Posterior fixation system

[0002] The present invention generally relates to orthopedic implants used for correction of spinal injuries or deformities, and more specifically, but not exclusively, concerns apparatuses for fixing a portion of the spine, such as the cervical spine, to allow correction or healing thereof.

[0003] In the realm of orthopedic surgery, it is well known to use implants to fix the position of bones. In this way, the healing of a broken bone can be promoted, and malformations or other injuries can be corrected. For example, in the field of spinal surgery, it is well known to place such implants into vertebrae for a number of reasons, including (a) correcting an abnormal curvature of the spine, including a scoliotic curvature, (b) to maintain appropriate spacing and provide support to broken or otherwise injured vertebrae, and (c) perform other therapies on the spinal column.

[0004] Typical implant systems include several pieces, which commonly are useful and may be associated with only specific other pieces. Bone screws, hooks, and clamps are well know as fixation devices, which are connected or adjoined to a particular bone as a connection between the remainder of the implant and the bone. Specially formed plates or rods are commonly used as stabilization and support members. Thus, in a common spinal implant system, a spinal plate is implanted along one or more vertebrae by driving a bone screw through the plate and into each of two vertebrae. The vertebrae are thus supported and kept in a particular position by the plate, so as to promote healing. One example of such an instrumentation system is U.S. Pat. No. 5,735,853 to Olerud.

[0005] Alternatively, a rod can be used as the support and stabilizing member. In such an implant, a series of two or more screws are inserted into two or more vertebrae to be instrumented. A rod is then placed within or coupled to the heads of the screws, or is placed within a connecting device that links the rod and a screw head, and the connections are tightened. In this way, a rigid supporting structure is fixed to the vertebrae, with the rod providing the support that promotes correction of the vertebral malformation or injury.

[0006] Many varieties of bone fixation devices (e.g. screws and hooks) are monoaxial in construction. That is, such devices are connected to the rod or plate such that a longitudinal axis through the rod or plate and a longitudinal axis through the fixation device are capable of only a single position with respect to each other. While useful in certain circumstances, in many therapeutic situations the degree of precision required to use such an inflexible device is impractical, or can lead to a longer duration of surgery, potentially awkward angles for the surgeon and for the patient, with the potential for attendant complications such as pain and/or extended rehabilitation.

[0007] More recently, bone fixation devices having multi-axial capability have been introduced. Examples of such constructs are shown in U.S. Pat. Nos. 5,797,911, 5,954,725, and 5,810,818. These devices help to reduce the required precision of placement of the fixation device, since a head portion of the fixation device is multi-axially positionable around the bone-threaded or hook portion. The head can thus be positioned so as to easily receive the rod, limiting or removing much of the positioning difficulty inherent in prior devices.

[0008] Most such devices are designed for spinal fixation at the thoracic and lumbar levels. Accordingly, there is a need in the art for a comprehensive multi-axial spinal implant system, and particularly one that is useful in the cervical region of the spine.

[0009] One form of the present invention is a unique multi-axial bone attachment assembly. Other forms concern a unique spinal implant system, a unique orthopedic fixation plate, a unique cross-link connector, and another unique multi-axial bone attachment assembly.

[0010] A further form of the present invention is directed to a unique multi-axial bone attachment assembly that includes a saddle member, a bone anchoring member, and a washer (crown member). The saddle member has a plurality of upright portions that define a channel through the saddle member. The saddle member further has a hole therethrough bounded by an inner wall, and the hole forms a lower opening in the saddle member. The bone-anchoring member extends through the opening. The bone-anchoring member includes a head portion and an anchoring portion. The washer has a recessed portion for accommodating an orthopedic rod and may include a radially extending projection. The washer is fitted within the hole of the saddle member and atop the bone-anchoring member.

[0011] Yet another form concerns a unique spinal implant system. A saddle member has a plurality of upright portions that define a channel through the saddle member. The saddle member further has a transverse hole defined through the upright portions that is transverse with respect to the channel. A bone-anchoring member is coupled to the saddle member for anchoring the saddle member to bone. An offset member is adapted to couple to an orthopedic rod, and the offset member has a coupling member and a body adapted to couple to the rod. The coupling member extends from the body and through the transverse hole of the upright members.

