 includes an outer sleeve 330 configured to receive the inner shaft 306, a barrel 332, and a button 334. The outer sleeve 330 includes a tubular or cylindrical body sized and dimensioned to receive the inner shaft 306. The outer sleeve 330 can define one or more transverse windows or openings for viewing the inner shaft 306. The outer sleeve 330 can be attached to the inner shaft 306 via a spring-loaded release button 334 that engages a groove 336 on the inner shaft 306. The groove 336 is located on the inner shaft 306 distal to the radial teeth 332 on the rotation lock 308. The outer sleeve 330 can be removed from the inner shaft 306 by depressing the release button 334.

[0071] The barrel 332 includes a proximal opposing surface having radially extending teeth 328 defined therein. The teeth 328 may include serrated teeth that engage similar shaped teeth 322 on the rotary lock 308. The distal tip of the outer sleeve 330 may include a male thread 340 configured to mate with the female thread 34 on the screw head 12 to hold the implant 10 in the instrument 300. As best seen in FIGS. 19A-19B, the outer sleeve 330 may be connected to the tulip-shaped head 12 via mating threads 34, 340. The driver tip 318 of the inner shaft 306 may be inserted into the recess 80 to insert the tulip-shaped assembly 10 into the bone.

[0072] Referring now to FIG. 20, the modular screwdriver 300 may have a modified outer sleeve assembly 304 configured to interact with the modular implant 140, with the screw 14 first inserted into the bone before the tulip-shaped assembly 142 is secured to the screw head 70. In one embodiment, the thread 340 on the outer sleeve 330 is replaced with a collet 344. The collet 344 may include a cylindrical body having longitudinal slits that increase the flexibility of the collet, firmly grip the inserted screw head 70, and allow the screw head 70 to be smoothly released when the collet 344 is loosened.

[0073] As best seen in FIG. 21B, the distal end of the collet 344 defines an internal spherical pocket 346 configured to engage the spherical head 70 of the bone screw 14. The collet 344 is configured to compress and conform to the size of the spherical head 70 it holds, thereby providing a secure grip. The collet 344 may include an outer thread 348 configured to engage a corresponding thread 350 inside the outer sleeve 330. The collet 344 can be retracted, for example, by rotating the inner shaft 306 or other suitable mechanism to rotate the collet 344 and return it into the outer sleeve 330. Alternatively, the collet 344 may have a toothed contact surface that gradually secures the collet 344 as it is pulled back into the outer sleeve 330. The outer sleeve 330 may have a tapered interior to clamp the collet 344 as it retracts. It will be appreciated that any mechanism for pulling the collet 344 into the sleeve 330 can be used to converge or clamp the segments of the collet 344 inwardly onto the screw head 70. A stopper 352 may be provided at the end of the collet 344, which fits into a groove inside the outer sleeve 330 to prevent the collet 344 from separating from the outer sleeve 330.

[0074] As best seen in FIGS. 21A - 21B, the collet 344 clamps the bone screw 14 as it retracts into the outer sleeve 330 and captures the screw 14 onto the tip of the instrument 300. The screw head 70 can be positioned within the pocket 346 of the collet 344. As the collet 344 is pulled back into the outer sleeve 330, the collet 344 tightens around the screw head 70. Once fixed to the instrument 300, the driver tip 318 at the tip of the inner shaft 306 mates with the drive recess 80 of the bone screw 14 to insert the screw 14 into the bone. Once fixed to the bone, the instrument 300 is removed and the modular tulip - type assembly 142 can be attached to the screw head 70.

[0075] Referring now to FIGS. 22A-27B, a one-step screwdriver 300 according to one embodiment is shown. The one-step screwdriver 300 includes a handle assembly 360 attached to the inner shaft 306 via an attachment contact surface 316. The handle assembly 360 is connected to the screwdriver 300 that holds the pedicle screw implant 14. The proximal end of the handle assembly 360 holds a stylet housing assembly 362 that holds a stylet 364. The stylet 364 is housed within the handle assembly 360, passes through the inner shaft 306, extends through the screw 14, and may project from the screw 14. The stylet 364 can be linearly actuated a fixed distance relative to the pedicle screw 14. In FIG. 22A, the stylet 364 is shown in a retracted state. In FIG. 22B, the stylet 364 is shown in a fully advanced state. The stylet 364 is removably fitted into the stylet housing assembly 362, and thus, multiple lengths of stylets 364 may be used to accommodate different screw lengths.

[0076] As best seen in FIG. 23, the stylet housing assembly 362 includes a stylet housing body 366 and a spring-loaded button 368 for holding the stylet 364. The stylet housing body 366 extends along a central tool axis from a proximal end 370 to a distal end 372. The stylet housing 366 has a cannula inserted therein along the central tool axis for holding the stylet 364 therein. The proximal end 370 of the stylet housing 366 includes a cylindrical indicator 374 having a marking 376 indicating the depth or position of the stylet 364. The marking 376 may include a graduated etching or other visual markings such as lines, numbers, etc. to assist in the accurate and safe positioning of the stylet 364 during the procedure. The distal end 372 of the stylet housing 366 includes a reduced diameter portion 378 that is receivable within a quick connect housing assembly 404. The reduced diameter portion 378 may have longitudinal flats 380 that form, for example, a hexagonal shape or other suitable shape to engage the quick connect housing assembly 404 and keep the components rotatably coupled together. The central portion 382 of the stylet housing 366 between the indicator 374 and the reduced diameter portion 378 may include a cylindrical section configured to engage a screw button 414 within the handle assembly 360. The central portion 382 may be a threaded 383 (not shown in FIG. 23) that threads into a corresponding thread 415 within the button 414, as will be described in more detail with respect to FIGS. 25A-25B.

[0077] The stylet housing 366 defines a lateral bore 384 configured to receive a button 368. The button 368 can be positioned substantially perpendicular to the stylet 364. The button 368 is spring-loaded, for example, via two springs 386 and is fixed to the indicator 374 via a pin 388. The button 368 defines a bore 390 configured to receive the stylet 364. The stylet 364 is snap-fitted into the handle assembly 360 via a spring-loaded button 366 of the stylet housing 362 that mates with a groove on the proximal end of the stylet 364. In this way, the stylet housing 362 is configured to hold one end of the stylet 364 and translate the stylet 364 along the central tool axis.

