Abstract: An intervertebral implant assembly includes and inserter tool and an implant having a U-shaped body shaped and dimensioned to be placed between two adjacent vertebras. The U-shaped body comprises a rounded front end, an open back end, first and second elongated components extending from the rounded front end, forming the U-shaped body and ending at the open back end and at least one rigid strut extending from and connecting opposite inner side surfaces of the first and second elongated components. A first through-opening is formed in the space between the front end, the rigid strut and the opposite inner side surfaces of the front portions of the first and second elongated components and a second through-opening is formed in the space between the open back end, the rigid strut and the opposite inner side surfaces of the back portions of the first and second elongated components. The inserter tool comprises a shaft, a middle sleeve and an outer sleeve that work together to attach and lock to the implant.

Abstract: An intervertebral insert member and an instrument for positioning the insert in a space between vertebral bodies in vivo. The insert member is advanced by the instrument into a prepared site located between adjacent vertebral bodies. Upon reaching the appropriate insertion point, the sleeve is retracted and a pivotal motion is imparted to the insert. The insert member is pivotally attached to the distal end of the delivery instrument such that it can be articulated about a pivot point that is located on the insert member until it is properly positioned. The positioning instrument is then released from the insert member and removed from the space between the vertebral bodies. An adjustment screw is available to expand the surfaces of the insert member by displacement of a wedge member within the insert.

Abstract: A surgical blade (180) designed for use with an acetabular cup remover (30). The blade includes a body (182) from which teeth (190) extend distally forward. The body and teeth are disposed around the section of a sphere. On each side of the longitudinal axis of the blade body there is an outer tooth and at least two inner teeth. The teeth are further shaped so that one each side of the longitudinal axis through the blade body there are at least two adjacent inner teeth that have rake surfaces located along axes that, extending from the outer surface of the blade body to the inner surface of the blade body, do not intersect.

Abstract: A composite interbody bone implant device is provided including a body having a non-bone composition, such as a polymer, formed into a shape and including one or more cavities. An osteoinductive material, such as bone allograft tissue, may be retained in the one or more cavities of the body. The body is formable via injection molding and/or machining into a shape and size adapted for implantation at a surgical site. The dimensions of the body include a length, a width and a thickness, and the thickness of the body may be less than at least one of the length and width.

Abstract: A method of treating a facet joint of a patient. The facet joint has a superior facet with a superior articular face and an inferior facet with an inferior articular face. An implant delivery cannula is used to position a superior resurfacing implant and an inferior resurfacing implant between the superior articular face and the inferior articular face.

Abstract: An intervertebral insert member and an instrument for positioning the insert in a space between vertebral bodies in vivo. The insert member is advanced by the instrument into a prepared site located between adjacent vertebral bodies. Upon reaching the appropriate insertion point, the sleeve is retracted and a pivotal motion is imparted to the insert. The insert member is pivotally attached to the distal end of the delivery instrument such that it can be articulated about a pivot point that is located on the insert member until it is properly positioned. The positioning instrument is then released from the insert member and removed from the space between the vertebral bodies. An adjustment screw is available to expand the surfaces of the insert member by displacement of a wedge member within the insert.

Abstract: The present invention provides a surgical impactor that includes an impact head, an impacting portion connected to the impact head and a load-transmitting stem connecting the impacting portion to the impact head. The impact head has an impact surface that can be struck by a tool such as a mallet. The load-transmitting stem includes at least one load-limiting resistor. The load-limiting resistor is configured to lock to the impact head and unlock from the impact head when an overload force is applied to the impact surface of the impact head.

Abstract: A surgical instrument for reducing a rod into a saddle of a fixation member includes a distal end for engaging the saddle and a proximal end. A reducing device is disposed between the distal end and the proximal end. The reducing device is operative to reduce the rod into the saddle. The reducing device defines a throughbore. The throughbore provides access there through by a first drive member to secure a plug to the saddle.

Abstract: An expandable sizer instrument for distracting and spacing opposing vertebral bodies of a spine comprises an elongate hollow shaft defining a longitudinal axis and having opposed distal and proximal ends. An actuator is provided at the proximal end and an expandable distractor is provided at the distal end. An elongate push rod extends within the shaft, a proximal end of the push rod being coupled to the actuator and a distal end being coupled to the expandable distractor. The distractor comprises a lower plate immovably attached to the shaft, and an upper plate coupled to the lower plate by a linkage mechanism fully contained within the perimeter of the distractor and operable to move the upper plate away from the lower plate in an expansion direction substantially parallel to the lower plate. The linkage mechanism comprises two laterally spaced linkage pairs with a middle link disposed therebetween.