[0012] Another form is directed to a unique cross-shaped orthopedic plate. The plate includes a cross-shaped member. The cross-shaped member has a longitudinal axis connecting first and second longitudinal ends and a transverse axis connecting first and second transverse ends. The cross-shaped member has a plurality of apertures therethrough. At least one saddle member is attached to the cross-shaped member, and the saddle member has a plurality of upright portions that define a channel through the saddle member.

[0013] A further form concerns a unique cross-link connector. The connector includes a plurality of coupling ends each adapted to couple to an orthopedic rod. A cylindrical member is integrally connected to the coupling ends. The cylindrical member has a cylindrical shape for permitting multi-axial bending of the cylindrical member.

[0014] Still yet another form is directed to a unique multi-axial bone attachment assembly. A saddle member has a plurality of upright portions that define a channel through the saddle member. The saddle member further has a hole therethrough bounded by an inner wall, and the hole forms a lower opening in the saddle member. A bone-anchoring member extends through the opening. The bone-anchoring member includes a coupling portion provided in the hole for permitting multi-axial movement of the anchoring member and an anchoring portion. An expansion member is coupled to the anchoring member for expanding the coupling portion in order to lock the anchoring member into position.

[0015] The present invention provides a modular fixation system that allows a surgeon multiple treatment options for patients, allowing the surgeon to adapt the treatment to specific patient anatomy. The concepts surrounding the present invention are specifically designed for cervical vertebral fixation, but could be extended to include thoracic, lumbar and sacral fixation. Other advantages and objects of the present invention will be evident in view of the following specification and drawings.

[0016] FIG. 1 shows a partial cross-sectional view of a bone anchor assembly according to one embodiment of the present invention.

[0017] FIG. 2 shows a side view of a saddle member according to the embodiment shown in FIG. 1.

[0018] FIG. 3 shows a cross-sectional view of the saddle member taken along line III—III in FIG. 2.

[0019] FIG. 4 shows a top view of the saddle member of FIG. 2.

[0020] FIG. 5 shows an enlarged cross-sectional view of the saddle member taken along line V—V in FIG. 3.

[0021] FIG. 6 shows a side view of an anchor member according to one embodiment.

[0022] FIG. 6ashows a side view of an anchor member according to another embodiment.

[0023] FIG. 7 shows an enlarged cross-sectional view of threads of the embodiment of the anchor member shown in FIG. 6.

[0024] FIG. 8 shows a top view of the anchor member of FIG. 6.

[0025] FIG. 9 shows a perspective view of a washer according to one embodiment of the present invention.

[0026] FIG. 10 shows a top view of the washer of FIG. 9.

[0027] FIG. 11 shows a cross-sectional view of the washer of FIG. 9

[0028] FIG. 12 shows a top view of another embodiment of a washer according to the present invention.

[0029] FIG. 13 shows a side view of a set screw according to one embodiment of the present invention.

[0030] FIG. 14 shows a top view of the set screw of FIG. 13.

[0031] FIG. 15 shows a side view of a set screw according to another embodiment of the present invention.

[0032] FIG. 16 shows a top view of the set screw of FIG. 15.

[0033] FIG. 17 shows a perspective view of a snap ring for use in the present invention.

[0034] FIG. 17ashows a side view of an alternative embodiment of a snap ring for use in the present invention.

[0035] FIG. 18 shows a top view of the snap ring of FIG. 17.

[0036] FIG. 19 shows a top view of an orthopedic plate according to one embodiment.

[0037] FIG. 20 shows a side view of the orthopedic plate of FIG. 19.

[0038] FIG. 21 shows a cross-sectional view of the orthopedic plate taken along line XXI—XXI in FIG. 19.

[0039] FIG. 22 shows a cross-sectional view of a portion of the orthopedic plate taken along line XXII—XXII in FIG. 19.

[0040] FIG. 23 shows a cross-sectional view of a portion of the orthopedic plate taken along line XXIII—XXIII in FIG. 20.

[0041] FIG. 24 shows a perspective view of a bone anchor assembly according to another embodiment of the present invention.

[0042] FIG. 25 shows a perspective view of an embodiment of a hook member of the assembly of FIG. 24.

[0043] FIG. 26 shows a front view of the hook member of FIG. 25.

[0044] FIG. 27 shows a perspective view of the bone anchor assembly of FIG. 24 prior to assembly.

[0045] FIG. 28 shows a partial cross-sectional view of an offset member according to another embodiment of the present invention.

[0046] FIG. 28ashows a partial cross-sectional view of an offset member according to a further embodiment of the present invention.

