Implant receiver and connector with gripping groove for securing rod

Abstract

Implants having gripping grooves are disclosed herein. In some embodiments, the implant includes a rod-receiving recess that defines a rod axis, and the inner surface of the rod-receiving recess defines two gripping grooves that extend parallel to each other and the rod axis. Each gripping groove defines two edges where the gripping groove intersects the inner surface, and the four edges of the two gripping grooves together define a circular radius centered on the rod axis. The implant includes a retention member configured to move relative to the body and apply a force to a rod perpendicular to the rod axis, the force engaging the rod against the four edges of the gripping grooves, and engagement of the four edges of the gripping grooves with the rod limits rotational movement of the rod about the rod axis.

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Disclosed herein are implant receivers and connectors having gripping grooves for improved rod fixation. [Background technology]

[0002] Fixation systems can be used in orthopedic surgery to maintain a desired spatial relationship between multiple bones or bone fragments. For example, various conditions of the spine, such as fractures, deformities, and degenerative diseases, can be treated by attaching a spinal fixation system to one or more vertebrae. Such systems typically include spinal fixation elements, such as rigid or flexible rods or plates, that are connected to the vertebrae by attaching the elements to various anchoring devices, such as screws, hooks, or wires. Once in place, the fixation system holds the vertebrae in a desired position until healing or spinal fusion can occur, or for some other period of time.

[0003] In screw and rod spinal fixation constructs, the stability of the implanted construct is important in achieving bone fusion over the effective levels of the body. Instability of the implanted construct, or movement within it, can result in a pseudoarthrosis, a "non-union," where new bone formation cannot take over the loads that the screw and rod construct bears. If too much movement is permitted between the vertebrae to which the construct is attached, growth activity is prevented and new bone cannot fuse between two bodies that are constantly moving relative to each other. To solve this problem and provide stable fixation, polyaxial screw heads, rod-to-rod, and head-to-rod connectors, it is necessary to hold everything securely against the rod. These implants must resist movement relative to the longitudinal rod within the construct, including the rod sliding, rotating, or pulling out of the connector or bone screw.

[0004] There are many cases where it may be desirable to connect multiple implants to each other. For example, some revision surgeries involve extending a previously installed construct to additional vertebral levels by connecting a newly installed spinal rod to a previously installed rod. In addition, with vertebral implants or constructs fixed in the cervical and thoracic regions of the spine, rod-to-rod connectors can be used to bridge the transition between constructs or implants in the cervical and thoracic regions. In this example, and in other transition regions, torsional slippage between implants on the rod or rods connecting them to each other is a serious risk, which can occur through routine and repetitive movements, such as a patient twisting their head. As a further example, the patient's anatomy, the surgical technique used, or the aspect of the desired correction may require multiple spinal rods to be connected to each other. As yet another example, connecting multiple rods to each other can improve the overall strength and stability of the implanted construct.

[0005] There can be various difficulties associated with connecting multiple implants to one another: the space available for implanted constructs is often very limited, especially in the cervical region of the spine, and manipulating and handling these relatively small implants within the surgical wound can be difficult or cumbersome for the surgeon. Summary of the Invention [Problem to be solved by the invention]

[0006] There remains a need for improved implant connectors and related methods. [Means for solving the problem]

[0007] Certain embodiments of the present disclosure include an implant having a body with a rod-receiving recess, the body having a first side and a second side defining an opening to the rod-receiving recess, the rod-receiving recess defining a central longitudinal rod axis extending between the opening in the first side and the opening in the second side. At least a portion of the rod-receiving recess can be formed by an inner surface of the implant, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis. Each gripping groove defines two edges where the gripping groove intersects the inner surface, the four edges of the two gripping grooves together defining a circular radius centered on the central longitudinal rod axis. The implant also includes a retention member configured to move relative to the body and exert a force on a rod in the rod-receiving recess that may be perpendicular to the central longitudinal rod axis and engage the rod against the four edges of the two gripping grooves. Additionally, engagement of the four edges of the gripping groove on the rod can constrain rotational movement of the rod about the central longitudinal rod axis.

[0008] In some embodiments, the rod-receiving recess defines a gap between two gripping grooves that is sized and positioned to allow a force on the rod within the rod-receiving recess to deflect one or both of the edge and the rod where the edge engages the rod, the deflection moving the rod into the gap. An inner surface of the rod-receiving recess between the two gripping grooves can be positioned away from the central longitudinal rod axis a distance greater than a radius of the rod.

[0009] In some embodiments, the implant comprises a compression member disposed in a cavity formed in the body, the compression member having an inner surface that defines at least a portion of a rod-receiving recess, the inner surface of the compression member having two gripping grooves formed therein. In some embodiments, the gripping grooves extend along the entire length of the inner surface of the rod-receiving recess in the direction of the central longitudinal rod axis. In some embodiments, the gripping grooves are positioned opposite the retention member with respect to the central longitudinal rod axis.

[0010] The rod-receiving recess can define an open end sized to receive a rod and a closed end sized to contact the rod, with the gripping grooves disposed symmetrically about an axis extending from the open end to the closed end. The body of the implant can define an interior surface that forms the rod-receiving recess. In some examples, the intersection between the gripping groove and the interior surface defines a sharp edge.

[0011] The inner surface can define a groove that intersects with the at least one gripping groove, the intersection of the grooves dividing an edge of the at least one gripping groove to define four corners for resisting translation of the rod along the central longitudinal rod axis when the rod engages the edge. In some embodiments, the groove that intersects with the at least one gripping groove is oriented perpendicular to the gripping groove.

[0012] The gripping grooves can be formed by protrusions extending from an inner surface, in some embodiments, at least one gripping groove defines an inner surface having one or more protrusions formed therein, the one or more protrusions extending to an edge positioned to contact the rod when the rod engages the edge of the gripping groove.

[0013] In some embodiments, the implant comprises a connector, the rod receiving recess is a first rod receiving recess, the body defines a second rod receiving recess, one or both of the first rod receiving recess and the second rod receiving recess have two gripping grooves, the body has proximal and distal ends defining a proximal-distal axis extending therebetween, and the retention member is slidably disposed within a tunnel formed in the body and configured to translate relative to the body along the rod pusher axis.

[0014] In some embodiments, the second rod-receiving recess is defined by a pair of spaced apart arms of the body. The first rod-receiving recess can be open in a distal direction and the second rod-receiving recess can be open in a proximal direction. The rod pusher axis can be substantially perpendicular to the proximal-distal axis. In some embodiments, the implant further comprises a set screw threadably received in the body for locking the first rod in the first rod-receiving recess and the second rod in the second rod-receiving recess.

[0015] The implant may include a bone anchor assembly, the body having a receiving member for the bone anchor assembly and the retaining member having a set screw or locking element.

[0016] Another embodiment of the present disclosure is an implant having a body having a rod-receiving recess, a gripping insert configured to be positioned at an open end of the receiving recess, and a retention member configured to move relative to the body. The body has a first side and a second side defining an opening to the rod-receiving recess, the rod-receiving recess defining a central longitudinal rod axis extending between the opening in the first side and the opening in the second side. The gripping insert has an inner surface for contacting a rod disposed in the rod-receiving recess, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis, each gripping groove defining two edges where the gripping groove intersects the inner surface, and the four edges of the two gripping grooves together define a circular radius centered about the central longitudinal rod axis. The retaining member can be configured to exert a force against the rod within the rod-receiving recess and to engage four edges of the gripping groove with the rod, the engagement of the four edges of the gripping groove with the rod serving to restrain rotational movement of the rod about a central longitudinal rod axis.

[0017] Any of the above features or variations may be applied to any particular embodiment of the present disclosure in many different combinations, and no explicit mention of any particular combination is made, simply to avoid redundancy in this summary. [Brief description of the drawings]

[0018] [Figure 1A] FIG. 1 is a perspective view of a bone anchor assembly according to the prior art. [Figure 1B] FIG. 1B is an exploded view of the bone anchor assembly of FIG. [Figure 1C] FIG. 1B is a top view of the bone anchor assembly of FIG. [Figure 1D] FIG. 1B is a cross-sectional view of the bone anchor assembly of FIG. [Figure 2A] FIG. 1 is a perspective view of a connector according to the prior art. [Figure 2B] 2B is an exploded perspective view of the connector of FIG. 2A shown with a first spinal rod and a second spinal rod. [Figure 2C] 2B is a cross-sectional side view of the connector of FIG. 2A in a first configuration. [Figure 2D] FIG. 2B is a cross-sectional top view of the connector of FIG. 2A in a first configuration. [Figure 2E] FIG. 2B is a cross-sectional side view of the connector of FIG. 2A in a second configuration. [Figure 2F] FIG. 2B is a cross-sectional top view of the connector of FIG. 2A in a second configuration. [Figure 2G] FIG. 2B is a cross-sectional side view of the connector of FIG. 2A in a third configuration. [Figure 2H] FIG. 2B is a cross-sectional top view of the connector of FIG. 2A in a third configuration. [Figure 2I] 2B is a side view of the connector of FIG. 2A coupled to a first spinal rod and a second spinal rod. [Figure 2J] FIG. 2B is a perspective view of the connector of FIG. 2A shown with a saddle. [Figure 2K] FIG. 2J is an exploded perspective view of the connector and saddle of FIG. 2J shown with a first spinal rod and a second spinal rod. [Figure 2L] FIG. 2J is a side cross-sectional view of the connector and saddle of FIG. 2J coupled to a first spinal rod and a second spinal rod. [Figure 3A] FIG. 13 is a cross-sectional view of one embodiment of a connector in which a rod recess has two gripping grooves. [Figure 3B]3B is a cross-sectional view of a rod-receiving recess of the connector of FIG. 3A. [Figure 3C] 3B is a cross-sectional view of a gripping groove of a rod-receiving recess of the connector of FIG. 3A. FIG. [Figure 4A] FIG. 1 is a cross-sectional view of a rod-receiving recess according to the prior art. [Figure 4B] FIG. 13 is a cross-sectional view of one embodiment of a rod-receiving recess having a V-shaped gripping groove. [Figure 4C] 4C is a cross-sectional view of the rod-receiving recess of FIG. 4B showing a comparison of the position of the rod with and without the gripping groove. [Figure 4D] 4C is a perspective view of a rod showing the contact line formed by the edges of the two gripping grooves of FIG. 4B when the rod is positioned within the rod-receiving recess of FIG. 4B. [Figure 4E] FIG. 13 is a perspective view of a surface of one embodiment of a rod-receiving recess having segmented gripping grooves. [Figure 4F] FIG. 4F is a top view of the segmented gripping groove of FIG. 4E. [Figure 4G] FIG. 4F is a schematic diagram of a contact point on a rod engaged with the segmented gripping groove of FIG. 4E. [Figure 4H] 4E is a perspective view of the surface of the rod showing the contact line formed by the edges of the two segmented gripping grooves of FIG. 4E when the rod is positioned within the rod-receiving recess of FIG. 4E. [Figure 5A] 11A-11C are cross-sectional views of one embodiment of a rod-receiving recess having alternatively shaped gripping grooves. [Figure 5B] FIG. 13 is a cross-sectional view of one embodiment of a rod-receiving recess having a gripping groove formed by a protrusion. [Figure 6A] FIG. 13 is a cross-sectional view of one embodiment of a rod pusher having a rod-receiving recess and a gripping groove. [Figure 6B] 13 is a cross-sectional view of an alternative embodiment of a rod-receiving recess and of a rod pusher having a gripping groove. FIG. [Figure 6C] FIG. 13 is a cross-sectional view of an embodiment in which the rod-receiving recess and the rod pusher both have gripping grooves. [Figure 7A]FIG. 13 is a cross-sectional view of one embodiment of a single gripping groove having an internal protrusion positioned to contact a rod within the gripping groove perpendicular to the edge of the gripping groove. [Figure 7B] FIG. 7B is a top view of the gripping groove of FIG. 7A showing the vertical edge of the internal projection. [Figure 7C] 7B is a cross-sectional view of the gripping groove of FIG. 7A showing the edge of the internal projection that contacts the rod when the rod engages the gripping groove. [Figure 7D] FIG. 7B is a perspective view of the rod showing the contact line formed by the edges of the two gripping grooves of FIG. 7A with an internal protrusion. [Figure 7E] 11A-11C are cross-sectional views of an embodiment of a single gripping groove having internal protrusions with two different configurations. [Figure 7F] 11A-11C are cross-sectional views of an embodiment of a single gripping groove having internal protrusions with two different configurations. [Figure 8A] FIG. 1 is a cross-sectional view of a rod-receiving recess according to the prior art. [Figure 8B] FIG. 13 is a cross-sectional view of one embodiment of a rod-receiving recess having two gripping grooves. [Figure 8C] FIG. 13 is a cross-sectional view of one embodiment of a rod-engaging element having a rod-receiving recess and two gripping grooves. [Figure 8D] 13 is a cross-sectional view of an alternative embodiment of a rod-engaging element having a rod-receiving recess and two gripping grooves. FIG. [Figure 9] FIG. 13 is a perspective view of one embodiment of a receiving member having a rod-receiving recess with two gripping grooves. [Figure 10] FIG. 13 is a perspective view of one embodiment of a receiving member having a rod-receiving recess with two circumferential grooves. [Figure 11A] FIG. 13 is a perspective view of one embodiment of a receiving member having a rod-receiving recess with two segmented gripping grooves formed by the intersection of two gripping grooves and two circumferential grooves. [Figure 11B] FIG. 13 is a perspective view of one embodiment of a receiving member having a rod-receiving recess with two segmented gripping grooves formed by the intersection of two gripping grooves and two circumferential grooves. [Figure 12]FIG. 13 is a perspective view of one embodiment of a receiving member having a rod-receiving recess with two gripping grooves having a plurality of internal projections. [Figure 13] FIG. 13 is a cross-sectional view of one embodiment of a connector in which the rod-receiving recess has two gripping grooves. [Figure 14] 1A is a cross-sectional view of an embodiment of a bone anchor assembly in which a compression member defines a rod-receiving recess and a rod-engaging element having two gripping grooves. FIG. [Figure 15] FIG. 1 is a perspective view of a human spine with a fixation system attached. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Disclosed herein are implants with gripping grooves and associated methods. The implants can include a connector and a receiving member of a bone anchor assembly. In some examples, the connector can include a low profile portion that facilitates use of the connector in surgical applications where space is limited. In some embodiments, the connector can include a biased rod pusher that allows the connector to "snap" onto and / or "resist" the rod, for example, to provisionally position the connector prior to locking.