Abstract: A method of loading an implant inserter with an implant tab and an intramedullary orthopedic implant includes placing the intramedullary orthopedic implant engaged with the implant tab in an implant tab press tool. The implant tab press tool closes the implant tab, which is then moved to a locked position. The implant press tool opens, and the implant tab coupled with the intramedullary orthopedic implant is removed therefrom. The implant tab coupled with the intramedullary orthopedic implant and the implant inserter are placed in an inserter press tool. The inserter press tool closes the implant inserter, which is then moved to a locked position. The inserter press tool opens, and the implant inserter loaded with the implant tab and the intramedullary orthopedic implant coupled therewith is removed from the inserter press tool.

Abstract: A spinal joint distraction system for treating a facet joint including articular surfaces having a contour is disclosed and may include a delivery device including a generally tubular structure adapted to engage a facet joint, an implant adapted to be delivered through the delivery device and into the facet joint, the implant comprising two members arranged in opposed position, and an implant distractor comprising a generally elongate member adapted to advance between the two members of the implant causing separation of the members and distraction of the facet joint, wherein the implant is adapted to conform to the shape of the implant distractor and/or the articular surfaces of the facet upon being delivered to the facet joint. Several embodiments of a system, several embodiments of an implant, and several methods are disclosed including a method for interbody fusion.

Abstract: An insertion device for deploying an implant includes an elongated main body having a distal locking portion for coupling to the implant and a proximal handle portion. The main body defines a central passage and the distal locking portion has outer ridges and slots to allow the outer ridges to flex radially inward when mounting to the implant. A plunger slides in the central passage for movement between an unlocked position for mounting the implant on the distal locking portion, a locked position for locking the implant on the distal locking portion, and an insertion instrument deployed position for deploying the actuation plunger to move the blades from the stowed position to the deployed position. A spike cap drive rotatably mounts on the main body having a socket end for engaging a drive nut on the implant to, in turn, move the spike cap.

Abstract: This present invention concerns a transforaminal intersomatic cage for an intervertebral fusion graft, and an instrument and method for implanting the cage, an embodiment of the cage having a body in the shape of a circular arc and comprising a lateral concave surface, a lateral convex surface, a straight upper surface, a straight lower surface and an end wall having at least one hole, called the end hole, designed to receive a rod of an instrument for implanting the cage between the vertebrae, wherein: the end hole has an orientation that is more or less tangential to the circular arc described by the body; the extremity opposite the end wall of the body includes a return part extending the body toward the center of the circle on which the circular arc described by the body lies.

Abstract: Instruments, kits, and methods are disclosed for installing an implant spacer through an incision and down a surgical corridor. The instruments also serve to align a drill guide and align and insert a spacer stabilizer for stabilization of adjacent bone portions. The instrument comprises an elongated guide bar body, an inserter face at a distal end of said guide bar body for abutting an instrument attachment portion of a spacer, a connection tip portion for securing a spacer against an inserter face, and a guide portion of said elongated guide bar body for aligning instruments with said spacer and for introducing a stabilizer to secure the spacer in a predetermined position between the bone portions. Included is a retractable graft block for securing graft material within an aperture of said spacer during insertion of the spacer.

Abstract: A prosthesis system comprises plates that can be positioned against vertebrae and a selected resilient core that can be positioned between the plates to allow the plates to articulate. The selected resilient core can be chosen from a plurality of cores in response to patient characteristics, such as age and/or intervertebral mobility, such that the prosthesis implanted in the patient is tailored to the needs of the patient. The plurality of cores may comprise cores with different resiliencies, and one of the cores can be selected such that the upper and lower plates articulate with the desired shock absorbing resiliency and/or maximum angle of inclination when the one selected core is positioned between the plates.