[0078] Referring now to FIG. 24A, an exploded view of the handle assembly 360 is shown. The handle assembly 360 includes a handle grip 402 configured to receive at its proximal end a sheath 404 for securing the stylet housing assembly 362, and a quick-connect housing assembly 406 for connection to the inner shaft 306 of the screwdriver 300 at its distal end. The handle grip 402 is configured to be gripped and rotated by a user. The sheath 404 includes a tubular body configured to receive the stylet housing body 366. The opening 408 of the sheath 404 is configured to receive one or more pins 410 for securing the stylet housing 366 to the sheath 404. A ring 412 can be received within a circumferential groove 413 defined on the outer surface of the sheath 404 for securing the sheath 404 to the handle grip 402. A screw button 414 is positioned through a bore transverse to the central tool axis. The button 414 can be positioned substantially perpendicular to the stylet assembly 362. The screw button 414 can be spring-loaded via a spring 416. The quick-connect housing assembly 406 can be fixed at the distal end of the handle grip 402 using, for example, a threaded ring 418 and a washer 420, or other suitable mechanism.

[0079] Referring now to FIG. 24B, an exploded view of the quick-connect housing assembly 406 is shown. The quick-connect housing assembly 406 includes a proximal casing 424, an inner casing 426, and a distal casing 428, all of which are cannulated along a central tool axis to allow the stylet 364 to pass therethrough. The proximal casing 424 may include a cylindrical body having a proximal stem 430 with a reduced diameter and a distal flange 432 with an enlarged diameter. The most proximal end of the stem 430 may be a male threaded 434 that mates with the female threaded ring 418. The distal flange 432 may include a radially projecting flange that fits into the distal end of the handle grip 402. One or more pins 436 may be used to secure the proximal casing 424 within the handle grip 402. The inner casing 426 includes a body sized and dimensioned to fit within the proximal casing 424. The proximal section 440 of the inner casing 426 may include a polygonal cross-section, and the distal section 442 may include a cylindrical cross-section. An annular band 444 may be provided between the two sections 440, 442. The annular band 444 defines a circular opening configured to receive a ball bearing 446. The distal casing 428 includes a cylindrical body having a distal flange 448. The distal flange 448 may include a radially projecting flange located outside the proximal casing 424. A spring 450 fits between the distal casing 428 and the inner casing 426 and around the distal section 442 of the inner casing 426. A washer or ring 452 may be used to secure the distal casing 428 to the assembly 406.

[0080] Referring now to FIGS. 25A - 25C, the assembled handle assembly 306 is shown in more detail. The central portion 382 of the stylet housing 366 is threaded 383 along its length and is configured to engage a corresponding screw 415 on the button 414. The stylet 364 can be actuated in two different ways. As best seen in FIG. 25B, in the first mode, a spring - loaded screw button 414 engages the central portion 382 of the stylet housing 366, allowing the housing 366 to move along a fixed linear track. The stylet housing 366 may have a male - threaded form 383 that mates with the same female - threaded form 415 of the screw button 414. By rotating the handle grip 402 about the stylet housing 366, the screw button 414 also rotates about the stylet housing 366. This action allows the stylet housing 366 to operate along a linear path fixed via the threads 383, 415. As best seen in FIG. 25C, in the second mode, by depressing the screw button 414, the female thread 415 disengages from the male thread 383 of the stylet housing 366. In this configuration, the stylet housing 366 is free to operate and translate forward when a force is applied directly to the top of the stylet housing 366. In each configuration, the stylet 364 translates with the stylet housing assembly 382 to accommodate different screw lengths.

[0081] Referring now to FIGS. 26A - 26B, the quick - connect housing assembly 406 is shown in more detail. The quick - connect housing assembly 406 is located at the distal end of the handle grip 402. The stylet housing assembly 362 is rotatably coupled to the quick - connect housing assembly 406. In particular, the reduced - diameter 378 of the stylet housing 366 is positioned within a corresponding opening in the proximal stem 430 of the quick - connect housing assembly 406. The connection can be further secured via a threaded ring 418 that threads onto the threads 432 at the end of the proximal stem 430.

[0082] The quick-connect housing assembly 406 is removably fitted, held, and rotatably coupled to the attachment contact surface 316 on the back of the pedicle screw driver 300 or other suitable instrument. This connection can be achieved using a ball bearing 446 that switches between a locked state and an unlocked state and mates with a groove 317 within the inner shaft 306. As shown in FIG. 26A, the distal casing 428 is translated distally, pushing the ball bearing 446 into a locked state where the ball bearing 446 engages the groove 317, thereby locking the handle assembly 360 to the screw driver shaft 306. In FIG. 26B, the distal casing 428 is translated proximally, and the ball bearing 446 is positioned in an unlocked state where the ball bearing does not engage the groove 317 and the shaft 306 is freely removable from the handle assembly 360. This allows the handle assembly 360 to be compatible with any screw driver, including those for fluoroscopic guidance, navigation, and / or robotic procedures.

[0083] The one - stage screwdriver 300 provides a series of different workflows to the user. An example of a workflow is shown in FIGS. 27A - 27C. The first step shown in FIG. 27A can be a docking step where the stylet 364 is inserted into the bone. With the stylet 364 protruding slightly from the distal tip 76 of the screw 14, the user applies an impact to the proximal surface of the instrument 300 to dock the stylet 364 and the screw tip 76 into the bone. As shown in FIG. 27B, the second step includes advancing the stylet 364 through the bone. Once the docking step is complete, the stylet 364 is advanced through the pedicle. This provides a preset path for the screw 14 to safely cross the pedicle. As shown in FIG. 27C, the third step includes inserting and advancing the screw 14 onto the stylet 364. When the user is satisfied with the trajectory set using the stylet 364, the user drives the screw 14 onto the stylet 364 into the pedicle. The handle assembly 360 actively retracts the stylet 364 into the screw 14 when the screw 14 is being driven into the bone while the user holds the handle 402 stationary relative to the screw - driving component. The speed of stylet retraction may be faster than the screw pitch to prevent the risk of driving the screw into the bone using a long protruding wire.

[0084] Referring now to FIGS. 28A - 28D, a screw extender 460 according to one embodiment is shown. The screw extender 460 is attached to the bone screw 14 to provide a rigid extension of the screw 14 such that the position of the vertebra can be registered and / or tracked through tracking of the screw extender or a marker attached to the screw extender. Examples of tracking methods can be found, for example, in U.S. Patent Application Publication No. 2023 / 0010173, which is hereby incorporated by reference in its entirety for all purposes.