[0020] Certain aspects of the present disclosure provide improved torsional gripping ability of the implant relative to the rod. One example presented is a rod-to-rod connector, but this feature can be applied to a variety of spinal implants, such as the screw head of a bone anchor assembly. Aspects of the present disclosure include single or multiple longitudinal grooves cut into the rod slot of the implant that add an additional line of contact between the connector and the rod. In operation, when locked, a very small portion of the cross-sectional rod circumference is wedged into the groove, causing both edges of the groove to begin to press into the rod. Even if the rod contact is not perfectly positioned against this groove, the groove provides an edge, rather than a flat surface, to rub against the rod and prevent further rotation if rotation begins to occur due to forces exerted on the rod or connector. Micro-shearing of the material is the principle that enhances the torsional gripping ability.

[0021] Alternatively, these gripping grooves can be on the surface of the rod instead of the connector, screw head, or receiving implant. In addition, the semicircular gripping grooves can be other geometric shapes such as rectangular, right angled or other angles, trapezoidal, etc.

[0022] A variation of the gripping groove to enhance axial slip (longitudinal rod sliding) gripping capability is to have the groove oriented circumferentially relative to the rod. Longitudinal and circumferential gripping grooves can also be combined to enhance torsional and axial resistance. The resulting feature can resemble a peg or corner.

[0023] Certain exemplary embodiments will now be described to provide a general understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will appreciate that the devices and methods described in detail herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. Features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments.

[0024] 1A-1D show a prior art bone anchor assembly 10 including a bone anchor 12, a receiving member 14 coupled to the bone anchor 12 for receiving a spinal fixation element, such as a spinal rod 22, and a closure mechanism 16 for capturing the spinal fixation element within the receiving member 14 and securing the spinal fixation element relative to the receiving member 14. The bone anchor 12 includes a proximal head 18 and a distal shaft 20 configured to engage bone. The receiving member 14 has a proximal end 26 having a pair of spaced apart arms 28A, 28B defining a recess 30 therebetween, and a distal end 32 having an inner surface 35 for polyaxially seating the proximal head 18 of the bone anchor 12 and a distal end face 34 defining an opening through which at least a portion of the bone anchor 12 extends. The closure mechanism 16 is positionable between and engageable with arms 28A, 28B to capture a spinal fixation element, such as a spinal rod 22, within the receiving member 14 and secure the spinal fixation element relative to the receiving member 14.

[0025] The proximal head 18 of the bone anchor 12 is generally in the shape of a truncated sphere having a planar proximal surface 36 and a generally spherical distal surface 38. The illustrated bone anchor assembly is a polyaxial bone anchor designed for posterior implantation into the pedicle or lateral mass of a vertebra. The proximal head 18 of the bone anchor 12 engages the distal end 32 of the receiving member 14 in a ball-joint-like configuration that allows the proximal head 18 and distal shaft 20 to pivot relative to the receiving member 14. The distal surface 38 of the proximal head 18 of the bone anchor 12 and the mating surface within the distal end 32 of the receiving member 14 can have any shape that facilitates this configuration, including, for example, spherical (as shown), annular, conical, frusto-conical, and any combination of these shapes.

[0026] The distal shaft 20 of the bone anchor 12 may be configured to engage bone and in an exemplary embodiment includes external threads 40 for engaging bone. The thread configuration of the distal shaft 20, including the number of threads, pitch, major and minor diameters, and thread profile, can be selected to facilitate connection with bone. Exemplary thread configurations are disclosed in U.S. Patent Application Publication No. 2011 / 0288599, filed May 18, 2011, and U.S. Provisional Patent Application No. 61 / 527,389, filed August 25, 2011, both of which are incorporated herein by reference. The distal shaft 20 can also include other structures for engaging bone, including hooks. The distal shaft 20 of the bone anchor 12 can be cannulated, having a central passage or cannula extending the length of the bone anchor to facilitate delivery of the bone anchor over a guidewire, for example, in a minimally invasive procedure. Other components of the bone anchor assembly, including, for example, the blocking member 16, the receiving member 14, and the compression member 60 (discussed below), may be cannulated or otherwise have openings to allow delivery over a guidewire or to allow insertion of a driver instrument to manipulate the bone anchor. The distal shaft 20 may also include one or more sidewall openings or fenestrations that communicate with the cannula to allow bone ingrowth or to allow distribution of bone cement or other materials through the bone anchor 12. The sidewall openings may extend radially from the cannula through the sidewall of the distal shaft 20. Exemplary systems for delivering bone cement to the bone anchor assembly 10, as well as alternative bone anchor configurations for facilitating cement delivery, are described in U.S. Patent Application Publication No. 2010 / 0114174, filed October 29, 2009, and incorporated herein by reference. The distal shaft 20 of the bone anchor 12 may also be coated with a material to allow bone ingrowth, such as, for example, hydroxylapatite, and the bone anchor assembly 10 may be partially or entirely coated with an anti-infective material, such as, for example, triclosan.

[0027] The proximal end 26 of the receiving member 14 includes a pair of spaced apart arms 28A, 28B defining a U-shaped recess 30 therebetween for receiving a spinal fixation element, e.g., a spinal rod 22. Each of the arms 28A, 28B can extend from the distal end 32 of the receiving member 14 to a free end. The outer surface of each of the arms 28A, 28B can include features such as recesses, indentations, notches, protrusions, etc., to facilitate connection of the receiving member 14 to an instrument. For example, the outer surface of each arm 28A, 28B can include an arcuate groove at the respective free end of the arm. Such grooves are described in more detail in U.S. Patent No. 7,179,261, issued February 20, 2007, which is incorporated herein by reference. At least a portion of the proximal end surface 48 of the receiving member 12 defines a plane Y. The receiving member 14 has a central longitudinal axis L.

[0028] The distal end 32 of the receiving member 14 includes a generally annular shaped distal end face 34 that defines a circular opening through which at least a portion of the bone anchor 12 extends. For example, the distal shaft 20 of the bone anchor 12 can extend through the opening. At least a portion of the distal end face 34 defines a plane X.

[0029] The bone anchor 12 can be selectively secured to the receiving member 14. Prior to securing, the bone anchor 12 is movable relative to the receiving member 14 within an angular cone generally defined by the geometry of the distal end 32 of the receiving member and the proximal head 18 of the bone anchor 12. The illustrated bone anchor is a polyaxial screw of a desired angle, with the angular cone biased in one direction. Thus, the bone anchor 12 is movable relative to the receiving member 14 at a first angle C relative to the central longitudinal axis L of the receiving member 14 in at least a first direction indicated by arrow A in FIG. 1D. The bone anchor 12 is also movable at a second angle D relative to the longitudinal axis L in at least a second direction indicated by arrow B in FIG. 1D. The first angle C is greater than the second angle D, and thus the shaft 20 of the bone anchor 12 is movable in the direction indicated by arrow A to a greater extent than in the direction indicated by arrow B. The distal shaft 20 of the bone anchor 12 defines a neutral axis 48 relative to the receiving member 14. The neutral axis 48 may be perpendicular to a plane X defined by the distal end face 34 and intersects a center point of the opening in the distal end face 34 through which the distal shaft 20 of the bone anchor 12 extends. The neutral axis 48 may be oriented at an angle relative to a central longitudinal axis L of the receiving member 14. A plane Y defined by at least a portion of the proximal end face 48 of the receiving member 14 intersects with a plane X defined by at least a portion of the distal end face 34 of the receiving member 12. The proximal end 26 of the receiving member 14 may include a proximal first bore 50 coaxial with a first central longitudinal axis N (coincident with the longitudinal axis L) and a distal second bore 52 coaxial with a second central longitudinal axis M (coincident with the neutral axis 48), which may intersect with one another. The angles between planes X and Y and between axes L and M may be selected to provide the desired degree of biased angle. Examples of desirable angled polyaxial screws are described in more detail in U.S. Patent No. 6,974,460, issued December 13, 2005, and U.S. Patent No. 6,736,820, issued May 18, 2004, both of which are incorporated herein by reference.Alternatively, the bone anchor assembly may be a conventional (unbiased) polyaxial screw in which the bone anchor pivots the same amount in all directions and has a neutral axis that coincides with the central longitudinal axis L of the receiving member.