[0047] FIG. 29 shows a side view of the offset member of FIG. 28.

[0048] FIG. 30 shows a top view of the offset member of FIG. 28.

[0049] FIG. 31 shows an end view of the offset member of FIG. 28.

[0050] FIG. 32 shows a cross-sectional view of the offset member of FIG. 28.

[0051] FIG. 33 shows a side view of an offset member and a set screw according to a further embodiment of the present invention.

[0052] FIG. 34 shows a cross-sectional view of the offset member of FIG. 33.

[0053] FIG. 35 shows a top view of the offset member of FIG. 33.

[0054] FIG. 36 shows an end view of the offset member of FIG. 33.

[0055] FIG. 37 shows an end view of the set screw of FIG. 33.

[0056] FIG. 38 shows a cross-sectional view of the set screw taken along line XXXVIII—XXXVIII in FIG. 37.

[0057] FIG. 39 shows a cross-sectional view of the set screw of FIG. 37.

[0058] FIG. 40 shows a side view of a cross-link connector according to another embodiment of the present invention.

[0059] FIG. 41 shows a top view of the cross-link connector of FIG. 40.

[0060] FIG. 42 shows an enlarged view of a portion of the cross-link connector of FIG. 40.

[0061] FIG. 43 shows a cross-link connector with an arched cylindrical member.

[0062] FIG. 44 shows an end view of a set screw according to another embodiment of the present invention.

[0063] FIG. 45 shows a cross-sectional view of the set screw taken along line XLV—XLV in FIG.44.

[0064] FIG. 46 shows a perspective view of a bone anchor assembly according to a further embodiment of the present invention.

[0065] FIG. 47 shows an exploded view of the bone anchor assembly of FIG. 46.

[0066] FIG. 48 shows a cross-sectional view of a hook member.

[0067] FIG. 49 shows a top view of an occipital-cervical rod.

[0068] FIG. 50 shows a side view of an occipital-cervical rod.

[0069] FIG. 51 shows a cross-sectional view of the occipital-cervical rod taken along line LI—LI in FIG. 49.

[0070] FIG. 52 shows a cross-sectional view of the occipital-cervical rod taken along line LII—LII in FIG. 49.

[0071] FIG. 53 shows a partial cross-sectional view of a bone anchor assembly according to another embodiment of the present invention.

[0072] FIG. 54 shows a cross-sectional view of an embodiment of a saddle member shown in FIG. 53.

[0073] FIG. 55 shows a top view of the saddle member of FIG. 54.

[0074] FIG. 56 shows a cross-sectional view of a washer shown in FIG. 53.

[0075] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein, being contemplated as would normally occur to one skilled in the art to which the invention relates.

[0076] In FIG. 1, there is shown an embodiment of a multi-axial bone anchor assembly 20 according to the present invention. Bone anchor assembly 20 includes a saddle member 22, a bone anchoring member 24, and a washer (crown member) 26. In some embodiments, assembly 20 will further include a C-shaped snap ring 28 and a set screw 30, which are fitted with saddle member 22 as will be described hereafter.

[0077] As shown in FIGS. 1-4, saddle member 22 generally has a U-shape, with two upright portions 32 defining a channel 34 extending through saddle member 22. Channel 34 is then configured to accommodate an elongated member 36, such as a spinal rod. For posterior cervical fixation, rod 36 may have one of a number of desired lengths. As seen in FIG. 1, the width of channel 34 is slightly larger than the diameter of rod 36, which allows easier insertion of rod 36 into channel 34, also allows for compensation for contouring of the rod, and allows use of a range of rod sizes with the same saddle member 22. Saddle member 22 further includes a hole 38 therethrough, hole 38 being in one particular embodiment substantially perpendicular to channel 34 and substantially parallel to upright portions 32.

[0078] In a particular embodiment of saddle member 22, illustrated in FIGS. 2-5, upright portions 32 each have an outer surface 40 and an inner surface 42. Inner surfaces 42 are parallel to hole 38, along a longitudinal axis of saddle member 22. Outer surfaces 40 are angled with respect to inner surfaces 42 and the longitudinal axis of saddle member 22. In one specific embodiment, outer surfaces 40 have an inward taper 43, which taper allows for easier handling of the saddle member 22 and reduced bulk of saddle member 22. Near the bottom of saddle member 22, hole 38 is narrowed by a wall portion 44. Below wall portion 44, hole 38 opens outward by virtue of a conical wall portion 46. Conical wall portion 46 allows bone anchor member 24 to be positioned in any of an infinite number of angular positions relative to saddle member 22 by reducing interference of the lower portion of saddle member 22 with a shank portion of bone anchor member 24.