[0085] The screw extender 460 may include an outer sleeve 462, an inner shaft 464 extending through the outer sleeve 462, and one or more ball bearings 466. The drive recess 80 within the screw head 70 includes a concave drive portion 468 configured to interact with the outer sleeve 462 and one or more concave engagement portions 470 configured to interact with the one or more ball bearings 466 of the screw extender 460. The drive recess 80 of the screw 70 is engaged by a tip portion similarly shaped to the outer sleeve 462. For example, the drive portion 468 of the screw 14 may interact with the outer sleeve 462 using a Torx drive or other suitable screw drive mechanism.

[0086] Within the drive portion 468, each concave engagement portion 470 may define an undercut having a circular or spherical cross-section sized and dimensioned to interact with a ball bearing 466 of complementary size and shape. The undercut 470 interacts with a ball bearing 466 of similar size that transitions into engagement with the groove 470 to prevent disengagement of the screw extender 460 by the distal tip of the inner shaft 464. The distal tip of the inner shaft 464 may be angled, beveled, or tapered, for example. As the distal tip of the inner shaft 464 advances distally, the ball bearings 466 seat within the concave engagement portions 470. When one or more ball bearings 466 are received within one or more engagement portions 470, disengagement of the screw extender 460 is thereby prevented, allowing for a rigid connection between the instrument 460 and the screw head 70. A caging member 472 may be installed and welded in place to hold the ball bearings 466 within the assembly. The caging member 472 may be provided at the most distal end of the outer sleeve 462. The caging member 472 may define a groove or channel 474 configured to guide the ball bearings 466 into position. The inner shaft 464 may be threaded or spring-loaded onto the outer sleeve 462 of the screw extender 460 such that the user may tighten or release the assembly.

[0087] The screw extender 460 can be coupled to a screwdriving instrument 490, whereby the user can align the screw 14 with the intended trajectory and apply the torque necessary to insert the screw 14 into the vertebral body. As shown in FIG. 28C, the rear or proximal end of the screw extender 460 is configured to connect to the screwdriver 490. The proximal end of the outer sleeve 462 includes a drive contact surface 476 and a circumferential groove 478 that enables the screw extender 460 to be firmly constrained to the screwdriving instrument 490. The drive contact surface 476 may include a plurality of flat surfaces or straight lobes configured to mate with the screwdriving body 490. The proximal end of the inner shaft 464 may include a ribbed neck 480 having a plurality of longitudinal ribs extending along the length of the inner shaft 464.

[0088] Highlighting FIG. 28D, the screwdriving instrument 490 may include a two-piece body. The first portion 492 may include a handle portion configured to receive the ribbed neck 480 of the inner shaft 84. The second portion 494 may include a tubular body configured to receive the outer sleeve 462 of the screw extender 460. The female drive seat 496 may mate with the drive contact surface 476 of the outer sleeve 462. The flexible mechanical spring 498 may engage the groove 478 at the rear of the screw extender 460. The screwdriver 490 enables the user to apply the torque necessary to insert the screw 14 into the bone.

[0089] Referring now to FIGS. 29A - 33, a modular head inserter 500 according to one embodiment is shown. The modular head inserter 500 assists a user in applying a modular tulip - type head 140 to a screw 14 in the field. When the modular tulip - type assembly 140 is locked to the screw head 70, the modular head inserter 500 functions to provide feedback to the user to confirm whether the screw 14 is attached to the tulip - type assembly 140. FIGS. 29A - 29B show a front view and a rear view illustrating the overall instrument 500 used by a surgeon to deploy the mechanism.

[0090] The modular head inserter 500 includes an outer sleeve 502, an inner sensing shaft 504, an inner release shaft 506, a fixed handle 508, and a movable handle 510. The outer sleeve 502 includes a tubular body for receiving the inner sensing shaft 504 and the inner release shaft 506. As best seen in FIG. 30, the outer sleeve 502 includes a distal end 512 having spring tabs 514 configured to mate with the arms 26 of the tulip - type head 142. Each of the spring tabs 514 includes an inwardly projecting portion 516 sized and dimensioned to fit within a groove 38 within the tulip - type head 142. The modular tulip portion 142 is held to the distal portion 512 of the instrument 500 via releasable spring tabs 514 that interact with a groove 38 on the outer surface 36 of the modular tulip portion 142. The interaction between the spring tabs 514 and the groove 38 can form a dovetail connection that axially constrains the instrument 300 relative to the tulip - type head 142. The inward angle may serve to prevent disengagement of the instrument 300 under load by directing the force inwardly and towards the central axis of the tulip - type head 142.

[0091] The sensing shaft 504 may include a cannula insertion body having a distal end portion 517 and a proximal end portion 518 spring-loaded via a spring 519. The distal surface 518 of the sensing shaft 504 of the head inserter 500 is configured to contact the proximal surface of the saddle 144 of the modular tulip-type assembly 140. When the screw shaft portion 72 is inserted into the modular tulip portion 142, the head 70 of the screw 14 pushes the saddle 144 in the proximal direction, and as a result, pushes the sensing shaft 504 of the head inserter 500 in the same direction.

[0092] As best seen in FIGS. 31A - 31B, when the sensing shaft 504 is pushed in the proximal direction, the spring-loaded lock button 520 snaps into a groove 522 of the sensing shaft 504 that is only accessible when pushed. When this button 520 engages the sensing shaft 504, the button 520 simultaneously disengages the actuating mechanism from the body of the head inserter 500. Next, the user can operate a handle 510 connected to the release shaft 506. The release shaft 502 is positioned between the outer sleeve 502 and the inner sensing shaft 504. As best seen in FIG. 32, the release shaft 506 laterally pushes a spring tab 514 that holds the tulip portion 142, thereby releasing the tulip portion 142 from the instrument 500. The inner surface of the outer sleeve 502 may define a protrusion 524, and the outer surface of the inner release shaft 506 may define a tapered distal end portion 526. When the release shaft 502 translates proximally, the tapered end portion 526 of the release shaft 502 pushes the protrusion 524, pushing the spring tabs 514 outwardly and away from each other. The modular tulip-type assembly 140 remains attached in place to the screw shaft portion 72.

[0093] After the sensing mechanism has been actuated, the sensing shaft 504 must be reset for reuse. This is accomplished by pressing the reset button 528 to open the locking portion 520 and returning the locking portion 520 to its locked state to interfere with the body of the head inserter 500. Since the sensing shaft 504 is spring-loaded via the spring 519, the retraction of the locking button 520 returns the sensing shaft 504 to its starting position. The release mechanism in this state cannot be actuated again until the sensing mechanism is actuated again.