[0030] A spinal fixation element, such as spinal rod 22, can directly contact the proximal head 18 of the bone anchor 12 or can contact an intermediate element, such as compression member 60. The compression member 60 can be positioned within the receiving member 14 interposed between the spinal rod 22 and the proximal head 18 of the bone anchor 12 to press the distal outer surface 38 of the proximal head 18 into direct fixed engagement with the distal inner surface of the receiving member 14. The proximal portion of the compression member 60 can include a pair of spaced apart arms 62A and 62B that define a U-shaped seat 64 for receiving the spinal rod 22. The distal portion of the compression member 60 can include a sidewall having an inner cylindrical surface 67 connected by a distal facing surface 66 to an outer cylindrical surface 68.

[0031] At least a portion of the distal surface 66 of the compression member 60 may be molded as a mold of the proximal portion 18 of the bone anchor 20 against which the distal surface 66 abuts when the compression member 60 is fully inserted into the receiving member 14. Thus, the contact area between the distal surface 66 of the compression member 60 and the proximal head 18 is maximized when the shaft 20 of the bone anchor 12 is oriented along the longitudinal axis L. However, if the angle of the shaft 20 relative to the longitudinal axis L is non-zero, the contact area between the distal surface 66 of the compression member 60 and the head 18 may be reduced, thus increasing the risk of slippage of the bone anchor 12 relative to the receiving member 14.

[0032] As best seen in FIG. 1B , the compression member 60 is configured to slide freely within the recess 30 of the receiving member 14 along the longitudinal axis L. To secure the compression member 60 within the receiving member 14, the compression member 60 can be configured to mate with the receiving member, for example, by mechanically deforming a portion of the compression member 60 relative to the receiving member 14. In the illustrated embodiment, opposing bores formed in the arms 62A, 62B of the compression member 60 are aligned with bores formed in the arms 62A, 62B of the receiving member 14 such that opposing pins can be inserted through the passages defined by the bores to press or "swage" the compression member 60 against the receiving member 14. The swaging process can prevent subsequent removal of the compression member 60 from the receiving member 14.

[0033] The proximal end 26 of the receiving member 14 can be configured to receive a closure mechanism 16 positionable between and engaging the arms 28A, 28B of the receiving member 14. The closure mechanism 16 can be configured to capture a spinal fixation element (e.g., spinal rod 22) within the receiving member 14, secure the spinal rod 22 relative to the receiving member 14, and secure the bone anchor 12 relative to the receiving member 14. The closure mechanism 16 can be a single set screw having external threads for engaging the internal threads 42 provided on the arms 28A, 28B of the receiving member 14. However, in the illustrated embodiment, the closure mechanism 16 comprises an outer set screw 70 positionable between and engaging the arms 28A, 28B of the receiving member 14, and an inner set screw 72 positionable within the outer set screw 70. The outer set screw 70 is operable to act on the compression member 60 to secure the bone anchor 12 relative to the receiving member 14. The inner set screw 72 is operable to act on the spinal rod 22 to secure the spinal rod 22 relative to the receiving member 14. In this manner, the closure mechanism 16 allows the bone anchor 12 to be secured to the receiving member 14 independent of the spinal rod 22 being secured to the receiving member 14. Specifically, the outer set screw 70 can engage the proximal end faces of the arms 62A, 62B of the compression member 60 to bring the distally facing surfaces 66 of the compression member 60 into contact with the proximal head 18 of the bone anchor 12, which in turn brings the distal face 38 of the proximal head 18 into fixed engagement with the distal inner surface of the receiving member 14. The inner set screw 72 can engage the spinal rod 22 to secure the spinal rod 22 into fixed engagement with the rod seat 64 of the compression member 60.

[0034] The outer set screw 70 includes a first external thread 74 for engaging the complementary internal thread 42 of the arms 28A, 28B of the receiving member 14. The outer set screw 74 includes a central passage 96 from a top surface 98 of the outer set screw 74 to a bottom surface 100 of the outer set screw 74 for receiving the inner set screw 72. The central passage 96 may include internal threads 102 for engaging the complementary external threads 104 of the inner set screw 72. The thread forms of the internal threads 102 and external threads 104, including the number of threads, pitch, major and minor diameters, and thread form, may be selected to facilitate connection between the components and transmission of a desired axial clamping force. The top surface 98 of the outer set screw 74 may have one or more drive features to facilitate rotation and advancement of the outer set screw 74 relative to the receiving member 14. The illustrated outer set screw 74 includes a drive feature in the form of a plurality of notches 106 spaced about the periphery of the top surface 98. The inner set screw 104 may include a drive feature for receiving an instrument to rotate and advance the inner set screw 72 relative to the outer set screw 74. The illustrated inner set screw 104 includes a drive feature in the form of a central passage 108 having a plurality of spaced, longitudinally oriented notches for engaging complementary features on an instrument.

[0035] The bone anchor assembly 10 can be used with spinal fixation elements such as a rigid spinal rod 22. The various components of the bone anchor assemblies disclosed herein, as well as the spinal rod 22, can be constructed from a variety of materials, including titanium, titanium alloys, stainless steel, cobalt chrome, PEEK, or other materials suitable for rigid fixation. In other embodiments, the spinal fixation elements can be dynamic stabilizing members that allow controlled mobility between the instrumented vertebrae.

[0036] In use, a bone can be prepared to receive the bone anchor assembly 10, generally by drilling a hole in the bone that is appropriately sized to receive the bone anchor 12. If not already completed, the bone anchor assembly 10 can be assembled, which may include assembling the bone anchor 12 and the receiving member 14, such that the distal shaft 20 extends through an opening in the distal end 32 of the receiving member 14 and the proximal head 18 of the bone anchor 12 is received in the distal end 32 of the receiving member 14. A driver tool can be fitted to the bone anchor 12 to drive the bone anchor 12 into the prepared hole in the bone. The compression member 60 can be positioned within the receiving member 14 such that the arms 62A, 62B of the compression member are aligned with the arms 28A, 28B of the receiving member 14 and the underside of the compression member 14 contacts the proximal head 18 of the bone anchor 12. A spinal fixation element, e.g., a spinal rod 22, can be positioned in the recess 30 of the receiving member 14. The closure mechanism 16 can engage with the internal threads 42 on the arms 28A, 28B of the receiving member 14. A torsional force can be applied to the outer set screw 70 to move it within the recess 30 using a tool that can engage a number of notches 106 on the upwardly facing surface of the outer set screw 70 to compress the compression member 60 onto the proximal head 18 of the bone anchor 12. A torsional force can then be applied to the inner set screw 72 to move it relative to the outer set screw 70, thereby contacting the spinal rod 22 and, for example, securing the spinal rod 22 relative to the receiving member 14 and bone anchor 12.

[0037] One or more embodiments of the bone anchor assembly of the present invention are described below. Except as indicated below, the structure, operation, and use of these embodiments are similar or identical to that of the bone anchor assembly 10 described above. Accordingly, detailed descriptions of the structure, operation, and use are omitted here for the sake of brevity. Figures 3A-12 are similar to the recess formed by the receiving member 14 and / or compression member 60 shown in Figure 1B, but the rod-receiving recess has a gripping recess or feature formed on the inner surface thereof for gripping the cylindrical rod 22 with greater friction compared to the receiving member 14 and / or compression member 60 of the bone anchor shown in Figure 1B. The rod-receiving recess shown in Figures 3A-12 can be used with the bone anchor assembly shown in Figures 1A-1D, or with various other bone anchor assemblies known in the art. Figures 8C and 8D show a rod-receiving recess in which a locking member is positioned to press an insert having a gripping recess or feature formed therein against the cylindrical rod 22. The insert shown in Figures 8C and 8D can be used with the bone anchor assembly shown in Figures 1A-1D, or with various other bone anchor assemblies known in the art, and can be biased against the cylindrical rod 22 by a locking mechanism, such as an external set screw 70 or an internal set screw 72 shown in Figures 1A-1D.

[0038] 2A-2L show a prior art connector 200 having a conventional configuration for securing a rod to the connector 200. As shown, the connector 200 can include a body 202 defining first and second rod receiving recesses 204, 206, a rod pusher 208, a biasing element or spring wire 212, and a locking element or set screw 216. The rod pusher 208 can be configured to translate laterally within the body 202 and can be biased by the spring wire 212 in a direction to urge the rod pusher toward a first rod R1 disposed within the first rod receiving recess 204. The set screw 216 can be tightened to lock the connector 200 to both the first rod R1 and the second rod R2 disposed within the second rod receiving recess 206. Thus, the illustrated connector 200 may allow for a first rod and a second rod R1, R2 to be locked to the connector in one step. The connector 200 may include one or more low profile portions to facilitate use in tight spaces. For example, the first rod receiving recess 204 may be formed in a portion of the connector body 202 having a reduced profile to fit between bone anchors implanted, for example, at adjacent levels of the cervical spine.

[0039] The body 202 can include a proximal end 202p and a distal end 202d that define a proximal-distal axis A1. The proximal end 202p of the body 202 can include a pair of spaced apart arms 218, 220 that define a second rod-receiving recess 206 therebetween. A rod R2 disposed within the second rod-receiving recess 206 can have a central longitudinal rod axis A2. The second rod-receiving recess 206 can open in a proximal direction such that a rod can be inserted into the recess by moving the rod R2 distally relative to the connector 200. Each of the arms 218, 220 can extend from a distal portion 202d of the body 202 to a free end. An outer surface of each of the arms 218, 220 can include features (not shown), such as recesses, indentations, notches, protrusions, etc., to facilitate coupling of the connector 200 to various instruments. For example, the outer surface of each arm 218, 220 can include an arcuate groove at the respective free end of the arm for attaching the connector 200 to an extension tower or retractor. The arms 218, 220 can include or be coupled to an extension or reduction tab (not shown) extending proximally from the body 202 to operatively extend the length of the arms 218, 220. The extension tab can facilitate the insertion and reduction of a rod or other implant, as well as the insertion and locking of the set screw 216. The extension tab can be configured to break or otherwise separate from the arms 218, 220. The inner surface of each arm 218, 220 can be configured to mate with the set screw 216. For example, the inner surface of the arms 218, 220 can include threads that correspond to the male threads formed on the set screw 216. Thus, rotation of the set screw 216 relative to the body 202 about axis A1 can be effective to axially translate the set screw along axis A1 relative to the body.

[0040] The distal end 202d of the body 202 can define a tunnel 228 in which the rod pusher 208 can be disposed. The tunnel 228 can extend between the second rod receiving recess 206 and the first rod receiving recess 204 along a rod pusher axis A3. The rod pusher 208 can be configured to translate within the tunnel 228 along axis A3. The axis A3 can be perpendicular or substantially perpendicular to axis A1. The axis A3 can also be perpendicular or substantially perpendicular to axis A2. The tunnel 228 can have a shape that substantially molds to the profile of the rod pusher 208. A through hole 224 can be formed within the body 202 to intersect with the tunnel 228. The through hole 224 can extend perpendicular or substantially perpendicular to axis A3. As described in more detail below, the through hole 224 can be dimensioned to receive the spring wire 212 therein. Through-hole 224 may be open at both ends or may be closed at one or both ends.