[0079] The illustrated embodiment of saddle member 22 further includes an inner groove 48 that extends around hole 38. Groove 48 is configured to accommodate snap ring 28 in a compressed condition, i.e., the outer diameter of groove 48 is at least slightly smaller than the normal uncompressed outer diameter of snap ring 28. The illustrated embodiment of saddle assembly 22 further includes a trough 50 extending longitudinally within each of upright portions 32. Trough 50 accommodates placement of washer 26, as further described below, and may have a rounded (e.g. cylindrical), squared, or other appropriate shape to accommodate washer 26. Upright portions 32 further include an internally threaded portion 52, as shown in FIGS. 1 and 3. Internally threaded portions 52 are configured to be threadedly coupled with set screw 30, as described hereafter.

[0080] As shown in FIGS. 6-8, one embodiment of the bone anchor member 24 of the present invention has a threaded portion 56 and a head portion 58. In a specific embodiment, threaded portion 56 includes a thread 60 having a forward or leading flank 62 and a rearward or load flank 64 and a root surface 66, in which load flank 64 and root surface 66 form an acute angle. Such an acute angle between load flank 64 and root surface 66 may be termed a “reverse angle” thread.

[0081] Head portion 58 of bone anchor member 24 includes a lower head portion 68 and an upper head portion 70. Lower head portion 68 is generally convex, and in one embodiment forms part of a sphere. In the illustrated embodiment, the lower head portion 68 extends from a shank portion 72 in a direction away from threaded portion 56, and stops at/or before a tangent to lower head portion 68 would be parallel to a longitudinal axis L of bone anchor member 24. Upper head portion 70 is also generally convex, and forms a part of a sphere in the illustrated embodiment. Upper head portion 70 is diametrally smaller than lower head portion 68 and head portions 68 and 70 are connected by a lip 74. A tool-engaging recess 76 is formed in upper head portion 70, and may extend into lower head portion 68. In another embodiment shown in FIG. 53, head portion 58aof bone anchor member 24adoes not have a lip 74.

[0082] Referring now to FIGS. 9-11, there is shown an embodiment of washer 26 of the present invention. Washer 26 includes an upper portion 80, a lower portion 82, and a hole 84 therethrough. Upper portion 80 and lower portion 82 may be constructed integrally or may be separately constructed and attached together in any known manner. An upper surface 86 of upper portion 80 includes recessed portions 88 in the illustrated embodiment, which recessed portions 88 form a part of a cylinder sized and configured to accommodate placement of an elongated member (such as rod 36 of FIG. 1) therein. Lower portion 82 further includes an upper surface 83 that faces snap ring 28.

[0083] Referring now to FIG. 11, washer 26 has a hole 84 provided through both upper portion 80 and lower portion 82. Hole 84 includes a lower concave surface 96 and a cylindrical surface 98. Concave surface 96 in one specific embodiment has a spherical shape so as to substantially coincide with a portion of upper head portion 70 of anchoring member 24. Lower portion 82 is generally in the shape of a circular disc, and includes two projections 90 extending radially therefrom. Projections 20 in conjunction with troughs 50 align recessed portions 88 of washer 26 with channel 34 and prevent rotation of washer 26 so as to minimize misalignment between rod 36 and recessed portions 88.

[0084] In one embodiment, shown in FIGS. 9-10, projections 90 each include two substantially planar side surfaces 92, and an end surface 94 that is rounded and may form a portion of a cylinder. Projections 90 are sized and shaped so as to fit and slide easily within the troughs 50 upright portions 32 of saddle member 22. In another embodiment illustrated in FIG. 12, projections 90a each include a rounded end surface 100.

[0085] Multi-axial bone anchor assembly 20 can further include a set screw 30. As illustrated in FIGS. 13-16, set screw 30 is generally cylindrical and has external threads 102. External threads 102, in one embodiment, are buttress threads. In another embodiment, threads 102 could be reverse angle threads so as to minimize splaying between the two upright members 32. An example of such reverse angle threading is disclosed in U.S. patent application Ser. No. 09/188,825, which is hereby incorporated by reference.

