US20040143332A1 - Movable disc implant - Google Patents

Abstract

A disc implant is provided which maintains intervertebral spacing and stability within the spine. In an embodiment, a disc implant may include three or more components. Components of the implant may imitate certain physiological movements associated with a healthy spine. In certain embodiments, the components of the implant may limit physiological movements to within certain ranges, imitating normal spinal movements.

Description

PRIORITY CLAIM
• This application claims priority to U.S. Provisional Patent Application No. 60/422,764 entitled “MOVABLE DISC IMPLANT” filed on Oct. 31, 2002. The above-referenced provisional application is incorporated by reference as if fully set forth herein.[0001]
BACKGROUND
• 1. Field of Invention[0002]
• The present invention generally relates to the field of medical devices. Some embodiments of the invention relate to spinal disc implants and instruments used to insert the implants. Other embodiments of the invention relate to methods of forming spinal disc implants and methods for positioning the implants during surgical procedures.[0003]
• 2. Description of Related Art[0004]
• Bone may be subject to degeneration caused by trauma, disease and/or aging. Degeneration may destabilize bone and affect surrounding structures. For example, destabilization of a spine may result in alteration of a natural spacing between adjacent vertebrae. Alteration of a natural spacing between adjacent vertebrae may subject nerves that pass between vertebral bodies to pressure. Pressure applied to the nerves may cause pain and/or nerve damage. Maintaining the natural spacing between vertebrae may reduce pressure applied to nerves that pass between vertebral bodies. A disc implant may be used to maintain the natural spacing between vertebrae and to inhibit relative motion of the vertebrae.[0005]
• A disc space may be created by full or partial removal of an intervertebral disc between two vertebral bodies. Spinal implants for a lumbar region of the spine may be positioned in an intervertebral space after a discectomy procedure. The implant may be inserted using an anterior, lateral and/or posterior approach. The spinal implant may be a fusion device or an artificial disc. Conventional systems and methods for posterolateral spinal fusion may involve dissecting and retracting soft tissue proximate the surgical site. Dissection and retraction of soft tissue may cause trauma to the soft tissue and extend recovery time. Minimally invasive procedures and systems may reduce recovery time as well as trauma to the soft tissue surrounding a stabilization site.[0006]
• Spinal disc implants and/or disc implant insertion instruments are described in U.S. Pat. No. 5,676,701 to Yuan et al.; U.S. Pat. No. 5,401,269 to Buttner-Janz et al.; U.S. Pat. No. 5,370,697 to Baumgartner; U.S. Pat. No. 5,314,477 to Marnay and International Application No. WO 01/19295 to Marnay, all of which are incorporated by reference as if fully set forth herein.[0007]
SUMMARY
• In certain embodiments, a disc implant may be used to stabilize vertebrae of a human spine while allowing normal movement of the vertebrae relative to each other. An artificial disc implant may replace a diseased or defective intervertebral disc. An artificial disc implant may be easy to install with only minimal intrusion to adjacent tissue and muscle. A disc implant may introduce minimal risk of dural damage or neural damage during installation and use.[0008]
• An artificial disc implant may include one or more engaging plates and one or more members. Engaging plates may fit between and engage adjacent vertebrae of the spine. The plates may maintain a space between the adjacent vertebrae. One or more members may be positioned in the space between the engaging plates. Engaging plates and members may be designed to allow axial rotation, anteroposterior movement and/or lateral movement of adjacent vertebrae (i.e., the spine). Lateral movement may include lateral bending. Anteroposterior movement may include flexion and/or extension. In some embodiments, a range of motion of one engaging plate relative to another engaging plate may be limited.[0009]
• In some embodiments, an engaging plate may include a recess complementary to a portion of a member. In certain embodiments, an engaging plate may include slots. The slots may be dovetailed. The slots may be complementary to a portion of an instrument used to insert engaging plates between vertebrae. In some embodiments, slots may be formed at an angle relative to an anterior-posterior axis of an engaging plate. In some embodiments, an angular orientation of a recess may correspond to an angle of slots in an engaging plate. Angulation of the slots may allow insertion of a disc implant using a modified (e.g., angulated) anterior approach. A modified anterior approach may facilitate retraction of blood vessels above the L5 vertebrae.[0010]
• In certain embodiments, an engaging plate may include one or more coupling projections. One or more coupling projections may penetrate a vertebral surface. In some embodiments, a coupling projection may be positioned in a recess formed in a vertebral surface. Once positioned in the vertebra, the coupling projection may inhibit movement of an engaging plate relative to the vertebra.[0011]
• In some embodiments, a disc implant may include two engaging plates and a member. The member may have a convex portion. The engaging plates may be shaped to complement surfaces of the member, including the convex portion. The member may be positioned between the engaging plates to allow axial rotation, lateral and/or anteroposterior movement of a first engaging plate relative to a second engaging plate.[0012]
• In disc implant embodiments including two engaging plates and a member, the member may allow the engaging plates to undergo three independent components of motion relative to each other. The member may have a convex portion and a recess. The recess of the member may complement a projection on a first engaging plate to allow rotation of a first engaging plate relative to the member. The convex portion of the member may complement a concave portion of the second engaging plate to allow anteroposterior and/or lateral movement of the second engaging plate relative to the member.[0013]
• In some embodiments, a disc implant may include two engaging plates and two members. The members may allow the engaging plates to undergo three independent components of motion relative to each other. A convex portion of a first engaging plate may complement a concave portion of a first member to allow lateral bending of the first engaging plate relative to a second engaging plate. A projection on the first member may complement a recess in a second member to allow axial rotation of the first engaging plate relative to the second engaging plate. A convex portion of the second member may complement a concave portion of the second engaging plate to allow movement of the engaging plates relative to each other.[0014]
• In other disc implant embodiments including two engaging plates and two members, a first member may couple to a first engaging plate to allow axial rotation of the first engaging plate relative to a second engaging plate. A convex portion of the first member may complement a concave portion of a second member to allow lateral bending of the engaging plates relative to each other. A convex portion of the second member may complement a concave portion of the second engaging plate to allow flexion and/or extension of vertebrae adjacent to the engaging plates.[0015]
• In disc implant embodiments including a member and two engaging plates, a member may have a spherical shape. The member may be positioned between concave portions of the engaging plates. The member may allow axial-rotation, anteroposterior movement and/or lateral movement of the engaging plates relative to each other.[0016]
• An instrumentation set for a disc implant insertion procedure may include various guidance and/or insertion instruments. Insertion instruments may include, but are not limited to, chisels, reamers, hex drivers, slap hammers, inserters, distractors and pushers. An instrumentation set may include trial endplates and disc implant components. Trial endplates may be plates of various sizes and lordotic alignment. Trial endplates may include stops and/or instrument guides to facilitate removal of bone material from a vertebral surface. Distractors in combination with trial endplates may determine a size, height and lordotic alignment of implant components to be used in a disc implant insertion procedure. Implant components may include, but are not limited to, engaging plates of various sizes and lordotic alignment and members of various sizes and shapes.[0017]
• An inserter may be used to position engaging plates between two vertebrae. A distractor may be positioned between the engaging plates to establish a desired separation distance between the engaging plates. One or more members may be guided through a body of the distractor and into the space between the engaging plates. In some embodiments, members may be guided through a body of a distractor with a pusher. The pusher may maintain the position of the members when a distractor is removed from the inserter.[0018]
• In certain embodiments, trial endplates, members and engaging plates may be formed from various materials including plastics, ceramics, polymers, composites and metals. Materials may be chosen based on factors including, but not limited to, durability, biocompatibility, galling characteristics, mechanical strength and/or wear properties. In some embodiments, radiological markers may be used in combination with materials that are “invisible” to radiological techniques. In certain embodiments, steps may be taken to adjust a coefficient of friction of materials chosen to form members (e.g., surfaces may be polished or roughened). In other embodiments, surfaces of engaging plates and/or members may be coated to reduce noise created by contact of a member with an engaging plate and/or another member.[0019]
BRIEF DESCRIPTION OF THE DRAWINGS
• Advantages of the present invention will become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings in which:[0020]
• FIG. 1 is a perspective view of components of a disc implant.[0021]
• FIG. 2 is a bottom view of an embodiment of an engaging plate.[0022]
• FIG. 3 is a bottom view of an embodiment of an engaging plate.[0023]
• FIG. 4 is a cross-sectional view of an embodiment of a disc implant.[0024]
• FIG. 5 is a side view of components of a disc implant.[0025]
• FIG. 6 is a perspective view of components of a disc implant.[0026]
• FIG. 7 is a cross-sectional view of an embodiment of a disc implant.[0027]
• FIG. 8 is a bottom view of an engaging plate.[0028]
• FIG. 9 is a perspective view of components of a disc implant.[0029]
• FIG. 10 is a cross-sectional view of an embodiment of a disc implant.[0030]
• FIG. 11 is a perspective view of components of a disc implant.[0031]
• FIG. 12 is a top view of a member.[0032]
• FIG. 13 is a cross-sectional view of an embodiment of a disc implant.[0033]
• FIG. 14 is a perspective view of components of a disc implant.[0034]
• FIG. 15 is a cross-sectional view of an embodiment of a disc implant.[0035]
• FIG. 16 is a perspective view of components of a disc implant.[0036]
• FIG. 17 is a cross-sectional view of an embodiment of a disc implant.[0037]
• FIG. 18 is a perspective view of components of a disc implant.[0038]
• FIG. 19 is a cross-sectional view of an embodiment of a disc implant.[0039]
• FIG. 20 is a side view of an embodiment of a disc implant.[0040]
• FIG. 21 is a perspective view of an embodiment of a disc implant.[0041]
• FIG. 22 is a cross-sectional view of an embodiment of a disc implant.[0042]
• FIGS.[0043]23-27 depict embodiments of coupling projections.
• FIG. 28 is a perspective view of an embodiment of an inserter.[0044]
• FIG. 29 is a side view of a portion of an embodiment of an inserter coupled to engaging plates.[0045]