[0041] The body 202 may include a cantilevered wing portion 230 that defines a first rod-receiving recess 204. The rod R1 disposed within the first rod-receiving recess 204 may have a central longitudinal rod axis A4. The axis A4 may be parallel to the axis A2 as shown, or may be perpendicular or angled obliquely to the axis A2. The wing portion 230 may extend radially outward from the second arm 220 of the body 202. The wing portion 230 may have a width 230W and a height 230H. The ratio of the width 230W to the diameter of the first rod-receiving recess 204 (or of the rod R1 disposed therein) may be less than about 1.5:1, less than about 2:1, and / or less than about 3:1. The ratio of the height 230H to the diameter of the first rod-receiving recess 204 (or of the rod R1 disposed therein) can be less than about 0.5:1, less than about 1:1, and / or less than about 2:1. The height 230H can be less than about 5 mm, less than about 4 mm, and / or less than about 3 mm. The first rod-receiving recess 204 can open distally so that the rod R1 can be inserted into the recess by moving the connector 200 distally relative to the rod. The first rod-receiving recess 204 can open proximally, for example, by inverting the wing portion 230 to form the wing portion such that the wing portion extends from or laterally to the distal portion of the body 202.

[0042] As described above, the rod pusher 208 can be slidably disposed within the tunnel 228 of the body 202 and can be configured to translate relative to the body along the axis A3. The rod pusher 208 can include a first bearing surface 244A configured to contact and push against a first rod R1 disposed within the first rod receiving recess 204. The bearing surface 244A can extend at an oblique angle relative to a longitudinal axis of the rod pusher 208 such that the bearing surface is inclined. The bearing surface 244A can be planar as shown, or can be convex, concave, pointed, pointed, etc. For example, the bearing surface 244A can be concave and can define a cylindrical cross-section such that the bearing surface matches or approximates the profile of a cylindrical rod R1 disposed within the first rod receiving recess 204. The rod pusher 208 can include a second bearing surface 244B configured to contact and push against the second rod R2 disposed within the second rod receiving recess 206. The bearing surface 244B can extend at an oblique angle relative to a longitudinal axis of the rod pusher 208 such that the bearing surface is inclined. The bearing surface 244B can be planar as shown, or can be convex, concave, pointed, pointed, etc. For example, the bearing surface 244B can be concave and can define a cylindrical cross-section such that the bearing surface matches or approximates the profile of the cylindrical rod R2 disposed within the second rod receiving recess 206.

[0043] The rod pusher 208 may include a through hole 226. The through hole 226 may extend perpendicular or substantially perpendicular to the axis A3. The through hole 226 may be sized to receive the spring wire 212 therein. At least in some positions of the rod pusher 208 relative to the body 202, the rod pusher through hole 226 may be aligned with the body through hole 224 such that the spring wire 212 extends through both through holes 224, 226. As best shown in FIGS. 2D, 2F, and 2H, the through hole 226 may include a middle portion and opposing end portions. The middle portion of the through hole 226 may approximate the dimensions of the spring wire 212. For example, the middle portion may be cylindrical and may have a diameter substantially equal to the diameter of the spring wire 212. An end portion of the through hole 226 may be elongated or otherwise have a dimension larger than the diameter of the spring wire 212 to allow the rod pusher 208 to translate along the axis A3 and conform to the bending radius of the spring wire 212 during such translation.

[0044] The biasing element may be configured to bias the rod pusher 208 toward the first rod-receiving recess 204. In the illustrated illustration, the biasing element is a cylindrical spring wire 212. The spring wire 212 may be formed from a resilient material such that when deformed from a straight line, the spring wire has a tendency to flex back toward its straight, resting configuration. Thus, upon deformation due to movement of the rod pusher 208, the spring wire 212 may exert a force against the interior of the through hole 226 to urge the rod pusher 208 toward the first rod-receiving recess 204. Although a straight, cylindrical spring wire 212 is shown, various other biasing elements may be used instead or in addition, such as non-straight or non-cylindrical wires, leaf springs, spring clips, wave springs, coil springs, etc. The biasing element may be omitted. For example, the rod pusher 208 may be free to float within the tunnel 228 or may be held by a pin or other retaining mechanism without being biased toward the first rod-receiving recess 204.

[0045] The set screw 216 may include male threads configured to mate with female threads formed on the arms 218, 220 of the body 202 to allow the set screw to advance or retract along the axis A1 relative to the body by rotating the set screw about the axis A1. The set screw 216 may include a drive interface 248 configured to receive a driver for applying a rotational force to the set screw about the axis A1. A distal face of the set screw 216 may be configured to contact and press against the rod R2 disposed within the second rod-receiving recess 206 to lock the rod to the connector 200. When tightened against the rod R2, the set screw 216 may prevent the rod from translating along the axis A2 relative to the connector 200 and / or from rotating about the axis A2 relative to the connector. Although the set screw 216 is shown, it should be understood that other locking elements may be used instead or in addition, such as a closure cap that locks by advancing and turning a quarter turn, a closure cap that slides laterally without rotation, a nut that threads onto the exterior of the connector 200, etc.

[0046] The operation of connector 200 is illustrated generally in Figures 2C-2H.

[0047] 2C and 2D, the connector 200 can have a rest configuration in which no rod is disposed in the first or second rod-receiving recesses 204, 206. In this configuration, the biasing force of the spring wire 212 can cause the rod pusher 208 to slide toward the first rod-receiving recess 204.

[0048] In the rest configuration, the wing portion 230 of the body 202 and the free end of the rod pusher 208 can define an opening 250 that is smaller than the diameter of the first rod R1 to which the connector 200 is coupled. Thus, as shown in Figures 2E and 2F, when the rod R1 is inserted into the first rod-receiving recess 204, the rod presses against the rod pusher 208, moving the connector 200 from the rest configuration. Inserting the rod R1 can move the rod pusher 208 along the axis A3, thereby deforming the spring wire 212 from its rest state. When the maximum cross-sectional area portion of the rod R1 is positioned within the opening 250, the rod pusher 208 can be moved to its furthest distance from the first rod-receiving recess 204.

[0049] As shown in Figures 2G and 2H, when the maximum cross-sectional portion of the rod R1 passes through the opening 250 as the rod is seated in the first rod receiving recess 204, the biasing force of the spring wire 212 can retract the rod pusher 208 along the axis A3 toward the first rod receiving recess. This movement can at least partially close the opening 250 around the rod R1, trapping the rod in the first rod receiving recess 204. The biasing force of the spring wire 212 can resist the retracting movement of the rod pusher 208, and thus resist separation of the connector 200 from the first rod R1. The shape of the connector 200 can be selected such that the spring wire 212 deforms from its resting state when the rod R1 is fully seated in the first rod receiving recess 204. In this manner, the spring wire 212 can urge the rod pusher 208 against the rod R1 to provide a friction or resistance effect before the set screw 216 is tightened and / or before the second rod R2 is positioned within the connector 200.

[0050] The second rod R2 can be positioned in the second rod receiving recess 206, and the set screw 216 can be tightened to lock the connector 200 to the first and second rods R1, R2. When the set screw 216 is tightened, the second rod R2 can be pressed against the second bearing surface 244B of the rod pusher 208, urging the rod pusher toward the first rod receiving recess 204 and into firm contact with the rod R1. When the set screw 216 is tightened, the connector 200 can lock to the first and second rods R1, R2 to resist or prevent the rods R1, R2 from translating along the axes A2, A4 relative to the connector, and to resist or prevent the rods R1, R2 from rotating about the axes A2, A4 relative to the connector.

[0051] As shown in FIG. 2I, the second rod-receiving recess 206 can be shaped to promote contact between the second rod R2 and the second bearing surface 244B of the rod pusher 208. In other words, the recess 206 can be shaped to reduce or eliminate the risk that, when the set screw 216 is tightened, the second rod R2 will only press against the floor of the recess 206 without exerting sufficient force on the bearing surface 244B. As shown, the recess 206 can include a relief positioned in alignment with the end of the tunnel 228 so that the rod pusher 208 protrudes into the recess. Thus, the recess 206 can be asymmetric about the axis A1 and deviate from a symmetric U-shape. When the rod R2 reaches the bottom of the recess 206, the central longitudinal axis A2 of the rod can be offset from the axis A1. The central longitudinal axis of the rod R2 when the rod is fully seated is shown as axis A5 in FIG. 2I. Recess 206 may be configured such that when rod R2 is seated within recess 206, rod R2 translates distally along axis A1 and laterally along axis A3.

[0052] As shown in FIGS. 2J-2L, the connector 200 can include a saddle 210. The saddle 210 can be included in addition to or instead of the asymmetric recess 206. The saddle 210 can be positioned within a cavity 222 formed within the body 202. The saddle 210 can be generally cylindrical with a first arm 232 and a second arm 234 extending proximally to the respective free ends of the arms. The first arm 232 and the second arm 234 can be aligned with the first arm 218 and the second arm 220 of the body 202 such that a recess defined therebetween is aligned with the second rod-receiving recess 206. Thus, the second rod R2 can be supported simultaneously between the arms 232 and 234 of the saddle 210 and between the arms 218 and 220 of the body 202 when the rod is disposed within the second rod-receiving recess 206. The saddle 210 can include an inclined bearing surface 240 configured to contact and press against the second bearing surface 244B of the rod pusher 208. The bearing surface 240 can extend at an oblique angle relative to the axis A1. The bearing surface 240 can be planar as shown, or can be convex, concave, pointed, pointed, etc. In operation, a force applied to the saddle 210 along the direction A1, for example by tightening the set screw 216 to the saddle or to a rod R2 disposed within the saddle, can translate the saddle 210 distally relative to the body 202 and tilt the bearing surface 240 along the bearing surface 244B of the rod pusher 208, urging the rod pusher along the axis A3 toward the first rod receiving recess 204. Tightening the set screw 216 can thereby be effective to lock both rods R1, R2 into the connector 200 simultaneously. The saddle 210 allows for the locking of rods having different diameters within the second rod receiving recess 206 while at the same time ensuring that sufficient force is applied to the rod pusher 208 to lock the first rod R1 regardless of the diameter of the second rod R2.

[0053] At times, the arms 232, 234 can extend proximally beyond the maximum dimension of the rod R2, and the set screw 216 can include an outer thread configured to press against the proximally facing surface of the arm. The inner set screw can be threaded into the outer set screw. Thus, the outer set screw can be tightened first to compress the saddle 210 and lock the first rod R1 into the first rod receiving recess 204. The inner set screw can then be tightened to compress the second rod R2 and lock the second rod into the second rod receiving recess 206. In this manner, the dual set screws can facilitate independently locking the first and second rods R1, R2 to the connector 200. Although not shown in FIGS. 2J-2L, the connector 200 including the saddle 210 can also include a biasing element as described above to bias the rod pusher 208 toward the first rod receiving recess 204.

[0054] Thus, the connector 200 can be used to connect a first spinal rod R1 to a second spinal rod R2. Although the connector 200 is generally described herein for use with a first spinal rod and a second spinal rod, it will be understood that the connector may instead be configured for use with other types of orthopedic devices, whether implanted or external. For example, one or both halves of the connector 200 can be modified to connect various other components together (e.g., rods to plates, plates to plates, rods to cables, cables to cables, etc.).