[0086] Set screw 30, in the embodiment illustrated in FIGS. 13-14, has at one end a tool-engaging portion 104. Tool-engaging portion 104 has a rounded end surface 106 and substantially planar tool-engaging surfaces 108. Since end surface 106 is rounded, internal trauma to a patient can be reduced. Tool-engaging surfaces 108, in one embodiment, are oriented in a hexagonal configuration. Once set screw 30 is secured to saddle member 22, tool engaging portion 104 can be sheared off or otherwise removed so as to further reduce the profile of assembly 20. As illustrated in FIGS. 15-16, another embodiment of set screw 30aincludes a substantially flat end surface 110 in order to minimize the profile of assembly 20. Set screw 30afurther includes a tool-engaging bore 112. Tool-engaging bore 112 is used in conjunction with a tool for introducing set screw 30ainto saddle member 22.

[0087] In certain embodiments, multi-axial bone anchor assembly 20 includes snap ring 28 in order to secure washer 26 against anchoring member 24. One embodiment of such a snap ring 28 is shown in FIGS. 17-18. Snap ring 28 has a central opening 114 and a compression slot 116 defined therein. Snap ring 28 further has a first surface 118, an opposite second surface 120, an inner lateral surface 122 defining opening 114, and an outer lateral surface 124. Compression slot 116 allows snap ring 28 to compress and fit into inner groove 48 of saddle member 22. The diameter of the entrance of groove 48 is at least slightly smaller than the outer diameter 126 of an uncompressed snap ring 28. Opening 114 of snap ring 28 has an inner diameter, which allows snap ring 28 to fit around upper portion 80 of washer 26. One of the surfaces 118 and 120 engage the upper surface 83 of lower portion 82 in order to secure washer 26. Snap ring 28 can have a square cross-section, as shown in FIG. 1, or a circular or other appropriate shape cross-section, and in one particular embodiment is made of a shape memory alloy such as nitinol.

[0088] Another embodiment of snap ring 28′ is illustrated in FIG. 17a.Snap ring 28′ is non-planar, and in one embodiment has a series of undulations forming relative crests 129aand relative troughs 129btherein. Alternatively, non-planar snap ring 28′ could have other curved configurations, or could have extending finger-spring elements along it. When assembly 20 (or assembly 262 described below) is assembled, non-planar snap ring 28′ allows less play between saddle member 22, anchoring member 24 and washer 26 (or similar parts of assembly 262, described below) because non-planar snap-ring 28′ fills a greater portion of groove 48 of saddle member 22.

[0089] An embodiment of an orthopedic fixation plate 130 according to the present invention is illustrated in FIGS. 19-23. In one form, orthopedic plate 130 is secured to the occipital bone of a skull. However, it should be appreciated that plate 130 can be secured to other bones. Orthopedic plate 130 includes a cross-shaped member 132 having a first longitudinal arm (end) 134 to a second longitudinal arm (end) 136 along a longitudinal axis. Cross-shaped member 132 further has a first transverse arm (end) 138 and a second transverse arm (end) 140 connected together along an axis transverse with respect to the longitudinal axis. Orthopedic plate 130 further includes a pair of saddle members 22aintegrally formed on or joined to longitudinal arms 134 and 136. It should be appreciated that saddle members 22 can also be pivotally coupled to cross-shaped member 132 so as to provide greater positioning freedom. As illustrated in FIG. 22, saddle members 22aeach include a pair of upright members 32aand a channel 34adefined between upright members 32a.Upright members 32ainclude threaded portions 52aconfigured to be threadedly coupled to a set screw 30 in a manner as described above.

[0090] Orthopedic plate 130, in one embodiment, includes a set of apertures 142. Bone anchors 24b(FIG. 6a) are secured in apertures 142 in order to secure plate 130 to the occipital bone of the skull. As shown in FIG. 6a,anchor 24bincludes a head portion 58b having a convex underside 59a,which may be spherical, and a beveled top 59baround a tool-engaging recess 59c.Apertures 142 shown in FIGS. 19-23 for the particular embodiment are provided on both the longitudinal arms 134, 136 and the transverse arms 138, 140 in a cross configuration in order to provide greater stability. As shown in FIG. 23, aperture 142 includes a lower conical portion 144 and an upper conical portion 146. Lower conical portion 144 widens towards a lower surface 148 of orthopedic plate 130, and upper conical portion 146 widens towards an upper surface 150 of orthopedic plate 130. Upper and lower conical portions 144,146 allow a bone screw to be easily positioned at varying angular positions relative to orthopedic plate 130. In one embodiment, opposing walls of lower conical portion 146 are oriented at about sixty degrees (60°) with respect to one another, and opposing walls of upper conical portion 146 are oriented at about forty-five degrees (45°) with respect to one another. Cross member 130 further includes a beveled outer peripheral surface 152 between lower surface 148 and upper surface 150.