Abstract: An insertion tool for positioning intervertebral spacers into disc spaces. The insertion tool has a proximal end and a distal end, a T-handle secured to the proximal end and a pair of alignment rails extending to the distal end. The insertion tool includes a handle secured to the proximal end of the guide rails, and a shaft that extends through the handle, whereby the shaft has a threaded portion that extends to the T-handle. The insertion tool also includes a blocker that is secured to the distal end of the shaft. The blocker includes stop arms that guide the blocker through the guide rails and toward the distal end of the shaft. The blocker may be provided in a plurality of different sizes corresponding to the sizes of the implants to be inserted into a disc space. A lock is provided for locking the implant to the shaft.

Abstract: A bi-directional mechanically deployed rod mechanism utilizes non-parallel cam surfaces with a unique engagement, entrapment, and release methodology. The instrument utilizes a unique spring loading pivot point and lockout mechanisms to prevent early release of the pivot point and bi-directional cam surfaces.

Abstract: An implanting apparatus and an operating method thereof are provided. An implanting apparatus used for implanting an intervertebral cage into a location between two adjacent vertebral bodies, wherein the implanting apparatus comprises a sleeve and an extension member. The extension member has a rod and a coupling column, wherein the rod is screwed inside the sleeve, the coupling column is connected to one end of the rod and exposed outside the sleeve, and the axial direction of the coupling column is substantially perpendicular to that of the rod. When one end of the coupling column is disposed on an inner arc surface of a connecting portion of the intervertebral cage and the rod is rotated with respect to the sleeve, the distance between the coupling column and the sleeve is decreased so as to clamp the connecting portion of the intervertebral cage between the coupling column and the sleeve.

Abstract: Insertion tool assemblies for positioning an implant at a target location in a patient. Insertion tool assemblies that comprise first and second jaw portions configured to engage an implant; a sleeve assembly coupled to the first and second jaw portions; and a handle coupled to the sleeve assembly.

Abstract: A segmented disc nucleus replacement prosthesis and system for its implantation wherein the segments are made of a compliant, homogeneous material throughout. The prosthesis comprises a plurality of modular segments that mate together in a rail-and-slot arrangement. The rails and slots are configured to interlock and hold together under load despite being formed of compliant materials. In one embodiment, insertion tools and stabilizers are utilized for manipulation of the modular segments, the insertion tools and stabilizers being designed to accommodate for handling the compliant modular segments.

Abstract: An inserter can be used to implant a distractible intervertebral body fusion device into a disc space and expand the device. The inserter includes a shaft frame and a drive shaft assembly for expanding the device and a support shaft assembly for stabilizing the device extending distally from the shaft frame. A drive housing can be operably connected to the shaft frame and extend outwardly from shaft frame distal of a proximal end of the shaft frame. Drive housing can have an internal passage that provides access into the shaft frame to a proximal end of the drive shaft assembly. An actuation tool can be disposed with the drive housing with a distal end extending through the access into the shaft frame to interface with the proximal end of the drive shaft assembly such that activation of the actuation tool rotates the drive shaft assembly to expand the device.

Abstract: A surgical apparatus includes an orientation sensor that detects an actual orientation of a surgical tool. The apparatus also includes a tactile orientation feedback device that selectively provides a tactile orientation feedback signal. Moreover, the apparatus includes a controller that causes the tactile orientation feedback device to provide the tactile orientation feedback signal when the actual orientation of the surgical tool detected by the orientation sensor is substantially equal to a predetermined target orientation of the surgical tool.

Abstract: A modular acetabular cup assembly (10, 100, 200, 300, 350) for use with multiple bearing liners (32, 110, 212, 310, 354) is disclosed. The acetabular cup assembly includes a shell (12) having a tapered inner wall (28) and two circumferential grooves (24, 26). The shell (12) may be used with polyethylene, ceramic, metal, and other types of liners.

Abstract: A surgical instrument handle assembly configured for rigid and releasable connection to orthopedic devices including orthopedic shaping or cutting members such as a broaches, reamers and/or osteotomes adapted to prepare the intramedullary canal of a femur in total hip arthroplasty procedures.

Abstract: An extender comprises an inner member including a wall defining a thread form and at least one extension defining a first axial cavity and a second axial cavity, each cavity including first, second and third portions. An outer member includes an actuator and at least one arm having projections disposable with the portions of the axial cavities. The actuator is rotatable to axially translate the inner member such that the projections are disposable between a first position, a second position and a third position. Methods of use are disclosed.