[0094] In the alternative embodiment shown in FIG. 33, the head insertion instrument 500 can be modified to connect to other instruments such as the MIS tower 530. In this approach, instead of the release shaft 506 pressing on the spring tab 514 that holds the tulip portion 142, the release shaft 506 interacts with a clip 532 that holds the MIS tower 530 to the head inserter 500. The clip 532 includes an inward projection 516 similar to the spring tab 514 that interacts with a double-tail groove 38 on the outer surface 36 of the tower 530 to hold the MIS tower 530. The clip 532 can be pivotally coupled to the outer sleeve 502 via a pivot pin 534. When the release mechanism is actuated, a positive ledge 536 on the release shaft 506 contacts a built-in lever 538 on the release clip 532, cantilever supporting the release clip 532 to an unlocked state. The lever 538 can include a tapered surface or an inclined surface, and the positive ledge 536 presses on the tapered surface or the inclined surface to pivot the release clip 532 outward. In this mode, the head inserter 500 remains behind the tulip-type / tower assembly 530 when the release mechanism is actuated. The clip 532 can be spring-loaded via a spring 538 to return the clip 532 inward when the release shaft is returned proximally.

[0095] Referring now to FIGS. 34A - 34D, a rod retainer and inserter instrument 540 according to one embodiment is shown. The MIS rod retainer 540 assists the user in inserting and manipulating the MIS rod 18. The MIS rod retainer 540 includes a hollow tubular body 542 that extends from a proximal end 542 to a distal end 546. The tubular body 542 of the inserter 540 houses a lock pin 548. The body 542 can be a square or rectangular tube sized and dimensioned to receive the lock pin 548 therethrough. The proximal end 542 of the body 542 is attached to a handle 550, for example, via a neck 552. The neck 552 and handle 550 can be angled with respect to the tubular body 542. The handle 550 can provide an ergonomic grip for the user. As best seen in FIG. 34B, the distal end 546 of the body 542 may be angled downwardly or tapered towards the most distal tip 554. As best seen in FIG. 34C, the hollow body 542 defines a pocket 556 at the distal end 546 that is configured to receive one end of the rod 18.

[0096] The locking pin 548 extends from a proximal end 558 to a distal end 560 and enters into the pocket 556. The proximal end 558 can include a thumbwheel 562 configured to rotate the locking pin 548. The locking pin 548 may be threaded 564 into the body 542 and may be removed for cleaning. The distal tip 560 of the locking pin 548 can be configured to interact with the end of the MIS rod 18. For example, the distal tip 560 of the locking pin 548 can have a spherical boss 566 that mates with a corresponding spherical socket 264 on the MIS rod 18 (e.g., as shown in FIGS. 14A-14B) so that the rod 18 is not disengaged from the retainer 540. A flat portion 568 on the side of the rod connection pocket 556 can engage a corresponding flat portion 260 on the rod 18 to prevent rotation about the rod axis. The distal end 546 of the body 542 can have an enlargement 570 having, for example, a rounded or circular tip. The enlargement 570 can be sized so that the rod retainer 540 cannot pass through the screw head 12 and the rod slot 30 of the MIS tower. As best seen in FIG. 34D, one end 252 of the rod 18 is inserted into the pocket 556. The locking pin 548 is translated distally through a screw engagement 546 with the body 542, for example, by rotating the thumbwheel 562 of the locking pin 548. The spherical boss 566 enters the socket 264, thereby temporarily fixing the rod 18 to the rod retainer 540. After the rod 18 is installed, the locking pin 548 can be withdrawn from the socket 264 to remove the instrument 540.

[0097] Referring now to FIGS. 35A-37C, a MIS tower 600 according to one embodiment is shown. The MIS tower 600 is attached to a screw head such as a tulip type head assembly 10 and is used to provide a guide portion and a working channel in a percutaneous approach. As best seen in FIGS. 35A-35D, the MIS tower 600 includes a tower body 602 and two screw head retaining tabs 604. The tower body 602 includes a proximal base 606 and two distal arms 608, and a channel or rod slot 607 is defined therebetween. The rod slot 607 extends through the side of the tower body 602 and is sized to allow passage of a rod such as a spinal rod 18. The arms 608 of the tower body 602 may have a semi-circular cross-section and are substantially aligned with the arms 26 of the tulip type head 12. As best seen in FIG. 35C, a slot 609 extends through the length of the tower 600 and may allow a reducer and instruments to pass therethrough. The arms 608 of the tower body 602 each include a corresponding cutout 610 for receiving the respective retaining tab 604.

[0098] The retaining tab 604 extends from a proximal end 612 configured to capture the tulip head 12 to a distal end 614. The proximal end 612 of each tab 604 can be held to the arm 608 via a protrusion 616, pin, or other suitable attachment mechanism. The protrusion 616 can be press-fitted into a corresponding opening of the tab 604 to attach the tab 604 to the respective tower arm 608. As best seen in FIGS. 36A and 36B, the distal end 614 of the tab 604 includes an inwardly projecting portion or hook 618 configured to mate with the underside of the circumferential groove 38 on the screw head 12. Similar to the inwardly projecting portion 516, the interaction between the retaining tab 604 and the groove 38 can form a dovetail connection that axially constrains the instrument 500 relative to the tulip head 12. The inward angle may serve to prevent disengagement of the instrument 500 under load by directing the force inwardly and toward the central axis of the tulip head 12. The hook 618 can also serve to keep the tower 600 attached under tension.

[0099] As best seen in FIG. 36C, the distal end of the tower body 602 has a pocket sized to receive the screw head 12 and four ribs 620 that mate with four corresponding grooves or tower pockets 40 and the inwardly facing surface 41 on the screw head 12 to prevent rotation and spreading of the tower 600. Two of the ribs 620 can be provided at both ends of each tower arm 608 and can be aligned generally parallel to the tool axis. Each tower arm 608 can define a slot 622 for receiving the inwardly projecting portion 624 of the tab 604. The slot 622 that passes through the side of the tower body 602 provides access to the underside of the retaining tab 604 and allows the retaining tab to be spread outwardly by an instrument to release the screw head.

[0100] As best seen in FIG. 36D, the proximal end of the base 606 may include a cutout 626 that is aligned substantially perpendicular to the tool axis. The cutout 626 at the top of the tower 600 may provide an attachment point for instruments such as a reducer and a head inserter. The tower base 606 may be cannulated with a female thread 628 along its length. The female thread 628 at the proximal end of the tower 600 provides an additional interaction option for threaded reduction instruments. A flat portion 630 may be provided around the tower base 606. For example, four equally spaced flat portions 630 may be located outside the proximal end of the tower body 602 and provide a contact surface for a reverse torque instrument.