[0091] In one particular embodiment, cross member 132 is curved along the longitudinal axis between longitudinal arms 134 and 136, and is also slightly curved along the transverse axis. This curvature of cross member 132 allows orthopedic plate 130 to better match the contour of the occipital bone of the skull. It should be understood that cross member 132 can also be curved along only one of the axes or substantially flat along both axes or can be otherwise contoured prior to or during surgery in order to match specific patient anatomy.

[0092] In FIG. 24, there is shown another embodiment of a multi-axial bone anchor assembly 160 according to the present invention. Anchor assembly includes a saddle member 162 and an offset connector 164 coupled to saddle member 162. As shown in FIGS. 25-26, saddle member 162 essentially includes the same features as described above in reference to saddle member 22. Saddle member 162 includes two upright portions 32bdefining channel 34b.Channel 34bis configured to accommodate an elongated member 36b.Upright portions 32beach has outer surface 40bthat is angled with respect to inner surface 42b.Upright portions 32bfurther include an internally threaded portion 52b.Internally threaded portions 52bare configured to be threadedly coupled with set screw 30.

[0093] Additionally, saddle member 162 includes a transverse hole 166 defined in both upright portions 32b.Transverse hole 166 is oriented transverse with respect to channel 34b,and transverse hole 166 is adapted to receive a rod (such as rod 36 in FIG. 1) or offset connector 164. This configuration between channel 34band transverse hole 166 provides a physician with greater flexibility during surgery, since offset connector 164 can be oriented at different angles with respect to saddle member 162. Offset connector 164 further can be laterally positioned at any of an infinite number of distances from saddle member 162, because transverse hole 166 passes through both upright portions 32. Further, saddle member 162 is dually useful, because a rod (such as rod 36 in FIG. 1) or offset connector 164 can be coupled to either channel 34bor transverse hole 166.

[0094] Saddle member 162, in one embodiment, further includes a hook member 168 for engaging bones in a generally known manner. Hook member 168 has a curved portion 170 extending from upright portions 32 and a substantially straight portion 172 extending from curved portion 170. Straight portion 174 has a beveled bottom surface 174, which reduces trauma when hook member 168 is attached. It should be appreciated that hook member 168 could be replaced with another anchoring member, such as anchoring members 24 or 24a(FIGS. 6, 53) in order to attach saddle member 162 to a bone.

[0095] Referring now generally to FIGS. 27-32, offset connector 164 includes a coupling member 176 integrally formed or otherwise joined to a body 178. In one form, coupling member 176 is a cylindrical rod. Body 178 has a rod receiving bore 180 that is adapted to receive rod 36 and a threaded bore 182 that intersects rod receiving bore 180. A set screw 30 is screwed into threaded bore 182 in order to secure rod 36 to offset connector 164. Body 178 further can include a beveled outer edge 184 (FIG. 27) in order to minimize trauma to a patient. In another embodiment shown in FIGS. 28-32, rod receiving bore 180 has a slot 186 defined therein. Edges 187 are formed between slot 186 and rod receiving bore 180. Edges 187 along with set screw 30 provide three lines of contact with a rod 36 coupled to offset connector 164 so as to strengthen the connection. In still yet another embodiment shown in FIG. 28a,offset connector 164ahas a pair of upright portions 32cdefining a channel 34cadapted to receive a rod. Upright portions 32chave internally threaded portions 52cfor engaging a set screw 30.

[0096] Referring now to FIG. 27, offset connector 164 is coupled to saddle member 162 by inserting coupling member 176 in direction A into transverse hole 166. Set screw 30 is used to secure coupling member 176 to saddle 160. Offset connector 164 can be laterally positioned with respect to saddle member 162 by moving coupling member 176 within transverse hole 166.