• FIG. 30 is a side view of an embodiment of an inserter.[0046]
• FIG. 31 is a perspective view of an embodiment of a slap hammer coupled to an inserter.[0047]
• FIG. 32 is a perspective view of an embodiment of a distractor.[0048]
• FIG. 33 is a perspective view of an embodiment of a distractor positioned in an inserter.[0049]
• FIG. 34 is a perspective view of an embodiment of a pusher.[0050]
• FIG. 35 is a side view of an embodiment of a pusher coupled to an inserter.[0051]
• FIG. 36 is a perspective view of an embodiment of an instrument guide.[0052]
• FIG. 37 is a perspective view of an instrument guide coupled to an inserter[0053]
• FIG. 38 and FIG. 38A depict an embodiment of a chisel.[0054]
• FIG. 39 is a perspective view of a chisel in working relation to an instrument guide.[0055]
• FIG. 40 is a perspective view of a reamer in working relation to an instrument guide.[0056]
• FIG. 41 depicts embodiments of trial spacers.[0057]
• FIG. 42 is a bottom view of an embodiment of a trial endplate.[0058]
• FIG. 43 is a perspective view of a member seater.[0059]
• While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.[0060]
DETAILED DESCRIPTION
• An intervertebral disc implant may be used to stabilize a portion of the spine. The artificial intervertebral disc implant may replace all or a portion of an intervertebral disc that requires replacement due to degeneration from natural wear, trauma or disease. The artificial intervertebral disc may restore the normal separation distance between the vertebrae and allow normal movement and flexibility of the spine.[0061]
• Disc implants may allow movement of adjacent vertebrae relative to each other in ranges associated with normal limits for human vertebrae. Disc implants may allow axial rotation, axial compression and lateral and/or anteroposterior movement. In a human spine, axial rotation may include rotation of about 0.1° to about 3° about a longitudinal axis of the spine. An axis of rotation between vertebrae may be off-center due to the fibrocartilaginous nature of an intervertebral disc. An axis of rotation between two vertebrae may be located posterior to a mid-point between the vertebrae. Lateral movement may include lateral bending. Lateral bending may include motion to the left and/or right up to a maximum of about 0.5° to about 10°. Anteroposterior movement may include flexion and/or extension. Flexion may include anterior motion up to a maximum of about 0.5° to about 20°. Extension may include posterior motion up to a maximum of about 0.5° to about 10°.[0062]
• Some implant embodiments may inhibit movement outside of normal limits for vertebrae. Limiting a range of motion may decrease chances of injury. Tissue and structure adjacent to vertebrae separated by a disc may limit some ranges of motion. For example, surrounding tissue and structure may limit axial rotation of vertebrae.[0063]
• In some embodiments, artificial disc implants may be used to replace a disc or discs in the lumbar region of a spine. In certain embodiments, artificial disc implants may be used in cervical or thoracic portions of the spine. In some embodiments, artificial disc implants may be used with other systems or devices to provide stability to the spine. In other embodiments, a disc implant may be used as a stand-alone system.[0064]
• FIG. 1 is a perspective view of components of an embodiment of a disc implant that may be inserted between two vertebrae.[0065]Disc implant100 may include engagingplate102,member104 and engagingplate106. When the implant is installed in a patient, each engaging plate of the implant may cover at least 70% of the vertebral surface that the engaging plate contacts.Member104 may separate engagingplate102 from engagingplate106. In certain embodiments,member104 may be held between engagingplates102,106 at least partially by pressure resulting from natural compression of the spine.
• Engaging[0066]plates102,106 may contact adjacent vertebrae to anchor the disc implant to the spine. Couplingprojections108 positioned onouter surfaces110,110′ of engagingplates102,106 may be positioned in a recess of a vertebral surface. Couplingprojections108′ positioned onouter surfaces110,110′ of engagingplates102,106 may penetrate into vertebral surfaces to inhibit movement of the engaging plates relative to the vertebrae. In certain embodiments, engaging plates may be coupled to vertebrae using methods other than, or in addition to,coupling projections108,108′. For example, fasteners may be used to attach an engaging plate to a vertebra. Fasteners may include, but are not limited to, screws, nails, rivets, trocars, pins and barbs.
• [0067]Inner surface112 of engagingplate102 may includeslots114 andrecess116.Slots114 may have a cross-sectional shape including, but not limited to, square, rectangular, trapezoidal, or irregular.Inner surface112′ of engagingplate106 may includeslots114′ that align withslots114 of engagingplate102 whendisc implant100 is assembled.Slots114,114′ may include indents118.Indents118 may engage an instrument used to facilitate insertion ofimplant100 during a surgical procedure. In some embodiments,slots114,114′ may be dovetailed.Slots114,114′ may allow use of insertion instruments without adding a height and/or a thickness to the overall dimension ofimplant100.
• In some embodiments, slots in an engaging plate may be parallel or substantially parallel to an anterior-posterior axis of the engaging plates. FIG. 2 depicts an embodiment of engaging[0068]plate106 whereinslots114′ are parallel to anterior-posterior axis119. In some embodiments, slots may be at acute angle relative to the anterior-posterior axis of the engaging plate. FIG. 3 depicts an embodiment of engagingplate106 whereinslots114′ are angled relative to anterior-posterior axis119.Slots114,114′ may be formed at an angle ranging from about 15° to about 30° relative to anterior-posterior axis119. In some embodiments,slots114,114′ may be formed at about a 25° angle relative to anterior-posterior axis119. Angulation ofslots114,114′ may allow insertion ofimplant100 using a modified (e.g., angulated) anterior approach. In some embodiments, an angular orientation ofrecess116 may correspond to angulation ofslots114,114′. A modified anterior approach may facilitate retraction of blood vessels above the L5 vertebrae. In some embodiments, engagingplates102,106 withslots114,114′ angled relative to anterior-posterior axis119 may not include a central coupling projection (i.e., a keel).
• [0069]Recess116 of engagingplate102 may have a cross-sectional shape including, but not limited to, circular, elliptical, square, rectangular or irregular. Sides ofrecess116 may be tapered.Posterior side120 ofrecess116 may be at least twice the height ofanterior side122 ofrecess116. A height difference betweenanterior side122 andposterior side120 may minimize overdistraction of the vertebrae required during positioning ofmember104 between engagingplates102,106 in a disc implant procedure. In some embodiments, a bottom portion of the recess may include an opening or openings to allow residual body fluids and/or bone matter to be removed from the recess.
• [0070]Base124 ofmember104 may fit inrecess116 of engagingplate102.Base124 may substantially conform to the shape ofrecess116. In some embodiments,member104 may be a tapered boss. A width ofbase124 that fits inrecess116 may be slightly less than a width of the recess to allowmember104 to translate in the recess. Recess116 may maintain a position ofmember104 between engagingplates102,106.
• [0071]Member104 may includecenter section126. A height ofcenter section126 ofmember104 may add thickness to a height ofimplant100.Center section126 may range in height from about 5 mm to about 20 mm. In certain embodiments,center section126 may have a height of about 9 mm. In some embodiments,center section126 may have a height of about 11 mm. In other embodiments,center section126 may have a height of about 13 mm.
• [0072]Center section126 may includeprojections128.Projections128 may be an integral part ofcenter section126. In some embodiments,projections128 may be glued, press fit and/or welded tocenter section126.Projections128 may be the same height ascenter section126.Projections128 may engage an instrument to facilitate insertion ofmember104 between engagingplates102,106.
• [0073]Member104 may includeconvex portion130.Convex portion130 may be, but is not limited to being, an ellipsoidal section, an ovate section or a spherical section.Inner surface112′ of engagingplate106 may include a recess. FIG. 2 depicts a bottom view ofinner surface112′ of engagingplate106 shown in FIG. 1. Recess132 may complementconvex portion130 ofmember104. In some embodiments, a height ofconvex portion130 may exceed a depth ofrecess132. As used herein, “complement” or “complementary” refers to shapes of implant components that fit together to allow smooth relative motion of the components.
• FIG. 3 depicts a bottom view of[0074]inner surface112′ of an embodiment of engagingplate106 withslots114′ angled relative to anterior-posterior axis119.Slots114′ may be formed at an angle ranging from about 15° to about 30° relative to anterior-posterior axis119. In some embodiments,slots114′ may be formed at about a 25° angle relative to anterior-posterior axis119. In certain embodiments, an orientation ofrecess132 may be angled to correspond to an angle ofslots114′. Angulation ofslots114′ may allow insertion ofimplant100 using a modified (e.g., angulated) anterior approach.
• FIG. 4 depicts a cross-sectional view of the implant shown in FIG. 1 after the implant has been assembled.[0075]Convex portion130 ofmember104 may complementrecess132 of engagingplate106. A shape ofconvex portion130 may allow engagingplate106 to move (e.g., rock) in an anteroposterior plane and/or a mediolateral plane relative to engagingplate102. Movement of engagingplate106 relative to engagingplate102 in the anteroposterior plane indicated byarrow134 may allow flexion and extension of vertebrae adjacent to the engaging plates. Movement of engagingplate106 relative to engagingplate102 in the mediolateral plane indicated byarrow136 in FIG. 1 may allow lateral bending of the vertebrae adjacent to engagingplates102,106. Engagingplate106 may rotate relative to engagingplate102 around axis ofrotation138 in the plane indicated byarrow140. In some embodiments, axial rotation of engagingplate106 relative to engagingplate102 may be limited by tissue, bone or other material in the patient.
• In some embodiments, a height of[0076]convex portion130 and a depth ofrecess132 may be chosen to limit lateral movement of engagingplate106 relative to engagingplate102. For example, a height ofconvex portion130 may allow engagingplate106 to contact engagingplate102 when engagingplate106 rocks in the direction of engagingplate102. Contact ofinner surfaces112,112′ of engagingplates102,106 may provide a limit to anteroposterior movement of engagingplate106 relative to engagingplate102. Contact ofinner surfaces112,112′ of engagingplates102,106 may limit flexion and/or extension of the adjacent vertebrae. A height ofconvex portion130 may determine maximum flexion and/or extension allowed by the implant. In some embodiments, a maximum amount of flexion may be limited to a range between about 0.5° and about 20°. In some embodiments, maximum flexion allowed by the implant may be about 10°. In other embodiments, maximum flexion allowed by the implant may be about 15°. In some embodiments, a maximum amount of extension may be limited to a range between about 0.5° and about 12°. In some embodiments, maximum extension allowed by the implant may be about 8°. In other embodiments, maximum extension allowed by the implant may be about 5°.