[0101] Referring now to FIGS. 37A - 37C, an assembly of a MIS tower 600 according to one embodiment is shown. As shown in FIG. 37A, the tower 600 is aligned coaxially with the screw head 12. The tower 600 is oriented such that the tower arm 608 aligns with the tulip - type arm 26. As shown in FIG. 37B, the tower 600 is pressed distally onto the screw head 12. The retaining tab 604 spreads outward as the screw head 12 is inserted. As shown in FIG. 37C, the tower 600 and the screw head 12 are fully engaged. The hook 618 of the retaining tab 604 is snap - locked into the dovetail groove 38 on the screw head 12 to prevent unintentional removal. After the procedure, the tower 600 is removed, for example, by spreading the retaining tab 604 outward via engagement with the inner protrusion 624, thereby enabling removal of the tulip - type head 12.

[0102] Referring now to FIGS. 38A - 40C, a MIS tower removal tool 640 according to one embodiment is shown. The MIS tower removal tool 604 is configured to be inserted into the tower 600 and engage the inner projection 624 to release the retaining tab 604, thereby releasing the tulip - shaped head 12. The tower removal tool 640 includes a handle assembly 642, an inner shaft 644, an outer sleeve 646, and a pair of opposing spreaders 648.

[0103] The handle assembly 642 includes a fixed handle 650 and a movable handle 652 having a gripping portion configured to be gripped by a user. The handle assembly 642 is used to actuate the inner shaft 644 inside the outer sleeve 646, enabling the two spreaders 648 at the tip to extend or retract. The spreaders 648 extend when the handle 652 is pushed down and retract when the handle 652 is released. A return spring 654 within the handle assembly 642 provides a retracting force. The outer sleeve 646 may include a guiding portion 656 at the proximal end of the sleeve 646. The guiding portion 656 may include axial tabs provided on both sides of the outer sleeve 646. A pair of opposing guiding portions 656 may mate with corresponding slots inside the MIS tower 600. The guiding portion 656 ensures that the instrument 640 is in the proper orientation with respect to the screw tower 600 and cannot be inserted in the wrong orientation.

[0104] As best seen in FIG. 38B, the distal end of the outer sleeve 646 includes an elongated opening 658 sized and dimensioned to receive the spreader 648. The opening 658 and the spreader 648 may have an elongated or oval shape. The distal end of the outer sleeve 646 may also include an axial tab 660 that fits into the slot 609 of the tower body 602 to assist in retaining the spreader 648. As best seen in FIGS. 39A-39B, the spreader 648 has angled slots 662 that ride on pins 664 press-fitted onto the inner shaft 644. The angled slots 662 may include a pair of parallel slots on each spreader 648. The upper spreader 648 may have a pair of angled slots 662 where the lower distal portion is inclined relative to the upper proximal portion. The lower spreader 648 may be reflected about the tool axis using a pair of angled slots 662 where the higher distal portion is inclined relative to the lower proximal portion. It will be appreciated that the angled slots 662 may be configured in any suitable manner to extend the spreaders 648 outwardly away from each other. As best seen in FIG. 39A, the spreader 648 is fully retracted inside the outer sleeve 646. As best seen in FIG. 39B, the spreader 648 is fully extended through the opening 658 in the outer sleeve 646. When the inner shaft 644 is advanced distally, the spreader 648 rides along the pins 664, thereby extending the spreaders 648 outwardly and away from each other. As the spreaders 648 extend outwardly, the spreaders pass through the slots 622 in the walls of the tower 600 and contact the lower side 624 of the tulip-shaped retaining tabs 604. This causes the retaining tabs 604 to separate from the tulip portion 12, allowing the tower 600 to be removed. The slots 622 in the walls of the tower 600 also allow the tower 600 to be held by the instrument 640 while the spreaders 648 are extended.

[0105] The MIS tower removal process according to one embodiment is shown in FIGS. 40A-40C. In FIG. 40A, the removal tool 640 is inserted into the MIS tower 600. In FIG. 40B, the handle 652 is pushed down to translate the inner shaft 655 forward in the distal direction. As a result, the spreader 648 extends outward and presses the inner protrusion 624 on the retaining tab 604. The retaining tab 604 spreads open to release the tulip-shaped head 12 from the tower 600. In FIG. 40C, while the handle 652 is pushed down, the removal tool 640 is pulled away from the tulip portion 12. The tower 600 remains held on the instrument 640 until the handle 652 is released.

[0106] Referring now to FIGS. 41A-42B, a reducer assembly 680 for interacting with the MIS tower 600 is shown. The reducer assembly 680 is configured to push the spinal rod 18 into the tulip-shaped assembly 10. When reduced within the tulip-shaped assembly 10, the locking cap 16 can be inserted into the tulip portion 12 to capture the rod 18 within the tulip portion 12. In this embodiment, the reducer assembly 680 includes a MIS dip reducer having an outer housing 682, an inner pusher 684, and a locking cap driver 686 aligned along the tool axis.

[0107] The MIS zip reducer housing 682 includes a hollow body extending from a proximal end 688 to a distal end 690. The outer housing 682 is sized and dimensioned to receive an inner pusher 684 therethrough. The housing 682 is attached to a cutout 626 on the proximal end of the MIS tower 600 via a releasable spring clip 692. The spring clip 692 can be pivotally coupled to the housing 682 via a pivot pin 694. The distal end of the clip 692 can include an outwardly projecting portion or keying projection 696 that interacts with a corresponding through slot 626 on the MIS tower 600 to prevent rotation during use. The clip 692 is spring-loaded via a spring 698 to bias the projection 696 outwardly, thereby securing the reducer assembly 680 to the MIS tower 600.

[0108] The inner pusher 684 includes a tubular body 702 sized and dimensioned to receive a locking cap driver 686 therethrough. The tubular body 702 terminates at a distal tip 704 configured to contact the spinal rod 18. The distal tip 704 can include a concave rounded surface configured to engage the spinal rod 18. When the spinal rod 18 seats through a slot 607 within the MIS tower 600, the distal tip 704 of the pusher 684 pushes the rod 18 in the distal direction to engage the tulip-shaped head 12. As best seen in FIG. 42A, the proximal portion of the inner pusher 684 can include one or more threads 706 configured to mate with corresponding threads 708 on a half nut 710 retained inside the housing 682.