[0055] The connector 200 can provide various advantages for the user and / or patient. For example, once the connector 200 is "snap-fitted" onto the first rod R1, the biased rod pusher 208 can provide tactile feedback to give the user confidence that the rod is successfully attached before tightening the connector. The biased rod pusher 208 can also add friction or "resistance" to the rod R1 before locking the set screw 216, helping to hold the connector in place and prevent "wobble," while still allowing free movement when intended by the user. As a further example, the low-profile geometry of the wing portion 230 of the connector 200 can allow the connector to be used in surgical areas where space is limited (e.g., in the cervical region of the spine). In an exemplary method, the wing portion 230 of the connector 200 can be hooked onto the first rod R1 at a location between two bone anchors to which the rod is connected, the two bone anchors being implanted in adjacent spinal levels of the cervical spine. As yet another example, the connector 200 can facilitate simultaneous and / or single-step locking of the first and second rods R1, R2, allowing the connector 200 to lock to both rods R1, R2 with minimal steps. In other cases, the connector 200 can facilitate independent locking of the rods R1, R2, for example, with a saddle 210 and dual set screws.

[0056] Exemplary connectors and implants are disclosed in U.S. Patent Application Publication No. 2017 / 0333088, filed October 4, 2016, and U.S. Patent Application Publication No. 2017 / 0333087, filed May 18, 2016, both of which are incorporated by reference herein.

[0057] FIG. 3A is a cross-sectional view of a connector having a rod recess with two gripping grooves. As shown, the connector 300 can include a body 202 defining a first rod receiving recess 304 and a second rod receiving recess 306 and a rod pusher 308. The rod pusher 308 can be configured to translate laterally within the body 302 and can be biased in a direction to urge the rod pusher 308 against a first rod R1 disposed within the first rod receiving recess 304. The set screw 216 can be tightened to lock the connector 300 to both the first rod R1 and the second rod R2 disposed within the second rod receiving recess 306. Thus, the illustrated connector 300 can allow the first rod R1 and the second rod R2 to be locked to the connector in one step (as shown in FIGS. 2A-2L). The connector 300 can include one or more low-profile portions to facilitate use in tight spaces. For example, the first rod-receiving recess 304 can be formed in a portion of the connector body 202 that has a reduced profile to fit between bone anchors implanted, for example, at adjacent levels of the cervical spine.

[0058] The body 302 may include a proximal end and a distal end that define a proximal-distal axis A1, as shown in FIG. 2B. The proximal end 202 of the body may include a pair of spaced apart arms 318, 320 that define a second rod-receiving recess 306 therebetween. A rod R2 disposed within the second rod-receiving recess 306 may have a central longitudinal rod axis A2, as shown in FIG. 2B. The second rod-receiving recess 306 may open in a proximal direction such that a rod may be inserted into the recess by moving the rod R2 distally relative to the connector 200. Each of the arms 318, 320 may extend from a distal portion of the body 302 to a free end. An outer surface of each of the arms 318, 320 may include features (not shown), such as recesses, indentations, notches, protrusions, etc., to facilitate coupling of the connector 300 to various instruments. For example, the outer surface of each arm 318, 320 can include an arcuate groove at the respective free end of the arm for attaching the connector 300 to an extension tower or retractor. The arms 318, 320 can include or be coupled to an extension or reduction tab (not shown) extending proximally from the body 302 to operatively extend the length of the arms 218, 220. The extension tab can facilitate the insertion and reduction of a rod or other implant, as well as the insertion and locking of the screw 216, as shown in FIG. 2B. The extension tab can be configured to break or otherwise separate from the arms 218, 220. The inner surface of each arm 318, 320 can be configured to mate with the set screw 216. For example, the inner surface of the arms 318, 320 can include threads that correspond to the male threads formed on the set screw 316. Thus, rotation of the set screw 316 relative to the body 302 about axis A1 may be effective to translate the set screw axially along axis A1 relative to the body.

[0059] The body 302 can include a cantilevered wing portion 330 that defines a first rod receiving recess 304. As shown in FIG. 2B, the rod R1 disposed in the first rod receiving recess 304 can have a central longitudinal rod axis A4. The axis A4 can be parallel to the axis A2 as shown, or can be perpendicular or angled obliquely to the axis A2. The wing portion 330 can extend radially outward from the second arm 320 of the body 302. The first rod receiving recess 304 can open distally such that the rod R1 can be inserted into the recess by moving the connector 300 distally relative to the rod. The first rod receiving recess 304 can open proximally, for example, by inverting the wing portion 330 to form the wing portion such that the wing portion extends from or laterally to a distal portion of the body 302.

[0060] The rod pusher 308 can be slidably disposed within the tunnel 328 of the body 302, as shown in FIG. 2B, and can be configured to translate relative to the body along an axis A3. The rod pusher 308 can include a first bearing surface 344A configured to contact and push against a first rod R1 disposed within the first rod receiving recess 304. The bearing surface 344A can extend at an oblique angle relative to a longitudinal axis of the rod pusher 308 such that the bearing surface is inclined. The bearing surface 344A can be planar as shown, or can be convex, concave, pointed, pointed, etc. For example, the bearing surface 344A can be concave and can define a cylindrical cross-section such that the bearing surface matches or approximates the profile of a cylindrical rod R1 disposed within the first rod receiving recess 204. The rod pusher 308 can include a second bearing surface 344B configured to contact and push against the second rod R2 disposed within the second rod receiving recess 306. The bearing surface 344B can extend at an oblique angle relative to a longitudinal axis of the rod pusher 208 such that the bearing surface is inclined. The bearing surface 344B can be planar as shown, or can be convex, concave, pointed, pointed, etc. For example, the bearing surface 344B can be concave and can define a cylindrical cross-section such that the bearing surface matches or approximates the profile of the cylindrical rod R2 disposed within the second rod receiving recess 306.

[0061] Figure 3A shows a first rod-receiving recess 304 that includes two gripping grooves 301 facing bearing surface 344A. The gripping grooves 301 are formed as recesses in the inner surface of the first rod-receiving recess 304, as shown more clearly in Figure 3B.

[0062] 3B is a cross-sectional view of the rod receiving recess 304 of the connector of FIG. 3A. FIG. 3B shows that the gripping groove 301 defines two edges 312, 313, 322, 323, each configured to contact a surface of a cylindrical rod R1 disposed within the first rod receiving recess 304. The gripping groove 301 extends along the axis A4, and the first rod receiving recess 304 is sized and shaped such that a side of the cylindrical rod R1 facing the gripping groove 301 is urged by the rod pusher 308 into contact with the edges 312, 313, 322, 323, such that additional force applied to the cylindrical rod R1 by the rod pusher 308 further engages the cylindrical rod R1 with the edges 312, 313, 322, 323. This can be accomplished, for example, as shown in more detail in FIG. 3C , by having edges 312, 313, 322, 323 define a radius about axis A4 that approximately corresponds to the radius of cylindrical rod R1, and having the inner surface of rod receiving recess 304 and the position of gripping groove 301 sized and shaped such that when cylindrical rod R1 is urged into rod receiving recess 304, the half of cylindrical rod R1 facing rod pusher first bearing surface 344A contacts rod receiving recess 304 and engages only at edges 312, 313.

[0063] FIG. 3C is a cross-sectional view of the gripping grooves 301 of the rod-receiving recess 304 of the connector 300 of FIG. 3A. FIG. 3C shows a cylindrical rod R1 (solid lines) disposed in the rod-receiving recess 304 in contact with edges 312, 313 such that a small portion of the outer surface of the cylindrical rod R1 is received inside each gripping groove 301. This illustrated configuration shows that the cylindrical rod R1 contacts the rod-receiving recess 304 along four contact points, in contrast to the prior art rod-receiving recess 204 without gripping grooves. This prior art configuration is shown in FIG. 3C as the position of the cylindrical rod R1' overlaps the cylindrical rod R1. The position of the cylindrical rod R1' (dashed lines) corresponds to the position of the cylindrical rod R1' in the rod-receiving recess 304 without the gripping grooves 301, as shown more clearly in FIG. 4A. FIG. 3C shows that the radius 398 of the cylindrical rod R1 and the distance 399 of each edge 312, 313 from the central longitudinal axis A4 of the rod-receiving recess 304 are approximately the same.

[0064] FIG. 4A is a cross-sectional view of a rod-receiving recess according to the prior art. FIG. 4A shows a cylindrical rod R1 disposed in a rod-receiving recess 204 according to the prior art that does not have a gripping groove. In this configuration, the cylindrical rod R1 contacts the inner surface of the rod-receiving recess 204 at two points P1, P2. In operation, these two points P1, P2 can define parallel contact lines along the axis A4 (e.g., along the surface of the cylindrical rod R1 that contacts the inner surface of the rod-receiving recess 204). The particular interface of the cylindrical rod R1 and the rod-receiving recess 204 at these points P1, P2 is a curved surface (e.g., the cylindrical rod R1) or an angled surface (e.g., the rod-receiving recess 204) relative to a plane. With this engagement, rotation of cylindrical rod R1 about axis A4 and translation of cylindrical rod R1 in the A4 direction are both constrained by a force exerted on cylindrical rod R1 by the surface of rod-receiving recess 204, which force depends on the force exerted by rod pusher 208 and the frictional force between cylindrical rod R1 and the surface of rod-receiving recess 204. A radius 498 of cylindrical rod R1 is shown relative to the central axis R of cylindrical rod R1.

[0065] As illustrated in FIG. 4B, aspects of the present disclosure provide improved retention of a cylindrical rod R1 in the rod receiving recess 304. FIG. 4B is a cross-sectional view of a rod receiving recess 308 having a V-shaped gripping groove 401. The V-shaped gripping groove 401 defines edges 412, 413 that are positioned to contact the surface of the cylindrical rod R1 at points E1-E4. That is, the V-shaped gripping groove 401 is formed in the surface of the rod receiving recess 304 such that the edges 412, 413 define four points on a circle having approximately the same radius as the cylindrical rod R1. In operation, the cylindrical rod R1 rests against the four edges 412, 413, and the rod pusher 308 applies a force 488 to the cylindrical rod R1 that urges the surface of the cylindrical rod R1 against the edges 412, 413. In contrast to the prior art surface-to-surface engagement of FIG. 4A, the curved surface of the cylindrical rod R1 is forced against the sharp edges 412, 413 (e.g., corners or vertices that can be deformed by the cylindrical rod R1 or that form edges of a radius or thickness small enough to deform the surface of the cylindrical rod R1 to allow the cylindrical rod R1 to be forced into the gripping groove 401), such that rotation of the cylindrical rod R1 while pressing against the four edges 412, 413 requires micro-shearing of the edges 412, 413 at the contact points E1-E4. Thus, the gripping groove 401 constrains rotation of the cylindrical rod R1 within the rod receiving recess 304 in a manner that requires material properties that cannot allow movement between the edges 412, 413 and the cylindrical rod R1. As a result, for equal forces applied to the cylindrical rod R1 by the rod pusher 308, the gripping groove 401 can withstand a higher torque on the cylindrical rod R1 about the axis A4 before movement occurs.