• In some embodiments, components of an implant may include surfaces that contact to limit a maximum amount of lateral bending. In some embodiments, an implant may allow equal amounts of lateral bending so that the patient can laterally bend the same amount to the right or the left. In some embodiments, a maximum amount of lateral bending to the left may be different than a maximum amount of lateral bending to the right to accommodate specific needs of a patient. In some embodiments, an implant may be designed to allow a maximum amount of lateral bending within a range between ±0.5° to about ±15°. In some embodiments, the maximum amount of lateral bending may be about ±10°. In some embodiments, the maximum amount of lateral bending allowable by an implant may be about ±5°.[0077]
• In alternative embodiments, a concave portion of a member may complement a convex portion of an engaging plate. As shown in FIG. 5,[0078]convex portion142 of engagingplate106 may complementrecess144 ofmember104 to form an implant. A large contact area between engagingplate106 andmember104 may advantageously distribute a compressive load applied to the implant over a relatively large area.
• FIG. 6 depicts a perspective view of components of an implant embodiment.[0079]Implant100 may allow a full range of physiological movement of vertebrae adjacent to the implant.Inner surface112 of engagingplate102 may include at least one projection.Projection146 may be coupled to engagingplate102. In some embodiments,projection146 may be an integral part of engagingplate102.Projection146 may have a shape that allows engagingplate102 to rotate freely relative tomember104. The shape ofprojection146 may be, but is not limited to being, tapered, round or square.Member104 may include recess148 (shown in FIG. 7). Recess148 may complementprojection146. Recess148 may have a slightly larger cross section thanprojection146 to allow engagingplate102 to move relative tomember104. A size and/or shape ofrecess148 relative toprojection146 may determine a range of rotation ofmember104 relative to engagingplate102.
• As depicted in FIG. 7,[0080]recess148 andprojection146 may define axis ofrotation138. Friction between engagingplate102 andmember104 may be low enough to allow rotation of the engaging plate relative to the member. Engagingplate102 may rotate relative tomember104 as indicated byarrow140. Rotation of engagingplate102 relative tomember104 may imitate axial rotation of the spine. A large contact area betweenrecess148 ofmember104 andprojection146 of engagingplate102 may distribute a compressive load applied to implant100 over a relatively large surface area.
• [0081]Member104 may includeconvex portion150.Inner surface112′ of engagingplate106 may includerecess152. Recess152 of engagingplate106 may complementconvex portion150 ofmember104. The shape ofconvex portion150 may allow engagingplate106 to move (e.g., rock) relative tomember104. Movement of engagingplate106 relative tomember104 may allow lateral movement (e.g., lateral bending) of vertebrae adjacent to the engaging plates. In an alternative embodiment,member104 may include a recess complementary to a convex part of engagingplate106.
• [0082]Convex portion150 may have an arcuate cross-sectional shape in an anteroposterior plane and/or in a mediolateral plane. An arcuate shape ofconvex portion150 in the anteroposterior plane may allow engagingplate106 to rock relative to engagingplate102 in the directions indicated byarrows134 in FIG. 7. Movement of engagingplate106 relative to engagingplate102 in the anteroposterior plane may allow flexion and extension of vertebrae adjacent to the engaging plates. An arcuate shape ofconvex portion150 in the mediolateral plane may allow engagingplate106 to move relative to engagingplate102 in directions indicated byarrow136 in FIG. 6. Movement of engagingplate106 relative to engagingplate102 in the mediolateral plane may allow lateral bending of vertebrae adjacent to the engaging plates.
• FIG. 8 depicts a bottom view of[0083]inner surface112′ of engagingplate106 shown in FIG. 7. Engagingplate106 may includerecess152. A shape ofrecess152 may complementconvex portion150 ofmember104. Recess152 may be concave with an arcuate cross-sectional shape in an anteroposterior plane and/or in a mediolateral plane. A shape ofrecess152 may allow movement of engagingplate106 relative tomember104 in an anteroposterior plane and/or in a mediolateral plane. Movement of engagingplate106 relative tomember104 in an anteroposterior plane and/or in a mediolateral plane may allow flexion, extension and/or lateral bending of vertebrae adjacent to engagingplates102,106.
• In some embodiments, engaging[0084]plate106 may includelimiter154, as shown in FIG. 7.Limiter154 may be positioned to contactsurface156 ofmember104. Contact oflimiter154 andsurface156 may limit posterior movement of engagingplate106 relative to engagingplate102. Contact oflimiter154 andsurface156 may therefore limit extension of vertebrae adjacent to engagingplates102,106. A height oflimiter154 relative toinner surface112′ of engagingplate106 and/or a height ofsurface156 relative toinner surface112 of engagingplate102 may be chosen to limit extension of vertebrae adjacent the implant. Maximum extension allowed byimplant100 may range from about 3° to about 12°. In some embodiments, maximum extension allowed byimplant100 may be about 8°. In other embodiments, maximum extension allowed byimplant100 may be about 5°.
• In some embodiments,[0085]inner surface112′ of engagingplate106 may contactsurface156 ofmember104. Contact ofinner surface112′ withsurface156 may limit anterior movement of engagingplate106 relative to engagingplate102. Contact ofinner surface112′ of engagingplate106 withsurface156 ofmember104 may limit flexion of vertebrae adjacent engagingplates102,106. A height ofsurface156 relative toinner surface112 of engagingplate102 may be chosen to limit flexion of vertebrae adjacent to engagingplates102,106. Maximum flexion allowed byimplant100 may range from about 5° to about 20°. In some embodiments, maximum flexion allowed byimplant100 may be about 10°. In other embodiments, maximum flexion allowed byimplant100 may be about 15°.
• FIG. 9 depicts a perspective view of components of an embodiment of an implant.[0086]Implant100 may allow limited axial rotation of vertebrae adjacent to engagingplates102,106. Engagingplate102 may includerecess158. Edges ofrecess158 may be arced. The arcs may share a common center point.Base124 ofmember104 may fit inrecess158. A surface ofbase124 may substantially conform to an arced surface ofrecess158. A width ofbase124 may be less than a width ofrecess158 such thatmember104 may be able to translate inrecess158 along curves defined by the edges of the recess.
• FIG. 10 depicts a cross-sectional view of the implant shown in FIG. 9 after the implant has been assembled.[0087]Base124 ofmember104 may complementrecess158 of engagingplate102. Axis ofrotation138 may be at or near the centroid of engagingplates102,106 or offset from the engaging plates. Rotation of engagingplate102 relative to engagingplate106 may allow rotation of vertebraeadjacent implant100.
• A shape of[0088]recess158 may allow engagingplate102 to rotate axially relative to engagingplate106 in the plane indicated byarrow140. Movement ofbase124 inrecess158 may limit axial rotation of the vertebrae adjacent to engagingplates102,106. Maximum axial rotation allowed byimplant100 may range from about ±0.1° to about ±6°. In some embodiments, maximum axial rotation allowed byimplant100 may be about ±3°. In other embodiments, maximum axial rotation allowed byimplant100 may be about ±1°.
• Engaging[0089]plate106 may includerecess152. Recess152 may complementconvex portion150 ofmember104. In an alternative embodiment,member104 may include a recess complementary to a convex portion of engagingplate106.Convex portion150 may have an arcuate cross-sectional shape in an anteroposterior plane and/or in a mediolateral plane. An arcuate shape ofconvex portion150 in an anteroposterior plane may allow engagingplate106 to move (e.g., rock) relative tomember104 in the directions indicated byarrow134. Movement of engagingplate106 relative tomember104 in the anteroposterior plane may allow flexion and/or extension of the vertebrae adjacent to the engaging plates. An arcuate shape ofconvex portion150 in a mediolateral plane may allow engagingplate106 to move (e.g., rock) relative tomember104 in the directions indicated byarrows136 in FIG. 9. Movement of engagingplate106 relative tomember104 in the mediolateral plane may allow lateral bending of the vertebrae adjacent to the engaging plates.
• In some embodiments,[0090]inner surface112′ of engaging plate106 (shown in FIG. 10) may contactsurface156 ofmember104. Contact ofinner surface112′ withsurface156 may limit movement of engagingplate106 relative to engagingplate102 in the anteroposterior plane. Contact ofinner surface112′ withsurface156 may limit flexion of the spine. In certain embodiments, a height of asurface156 relative toinner surface112 may be chosen to limit flexion of the spine. Maximum flexion allowed byimplant100 may range from about 5° to about 20°. In some embodiments, maximum flexion allowed byimplant100 may be about 10°. In other embodiments, maximum flexion allowed byimplant100 may be about 15°.
• In some embodiments, posterior movement of engaging[0091]plate106 relative to engagingplate102 may be limited. Engagingplate106 may includelimiter154. During use,limiter154 may contactsurface156 to limit posterior movement of engagingplate106 relative to engagingplate102. Contact oflimiter154 withsurface156 may limit extension of the spine. A height oflimiter154 relative toinner surface112′ and/or a height ofcontact surface156 relative toinner surface112 may be chosen to limit extension of the spine. Maximum extension allowed byimplant100 may range from about 3° to about 12°. In some embodiments, maximum extension allowed byimplant100 may be about 8°. In other embodiments, maximum extension allowed byimplant100 may be about 5°.
• In some embodiments,[0092]inner surface112 of engagingplate102 may have a convex portion. Engagingplate102 ofimplant100 shown in FIG. 11 includesconvex portion160.Convex portion160 may have an arcuate cross-sectional shape in an anteroposterior plane and/or in a mediolateral plane.Member104 may includerecess162, as shown in FIG. 12. Edges ofrecess162 may be arced. The arcs may share a common center point.Convex portion160 may fit inrecess162 ofmember104.Convex portion160 of engagingplate102 may complementrecess162. A width ofconvex portion160 may be less than a width ofrecess162. Engagingplate102 may translate inrecess162 along curves defined by edges of the recess.
• FIG. 13 depicts a cross-sectional view of the implant shown in FIG. 11 after the implant has been assembled. Recess[0093]162 ofmember104 may complementconvex portion160 of engagingplate102. A shape ofconvex portion160 may allow relative movement of engagingplates102,106 in the plane indicated byarrow140 about axis ofrotation138. Axis ofrotation138 may be at or near the centroid ofimplant100 or offset from the centroid.
• Maximum axial rotation allowed by[0094]implant100 may range from about ±0.1° to about ±6°. In some embodiments, maximum axial rotation allowed byimplant100 may be about ±3°. In other embodiments, maximum axial rotation allowed byimplant100 may be about ±1°. Rotation of engagingplate102 relative to engagingplate106 may be limited by a height ofconvex portion160 relative to a depth ofrecess162. In some embodiments, rotation of engagingplate102 relative to engagingplate106 may be limited by a curvature ofconvex portion160 and/or a curvature ofrecess162.
• [0095]Inner surface112′ of engagingplate106 may includerecess152. Recess152 may be complementary in shape toconvex portion150 ofmember104.Convex portion150 may complementrecess152.Convex portion150 may allow engagingplate106 to move (e.g., rock) relative tomember104. Movement of engagingplate106 relative tomember104 may allow lateral movement of the spine. In some embodiments,member104 may include a recess complementary to a convex portion of engagingplate106.