[0109] As best seen in FIG. 42B, the half nut 710 can be fixed within the housing 682 on the pin 712. The pin 712 can be configured to move along the inclined portion 714. The inclined portion 714 can include an angled slot defined through the housing 682. For example, the pair of angled slots 714 may be angled such that at the proximal end of the slot 714 it is directed towards the central tool axis and at the distal end it is directed away from the central tool axis. The half nut 710 may be spring loaded to ensure engagement with the threaded pusher 684. The threaded portion 706 on the pusher 686 is configured to interact with the threaded portion 708 of the half nut 710 held within the housing 682 to push the rod 18 in the distal direction. By screwing the pusher 684 into the housing 682, the rod 18 is advanced into the tulip head 12. The threaded mechanism 708 within the housing 682 is releasable via the inclined half nut mechanism. When an axial force is applied distally to the pusher 684, the half nut 710 is opened by translating within the inclined slot 714 away from the centerline, allowing the threaded pusher 684 to bypass the threads 708 of the nut 710 within the housing 682. When an axial force is applied proximally (e.g., under reduced load) to the pusher 684, the half nut 710 is locked by translating within the inclined slot 714 towards the centerline. The inner pusher 684 can translate the rod 18 along the slot 617 of the MIS tower 60, thereby allowing for the accurate positioning and alignment of the spinal rod 18 to its designated location within the tulip assembly 10.

[0110] Once the spinal rod 18 is securely seated within the tulip head 12, the locking cap 16 can be threaded into the tulip portion 12. The locking cap driver 686 can include an elongate shaft that extends through the inner pusher 684. The locking cap driver 686 includes a distal tip configured to interact with the locking cap 16, for example, via engagement with the drive recess 58. The locking cap driver 686 is configured to tighten the locking cap 16 within the tulip head 12, thereby locking the structure and providing stability to the structure.

[0111] Referring now to FIGS. 43A-43D, an open reducer 720 according to one embodiment is shown. The open reducer 720 connects directly to the tulip portion 12 in the same manner as the MIS tower 600 interacts with the tulip portion 12. The open reducer 720 includes a reducer body 722 having two screw head retaining tabs 724. However, in this embodiment, the retaining tabs 724 that interact with the double tail portion 38 of the tulip portion 142 are laterally supported in the unlocked state.

[0112] The reducer body 722 includes two distal arms 726 that define a channel or rod slot 728 sized to permit the passage of a rod, such as the spinal rod 18. The retaining tabs 724 are configured to capture the tulip head 12. As best seen in FIG. 43C, the distal ends of the tabs 724 include inwardly projecting portions or hooks 730 configured to mate with the underside of the circumferential groove 38 on the screw head 12. The interaction between the retaining tab 724 and the groove 38 can form a double tail connection that axially constrains the instrument 720 relative to the tulip head 12. The retaining tab 724 can be switched between a locked position and an unlocked position by actuating the slider 732 in the distal and proximal directions.

[0113] Slider 732 may be fixed to two blockers 734 that prevent the tabs 724 from laterally displacing in the locked state. The blockers 734 may include distal arms 736 that extend between the retaining tabs 724 and the arms 726. The arm 736 terminates at a distal tip 738 configured to prevent movement of the retaining tab 724. The proximal portion 740 of the blocker 734 may include a convex protrusion configured to interact with the slider 732. The slider 732 may be pinned or otherwise fixed to the blocker 734. In the unlocked state, the blockers 734 allow the retaining tabs 724 the freedom to return to their natural unlocked state. In the locked state, as shown in FIG. 43C, the blockers 734 are translated in the distal direction to prevent the tabs 724 from laterally moving to their unlocked state.

[0114] As best seen in FIG. 43B, the proximal end 740 of the blocker 734 may include a protruding surface 742 that interacts with teeth 744 on the body of the reducer 722. Note that in FIG. 43B, the slider 732 is omitted for clarity. The protruding surface 742 may include a lateral protrusion that extends along the side of the proximal portion 740 of the blocker 734. The teeth 744 may include inward protrusions along the body of the reducer 722. These teeth 744 may be arranged so that the blocker 734 is locked in place in the locked position. As best seen in FIG. 43D, to unlock the blocker 734, the proximal end 740 of the blocker 734 must be pushed inward to bypass the teeth 744 on the body 722. In this state, the slider 732 is free to return to the unlocked position and the retaining tabs 724 are free to laterally return to their natural unlocked state. The release reducer 720 may have options for longer, shorter, or reduced outer diameters to accommodate different procedures and patient populations.

[0115] Referring now to FIG. 44, a detwister assembly 760 according to one embodiment is shown. The detwister assembly 760 can include a plurality of reducers 720 or other reducer types secured together with one or more detwist clamps 762. The detwist clamps 762 may be attached directly to the reducer body or to a separate adapter 764 that connects to the proximal end of the reducer 720. These clamps 762 can connect two or more reducers 720 to each other to perform a wide corrective operation. The knurled inner surface 766 of the detwist clamp 762 can be tightened against the knurled outer surface of the reducer 720 or adapter 764 using a drive nut to provide a secure connection between the reducers 720. Further details of the detwist system and clamp members are described in U.S. Patent No. 10,687,867, which is hereby incorporated by reference in its entirety for all purposes.

[0116] Referring now to FIGS. 45A - 47B, MIS compression / extension instruments 800, 840 for manipulating vertebrae during spinal surgery are shown. In the embodiments shown in FIGS. 45A - 45B, the compressor / extender 800 is configured for multi - level compression and / or extension of the vertebrae to which they are coupled. The multi - level instrument 800 has an increased travel length and its movable arm 806 can span over one or more vertebrae. In the embodiments shown in FIGS. 46A - 47B, the compressor / extender 840 is configured for single - level compression and / or extension of the vertebrae to which they are coupled. The single - level instrument can reduce the travel length so as not to occupy unnecessary workspace during use.

[0117] As best seen in FIGS. 45A-45B, the multi-level compressor / expander 800 can include an outer rod housing 802, an inner drive rod 804, and two arms 806, 808. One arm 806 is a movable arm, and the other arm 808 is a fixed arm configured to be attached to the MIS tower 600, or other suitable mechanism for attachment to a tulip-type assembly. The drive rod 804 is positioned through the outer rod housing 802 and can include a threaded rod rotatable about a central axis 810. The threaded drive rod 804 can be actuated, for example, by a removable handle 854 coupled to a tool engagement contact surface 812 at an end of the drive rod 804 (best seen in FIG. 47B). The rod housing 802 can include an elongated opening 814 at the top of the housing 802 to expose the threaded rod 804 to the movable arm 806.