Abstract: Provided is a surgical instrument having an adjustable distal end that can securely engage an interbody for introduction of the interbody into an intervertebral space, can be adjusted before and during the surgical procedure to vary the angle of the distal end of the device and the angle of introduction of the interbody, and after positioning that interbody at the surgical site, can be easily disengaged and removed.

Abstract: A handling apparatus for automated or robot-supported contact tasks is disclosed. The handling apparatus has the following components: a mechanical interface for releasably or fixedly connecting the handling apparatus to a manipulator; a holder, which is movable in relation to the interface, for holding a tool; at least one static-frictionless adjusting element for positioning the holder in relation to the interface to the manipulator; a sensor device for directly or indirectly measuring the force acting on the at least one adjusting element; and a closed-loop controller which is configured to regulate the contact force depending on a predefinable force profile when there is contact between the handling apparatus and a surface.

Abstract: An apparatus for use in spinal interbody fusion comprises, in combination, a spinal interbody fusion implant and an inserter releasably attached thereto. The implant comprises a hollow interior through which the inserter extends, the inserter having a tapered distal tip projecting exteriorly beyond the distal end of the implant to initially distract opposing tissue surfaces and to facilitate insertion of the implant into the intradiscal space between the vertebral bodies.

Abstract: An apparatus for inserting an implant between vertebrae includes a body having a through bore, a central shaft movable within the through bore, the central shaft having a proximal end and a distal end. The apparatus includes a pair of distractor arms having proximal portions and distal portions, the proximal portions pivotally coupled to the body and distal portions for engagement between the vertebrae. Tracking slots are formed in and extend through surfaces of and along a longitudinal axes of the distractor arms and an attachment tip is operably connected to the central shaft, the attachment tip is configured to grip the implant. The apparatus includes a single guide member projecting outward from the attachment tip and the attachment tip is removably connectable to the central shaft in multiple configurations.

Abstract: Implants, tools and methods for performing unilateral posterior lumbar interbody fusion are provided. An interbody implant includes a body having a top and bottom surface extending along a length thereof; and first and second side surfaces extending between the top and bottom surfaces on opposite sides of the body. The height of the first side surface is greater than the height of the second side surface.

Abstract: A surgical instrument is disclosed that facilitates the implantation of one of a number of differently sized or differently configured hip stem prostheses into a proximal end of a femur while also providing a surgeon with a substantial amount of rotational control over the prosthesis during the implantation. A suitable hip stem prosthesis is selected from a family of hip stem prostheses of varying sizes and dimensions. The surgical instrument attaches to the selected hip stem prosthesis via first and second spaced engagement portions such that the instrument is operable to exert rotational control over the selected hip stem prosthesis. The first engagement portion is an impaction portion configured to engage a corresponding impaction feature on a proximal body portion of the hip stem prosthesis. The second engagement portion is an adjustable clamping portion configured to clampingly receive the neck of the hip stem prosthesis, regardless of the prosthesis size.

Abstract: An intervertebral disc prosthesis designed to be substituted for fibrocartilaginous discs ensures a connection between the vertebra of the vertebra column or the end of the latter. The prosthesis includes a pair of plates spaced from each other by a nucleus. The prosthesis has increased stability by providing the nucleus with a translation or rotation stop, or by inducing an angular correction between its plates contacting vertebra, or a combination of these characteristics. The stop includes parts external to the nucleus and contact surfaces perpendicular to their contact directions. Surgical methods and instrumentation for implanting the prosthesis are also described.

Abstract: An end effector assembly for use with an electrosurgical instrument is provided. The end effector assembly has a pair of opposing jaw members. One or more of the jaw members includes a support base, an electrical jaw lead, and a sealing plate coupled to the electrical jaw lead. The sealing plate has a stainless steel layer and one or more piezoelectric sensors. The jaw member also includes an insulative plate disposed between the support base and the sealing plate.

Abstract: A number of orthopaedic surgical instruments are disclosed. A method, apparatus, and system for fabricating such instruments are also disclosed.

Abstract: Bone anchors and surgical instruments (e.g., bone taps, drivers, etc.) are disclosed herein that include integrated guide tips. Use of these anchors or instruments can eliminate one or more of the steps in a conventional bone anchor installation procedure, improving surgical efficiency and safety. For example, a surgical instrument can include a guide projection configured for insertion through a cannulation formed in a bone anchor when the surgical instrument is coupled to the bone anchor. The surgical instrument can also include various mechanisms for adjusting the position of the guide projection relative to the bone anchor. The guide projection can replace the needle, stylet, and guidewire used in typical insertion procedures. The bone anchor can also include integrated tapping features to eliminate the need for a separate bone tap instrument. Thus, in some embodiments, targeting, tapping, and driving the bone anchor can be performed in a single step.