• [0096]Convex portion150 may have an arcuate cross-sectional shape in an anteroposterior plane and/or in a mediolateral plane. An arcuate shape ofconvex portion150 in the anteroposterior plane may allow engagingplate106 to move relative tomember104 in the directions indicated byarrow134. Movement of engagingplate106 relative to engagingplate102 in the anteroposterior plane may allow flexion and/or extension of the spine. The arcuate shape ofconvex portion150 in the mediolateral plane may allow engagingplate106 to move relative tomember104 in the directions indicated byarrow136 shown in FIG. 11. Movement of engagingplate106 relative tomember104 in the mediolateral plane may allow lateral bending of the spine.
• [0097]Inner surface112′ of engagingplate106 may contactsurface156 ofmember104. Contact ofinner surface112′ withsurface156 may limit anterior movement of engagingplate106 relative to engagingplate102. Contact ofinner surface112′ withsurface156 may therefore limit flexion of vertebrae adjacent to engagingplates102,106. A thickness of an edge ofmember104 may limit flexion allowed byimplant100. Maximum flexion allowed byimplant100 may range from about 5° to about 20°. In some embodiments, maximum flexion allowed byimplant100 may be about 10°. In other embodiments, maximum flexion allowed byimplant100 may be about 15°.
• In certain embodiments,[0098]disc implant100 may include two engaging plates and two members as depicted in FIGS. 14 and 16. FIGS. 15 and 17 are cross-sectional views ofimplants100 shown in FIGS. 14 and 16, respectively. Engagingplate102 ofimplants100 may haveconvex portion164.Convex portion164 may have an arcuate cross-sectional shape along at least one axis. The arcuate cross-sectional shape along one axis ofconvex portion164 may increase an area of contact between engagingplate102 andmember104.Member104 may includerecess166. Recess166 may complementconvex portion164. A shape ofconvex portion164 may allow anteroposterior translation ofmember104 relative to engagingplate102. Translation ofmember104 relative to engagingplate102 may allow positioning ofimplant100 during a spinal stabilization procedure.
• A thickness of engaging[0099]plate102 proximateconvex portion164 may exceed a thickness of engagingplate102proximate edges168,168′ such thatinner surfaces112,112″ are sloped relative to an outer surface of the engaging plate. In some embodiments, a slope ofinner surface112 may be different than a slope ofinner surface112″. In certain embodiments, a thickness ofmember104proximate recess166 may exceed a thickness of the member atedges170,170′ such thatsurfaces172,172′ are sloped relative tosurface156.
• Inner surfaces[0100]112,112″ and surfaces172,172′ may be sloped to allow movement (e.g., rocking) of engagingplate102 relative tomember104 in a mediolateral plane. Movement ofmember104 in the direction indicated byarrow136 may allow lateral bending of vertebrae adjacent to engagingplates102,106.Inner surfaces112,112″ and surfaces172,172′ may be sloped such that lateral movement of the spine in a mediolateral plane is restricted. In some embodiments, a slope ofsurface172 relative to surface156 may be different than a slope ofsurface172′ relative to surface156. In some embodiments, slopes ofsurfaces172,172′ may be opposite in sign to slopes ofinner surfaces112,112″. Movement of engagingplate102 relative tomember104 may allowinner surfaces112,112″ to contactsurfaces172,172′. Contact ofinner surfaces112,112″ and surfaces172,172′ may distribute a compressive load applied to implant100 over a relatively large surface area.
• [0101]Member104 may includeprojection146.Projection146 may be coupled tomember104. In some embodiments,projection146 may be an integral part ofmember104. A shape ofprojection146 may be, but is not limited to being, tapered, round or square.Member174 may includerecess148, as depicted in FIGS. 15 and 17. Recess148 may complementprojection146. Recess148 may have a slightly larger cross section thanprojection146 to allow relative movement ofmembers104,174. In some embodiments,member174 may rotate relative tomember104 about axis ofrotation138 indicated byarrow140. As shown in FIG. 15, axis ofrotation138 may be near a center ofimplant100. In some embodiments, axis ofrotation138 may be located more off-center, as depicted in FIG. 17. A range of rotation ofmember174 relative tomember104 may be limited by a size and/or shape ofrecess148 relative to a size and/or shape ofprojection146.
• [0102]Surface176 ofmember174 may contactsurface156 ofmember104 whenprojection146 fits inrecess148. A relatively large contact area betweenmember104 andmember174 may distribute an effective load applied to implant100 while allowing rotation of vertebrae adjacent to the implant. For example, projection146 (shown in FIG. 14) has a flat surface that may increase a contact area betweenprojection146 andrecess148. Reducing friction betweenmember104 andmember174 may allow facile rotation of the members relative to each other.
• [0103]Member174 may haveconvex portion178.Convex portion178 may have an arcuate cross-sectional shape in an anteroposterior plane. Engagingplate106 may include recess180 (shown in FIG. 15 and FIG. 17). Recess180 may be concave with an arcuate cross-sectional shape in an anteroposterior plane. Recess180 may complementconvex portion178 ofmember174. In some embodiments,recess180 may have a slightly larger cross section thanconvex portion178 to allow movement of engagingplate106 relative tomember174. Movement of engagingplate106 relative tomember174 may allow for flexion and/or extension of vertebrae adjacent to the engaging plates in the plane indicated byarrows134 in FIGS. 15 and 17.
• In some embodiments, anteroposterior and/or lateral movement of components of[0104]implant100 relative to each other may be limited. As shown in FIGS. 14 and 15, engagingplate106 may includelimiter154.Limiter154 may be a projection extending frominner surface112′ of engagingplate106. In an embodiment,limiter154 may extend along a side of engagingplate106.Limiter154 may be positioned to contactsurface182 ofmember174 when engagingplate106 rocks in a posterior direction toward engagingplate102. Increasing a length oflimiter154 may increase an area of contact betweenlimiter154 andmember174. Increasing the area of contact betweenlimiter154 andmember174 may distribute a compressive load onimplant100 over a relatively large area. Distributing the load over a relatively large area may reduce stress among components ofimplant100.
• Contact of[0105]limiter154 withsurface182 may limit movement of engagingplate106 relative tomember174. A height oflimiter154 relative toinner surface112′ and/or a distance betweensurfaces176 and182 ofmember174 may be chosen to limit movement of engagingplate106 relative tomember174. In certain embodiments,surface182 ofmember174 may be sloped relative to surface176 to increase an area of contact betweensurface182 andlimiter154.Surface182 may be sloped to increase a range of motion between engagingplate106 andmember174. In some embodiments, a slope ofsurface182 may limit movement of engagingplate106 relative tomember174. In certain embodiments, maximum extension allowed byimplant100 may range from about 3° to about 12°. In some embodiments, maximum extension allowed byimplant100 may be about 8°. In other embodiments, maximum extension allowed byimplant100 may be about 5°. Some implant embodiments may include a limiter designed to limit another component of motion of a disc implant. Other implant embodiments may include one or more additional limiters designed to limit other components of motion of a disc implant.
• In certain embodiments,[0106]inner surface112′ of engagingplate106 may contactsurface182 ofmember174. Contact ofinner surface112′ withsurface182 may limit flexion of vertebrae adjacent to engagingplates102,106. A distance betweensurfaces176 and182 ofmember174 may be chosen to limit flexion between vertebrae adjacent to engagingplates102,106. Maximum flexion allowed byimplant100 may range from about 5° to about 20°. In some embodiments, maximum flexion allowed byimplant100 may be about 10°. In other embodiments, maximum flexion allowed byimplant100 may be about 15°.
• In certain embodiments, components of[0107]implant100 may be coupled to one another. Coupling of components ofimplant100 may allow partial assembly of the implant prior to a surgical procedure. In some embodiments, a manufacturer ofimplant100 may at least partially assemble the implant prior to shipment. Some of the components ofimplant100 may be held together during use, at least partially, by pressure resulting from the natural compression of the spine.
• FIG. 18 depicts a perspective view of components of[0108]implant100, including engagingplate102,members104 and174, and engagingplate106. FIG. 19 depicts a cross-sectional view of the implant shown in FIG. 18 after the implant has been assembled. As shown in FIGS. 18 and 19, engagingplate102 may includeprojection146 andopening184.Projection146 may be coupled to engagingplate102. In some embodiments,projection146 may be an integral part of engagingplate102. A shape ofprojection146 may be, but is not limited to being, round, square, rectangular or irregular.Projection146 may complement recess148 (shown in FIG. 19) inmember104. In certain embodiments,recess148 may have a slightly larger cross section thanprojection146 to allow engagingplate102 to move relative tomember104. In some embodiments,recess148 may have a cross section substantially equal to a cross section ofprojection146 to inhibit rotation of engagingplate102 relative tomember104.
• In some embodiments, opening[0109]184 may extend through engagingplate102. In other embodiments, opening184 may extend to a fixed depth in engagingplate102. Opening184 may be designed (e.g., threaded) to receive a coupling device such ascoupler186.Coupler186 may be, but is not limited to being, a screw, a bolt or a pinch clamp.Coupler186 may couplemember104 to engagingplate102. During use,coupler186 may extend through at least a portion ofmember104 into opening184 of engagingplate102. A head ofcoupler186 may be recessed in opening188 ofmember104.Coupler186 may allow engagingplate102 to move relative tomember104. In some embodiments, engagingplate102 may rotate around axis ofrotation138 relative tofirst member104 in the plane indicated byarrow140 in FIG. 19. Relative movement of engagingplates102,106 may allow axial rotation of vertebrae adjacent to implant100. Axis ofrotation138 may be offset from a center of engagingplates102,106 to imitate a longitudinal axis of rotation of a spine.
• As shown in FIG. 18,[0110]member104 may haveconvex portion164.Convex portion164 may have an arcuate cross-sectional shape along at least one axis.Member174 may includerecess166. Recess166 may have an arcuate cross section along at least one axis. Recess166 may complementconvex portion164 ofmember104, as shown in the side view ofimplant100 in FIG. 20. In some embodiments, a thickness of engagingplate102proximate member104 may exceed a thickness of the engaging plate at ends168,168′ such thatinner surfaces112,112″ slope toward an outer surface of the engaging plate. In some embodiments, a slope ofinner surface112 may be different than a slope ofinner surface112″. A thickness ofmember174proximate recess166 may exceed a thickness of the member at ends190,190′ such thatsurfaces192,192′ ofsecond member174 slope away from engagingplate102. In some embodiments, a slope ofsurface192 may be different than a slope ofsurface192′. In some embodiments, slopes ofsurfaces192,192′ may be substantially the same magnitude as slopes ofinner surfaces112,112″, respectively.
• Sloped surfaces[0111]112,112″ may allow engagingplate102 to move (e.g., rock) relative tomember104 in a mediolateral plane. Relative movement of engagingplates102,106 may allow lateral bending of vertebrae adjacent to the engaging plates in the plane indicated byarrow136 in FIG. 18. Contact ofsurfaces112,112″ and192,192′, respectively, may distribute a compressive load applied to implant100 over a relatively large area.