[0118] The arms 806, 808 may include double-jointed member arms. For example, the arms 806, 808 can include two arm segments 816, 818 coupled to each other at a joint, and can allow for articulation between the arm segments 816, 818. Each arm 806, 808 can utilize a cam lever 820 to fix the relative position between the segments 816, 818. The movable arm 806 can be attached to the rigid housing track 802 and the threaded rod 804 by a collar 822. The collar 822 can define a threaded portion 824 that engages the threaded rod 804. When the threaded rod 804 rotates, the movable arm 806 is configured to move along the threaded rod 804 to a desired position. The movable arm 806 can reciprocate along the threaded rod 804 and the rigid housing track 802. Further, the movable arm 806 can be connected to the collar 822 at another joint that allows for further position adjustment. In this way, the movable arm 806 has the ability to articulate and pivot in multiple directions.

[0119] The movable arm 806 can be fixed along the threaded rod 804 using a selectively engaging button mechanism with threads. In one embodiment, the position of the movable arm 806 includes a locked position and an unlocked position and can be fixed via a cam lever 826. In the unlocked position, the cam lever 826 does not engage the threaded rod 804, and the collar 822 and the arm 806 can be freely slid along the drive rod 804, for example, by hand. In the locked position, the cam lever 826 is engaged with the threaded rod 804, and when the threaded rod 804 rotates, the collar 822 and the arm 806 translate. It will be understood that the cam levers 820, 826 may be replaced by spring-loaded buttons or other fixing mechanisms.

[0120] The fixed arm 808 can be attached to the housing 802 by a fixed collar 828. The fixed arm 808 is locked in a fixed position along the axis 810, but still freely articulates and pivots around the joint connecting the arm segments 816, 818 to the collar 828. Any of the joints may include Bellville washers or other mechanisms that provide memory in their movement and allow the device to remain in a fixed position during use. In this embodiment, the fixed arm 808 may be positioned in a fixed axial position, and the movable arm 806 may translate relative to the fixed arm 808 by rotation of the drive rod 804. However, it will be understood that depending on the application, the arms 806, 808 may be reversed, or both arms 806, 808 may be movable arms. Further details of the multi-level compressor / extender instrument 800 are provided in U.S. Patent Application Publication No. 2023 / 0329758, which is hereby incorporated by reference in its entirety for all purposes.

[0121] As best seen in FIGS. 46A - 46B, a single - level compressor / expander 840 according to one embodiment is shown. Similar to compressor / expander 800, the single - lever compressor / expander 840 includes a threaded drive rod 844 having a movable arm 846 and a fixed arm 848. The threaded drive rod 844 extends along a central axis 852, and each end of the drive rod 844 includes a tool - engagement contact surface 852. The tool - engagement contact surface 852 can be actuated by a removable handle 854 (best seen in FIG. 47B) to rotate the drive rod 844 and translate the movable arm 846 along its length.

[0122] Each arm 846, 848 may include a body extending from a proximal portion 856 to a distal portion 858. Each arm 846, 848 may have a block - shaped body having a generally rectangular form with a flat front face, a rear face, and side faces 860. The proximal and distal portions 856, 858 of arms 846, 848 may have semi - circular or curved ends and be rounded. The proximal portion 856 may have a nested configuration 862 where arms 846, 848 fit closely together. A prominent rounded male - type contact surface 864 at the proximal end 856 is nested within a corresponding rounded female - type contact surface 866, which may provide a pivoting motion between arms 846, 848. Arms 846, 848 may extend between the proximal end 856 and the distal end 858 and may have an elongated oval slot 868 that forms a hollow body between the front and rear faces of arms 846, 848.

[0123] Each arm 846, 848 includes a threaded through-opening 870 for receiving a threaded rod 844 along a central axis 850. Each arm 846, 848 includes bores 872, 876 for receiving a removable fulcrum device 880. A first set of bores 872 through the arms 846, 848 may be provided along an axis 874 parallel to the central axis 850. A second set of bores 876 through the arms 846, 848 may be provided along an axis 878 perpendicular to the central axis 850. Depending on which set of bores 872, 876 is selected, the user can switch between parallel motion and forward bending motion. When the removable fulcrum 880 is inserted through the first set of bores 872, the fulcrum functions as a guide rail for the arms 846, 848 to translate across. As shown in FIG. 46A, when the removable fulcrum 880 is inserted through the second set of bores 876, the fulcrum 880 functions as a pivot point for the arms 846, 848.

[0124] In both embodiments, for the multilevel compressor / expander 800 and the single level compressor / expander 840, the modular connector tip 890 can be coupled to each respective arm 806, 808, 846, 848 to secure the MIS tower 600 or other suitable tulip-type connector. While the connection to arm 848 will be described in more detail, it will be understood that the same equally applies to all other arms 806, 808, 846. The distal end 858 of arm 848 includes a connector post 892 configured to secure the modular connector tip 890 (best seen in FIG. 46A), enabling the instruments 800, 840 to be used across multiple platforms or in a hybrid situation. The connector post 892 extends from an attachment end 894 to a free end 896 and has a tapered or rounded nose. The connector post 892 defines a circumferential groove 900 configured to interact with the modular connector tip 890. In the case of the multilevel instrument 800, the connector post 892 extends distally from the second arm segment 818 but can be reoriented around the joint between segments 816, 818. In the case of the single level instrument 840, the connector post 892 is fixed and oriented along an axis 898 substantially perpendicular to the central axis 850.

[0125] The modular connector tip 890 can rotate 360° around the post 892. The position of the connector tip 890 can be locked by a lockable gear tooth connection 902, which can be similar to the rotation lock 308. The gear tooth connector 902 can include a plurality of radial teeth around the post 892. The base of the connector tip 890 includes corresponding gear teeth that mate with the gear teeth 902, thereby locking the relative position of the connector tip 890 with respect to the post 892. The gear teeth 902 can be spring-loaded within the connector 890 to achieve maximum tooth engagement. The modular connector tip 890 includes a body that defines a circular through-opening 904 sized and dimensioned to receive the MIS tower 600 or other tulip-type connector. The opening 904 can extend along an axis 906 that is substantially perpendicular to the post axis 898. As best seen in FIG. 46B, the tip connector 890 can be fixed to the post 892 via a button 908. The tip connector 890 can use a spring-loaded button 892 that locks firmly within the groove 900 around the gear teeth 902. When the post 892 is inserted into the post opening 910 of the tip 890, the button 908 can be spring-loaded such that the protrusion 912 automatically engages the groove 900 of the post 892. In this way, the modular connector tip 890 is locked to the post 892 in the axial and rotational directions. When the button 908 is depressed, the protrusion 912 exits the groove 900 and the post 892 can be withdrawn from the connector tip 890.