[0097] An offset connector 188 along with a set screw 189 according to still yet another embodiment of the present invention are shown in FIGS. 33-39. As shown in FIGS. 33-36, offset connector 188 includes a coupling member 176, and a pair of laterally oriented body members 190 and 192. A channel 194 is defined between body members 190 and 192, and channel 194 is adapted to receive rod 36. One of the body members 192 is slightly longer than the other and has a threaded bore 196 defined therein. Set screw 189 is threaded into bore 196 so as to secure rod R to offset connector 188. As illustrated in FIGS. 37-39, set screw 189 is generally cylindrical and has threads 198. Set screw 189 further has a tool engaging bore defined in one end and a pointed tip 202 at the other end. Pointed tip 202 engages rod 36 when rod 36 is coupled to offset connector 188.

[0098] A cross-link connector 204 according to one embodiment, which is illustrated in FIGS. 40-42, is adapted to be bent about multiple axes. Cross-link connector 204 has a pair of coupling ends 206 integrally connected together with a cylindrical member 208. The cylindrical shape of cylindrical member 208 allows cross-link connector 204 to be bent in any of an infinite number of directions. In one particular embodiment shown in FIG. 43, cylindrical member 208ais pre-formed with an arch so as to avoid any obstructions between the two ends 206. Each coupling end 206 includes a threaded bore 210 with an opening 211 in which a set screw 30 is threaded and a curved member 212 that defines a cavity 214 adapted to receive rod R. Opening 215 of cavity 214 is defined in a side of cross-link connector 204 opposite opening 211 of threaded bore 210. This configuration allows cross-link connector 204 to be secured to adjacent rods after the adjacent rods are situated within the patient. In one embodiment, threaded bore 210 is positioned at about fifty-five degrees (55°) relative to a longitudinal axis that extends between the ends 206. Cross-link connectors are used to link adjacent rods within a patient. An obstruction (such as another rod or bone) may prevent a typical cross-link connector from linking adjacent rods together. The cross-link connector 204 of the present invention solves this problem by being adapted to bend along multiple axes.

[0099] One embodiment of a set screw 216 that is adapted to be threaded into threaded bore 210 is illustrated in FIGS. 44-45. Set screw 216 has one end with a tool engaging bore 218, a rod engaging end 222 and a threaded portion 220 provided between both ends. Rod engaging end 222 has a frusto-conical portion 224 adjacent threaded portion 220 and a flat portion 226, which frusto-conical portion 224 contacts rod 36. In one form, frusto-conical portion 224 has an angle 228 of about forty degrees (40°).

[0100] In FIG. 46, there is shown a multi-axial bone anchor assembly 230 according to another embodiment of the present invention. Assembly 230 has a generally U-shaped saddle member 22, which was described above with reference to FIGS. 2-5, coupled to a hook anchor member 168a.In this embodiment, saddle member 22 may be formed without groove 48. As previously discussed, saddle member 22 has a pair of upright portions 32 that define channel 34. Set screw 30 is threadedly secured to threaded portion 52 of saddle member 22 in order to secure rod 36 to saddle member 22. As shown in FIGS. 47-48, hook member 168ahas a curved portion 170aand a substantially straight portion 172a.In this embodiment, hook member 168afurther includes a coupling (head) portion 232 that is coupled to saddle member 22. Coupling portion 232 includes coupling members 234 and a threaded hole 236 adapted to receive expansion member 238. In one form, coupling portion 232 includes four members 234 having a part-spherical outer surface and expansion member 238 is a set screw. In one form, expansion member 238 at one end has a tool engaging portion 240 and a threaded portion 242 at the other end for securing expansion member 238 into hole 236. Expansion member 238 further includes an expansion portion 244 located between tool engaging portion 240 and threaded portion 242. Expansion portion 244 contacts and expands semispherical members 234 to anchor saddle member 22 to hook member 168 and prevents further rotation. In one form, expansion portion 244 has a conical shape.

[0101] In use, coupling portion 232 is inserted into hole 38 through the bottom of saddle member 22. When saddle member 22 is coupled to hook member 168a,the spherical shape formed between semispherical members 234 allows saddle member 22 to rotate about multiple axes. Expansion member 238, once secured in hole 236 causes coupling members 234 to splay into contact with saddle member 22, thereby fixing the relative position between saddle member 22 and hook member 168.