• In some embodiments,[0112]member174 may haveconvex portion178.Convex portion178 may have an arcuate cross-sectional shape. Engagingplate106 may includerecess180. Recess180 may be concave with an arcuate cross-sectional shape. Recess180 may complementconvex portion178. Recess180 may have a slightly larger cross section thanconvex portion178 to allow engagingplate106 to move (e.g., rock) toward engagingplate102 as indicated byarrow134 in FIG. 19. Movement of engagingplate106 relative tomember174 may allow flexion and/or extension of vertebrae adjacent to engagingplates102,106.
• [0113]Member104 may include one or more stops194 (shown in FIGS. 18 and 19).Stops194 may be coupled to one or both ends ofmember104. In some embodiments, stops194 may be an integral part ofmember104.Stops194 may restrict anteroposterior translation ofmember174 relative tomember104. Restriction of translation ofmember174 relative tomember104 may facilitate positioning ofimplant100 between vertebrae.
• In certain embodiments, contact of[0114]stop194 withinner surface112′ of engagingplate106 may limit extension of vertebrae adjacent to implant100. A height ofstop194 and/or a thickness of engagingplate106 may limit extension allowed byimplant100. Maximum extension allowed byimplant100 may range from about 3° to about 12°. In some embodiments, maximum extension allowed byimplant100 may be about 8°. In other embodiments, maximum extension allowed byimplant100 may be about 5°.
• [0115]Surface182 ofmember174 may be sloped relative tosurfaces192,192′ of the member.Inner surface112′ of engagingplate106 may be sloped relative to an outer surface of the engaging plate. A slope ofsurface182 and/or a slope ofinner surface112′ may be chosen to increase a contact area betweensurface182 andlimiter154 of engagingplate106. A slope ofsurface182 may be chosen to increase a range of motion between engagingplate106 andmember174. In some embodiments, a shape and/or size ofrecess180 may limit motion of engagingplate106 relative to another component of the implant.
• In certain embodiments,[0116]inner surface112′ of engagingplate106 may contactsurface182 ofmember174. Contact ofinner surface112′ andsurface182 may limit flexion of the spine. A distance betweensurface182 and surfaces192,192′ ofmember174 may be chosen to limit flexion between vertebrae adjacent to engagingplates102,106. Maximum flexion allowed byimplant100 may be from about 5° to about 20°. In some embodiments, maximum flexion allowed byimplant100 may be about 10°. In other embodiments, maximum flexion allowed byimplant100 may be about 15°.
• In some embodiments, a first engaging plate may be substantially the same as a second engaging plate. Manufacturing costs may be reduced for implants with substantially equivalent engaging plates. FIG. 21 depicts a perspective view of[0117]implant100 with substantially equivalent engagingplates102.Member104 may separate engagingplates102. In certain embodiments,member104 may have a rounded shape including, but not limited to, ovoid, spheroid and ellipsoid.Member104 may be formed from metal (e.g., chrome) or ceramic. In certain embodiments,member104 may be highly polished to inhibit wear. Engagingplates102 may includeconcave portions132.Concave portions132 may complementmember104. A thickness ofmember104 may exceed a cumulative depth ofconcave portions132.
• FIG. 22 depicts a cross-sectional view of the implant shown in FIG. 21 after the implant has been assembled. A separation of engaging[0118]plates102 bymember104 may allow the engaging plates to “rock” relative to one another. Rocking of engagingplates102 relative to one another in an anteroposterior plane may allow flexion and/or extension in the plane indicated byarrows134. Rocking of engagingplates102 relative to one another in a mediolateral plane may allow lateral bending in the plane indicated byarrows136 in FIG. 21.
• A shape of[0119]member104 may provide a large contact area between the surface ofmember104 andconcave portions132. A shape ofmember104 may decrease wear and/or failure ofimplant100.Concave portions132 with an oval shape may allowmember104 to imitate the movement of a human spine around axis ofrotation138. Engagingplates102 may freely rotate relative to one another around axis ofrotation138 in the plane indicated byarrow140. In some embodiments, a position of axis ofrotation138 may change asmember104 translates inrecesses132. In an embodiment, a range of motion (e.g., axial rotation) may be limited by the shape ofmember104 and/or the shape ofconcave portion132.
• In an embodiment, an inner surface of engaging[0120]plates102 proximateconcave portions132 may be elevated. An elevation of one ormore surfaces196A-196D (shown in FIG. 21) may be chosen to limit relative movement of engagingplates102. One ormore surfaces196A-196D may be sloped relative to outer surfaces of engagingplates102 as shown in FIGS. 21 and 22. Slopes ofsurfaces196A-196D may increase a contact area between engagingplates102. Increasing a contact area between engagingplates102 may inhibit wear of the implant.
• In certain embodiments, surfaces[0121]196D may limit flexion of vertebrae adjacent to the spinal implant.Surfaces196B may limit extension of vertebrae adjacent to implant100.Surfaces196A and196C may limit lateral bending of vertebra adjacent to implant100. In some embodiments, axial rotation of engagingplates102 relative to each other may be limited.
• In some embodiments, an implant may be curved to accommodate radial curvature of vertebrae. Implants may be provided with varying amounts of radial curvature. For example, disc implants may be provided with large, medium and/or small radial curvatures. An indication of an amount of radial curvature provided by an implant may be etched or otherwise marked on the implant.[0122]
• In some disc implant embodiments, engaging plates may be sloped to establish a desired lordotic curvature of a spine. Several different implant components with differing lordotic curvatures may be available to a surgeon so that the surgeon can form an implant with a desired lordotic angle. Lordotic indications may be etched or otherwise marked (e.g., color coded) on the disc implant to indicate the amount of lordosis that the implant will provide. In an embodiment, a lumbar disc implant may have a lordotic angle range of about 5° to about 20° (e.g., about 12°).[0123]
• An engaging plate may be designed to promote coupling of the engaging plate to a vertebral surface. Coupling engaging plates of an implant to adjacent vertebrae may stabilize the disc implant. An engaging plate may include one or more coupling projections to facilitate coupling of the engaging plate to a vertebra. A coupling projection may extend from an outer surface of an engaging plate. Coupling projections may be, but are not limited to being, press fit, welded, glued or otherwise affixed to an engaging plate. Alternatively, coupling projections may be formed as part of an engaging plate. Any combination of[0124]coupling projections108 may be used together to ensure stability ofimplant100.
• An engaging plate may include one[0125]coupling projection108, as shown, for example, in FIGS.9-11. FIG. 23 depicts a view of engagingplate102 with twocoupling projections108. In some embodiments, an engaging plate may include a plurality ofcoupling projections108, as shown in FIGS. 24 and 25. In some embodiments, an engaging plate may include coupling projections of substantially the same shape and size. In certain embodiments, an engaging plate may include coupling projections of different sizes and/or shapes. A shape and/or size of a coupling projection may be chosen based on factors including, but not limited to, durability, distribution of load and ease of forming a complementary recess in a vertebra.
• In certain embodiments, a coupling projection extending from an engaging plate may be positioned in a recess formed in a vertebra. The recess may complement the coupling projection.[0126]Coupling projection108 may have an arcuate cross section, as depicted, for example, in FIGS.9-11. In some embodiments, a coupling projection may have a square or rectangular cross section. FIG. 26 depicts a view ofcoupling projection108 with a rectangular cross section. In certain embodiments, a coupling projection may be tapered in one or more directions.Coupling projection108 shown in FIG. 27 is tapered in an anteroposterior direction. A tapered coupling projection may allow the coupling projection to be wedged into a recess in a bone to secure the engaging plate to the bone. Wedging the coupling projection in the recess may inhibit movement of the engaging plate relative to the vertebra and/or expulsion of the engaging plate from the bone. In some embodiments, surfaces of the coupling projection that are to be positioned adjacent to bone may be roughened or include a coating (e.g., hydroxyapatite) to promote osseointegration of the coupling projection with the bone. In some embodiments, coupling projections, such as those depicted in FIGS. 1, 24 and25, may penetrate adjacent bone to inhibit movement of the engaging plate relative to the vertebra and/or to inhibit expulsion of the engaging plate from the bone.
• In some embodiments, one or more coupling projections may be oriented substantially in an anteroposterior plane to facilitate implant insertion using an anterior approach. In some embodiments, one or more coupling projections may be oriented substantially in a mediolateral plane to facilitate implant insertion using a lateral approach. In certain embodiments, combinations of coupling projections of various cross-sectional shapes, such as those depicted in FIG. 1 may be used to inhibit movement of the engaging plate relative to the vertebra and/or expulsion of the engaging plate from the bone.[0127]
• In some embodiments, a fastening system may be used to couple an implant to a vertebra. The implant may include a tab with an opening in a face of the tab. The opening may engage or couple to a head of a bone fastener. A fastening system may include a fastener and a locking mechanism. The locking mechanism may be positioned between the implant and the fastener. The locking mechanism may inhibit backout of the fastener from the vertebra and from the implant. In some embodiments, the locking mechanism may be a ring positioned in an opening in the implant. When the ring is in the opening, a head of the fastener inserted through the ring may contact the ring if the fastener begins to back out of the opening. The ring and fastener head combination may be too large to exit the opening, thereby inhibiting backout of the fastener from the vertebrae and from the implant. When the ring is positioned in the opening, the ring may lock to the fastener head without locking to the implant, thus allowing the plate to be securely tightened to the vertebra. U.S. Pat. No. 6,454,769 to Wagner et al. and U.S. Pat. No. 6,331,179 to Freid et al., both of which are incorporated by reference as if fully set forth herein, describe fastening systems including locking mechanism for inhibiting backout of fasteners.[0128]
• In certain embodiments, one or more instruments may be used to insert and/or position a disc implant between adjacent vertebrae after a discectomy has been performed. An inserter may be used to position an implant in a prepared disc space between adjacent vertebrae. The inserter may be sufficiently long to allow placement of a distal end of the inserter in the disc space from above an incision in a patient. Engaging plates of an implant may be coupled to arms at the distal end of the inserter.[0129]
• FIG. 28 depicts a perspective view of an embodiment of[0130]inserter210.Inserter210 may includebody212 andarms214.Body212 may haveopening216. Opening216 may be sized to allow one or more guidance, insertion and/or removal instruments to be positioned ininserter210.Arms214 may includeextensions218 forcoupling inserter210 to engaging plates of an implant.Extensions218 may be chamfered, rounded, dovetailed or otherwise machined to engageslots114 in engagingplates102,106 (shown in FIG. 1).Extensions218 may includedetents220.Detents220 may be positioned inindents118 of engagingplates102,106 to couple inserter210 to an implant. FIG. 29 depictsextensions218 coupled to engagingplates102,106.