[0126] Figures 47A - 47B show a single lever compressor / extender 840 having a MIS tower 600 positioned through a modular tip 890 and removable pivot devices 880 arranged in two different orientations, forward bent and parallel. The removable pivot device 880 may include a smooth shaft 920 having a handle 922 aligned along a central tool axis. In Figure 47A, the single lever compressor / extender 840 is set in a forward bent mode. In the forward bent mode, the shaft 920 of the pivot 880 is positioned through a second set of bores 876 in the arms 846, 848. As the threaded shaft 844 rotates, the movable arm 846 translates along the shaft 844 and the arm 846 pivots about the pivot 880, thereby providing a forward bending motion to the tulip portion 12 attached to the MIS tower 600 (shown in Figures 37A - 37C). In Figure 47B, the single level compressor / extender 840 is set in a parallel mode. In the parallel mode, the shaft 920 of the pivot 880 is positioned through a first set of bores 872 passing through the arms 846, 848, and the pivot 880 functions as a guide rail for the arms 846, 848 to translate transversely in parallel. As the threaded shaft 844 rotates via a removable handle 854, the movable arm 846 translates along the shaft 844 and the arm 846 translates parallel across the pivot 880, thereby providing a parallel motion to the tulip portion 12 attached to the MIS tower 600 (shown in Figures 37A - 37C).

[0127] The devices and assemblies described herein provide a pedicle screw system with increased strength, decreased spread, improved instrument connection, and various implant options for different pathologies. The pedicle screw system can include various types of heads (multi-axial, modular, reduced, uniplanar, uniaxial, S2AI, closed head), and various types of screws (solid, cannulated, fenestrated, one-stage, ONE, cortical, DOD, cortico-cancellous, HA coated). The system can be used for both open and percutaneous (MIS) approaches for various conditions including degenerative conditions, deformities, tumors, trauma, and infections. The fitting instruments interact with connection features on the screw head and screw for implant insertion, manipulation, correction, and locking. The MIS tower can be attached to the screw head to provide a guide and working channel for percutaneous approaches. The screwdriver can be used to place the screw under fluoroscopy, image guidance, and robotic guidance approaches. The screw extender can be used for bone anatomical structure alignment and tracking. The correction instruments can be used for reduction, partial derotation, bulk derotation, global derotation, compression, and / or extension. The instruments may help improve the accuracy of navigation and robotic techniques and the ability to achieve correction through open and percutaneous approaches.

[0128] Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the invention is intended to cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. For example, it is expressly intended that all components of the various devices disclosed above can be combined or modified in any suitable configuration.

Claims

1. A tulip-shaped assembly comprising a tulip-shaped head, a saddle, a retaining clip, and a friction ring, wherein the tulip-shaped head has two arms defining a rod slot therebetween and a bore extending therethrough, the saddle is receivable within the bore of the tulip-shaped head, the saddle has an upper surface defining a rod seat aligned with the rod slot, the retaining clip is positioned at the bottom of the tulip-shaped head, and the friction ring is positioned between the saddle and the retaining clip. An orthopedic fixation assembly comprising a bone fixture including a screw head receivable within the tulip-shaped head and a shaft configured to engage bone.

2. The orthopedic fixation assembly of claim 1, wherein the retaining clip includes a split ring configured to be seated within a corresponding groove within the tulip-shaped head.

3. The orthopedic fixation assembly of claim 2, wherein the retaining clip includes an upper radially necked portion configured to be seated on a shelf within the groove within the tulip-shaped head.

4. The orthopedic fixation assembly of claim 1, wherein the friction ring includes a split ring configured to be seated within a corresponding groove within the tulip-shaped head.

5. The orthopedic fixation assembly of claim 4, wherein the friction ring has a smooth circular outer profile and the groove has a semi-circular cross-section for receiving the friction ring.

6. The orthopedic fixation assembly of claim 4, wherein the screw head includes a helical groove and the friction ring is positioned around the screw head and engages the helical groove to assist in holding the tulip-shaped head in its angular position relative to the bone fixture when positioned by a user.

7. The orthopedic fixation assembly of claim 1, further comprising a locking cap having an outer body defining a thread, the locking cap being threadable between the two arms of the tulip-shaped head to secure a rod therein.

8. The locking cap includes a circular groove in a top surface surrounding the drive recess, the circular groove being configured to receive one or more protrusions from a driver to hold the locking cap, the orthopedic fixation assembly of claim 7.

9. When the locking cap is screwed downward onto the rod, the rod presses against the rod seat of the saddle, and the saddle fixes the bone fixture in a locked position, the orthopedic fixation assembly of claim 7.

10. A tulip-shaped head having two arms that define a rod slot therebetween, the arms defining a circumferential groove, a tulip-shaped head, and a bone fixture including a screw head receivable within the tulip-shaped head and a threaded shaft for engaging bone, an implant, A tower body including a proximal base and two distal arms between which a rod slot is defined, the distal arms including retaining tabs having inner hooks configured to grip the circumferential groove of the tulip-shaped head, the rod slot of the tower body being configured to be aligned with the rod slot of the tulip-shaped head when connected to the distal arms, and a lower side of each retaining tab having a protrusion passing through a slot of the distal arm, a tower body, A tower removal tool configured to be inserted through the tower body, including an outer sleeve having an elongated opening, and a spreader sized and dimensioned to fit through the elongated opening and engage the protrusion on the lower side of each retaining tab to release the retaining tab from the tulip-shaped head, a tower removal tool, an orthopedic fixation system.

11. The elongated opening and the spreader have an oval shape, the orthopedic fixation system of claim 10.

12. The spreader defines an angled slot that moves along a pin connected to the outer sleeve of the tower removal tool, the orthopedic fixation system of claim 10.

13. The angled slots include a pair of parallel slots on each spreader, the first spreader having a first pair of angled slots with a lower distal portion inclined relative to an upper proximal portion, and the second spreader having a second pair of angled slots with an upper distal portion inclined relative to a lower proximal portion, the orthopaedic fixation system according to claim 10.

14. The tower removal tool includes an inner shaft, and when the inner shaft is translated in the distal direction, the spreader extends outwardly to engage the retaining tab, the orthopaedic fixation system according to claim 10.

15. The proximal end of the outer sleeve includes guide portions in the form of axial tabs on both sides of the outer sleeve, the guide portions being configured to fit into corresponding slots within the tower, the orthopaedic fixation system according to claim 10.

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