[0066] In some cases, to ensure engagement between the cylindrical rod R1 and the edges 412, 413, a pocket 450 is formed in the rod-receiving recess 304 such that movement of the cylindrical rod R1 relative to the edges 412, 413 when driven by the rod pusher 308 is not impeded by the cylindrical rod R1 contacting the inner surface of the rod-receiving recess 308. This configuration allows an initial bias of the cylindrical rod R1 against the edges 412, 413 to cause some deformation (e.g., deformation of either or both of the material of the cylindrical rod R1, the edges 412, 413) at the contact points E1-E4, such that any initial rotation of the cylindrical rod R1 induces further deformation of the material at the contact points E1-E4.

[0067] While FIG. 4B shows the body 302 having two gripping grooves 401, in some cases the body 302 has only one gripping groove 401, with the single gripping groove 401 positioned directly opposite the clamping force vector, for example, such that the force vector 488 and the center of the gripping groove 401 intersect the central axis A4 of the rod R1.

[0068] FIG. 4B also shows that the radius 498 of the cylindrical rod R1 and the distance 499 of each edge 412, 413 from the central longitudinal axis A4 of the rod receiving recess 304 can be approximately the same to enable the surface of the cylindrical rod R1 to uniformly contact the edges 412, 413, in which case the central axis R of the cylindrical rod R1 is concentric with the central longitudinal axis A4 of the rod receiving recess 304.

[0069] FIG 4C is a cross-sectional view of the rod receiving recess 304 of FIG 4B showing a comparison of the position of the cylindrical rod R1 with and without the gripping groove 401. FIG 4C shows the position of both the cylindrical rod R1 engaged with the gripping groove 401 as shown in FIG 4B as well as the same cylindrical rod R1 (shown by dotted line R1') positioned in the rod receiving recess 204 without the gripping groove 401. Compared to the position of the cylindrical rod R1' relative to the rod receiving recess 204, the cylindrical rod R1 in the rod receiving recess 304 with the gripping groove 401 is positioned deeper into the pocket 450 because only a portion of the surface of the cylindrical rod R1 is received in the gripping groove 401, allowing all of the edges 412, 413 to contact the surface of the cylindrical rod R1.

[0070] FIG. 4D is a perspective view of the cylindrical rod R1 when it is positioned in the rod-receiving recess 304 (as shown in FIG. 4B), showing the contact lines E1-E4 formed by the edges 412, 413 of the two gripping grooves 401. FIG. 4D shows the resulting contact points between the rod-receiving recess 304 with the gripping grooves 401 that span the length of the cylindrical rod R1. This allows the cylindrical rod R1 to be pressed into the edges 412, 413 along the contact lines E1-E4, such that the force applied to the cylindrical rod R1 is not compromised by contact between the cylindrical rod R1 and the rod-receiving recess 304, except along the contact lines E1-E4. In some cases, as described in more detail below, additional contact points and contact lines between the cylindrical rod R1 and the rod-receiving recess 304 are within the scope of the present disclosure. However, such additional contact still allows a sufficient portion of the force applied to cylindrical rod R1 to be directed along contact lines E1-E4 against edges 412, 413 to create a condition in which rotation of cylindrical rod R1 is resisted along contact lines E1-E4, due to the requirement of deformation of the material of either or both of cylindrical rod R1 and edges 412, 413. Figure 4D shows that contact lines E1-E4 are oriented to resist rotation of cylindrical rod R1 in both clockwise CW and counterclockwise CCW directions.

[0071] FIG. 4E is a perspective view of a surface 410 of a rod-receiving recess 304 having a segmented gripping groove 403. The segmented gripping groove 403 is formed when the gripping groove 401 intersects with one or more recesses or grooves 408. FIG. 4E shows a segmented gripping groove 403 formed by the gripping groove 401 intersecting with two recesses 408 oriented perpendicularly to the gripping groove 401. However, in some embodiments, other angles are possible, such as one or more recesses or grooves 408 being transverse (e.g., oblique, etc.) to the gripping groove 401. The intersection of the gripping groove 401 with the grooves 408 forms an interruption of the gripping groove edges 412, 413 along the length of the cylindrical rod R1, as shown in FIG. 4F, which are hereinafter referred to as segmented edges 412, 413.

[0072] FIG. 4F is a top view of the segmented gripping groove of FIG. 4E. In operation, the segmented edges 412, 413 serve to constrain the movement of the cylindrical rod R1 along the length of the segmented gripping groove 403 (i.e., translation along axis A4) by engaging the surface of the cylindrical rod R1 to form point edges 480 (e.g., slight corners when the rod is forced into the groove such that each point edge 480 forms a slight contact corner with the rod R1) that allow the segmented edges 412, 413 to apply a force to the cylindrical rod R1 in the A4 direction, as shown in FIG. 4G. FIG. 4G is a schematic diagram of contact points F1-F4 on the cylindrical rod R1 engaged with the segmented gripping groove 403 of FIG. 4E. FIG. 4G shows that the resulting contact lines F1, F2 of the segmented edges 412, 413 are similarly segmented when the cylindrical rod R1 is forced into engagement with the segmented gripping groove 403. By engaging the cylindrical rod R1 with the segmented edges 412, 413, the point edges or slight corners 480 define the transitions between the points on the cylindrical rod R1 where the segmented edges 412, 413 are in contact with the cylindrical rod R1 and where they are not in contact with the cylindrical rod R1. For example, if the material properties of the cylindrical rod R1 and the segmented edges 412, 413 are selected such that the surface of the cylindrical rod R1 is deformed when in contact with the segmented edges 412, 413, this movement resulting in two of the four illustrated point edges 480 being driven into undeformed regions of the surface of the cylindrical rod R1 causes the point edges 480 to together resist translation of the rod along the segmented gripping groove 403 (i.e., translation along axis A4). Thus, the segmented gripping groove 403 can resist both rotation and translation of the cylindrical rod R1 within the rod receiving recess 403, as shown in FIG. 4F.

[0073] 4H is a perspective view of the surface of cylindrical rod R1 showing the segmented contact lines F1-F4 formed by the edges of the two segmented gripping grooves 403 when cylindrical rod R1 is positioned within rod-receiving recess 304. Clockwise CW and counterclockwise CCW rotation of cylindrical rod R1 is resisted by segmented gripping groove 403 in the same manner as described above for non-segmented gripping groove 401, and translation of cylindrical rod R1 is resisted by point edge 480 formed between segmented edges 412 and 413.

[0074] FIG 3A shows gripping groove 301 having a cylindrical shape and FIG 4B shows gripping groove 401 having a V-shape, although other shapes are possible. For example, FIG 5A is a cross-sectional view of rod-receiving recess 403 having a rectangular shaped gripping groove 501 with right angled edges 512, 513. Although FIGS 3A-5A show gripping grooves 301, 401, 501 as recesses formed in the inner surface of rod-receiving recess 304, the gripping grooves could also be formed by protrusions 540 extending from the inner surface of rod-receiving recess 304, as shown in FIG 5B.

[0075] 3A-5B show gripping grooves 301, 401, 501 formed in wing portion 330 of body 302 positioned such that rod pusher 308 applies a force to cylindrical rod R1 to drive cylindrical rod R1 against gripping grooves 301, 401, 501, although other configurations are possible. For example, FIG. 6A is a cross-sectional view of rod receiving recess 304 having rod pusher 308 with gripping groove 601. As shown, gripping groove 601 defines edges 612, 613 that contact cylindrical rod R1 at four contact points E1-E4 that define a circle of approximately the same radius as cylindrical rod R1. In FIG. 6A, the surface of the rod receiving recess facing the rod pusher 308 defines a curved surface 651 that contacts the cylindrical rod R1 to exert a force that counteracts the force exerted on the cylindrical rod R1 by the edges 612, 613 of the gripping groove 601 of the rod pusher 308. In operation, the gripping groove 601 of the rod pusher 308 functions in the same manner as the gripping grooves 301, 401, 501 described above. FIG. 6B is a cross-sectional view of the rod receiving recess 304 with the pocket 450 and the rod pusher 308 with the gripping groove 601. FIG. 6C shows both the rod receiving recess 304, the gripping groove 501, and the rod pusher 308 with the gripping groove 601. In this configuration, the position of the cylindrical rod R1 is highly constrained by the gripping grooves 501, 601 as all eight contacts E1-E8 engage the surface of the cylindrical rod R1. However, in some cases, the allowable force at the locations of the eight contact points E1-E8 is reduced upon initial contact with the cylindrical rod R1 such that the cylindrical rod R1 is highly constrained when sufficient force is applied to fully engage the cylindrical rod R1 with respect to the eight contact points E1-E8.

[0076] 7A is a cross-sectional view of a single gripping groove 501 having an internal protrusion 710 positioned to contact a surface of the cylindrical rod R1 between edges 512 and 513 of the gripping groove 501. To increase the restraint of the cylindrical rod R1 in the translational direction (i.e., along axis A4), additional gripping features can be included within the gripping groove 501 to provide translational restraint with minimal to negligible effect on the rotational restraint provided by edges 512, 513. In FIG. 7A, the gripping groove 501 includes one or more protrusions 701 along the length of the gripping groove 501. The internal protrusion 710 includes features such as an edge 711 that extends toward the cylindrical rod R1 and is positioned to contact the cylindrical rod R1 when the cylindrical rod R1 engages edges 512, 513 of the gripping groove 501. 7A shows an internal protrusion 710 having an edge 711 that contacts a cylindrical rod R1 along a contact line L1 that is perpendicular to the contact lines E1, E1 formed by edges 512, 513. In operation, the position and shape of the edge 711 of the gripping groove 501 can be configured to vary the strength of the contact line L1 between the cylindrical rod R1 and the edge 711 when the cylindrical rod R1 contacts the edges 512, 513, as shown in more detail in FIGS.

[0077] 7B is a top view of the gripping groove 501 of FIG. 7A showing the vertical edges 711 of the two internal projections 710 that form two parallel contact lines L1, L2 on the cylindrical rod R1. FIG. 7C is a cross-sectional view of the gripping groove 501 of FIG. 7A showing the edges 711 of the internal projections 710 that contact the cylindrical rod R1 when the rod engages with the gripping groove 501.

[0078] 7D is a perspective view of the cylindrical rod R1 showing the contact lines E1-E4 formed by the edges 512, 513 of the two gripping grooves 501 and the contact lines L1-L4 formed by the two internal protrusions 710 of each gripping groove 501. In operation, the contact lines E1-E4 formed by the edges 512, 513 resist rotation of the cylindrical rod R1 in the clockwise CW and counterclockwise CCW directions, and the contact lines L1-L4 formed by the two internal protrusions 710 resist translation of the cylindrical rod R1 in the A4 direction.