• Portions of[0131]arms214 may be angled relative to each other to establish a tapering separation distance between the arms. The angled portions ofarms214 may facilitate insertion of instruments that establish a desired separation distance between engagingplates102,106 attached toinserter210.
• [0132]Arms214 may includemechanisms222. FIG. 30 depicts a perspective side-view ofinserter210 that showsmechanisms222 onarms214. As depicted in FIG. 28,inserter210 may includeslots224.Slots224 may extend througharms214 andextensions218 from themechanism222 to a portion of the inserter neardetents220.Slots224 may allowsection226 ofinserter210 to bend. Pressingmechanisms222 may movesection226 and allow disengagement ofdetents220 from indents located in engaging plates. Whenmechanisms222 are pressed, detents may be disengaged from indents in engaging plates to separate inserter210 from the engaging plates. In some embodiments,arms214 may includereinforcement members228 that stabilize portions of the inserter that are not able to move whenmechanisms222 are pressed.Reinforcement members228 may limit outward movement ofsections226.
• A proximal end of[0133]inserter210 may be formed to engage a driving instrument or a guidance instrument, such as a slap hammer or a pusher.Slots230 in a proximal end of inserter210 (shown in FIG. 28) may be machined or otherwise designed to receive a coupling device such ascoupler232 shown in FIG. 31. FIG. 31 depicts a perspective view ofinserter210 coupled to slaphammer234.Coupler232 may engage an attachment mount of a driving instrument or a guidance instrument.Slap hammer234 may includeattachment mount236.Coupler232 may coupleattachment mount236 toinserter210.
• During some implant insertion procedures, an intervertebral space may be too small to allow insertion of implant components coupled to an inserter without scarring the surfaces of adjacent vertebrae. Shims may be placed adjacent to the vertebrae. Engaging plates coupled to an inserter may be positioned next to the shims. The inserter may be driven downwards to separate the vertebrae and insert the engaging plates between the vertebrae. After insertion of the engaging plates, the shims may be removed.[0134]
• In some embodiments, a distractor may be used to separate adjacent vertebrae and/or to separate engaging plates to allow insertion of a member between the engaging plates. FIG. 32 depicts a perspective view of an embodiment of a distractor.[0135]Distractor238 may includebody240,arms242 andattachment mount244.Body240 andarms242 may includegrooves246.Grooves246 may be slightly larger in cross-section thanprojections128 of member104 (shown in FIG. 1).Projections128 ofmember104 may fit ingrooves246 to allowmember104 to be guided throughbody240 andarms242 to a position between engaging plates.
• In some embodiments,[0136]grooves246 may be sized and/or shaped to accept only a particular sized member of an implant. For example, a member for a13 mm implant will not fit in a distractor that establishes a separation distance sized for an 11 mm implant. In some embodiments, members and distractors may be color coded substantially the same color. A surgeon may know to only put a member into a distractor of substantially the same color.
• In certain embodiments,[0137]arms242 may includereinforcement member248.Reinforcement member248 may inhibit movement ofarms242 during insertion of a member between engaging plates to form an implant.
• [0138]Slots250 onattachment mount244 may be machined to receive a coupler. A coupler may coupledistractor238 to a drive instrument, such as a slap hammer.
• FIG. 33 depicts a perspective view of[0139]distractor238 positioned ininserter210.Arms242 may separatearms214 ofinserter210. Asarms214 are separated bydistractor238, engagingplates102,106 are separated. Slots in engagingplates102,106 andarms242 may separatearms214 such that the engaging plates remain substantially parallel during the separation process. Engagingplates102,106 may remain substantially parallel during insertion of a member between the engaging plates. Separation ofarms214 withdistractor238 may minimize or eliminate contact of the distractor with engagingplates102,106. Minimizing or eliminating contact ofdistractor238 with engagingplates102,106 during distraction may inhibit undesired separation of the engaging plates from theinserter210.
• FIG. 34 depicts a perspective view of an embodiment of a pusher.[0140]Pusher252 may includebody254 andattachment mount256. A width of a distal end ofbody254 may be less than a width of a proximal end of the body.Body254 may includeprojections258.Projections258 may fit ingrooves246 of distractor238 (shown in FIG. 32) to allowpusher252 to be guided throughbody240 andarms242 of the distractor. In some embodiments, pushers may be color coded to match to a particular size of distractor. In some embodiments,projections258 may be sized so that the pusher fits in any size of distractor.
• [0141]Pusher252 may be used to move a member throughdistractor238 to a desired position between engaging plates. FIG. 35 depicts a side view of an embodiment ofpusher252 positioned indistractor238 andinserter210. Whenpusher252 is positioned ininserter210, the pusher may maintain a position of a member between engagingplates102,106 and allow for removal ofdistractor238 from the engaging plates.
• During some implant insertion procedures, a channel or channels may be formed in vertebrae. The channel or channels may correspond to a coupling projection or coupling projections of engaging plates. Instrument guides may be used to facilitate formation of a channel or channels in vertebrae. In some embodiments, two instrument guides may be coupled to an inserter. The instrument guides may be inserted into a disc space. A distractor may be introduced into the inserter to move the instrument guides against vertebrae. Channels may be formed in the vertebrae using instruments in combination with the instrument guides.[0142]
• FIG. 36 depicts a perspective view of[0143]instrument guide260.Instrument guide260 may includeslots261, stops262, and guidepiece264.Slots261 may allowinstrument guide260 to be coupled to extensions of arms of an inserter.Stops262 may limit an insertion depth ofinstrument guide260 between vertebrae.Stops262 may haveopenings266. Fasteners may be positioned throughopenings266 to secureinstrument guide260 to a vertebra during formation of a channel or channels in the vertebra. The fasteners may include, but are not limited to, screws, pins, barbs, or trocars. A head of a fastener may be too large to pass throughopening266.
• [0144]Guide piece264 may be used to place a cutting edge of an instrument (e.g., chisel, drill, reamer) at a desired location relative to a vertebra. The instrument may be passed throughguide piece opening268. Guide piece opening may properly orient a cutting portion of the instrument relative to a vertebra that the instrument is to form a channel in. A portion of the instrument may be positioned ingroove270 to guide the cutting edge of the instrument during formation of a channel in the vertebra. As the instrument travels alonggroove270, bone matter may be removed from the vertebral surface adjacent to instrument guide260 to form a groove in the vertebra. Bone matter may be removed to form an opening of a length and/or depth similar to a cross-sectional shape of a coupling projection on an engaging plate.
• FIG. 37 depicts a perspective view of[0145]distractor238,driver272 and instrument guides260 coupled toinserter210.Driver272 may position a shaft offastener274 through an opening instop262 so that the fastener couples instrument guide260 to the vertebra.
• FIG. 38 depicts a top view of[0146]chisel276. FIG. 38A depicts a side view ofchisel276.Chisel276 may includeend member278,shaft280 and handle282.End member278 may include a cutting edge capable of penetrating bone. In some embodiments,shaft280 may be bent to accommodate an angle between a proximal portion of an inserter and a channel guide positioned between vertebrae.
• FIG. 39 depicts a perspective view of instrument guides[0147]260,distractor238, and chisel276 coupled toinserter210.End member278 ofchisel276 may be inserted through a guide piece opening inguide piece264 and positioned ingroove270 ofinstrument guide260. Cutting edges ofend member278 may be forced into a vertebra. Insertion depth ofend member278 into the vertebra may be monitored using fluoroscopic imaging. In some embodiments,shaft280 may be marked with a scale. When the end member of the chisel first contacts the vertebra, a first reading of the scale relative to a top of the inserter may be taken. As the chisel is driven into the vertebra, an estimate of the insertion depth may be provided by taking the difference between the current scale reading relative to the top of the inserter and the first reading of the scale relative to the top of the inserter. In some embodiments, a stop may be positioned onshaft280 to limit insertion depth of the chisel into a vertebra. The stop may contact guidepiece264.
• FIG. 40 depicts a perspective view of a reamer in combination with[0148]inserter210,distractor238 and instrument guides260.Reamer284 may allow removal of bone matter from a vertebral surface to form a groove in the vertebral surface. The groove may have an arcuate cross-sectional shape to complement an arcuate shaped coupling projection on an engaging plate (as shown in FIGS.9-11).Reamer284 may includecutter286,body288 and handle290. In some embodiments, a drive shaft may be positioned inbody288. The drive shaft may be coupled tocutter286 and to handle290. The drive shaft may be flexible or include flexible joints so thatcutter286 will be oriented in a proper direction relative to the inserter and the vertebra.Cutter286 may be inserted in an opening ofguide piece264 ofinstrument guide260. Rotation ofhandle290 may allowcutter286 to remove vertebral bone and form a groove in the vertebra. Contact ofstop292 withguide piece264 may limit an insertion depth ofcutter286 into the vertebra. A position ofstop292 alongbody288 may be adjustable. In some embodiments, insertion depth ofcutter286 into the vertebra may be monitored during formation of the groove using fluoroscopic imaging.
• In certain embodiments, a trial spacer may be used during formation of a disc space between vertebrae. A trial spacer may be used to determine when an appropriate sized disc space is formed between vertebrae. The trial spacer may also determine a size of trial endplates and/or engaging plates. FIG. 41 depicts embodiments of[0149]trial spacers294. A distal end oftrial spacer294 may be similar in size (e.g., small, medium or large) to engaging plates and/or trial endplates.
• During some implant insertion procedures, trial endplates may be used to determine the proper height and lordotic angle of the implant to be inserted into the patient. Top surfaces of the trial endplates may be smooth and/or polished so that the trial endplates easily slide between vertebrae. FIG. 42 depicts a bottom view of[0150]trial endplate296.Trial endplate296 may includeslots114 to engage extensions of arms of an inserter.Slots114 may include indents118.Indents118 may engage detents of an inserter to securely couple the inserter totrial endplate296.
• [0151]Trial endplates296 may vary in thickness. For example, a thickness oftrial endplate296 at an edge nearslots114 may exceed a thickness of the trial endplate at an edge opposite the slots.Trial endplates296 may have slopes ranging from about 2° to about 22° (e.g., about 3°, about 6°, about 9°, about 12°). The combined angle of a top trial endplate and a bottom trial endplate may determine the lordotic angle that will be established by engaging plates of a implant that correspond to the trial endplates. For example, if two trial endplates with 3° of slope are used, an implant formed between the vertebrae may be formed with two engaging plates, each engaging plate having 3° of slope. The formed implant may establish a 6° lordotic angle between the vertebra. If the top trial endplate has 3° of slope and the bottom trial endplate has 6° of slope, an implant formed between the vertebrae may be formed with a top engaging plate having a 3° slope and a bottom engaging plate having a 6° slope. The formed implant may establish a 9° lordotic angle between the vertebrae.