[0102] An embodiment of an occipital-cervical rod 246, which can be attached to the above-described assemblies, is illustrated in FIGS. 49-52. Occipital-cervical rod 246 includes a plate portion 246a,through which a plurality of apertures 248 are formed, and a rod portion 246b.Apertures 248 may be oblong in shape. Defined along plate portion 246aare an upper surface 250, a curved lower surface 252, and a pair of beveled side surfaces 254 between upper surface 250 and lower surface 252. Each aperture 248 includes an upper portion 256 that widens towards upper surface 250 and a lower portion 258 that widens towards lower surface 252. Grooves 260 are defined around plate portion 246aof occipital-cervical rod 246 and between adjacent apertures 248. Bone screws 24b(FIG. 6a) are inserted into apertures 248 in order to secure plate portion 246ato the occipital bone of a patient. Rod portion 246bextends along the spinal column and can be attached to the spinal column using the above-described or other connectors. Alternatively, plate portion 246acan be attached to one or more vertebrae using bone screws 24b(FIG. 6a), and rod portion 246bcan extend upward and be attached to the occipital bone using screws, hooks, cable, or other attachment members.

[0103] In FIG. 53, there is shown another embodiment of a multi-axial bone anchor assembly 262 according to the present invention. Bone anchor assembly 262 includes a saddle member 22d,a bone anchoring member 24a,and a washer 26d.Bone anchoring member 24adoes not have a lip 74. In some embodiments, assembly 262 will further include a C-shaped snap ring 28 and a set screw 30, which are fitted with saddle member 22din a manner described below.

[0104] As shown in FIGS. 54-55, saddle member 22dgenerally has a U-shape, with two upright portions 32ddefining a channel 34dextending through saddle member 22d.Channel 34dis then configured to accommodate an elongated member 36 (as described above). Saddle member 22dfurther includes a hole 38dtherethrough, hole 38dbeing in one particular embodiment substantially perpendicular to channel 34dand substantially parallel to upright portions 32d.Upright portions 32dare angled in a manner similar to the one as described above with reference to FIGS. 2-3. Near the bottom of saddle member 22d,hole 38dis narrowed by a wall portion 44d.Below wall portion 44d,hole 38dopens outward by virtue of a wall portion 46d.Wall portion 46dallows bone anchor member 24ato be positioned in any of an infinite number of angular positions relative to saddle member 22dby reducing interference of the lower portion of saddle member 22dwith a shank portion of bone anchor member 24a.

[0105] The particular illustrated embodiment of saddle member 22dfurther includes an inner groove 48d.As illustrated, groove 48dextends around hole 38d,and in this particular embodiment, groove 48dis uniform between a top portion of groove 48dand the bottom portion thereof. Groove 48dis configured to accommodate snap ring 28 in a compressed condition. Groove 48dhas a thickness 264 that is, in one form, thicker than snap ring 28. Further, the illustrated embodiment of saddle assembly 22din FIGS. 54-55 does not include a trough 50 that extends longitudinally within each of upright portions 32d.Upright portions 32dfurther include internally threaded portions 52d,which are configured to be threadedly coupled with set screw 30.

[0106] Referring now to FIG. 56, there is shown another embodiment of washer 26daccording to the present invention. Washer 26dincludes an upper portion 80d,a lower portion 82d,a snap ring recess 266, and a hole 84dtherethrough. Upper portion 80d,lower portion 82d,and snap ring recess 266 may be constructed integrally or may be separately constructed and attached together in any known manner. Snap ring 28 fits within recess 266 in order to secure washer 26dwithin saddle member 22d.In one embodiment, assembly 262 is assembled by inserting anchoring member 24athrough hole 38din saddle member 22d.Washer 26d,with snap ring 28 in at least a portion of recess 266, is then inserted into hole 38d.Snap ring 28 contracts into recess 266 as washer 26dgoes through saddle member 22d,and expands into groove 48dto hold washer 26dwithin saddle member 22d.An elongated member is then inserted in channel 34d,and a set screw (such as those described above) is threaded into internally threaded portions 52d,saddle member 22dto lock the elongated member, washer 26dand anchoring member 24atogether.

[0107] Washer 26dhas a hole 84dprovided through both upper portion 80dand lower portion 82d.Hole 84dincludes a lower concave surface 96dand a cylindrical surface 98d.Lower concave surface 96dis adapted to accommodate head portion 58aof anchor member 24a.In the particular embodiment illustrated in FIG. 56, lower portion 82dis generally in the shape of a circular disc. In this particular embodiment, lower portion 82ddoes not have projections 90.

[0108] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.