[0079] 7E and 7F are cross-sectional views of a single gripping groove 501 with an internal protrusion 710 having two different edge configurations. In a first configuration shown in FIG. 7E, the internal protrusion 710 extends to a flat edge 711 that defines a contact line L1 with the cylindrical rod R1 that lengthens as the cylindrical rod R1 is forced against the edges 512, 513. Because the initial size of the contact line L1 is small, there is minimal resistance to the movement of the cylindrical rod R1 into the gripping groove 510, ensuring that a secure engagement is established between the cylindrical rod R1 and the internal protrusion 710. In a second configuration shown in FIG. 7F, the internal protrusion 710 has a curved edge 712 that is shaped to initially contact the cylindrical rod R1 with a longer contact line L1 to increase the restraint of translation of the cylindrical rod R1 upon initial contact with the edges 512, 513. The resulting strength of the restraint of the two different edge shapes 711, 712 can depend on the material properties of the cylindrical rod R1, the edges 512, 513, and the internal protrusion 710, as well as the location of the edges 711, 712 relative to the edges 512, 513. For example, if the cylindrical rod R1 is made of a metal that is softer than the metal of the internal protrusion 710, the edges 711, 712 can extend closer to the radius of the edges 512, 513 (i.e., the expected location of the cylindrical rod R1) so that the cylindrical rod R1 first contacts the edges 711, 712 and is driven into the surface of the cylindrical rod R1 when the cylindrical rod R1 interacts with the edges 512, 513.

[0080] 8A is a cross-sectional view of a prior art rod-receiving recess 206, for example, of the receiving member 14 of the bone anchor assembly 10 or the body 202 of the connector 200. A cylindrical rod R1 is disposed within the rod-receiving recess 206 and contacts the inner surface of the rod-receiving recess 206 at two points P1, P2 along the axis of the rod-receiving recess 206. A locking element or set screw 104, 216 contacts the cylindrical rod R1 at point P3 and applies a force to bias the cylindrical rod R1 into the rod-receiving recess 206 and against the two points P1, P2.

[0081] FIG. 8B is a cross-sectional view of the rod-receiving recess 306 having two gripping grooves 801 formed as parallel recesses in the inner surface of the rod-receiving recess 306. FIG. 8B shows a cylindrical rod R1 disposed within the rod-receiving recess 306 and engaged with edges 812, 813 of the gripping grooves 801. A threaded locking element or set screw 104, 216 is positioned to secure the cylindrical rod R1 within the rod-receiving recess 306 by applying a force to the cylindrical rod R1 to urge the cylindrical rod R1 against edges 812, 813 of the gripping grooves 801. FIG. 8B also shows the position of the cylindrical rod R1 within the rod-receiving recess 306 when displaced from the gripping grooves 801, indicated as R1′. The difference between R1' and the position of cylindrical rod R1 using gripping groove 801 is due to gripping groove 801 defining edges 812, 813 along the inner surface of rod-receiving recess 306 at four locations at approximately the same radius from the central axis of rod-receiving recess 306 as cylindrical rod R1, thereby allowing the central axis of cylindrical rod R1 to be concentric with the axis defined by the equal radial locations of edges 812, 813. In other words, gripping groove 801 is positioned to allow cylindrical rod R1 to rest against all four edges 812, 813 when urged into rod-receiving recess 306 by locking element or set screw 104, 216. In some cases, the rod receiving recess 306 defines a pocket or gap 850 below the designed position of the cylindrical rod R1 (determined by the gripping groove 801) to enable the set screws 104, 216 to additionally bias the cylindrical rod R1 into the rod receiving recess 306, increasing pressure on the edges 812, 813.

[0082] 8C and 8D show an embodiment in which the gripping groove 801 is positioned on an insert 816 that is driven against the cylindrical rod R1 in the rod receiving recess 306. The insert 816 is driven against the cylindrical rod R1 by the set screw 104, 216, but does not rotate with the set screw 104, 216 because the insert 816 is shaped to extend the gripping groove 801 along the length of the cylindrical rod R1. The insert 816 can include a peg 817 that is received by the set screw 104, 216 to couple the groove 801 with the body 302 (into which the set screw 104, 216 is threaded, not shown) so that the body 302 can resist rotation of the cylindrical rod R1 by engagement of the gripping groove 801 with the cylindrical rod R1. FIG. 8C shows a rod-receiving recess 306 having a circular cross-section to provide surface contact with the cylindrical rod R1 to counter the force of the insert 816, and FIG. 8D shows a rod-receiving recess 306 having a tapered closed end with a gap 850 that provides two contact lines P1, P2 with the cylindrical rod R1 to counter the force of the insert 816.

[0083] Figure 9 is a perspective view of a receiving member 902 having a rod-receiving recess 904 with two gripping grooves 801 formed therein. Figure 10 is a perspective view of a receiving member 902 having a rod-receiving recess 904 with two circumferential grooves 1020 cut into the rod-receiving recess 904 perpendicular to a central longitudinal axis of the receiving recess 904.

[0084] 11A and 11B are perspective views of a receiving member 902 having a rod receiving recess 904 formed therein by the intersection of two segmented gripping grooves 403, two gripping grooves 801 and two circumferential grooves 1020. FIG. 11B shows a point edge 480 formed by the segmented gripping groove 403. FIG. 12 is a perspective view of a receiving member 902 having a rod receiving recess 906 having a gripping groove 801 with a plurality of internal projections 710 formed therein. The receiving member 902 and rod receiving recess 904 of FIGS. 9-11B can be, for example, the body 302 of the connector 300, or the receiving member 14 of the bone anchor assembly 10, or any other implant configured to be secured to a rod, cable, or other spinal fixation element.

[0085] Figure 13 is an illustration of a connector 300 having a saddle 301 defining a rod-receiving recess having a gripping groove 1301. In the connector 300 of Figure 13, a cylindrical rod R1 is secured to the receiving member 14 by engaging with the rod-receiving recess formed by an inner surface of the saddle 301, the inner surface of the saddle 60 including two gripping grooves 1301 configured to grip the cylindrical rod R1 when the locking screw 216 applies a force to the cylindrical rod R1 to urge the cylindrical rod R1 into the gripping grooves 1301.

[0086] Figure 14 is an illustration of a bone anchor assembly 10 having a compression member 60 defining a rod-receiving recess having a gripping groove 1401. In the bone anchor assembly of Figure 14, a cylindrical rod R1 is secured to the receiving member 14 by contact with the compression member 60 disposed within the receiving member, and the inner surface of the compression member 60 that forms the rod-receiving recess includes a gripping groove 1401 that contacts the cylindrical rod R1. In operation, the internal set screw 102 applies a force to the cylindrical rod R1 to urge it into the gripping groove 1401.

[0087] FIG. 15 is a perspective view of a human spine with a fixation system attached.

[0088] Exemplary methods of using the bone anchors and connectors disclosed herein are described below. In some cases, the bone anchors and connectors are each secured to one or two rods, for example to bridge between constructs in the cervical and thoracic regions of a patient's spine. The bone anchors and connectors can be secured to the rods using rod-receiving recesses with gripping grooves to increase resistance to movement of the rods, connectors, and bone anchors relative to one another.

[0089] The procedure may begin by making an open or percutaneous incision in the patient to access the target site. The target site may be one or more vertebrae, a long bone or portions of a long bone, or any other bony or non-bony structure of the patient. As shown in FIG. 15, the target site may be multiple vertebrae in the patient's cervical and thoracic spine.

[0090] Bone anchors may be driven into one or more vertebrae, and spinal rods may be attached to the bone anchors using known techniques. In the illustrated embodiment, left and right spinal rods R1, R2 are connected to four adjacent vertebrae V1-V4 using eight bone anchors S1-S8. In addition, left and right rods R3, R4 are connected to the next two adjacent vertebrae V5-V6 using four bone anchors S9-S12. Rods R1, R2 may be connected to rods R3, R4, respectively, using four connectors C1-C4 (e.g., connector 300) of the type described herein, and bone anchors S1-S8 may be connected to rods R1-R4 using receivers (e.g., receiver 902) of the type described herein.

[0091] As shown, the low profile of connectors C1-C4 can allow them to be placed at adjacent vertebral levels of the same rod (e.g., between V2 / V3 and between V3 / V4). As also shown, connectors C1-C4 can connect to rods R1, R2 between bone anchors placed at adjacent vertebral levels.

[0092] The connectors C1-C4 are capable of receiving rods within their respective rod-receiving recesses which have gripping grooves for securing the connectors to the rods R1, R2, thereby providing improved rotational, and possibly axial, restraint of the rods R1, R2 relative to the connectors.

[0093] Connectors C1-C4 may include independent locking features so that they can lock onto rods R1, R2 before locking onto rods R3, R4, or vice versa.

[0094] Connectors C1-C4 may include single-step locking features so that they can simultaneously lock onto their respective rods, for example connector C1 may simultaneously lock onto rods R1 and R3.

[0095] Rods R1-R4, connectors C1-C4, and bone anchors S1-S12 can all be installed in a single procedure.

[0096] Alternatively, rods R1, R2 and bone anchors S1-S8 may have been placed in a previous procedure, and the current procedure may be a revision procedure in which rods R3, R4, connectors C1-C4, and bone anchors S9-S12 are placed to extend the previously placed construct to an additional level.

[0097] The connectors C1-C4 can be attached as shown to position the rods R1-R4 substantially parallel to one another and lying substantially in a common coronal plane. The connectors C1-C4 can also be rotated 90 degrees from the orientation shown to position the rod pairs R1, R3 and R2, R4 to lie substantially in their respective common sagittal planes.

[0098] The above steps may be repeated to place additional rods and / or connectors at the same or different vertebral levels. Final tightening or other adjustments of the construct can be performed using known techniques, the procedure can be completed, and the incisions are closed.

[0099] It should be noted that any order of method steps depicted or suggested in the above description or the accompanying drawings should not be construed as limiting the disclosed methods to performing the steps in that order. Rather, the various steps of each of the methods disclosed herein can be performed in any of a variety of orders. Additionally, the methods described are merely exemplary embodiments, and various other methods including additional or fewer steps are within the scope of the present disclosure.

[0100] Although the methods illustrated and described herein generally involve attaching spinal rods to multiple vertebrae, it should be understood that the connectors and methods herein can be used with a variety of other types of fixation or stabilization devices within any bone, non-bone tissue, or non-living or non-tissue object. The connectors disclosed herein can be fully implanted or can be used as part of an external fixation or stabilization system. The devices and methods disclosed herein can be used in minimally invasive and / or open surgery.

[0101] The devices disclosed herein and their various component parts can be constructed from any of a variety of known materials. Exemplary materials include materials suitable for use in surgical applications, including, for example, metals such as stainless steel, titanium, or alloys thereof, polymers such as PEEK, ceramics, and carbon fiber. The various components of the devices disclosed herein can be rigid or flexible. One or more components or portions of the device can be formed from a radiopaque material to facilitate visualization under fluoroscopy and other imaging techniques, or can be formed from a radiolucent material so as not to interfere with visualization of other structures. Exemplary radiolucent materials include carbon fiber and high strength polymers.

[0102] Although particular embodiments are described above, it should be understood that many variations can be made within the spirit and scope of the concepts described.