• An instrumentation kit for an implant insertion procedure may include individual trial endplates that correspond in height and slope to each engaging plate supplied in the instrumentation kit. If more than two engaging plates of the same size and slope are supplied in the instrumentation set, only two trial endplates corresponding to that size and slope engaging plate are needed in the instrumentation set. Having a trial endplate that corresponds to each engaging plate allows a surgeon to insert trial endplates that correspond to available engaging plates between the vertebrae. The surgeon is able to test every combination of implant that can be formed using the trial endplates supplied in the instrumentation kit. The surgeon can test an exact model of the implant that is to be formed in the disc space by choosing the appropriate trial endplates and distractor.[0152]
• When the trial endplates are coupled to an inserter and positioned in the disc space, a distractor may be positioned in the inserter to separate the trial endplates. If the distractor easily slides into the inserter, a larger distractor may be tried. If the distractor cannot be inserted into the inserter, a smaller distractor may be tried. If some force is needed to insert the distractor into the inserter, the distractor may be the appropriate distractor. An appropriate distractor may overdistract vertebrae by about 1.5 mm to about 2.0 mm. Overdistraction of vertebrae by about 1.5 mm to about 2.0 mm may extend ligaments proximate the vertebrae sufficiently to allow for relative movement of components of a disc implant once the implant has been inserted. A fluoroscopic image may be obtained to determine if the trial endplates establish desired lordosis and height between the vertebrae. If the lordosis or height is not correct, other trial endplates and/or distractors may be coupled to the inserter. The inserter may be positioned between the vertebra until the trial endplates and distractor establish a desired height and lordotic angle between the vertebrae. Engaging plates that correspond to the trial endplates and a member that will slide down the distractor may be obtained from the instrumentation kit.[0153]
• FIG. 43 depicts perspective view of a member seater.[0154]Member seater298 may facilitate seating of a member of an implant between engaging plates.Member seater298 may includearms300,300′ and handles302,302′.Arms300,300′ may be pivotally coupled tohandles302,302′.Arm300′ may be positioned on a topside ofprojection128 of member104 (depicted in FIG. 1).Arm300′ may engageslots114 of engaging plate102 (depicted in FIG. 1). Compression ofhandle302 in the direction ofhandle302′ may allowarm300′ to move towardarm300. Movement ofarm300′ towardarm300 may allowmember104 to be securely positioned inrecess116 of engagingplate102. After seatingmember104,member seater298 may be removed from the intervertebral space.
• Engaging plates, members and/or trial endplates may be made of one or more biocompatible materials including, but not limited to, metals, alloys, ceramics, polymers and/or composites. For example, an alloy may include cobalt-chrome-molybdenum (CoCrMo). Ceramics may include, but are not limited to, alumina, zirconia or composites. Polymers used for implant components may include ultra-high molecular weight polyethylene, polyfluorocarbons and/or polyesteresterketone (PEEK). In some embodiments, all components of a disc implant may be formed of metal. In certain embodiments, engaging plates and/or members may be formed of titanium, titanium alloys, steel and/or steel alloys. In addition, materials may be chosen based upon characteristics such as durability and ease with which biological tissue, such as human bone, fuse with the material. For example, titanium may wear poorly over time, but may fuse well with bone. A cobalt-chrome-molybdenum alloy may wear well, but may not fuse as well with biological tissue.[0155]
• In some embodiments, engaging plates and/or members may be or may include bioabsorbable material. Surfaces of engaging plates and/or members that contact bone may include a coating to promote osseointegration of the implant component with bone. The coating may be, but is not limited to, a bone morphogenic protein, hydroxyapatite and/or a titanium plasma spray.[0156]
• In certain embodiments, engaging plates, members and/or trial endplates of an implant may be formed of different materials to decrease wear of the implant over time. An implant embodiment may include engaging plates formed of titanium or cobalt-chrome-molybdenum and one or more members formed of ceramic (such as alumina) or polymer (such as ultra-high molecular weight polyethylene). Material choice may be influenced by various factors. For example, many polymers tend to “flow” when they are produced at less than a certain thickness, possibly deforming and leading to the failure of an implant. Ceramics, however, do not tend to deform, but may potentially shatter under pressure.[0157]
• In certain embodiments, an implant and/or trial endplates may be distributed and/or sold pre-assembled and stored in sterile packaging until needed. In some implant embodiments, radiological markers may be placed in components of an implant that are invisible to x-rays. The radiological markers may allow the position of the component to be determined using x-rays or other imaging techniques. The ability to determine the position of all components of an implant may eliminate a need to have a surgical procedure to determine the location of the implant.[0158]
• In some embodiments, steps may be taken to adjust the coefficient of friction of materials used to form engaging plates, members and/or trial endplates. Implant components may be machined, formed and/or chemically treated to decrease the coefficient of friction and reduce the amount of wear on engaging plates and/or members. In some implant embodiments, an insert, coating, liner or other covering may be placed on all, or a portion, of a surface of the engaging plates and/or members. The insert, coating, liner or covering may modify frictional or other physical properties of an engaging plate and/or member relative to another component of an implant. In some embodiments, a surface of a member and/or an inner surface of an engaging plate may include a surface coating to reduce noise resulting from contact between implant components.[0159]
• An implant may be positioned in an intervertebral space between adjacent vertebrae using an anterior, lateral and/or posterior approach. A surgeon may perform a discectomy to remove all or a portion of an intervertebral disc. Instruments such as curettes, rongeurs and bone shavers may be used to prepare the disc space for the implant. Vertebral surfaces that will contact engaging plates of an implant may be cleaned of cartilage or other tissue. The vertebral surfaces may be shaped to substantially conform to outer surfaces of engaging plates to be placed against the vertebral surfaces.[0160]
• In an implant insertion procedure, trial spacers may be inserted in the intervertebral space to determine if a formed disc space is sufficiently large and/or to determine a size of an implant to be inserted in the disc space (e.g., small, medium or large). Radiological images may be taken during the discectomy with a trial spacer positioned between the vertebrae to determine if a disc space of the proper width and depth has been formed. One or more marks may be scored or burned into a surface of a vertebra close to a center of an edge of the vertebra. The mark or marks may be used as references to determine a proper lateral position of the implant and/or instrumentation during insertion of the implant.[0161]
• If needed, instrument guides may be positioned against vertebrae. A reamer or a chisel may be used in conjunction with the instrument guides to form recesses in the vertebrae. The recess may have a shape that conforms to a shape of a coupling projection that extends from an engaging plate of an implant to be positioned between vertebrae.[0162]
• Trial endplates may be coupled to an inserter. The trial endplates may be positioned between the vertebrae. A distractor of a determined height may be positioned in the inserter to separate the trial endplates. During some insertion procedures, a mallet or other impact device may be used to drive the distractor into the inserter. If the trial endplates and distractor combination do not establish a desired separation height and/or lordotic angle between the vertebrae, different trial endplates and/or different distractors may be tested until a combination of trial endplates and distractor is found that establishes the desired separation height and lordotic alignment of the vertebrae. If removal of trial endplates from a disc space is difficult, a slap hammer or other impact device may be used to facilitate removal of the inserter and trial endplates from the disc space. Using various combinations of trial endplates and distractors may allow a surgeon to determine the correct lordotic angle and height of implant components to be inserted in the intervertebral space.[0163]
• Engaging plates that correspond to trial spacers that establish a desired separation height and lordotic angle may be chosen from available engaging plates supplied in an instrumentation kit. The chosen engaging plates may be coupled to arms of an inserter. The engaging plates may be positioned in the disc space. The chosen distractor may be positioned in the inserter. During some insertion procedures, a mallet or other impact device may be used to drive the distractor into the inserter. Positioning the distractor in the inserter may separate engaging plates attached to the arms to a desired separation distance. Separation of the engaging plates may force coupling projections of the engaging plates into surfaces of adjacent vertebrae to anchor the engaging plates to the bone.[0164]
• A member that will slide down channels of the distractor may be obtained from the instrumentation set. The member may be positioned in the distractor and guided between engaging plates with a pusher. The pusher may be coupled to the inserter to maintain a position of the member between the engaging plates. After the member is positioned between the engaging plates, a mechanism on the arms of the inserter may be engaged to release the extension on the arms from the engaging plates. The inserter, distractor and pusher may be removed from the disc space. During some insertion procedures, a slap hammer may be used to facilitate removal of the inserter, distractorand/or pusher from the disc space. Radiological images may be taken to ensure that the implant is positioned as desired.[0165]
• During some insertion procedures, a member seater may be used after an inserter has been removed from the engaging plates. The member seater may be positioned on a projection of a member and in a slot of an engaging plate. Handles of the member seater may be compressed to securely seat the member in a recess of the engaging plate. The handles may be released to disengage the arms from the projections and from the engaging plate. The member seater may be removed from the intervertebral space.[0166]
• In this patent, certain U.S. patents have been incorporated by reference. The text of such U.S. patents, is, however, only incorporated by reference to the extent that no conflict exists between such text and the other statements and drawings set forth herein. In the event of such conflict, then any such conflicting text in such incorporated by reference U.S. patents is specifically not incorporated by reference in this patent.[0167]
• Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.[0168]

Claims (45)

What is claimed is:

1. An artificial disc implant for a human spine, comprising:

two engaging plates, wherein each engaging plate comprises:

a recess; and

two or more slots configured to engage an insertion instrument during insertion of the disc implant, wherein the slots are at an angle relative to an anterior-posterior axis of the engaging plates; and

one or more members positionable between the engaging plates, wherein at least one of the members comprises a portion configured to complement at least one of the recesses to allow axial rotation, lateral movement and anteroposterior movement of the engaging plates relative to each other during use.

2. The implant ofclaim 1, wherein one or more sides of at least one of the recesses are tapered.

3. The implant ofclaim 1, wherein a height of a posterior side exceeds a height of an anterior side of at least one of the recesses.

4. The implant ofclaim 1, wherein the portion configured to complement at least one of the recesses is a convex portion, and wherein at least one of the recesses comprises a concave portion complementary to the convex portion.

5. The implant ofclaim 1, wherein at least one of the engaging plates comprises a convex portion, wherein at least one of the members comprises a concave portion, and wherein the convex portion is complementary to the concave portion.

6. The implant ofclaim 1, wherein the two engaging plates and the one or more members are made of metal.

7. The implant ofclaim 1, wherein the slots are dovetailed.

8. A system for inserting an artificial disc implant between human vertebrae, comprising:

an inserter having a body, a passage through the body, and arms, wherein the arms are configured to be releasably coupled to engaging plates of the artificial disc implant; and

a distractor positionable in the passage in the body, wherein the distractor is configured to separate the arms of the inserter such that engaging plates coupled to the arms of the inserter remain substantially parallel during separation of the engaging plates to form a disc space between the human vertebrae.

9. The system ofclaim 8, wherein the inserter is configured such that coupling the inserter to the engaging plates does not increase separation between the engaging plates.

10. The system ofclaim 8, wherein the arms of the inserter are configured to be releasably coupled to dovetailed slots in the engaging plates.

11. The system ofclaim 8, wherein the inserter and the distractor are configured such that the distractor does not contact the engaging plates during insertion of the engaging plates.

12. The system ofclaim 8, further comprising a pusher, wherein the pusher is configured to drive a member through a passage in the distractor and position the member between the engaging plates.

13. The system ofclaim 8, further comprising a member seater configured to seat a member in the engaging plates through the passage in the inserter.

14. The system ofclaim 8, further comprising trial endplates and one or more additional distractors, wherein the trial endplates are configured to be used in combination with the distractors to determine height and lordotic angle of the artificial disc implant to be inserted.

15. A method for forming an artificial disc implant between human vertebrae, comprising:

positioning two engaging plates between the human vertebrae;

separating the engaging plates such that the engaging plates remain substantially parallel;

positioning one or more members between the engaging plates such that a surface of at least one of the members contacts a complementary surface of at least one of the engaging plates; and

wherein the engaging plates and at least one of the members are configured to allow relative movement of the engaging plates during use.

16. The method ofclaim 15, further comprising determining a height, size and lordotic angle of the artificial disc implant to be formed between the vertebrae before positioning the engaging plates between the vertebrae.

17. The method ofclaim 15, further comprising forming a recess in at least one of the vertebrae to engage a projection on at least one of the engaging plates.

18. The method ofclaim 15, wherein positioning at least one of the members comprises positioning such members in a rounded recess in at least one of the engaging plates.

19. The method ofclaim 15, wherein the engaging plates are positioned using an angulated anterior approach to the vertebrae.

20. The method ofclaim 15, wherein the engaging plates are positioned using an anterior approach to the vertebrae.

21. A disc implant, comprising:

a first engaging plate and a second engaging plate;

a member positionable between the engaging plates;

wherein the first engaging plate comprises a recess configured to receive a base of the member, wherein one or more sides of the recess are tapered; and

wherein a surface of the second engaging plate complements a surface of the member to allow axial rotation, lateral movement and anteroposterior movement of the engaging plates relative to each other during use.

22. The implant ofclaim 21, wherein a height of a posterior side of the recess is greater than a height of an anterior side of the recess.

23. The implant ofclaim 21, wherein at least one of the engaging plates comprises a concave portion complementary to a convex portion of the member.

24. The implant ofclaim 21, wherein at least one of the engaging plates comprises a convex portion complementary to a concave portion of the member.

25. The implant ofclaim 21, wherein at least one of the engaging plates comprises at least one coupling projection.

26. The implant ofclaim 21, wherein the engaging plates comprise one or more slots, wherein the slots are configured to engage an instrument for insertion of the implant.

27. The implant ofclaim 21, wherein the engaging plates comprise one or more slots wherein the slots are configured to engage an instrument for insertion of the implant and wherein the slots are positioned at an angle relative to anterior-posterior axes of the engaging plates.

28. A system for inserting an artificial disc implant, comprising:

an inserter having a body, a passage through the body and arms, wherein the arms are configured to be releasably coupled to engaging plates of the artificial disc implant; and

one or more distractors positionable through the passage in the body, the distractors configured to move the arms to establish a separation distance between engaging plates coupled to the arms.

29. The system ofclaim 28, further comprising a pusher configured to drive a member down a passage through the distractor to a position between the engaging plates.

30. The system ofclaim 28, further comprising a member seater configured to seat a member between the engaging plates.

31. The system ofclaim 28, further comprising trial endplates, wherein the trial endplates in combination with at least one distractor are configured to determine height and lordotic angle of the artificial disc implant to be inserted.

32. An instrument kit, comprising:

one or more trial endplates;

a plurality of implant components; and

an inserter configured to couple to selected implant components to allow the components to be positioned in a disc space;

one or more distractors configured to couple to the inserter to establish a separation distance between the selected implant components coupled to the inserter.

33. The instrument kit ofclaim 32, wherein the inserter is configured to couple to the trial endplates.

34. The instrument kit ofclaim 32, wherein one or more of the trial endplates are sloped.

35. The instrument kit ofclaim 32, further comprising a pusher configured to position an implant component between the selected implant components coupled to the inserter.

36. The instrument kit ofclaim 32, further comprising a member seater, wherein the member seater is configured to apply pressure to one of the implant components.

37. The instrument kit ofclaim 32, further comprising a pusher configured to position an implant component between the selected implant components coupled to the inserter.

38. A method for forming an implant between vertebrae of a spine, comprising:

coupling a pair of engaging plates to a portion of an inserter;

positioning the engaging plates between adjacent vertebrae;

positioning one or more members between the engaging plates; and

wherein at least a portion of the engaging plates and at least a portion of at least one member is configured to allow at least some movement of a first vertebra relative to a second vertebra.

39. The method ofclaim 38, wherein positioning the engaging plates comprises an anterior approach to the vertebrae.

40. The method ofclaim 38, wherein positioning the engaging plates comprises an angled anterior approach to the vertebrae.

41. The method ofclaim 38, further comprising positioning a distractor in the inserter wherein the distractor is configured to separate in a substantially parallel direction one engaging plate from a second engaging plate.

42. The method ofclaim 38, further comprising positioning a distractor in the inserter wherein the distractor is configured to separate one engaging plate from a second engaging plate and wherein positioning a member of the one or more members between the engaging plates comprises guiding the member through the distractor with a pusher.

43. The method ofclaim 38, wherein the movement comprises at least axial rotation and lateral movement of the spine.

44. The method ofclaim 38, further comprising inserting one or more trial implants and one or more distractors in the vertebral space before coupling the engaging plates to the inserter to determine a lordotic angle of the engaging plates and a height of the members to be inserted.

45. An instrument for insertion of a disc implant, comprising:

a body;

one or more arms configured to couple to one or more engaging plates;

a distractor positionable in an opening of the body, wherein the distractor is configured to separate in a substantially parallel direction one engaging plate from a second engaging plate.

Images