[0103] [Embodiment] (1) An implant comprising: a body having a rod receiving recess, the body having a first side and a second side defining an opening into the rod receiving recess, the rod receiving recess defining a central longitudinal rod axis extending between the opening in the first side and the opening in the second side, at least a portion of the rod receiving recess being formed by an inner surface of the implant, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis; a body, each gripping groove defining two edges where the gripping groove intersects the inner surface, the four edges of the two gripping grooves together defining a circular radius about the central longitudinal rod axis; a retaining member configured to move relative to the body and exert a force perpendicular to the central longitudinal rod axis on a rod in the rod-receiving recess and engage the rod against the four edges of the two gripping grooves, a retention member, wherein the engagement of the four edges of the gripping groove to the rod serves to limit rotational movement of the rod about the central longitudinal rod axis. (2) The implant of embodiment 1, wherein the rod-receiving recess defines a gap between the two gripping grooves sized and positioned to allow the force on the rod within the rod-receiving recess to deflect one or both of the edge and the rod where the edge engages the rod, the deflection moving the rod into the gap. (3) The implant of embodiment 2, wherein the inner surface of the rod-receiving recess between the two gripping grooves is positioned away from the central longitudinal rod axis by a distance greater than a radius of the rod. (4) The implant of embodiment 1, further comprising a compression member disposed in a cavity formed in the body, the compression member having an inner surface that defines at least a portion of the rod receiving recess, the inner surface of the compression member having the two gripping grooves formed therein. (5) The implant of embodiment 1, wherein the gripping groove extends along the entire length of the inner surface of the rod-receiving recess in the direction of the central longitudinal rod axis.

[0104] (6) The implant of embodiment 1, wherein the gripping groove is positioned opposite the retaining member with respect to the central longitudinal rod axis. (7) The implant of embodiment 1, wherein the rod receiving recess defines an open end sized to receive the rod and a closed end sized to contact the rod, and the gripping grooves are symmetrically disposed about an axis extending from the open end to the closed end. (8) The implant of embodiment 1, wherein the body of the implant defines an inner surface that forms the rod receiving recess. (9) The implant of embodiment 1, wherein the intersection between the gripping groove and the inner surface defines a sharp edge. (10) The implant of embodiment 1, wherein the inner surface defines a groove that intersects with at least one gripping groove, the intersection of the grooves dividing the edge of the at least one gripping groove and defining four corners for resisting translation of the rod along the central longitudinal rod axis when the rod engages the edge.

[0105] (11) The implant of embodiment 9, wherein the groove that intersects at least one gripping groove is oriented perpendicular to the gripping groove. (12) The implant of embodiment 1, wherein at least one gripping groove defines an inner surface having one or more protrusions formed therein, the one or more protrusions extending into an edge configured to contact the rod when the rod engages the edge of the gripping groove. (13) The implant of embodiment 1, wherein the gripping groove is formed by a protrusion extending from the inner surface. (14) The implant includes a connector, the rod receiving recess is a first rod receiving recess, the body defines a second rod receiving recess, one or both of the first rod receiving recess and the second rod receiving recess include the two gripping grooves, and the body has proximal and distal ends defining a proximal-distal axis extending therebetween; 2. The implant of embodiment 1, wherein the retention member is slidably disposed within a tunnel formed in the body and configured to translate relative to the body along a rod pusher axis. (15) The implant of embodiment 14, wherein the second rod-receiving recess is defined by a pair of spaced apart arms of the body.

[0106] (16) The connector of embodiment 14, wherein the first rod receiving recess is open in a distal direction and the second rod receiving recess is open in a proximal direction. (17) The connector of embodiment 14, wherein the rod pusher axis is substantially perpendicular to the proximal-distal axis. (18) The connector of embodiment 14, further comprising a set screw threadably received in the body for locking a first rod within the first rod receiving recess and locking a second rod within the second rod receiving recess. (19) The implant of embodiment 1, wherein the implant comprises a bone anchor assembly, the body comprises a receiving member for the bone anchor assembly, and the retaining member comprises a set screw or a locking element. (20) An implant comprising: a body having a rod receiving recess, the body having a first side and a second side defining an opening to the rod receiving recess, the rod receiving recess defining a central longitudinal rod axis extending between the opening in the first side and the opening in the second side; a gripping insert configured to be positioned in an open end of the receiving recess and defining an inner surface for contacting a rod disposed in the rod-receiving recess, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis, each gripping groove defining two edges where the gripping grooves intersect the inner surface, the four edges of the two gripping grooves together defining a circular radius centered on the central longitudinal rod axis; a retaining member configured to move relative to the body to exert a force against a rod in the rod-receiving recess and to engage the four edges of the grip with the rod, a retention member, wherein the engagement of the four edges of the gripping groove to the rod serves to limit rotational movement of the rod about the central longitudinal rod axis.

Claims

1. An implant, a body having a rod receiving recess, the body having a first side and a second side, the first side and the second side defining the rod receiving recess therebetween, a rod disposed in the rod receiving recess defining a central longitudinal rod axis extending between the first side and the second side, at least a portion of the rod receiving recess being formed by an inner surface of the implant, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis; a body, each gripping groove defining two edges where the gripping groove intersects the inner surface, the four edges of the two gripping grooves together defining a circular radius about the central longitudinal rod axis; a retaining member configured to move relative to the body and exert a force on the rod in the rod-receiving recess perpendicular to the central longitudinal rod axis and engage the rod against the four edges of the two gripping grooves, a retaining member, wherein the engagement of the four edges of the two gripping grooves with the rod serves to limit rotational movement of the rod about the central longitudinal rod axis; The rod-receiving recess defines a gap between the two gripping grooves sized and positioned to allow the force on the rod within the rod-receiving recess to deflect one or both of the four edges and the rod where the four edges engage the rod, the deflection moving the rod into the gap.

2. The implant of claim 1 , wherein the inner surface of the rod-receiving recess between the two gripping grooves is positioned away from the central longitudinal rod axis a distance greater than a radius of the rod.

3. An implant, a body having a rod receiving recess, the body having a first side and a second side, the first side and the second side defining the rod receiving recess therebetween, a rod disposed in the rod receiving recess defining a central longitudinal rod axis extending between the first side and the second side, at least a portion of the rod receiving recess being formed by an inner surface of the implant, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis; a body, each gripping groove defining two edges where the gripping groove intersects the inner surface, the four edges of the two gripping grooves together defining a circular radius about the central longitudinal rod axis; a retaining member configured to move relative to the body and exert a force on the rod in the rod-receiving recess perpendicular to the central longitudinal rod axis and engage the rod against the four edges of the two gripping grooves, a retaining member, wherein the engagement of the four edges of the two gripping grooves with the rod serves to limit rotational movement of the rod about the central longitudinal rod axis; 11. The implant of claim 1, further comprising: a compression member disposed in a cavity formed in the body, the compression member having an inner surface that defines at least a portion of the rod receiving recess, the inner surface of the compression member having the two gripping grooves formed therein.

4. The implant of claim 1 , wherein the two gripping grooves extend along the entire length of the inner surface of the rod-receiving recess in the direction of the central longitudinal rod axis.

5. The implant of claim 1 , wherein the two gripping grooves are positioned on opposite sides of the retention member relative to the central longitudinal rod axis.

6. 2. The implant of claim 1, wherein the rod receiving recess defines an open end sized to receive the rod and a closed end sized to contact the rod, and the two gripping grooves are symmetrically disposed about an axis extending from the open end to the closed end.

7. The implant of claim 1 , wherein the body of the implant defines the inner surface that forms the rod-receiving recess.

8. The implant of claim 1 , wherein the intersection between the two gripping grooves and the inner surface defines a sharp edge.

9. An implant, a body having a rod receiving recess, the body having a first side and a second side, the first side and the second side defining the rod receiving recess therebetween, a rod disposed in the rod receiving recess defining a central longitudinal rod axis extending between the first side and the second side, at least a portion of the rod receiving recess being formed by an inner surface of the implant, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis; a body, each gripping groove defining two edges where the gripping groove intersects the inner surface, the four edges of the two gripping grooves together defining a circular radius about the central longitudinal rod axis; a retaining member configured to move relative to the body and exert a force on the rod in the rod-receiving recess perpendicular to the central longitudinal rod axis and engage the rod against the four edges of the two gripping grooves, a retaining member, wherein the engagement of the four edges of the two gripping grooves with the rod serves to limit rotational movement of the rod about the central longitudinal rod axis; The implant, wherein the inner surface defines a groove that intersects with at least one gripping groove, the intersection of the grooves dividing the edges of the at least one gripping groove and defining four corners for resisting translation of the rod along the central longitudinal rod axis when the rod engages the four edges.

10. The implant of claim 9, wherein the groove that intersects with the at least one gripping groove is oriented perpendicular to the at least one gripping groove.

11. An implant, comprising: a body having a rod receiving recess, the body having a first side and a second side, the first side and the second side defining the rod receiving recess therebetween, a rod disposed in the rod receiving recess defining a central longitudinal rod axis extending between the first side and the second side, at least a portion of the rod receiving recess being formed by an inner surface of the implant, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis; a body, each gripping groove defining two edges where the gripping groove intersects the inner surface, the four edges of the two gripping grooves together defining a circular radius about the central longitudinal rod axis; a retaining member configured to move relative to the body and exert a force on the rod in the rod-receiving recess perpendicular to the central longitudinal rod axis and engage the rod against the four edges of the two gripping grooves, a retaining member, wherein the engagement of the four edges of the two gripping grooves with the rod serves to limit rotational movement of the rod about the central longitudinal rod axis; An implant, wherein at least one gripping groove defines an inner surface having one or more protrusions formed therein, the one or more protrusions extending into edges positioned to contact the rod when the rod engages the four edges of the two gripping grooves.

12. The implant of claim 1 , wherein the two gripping grooves are formed by protrusions extending from the inner surface.

13. the implant comprises a connector, the rod receiving recess is a first rod receiving recess, the body defines a second rod receiving recess, one or both of the first rod receiving recess and the second rod receiving recess have the two gripping grooves, the body has proximal and distal ends defining a proximal-distal axis extending therebetween; The implant of claim 1 , wherein the retention member is slidably disposed within a tunnel formed in the body and configured to translate relative to the body along a rod pusher axis.

14. The implant of claim 13 , wherein the second rod-receiving recess is defined by a pair of spaced apart arms of the body.

15. 14. The implant of claim 13, wherein the first rod receiving recess is distally open and the second rod receiving recess is proximally open.

16. The implant of claim 13, wherein the rod pusher axis is substantially perpendicular to the proximal-distal axis.

17. 14. The implant of claim 13, further comprising a set screw threadably received in the body for locking a first rod in the first rod receiving recess and a second rod in the second rod receiving recess.

18. The implant of claim 1 , wherein the implant comprises a bone anchor assembly, the body comprises a receiving member for the bone anchor assembly, and the retaining member comprises a set screw or locking element.

19. An implant, a body having a rod receiving recess, the body having a first side and a second side, the first side and the second side defining the rod receiving recess therebetween, and a rod disposed in the rod receiving recess defining a central longitudinal rod axis extending between the first side and the second side; a gripping insert configured to be positioned in an open end of the rod-receiving recess and defining an inner surface for contacting the rod disposed in the rod-receiving recess, the inner surface defining two gripping grooves extending parallel to each other and to the central longitudinal rod axis, each gripping groove defining two edges where the gripping grooves intersect the inner surface, the four edges of the two gripping grooves together defining a circular radius centered on the central longitudinal rod axis; a retaining member configured to move relative to the body to exert a force on the rod in the rod-receiving recess and to engage the four edges of the two gripping grooves with the rod, a retention member, wherein the engagement of the four edges of the two gripping grooves on the rod serves to limit rotational movement of the rod about the central longitudinal rod axis.

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