Abstract: A spinal rod persuader, system and method can include an outer tube, an inner tube, and a locking element. A first actuation mechanism can be movable in a linear fashion along a longitudinal axis direction to cause the locking element to move in a linear fashion over the inner tube and to lock the inner tube onto a pedicle screw. A second actuation mechanism can be rotated to cause the outer tube to move in a longitudinal axis direction with respect to the inner tube to push the spinal rod into a final position with respect to the pedicle screw while the pedicle screw is locked to the inner tube. A slot and/or tab structure can be provided in the outer tube such that actuation of the slot/tab will allow disassembly of the inner tube, outer tube and locking element with respect to each other.

Abstract: A spinal fixation element fixation reduction system is provided herein. In general, the system can include a cap element with a bore having a central axis extending therethrough wherein the cap element is configured to releasably engage any type of surgical device (e.g., an access sleeve, a vertebral body rotator, etc.). Further, the system can include a driver configured to be slidably and removably positioned through the cap element. The system can also include an actuator configured to apply a force to the driver substantially along the central axis of the cap element thereby moving the driver in a distal direction so as to effect reduction of a spinal fixation element into a bone anchor. Additionally, a method of reducing a spinal fixation element into a bone anchor is also provided wherein the method can be performed as a minimally invasive surgical procedure or as an open procedure.

Abstract: An instrument system, associated milling or drilling guide and method include use of a trial implant of a size corresponding to an actual implant for the intervertebral space, with a milling guide mounted on the trial implant. The system also includes a cutting tool which is used to form a cutout in an adjacent vertebra.

Abstract: A femoral component instrument includes a rotatable locking mechanism such as a post and is capable of interchangeable use between posterior stabilizing (“PS”) and cruciate retaining (“CR”) femoral component types via the locking mechanism. The instrument further includes a modular pad so that a pad specific to the prosthesis type may be chosen. Each pad of a particular femoral component type is useable with a variety of sizes of that femoral component type. The locking mechanism of the instrument is alternatively useable with a variety of femoral component types. The locking end of the post keys to a pad aperture to rotatably align the post to an appropriate securement position. If a femoral component is not locked to the pad, the post of the instrument moves from an exposed position proximal to the proximal pad surface to a retracted position distal to the proximal pad surface, thereby permitting impaction.

Abstract: An intervertebral implant that can be surgically introduced between adjacent vertebrae and expanded in situ to occupy an optimal space between the vertebrae. The implant is inserted into the evacuated disc space obliquely and then oriented so as to extend laterally across the anterior adjacent vertebrae with its outer ends of the implant supported by the cortical rims on the opposite sides of the vertebrae. The implant has two body members with a space therebetween so the implant may be then distracted and a spacer of predetermined thickness that may be inserted within the space between the body members so as to maintain a desired amount of distraction. The upper and lower surfaces of the implant may have a desired lordotic angle. A method of using an implant is disclosed which permits endoscopic visualization of the disc space.

Abstract: This application describes surgical instruments and implants for building a posterior fixation construct across one or more segments of the spinal column. Extension guides are provided that attach to bone anchors implanted within the spine. The extension guides have a guide channel that align with a rod channel in the anchor to help direct the rod to the anchor. Instruments are provided to aid in insertion and positioning or the rod.

Abstract: In an artificial hip joint stem of the present invention, a distance between an inner wall portion and an outer wall portion is decreased as separating from an opening part in a sectional view that is parallel to a stem central axis and includes the inner wall portion and the outer wall portion, and both a front wall portion and a rear wall portion have a planar region in a sectional view that is parallel to the stem central axis and includes the front wall portion and the rear wall portion. A stem inserter of the present invention includes a disk-shaped front end part. The present invention also provides an artificial hip joint system including the artificial hip joint stem and the stem inserter, and an artificial hip joint including the artificial hip joint stem.

Abstract: Disclosed herein are methods and devices for distracting adjacent vertebrae during surgical procedures for implanting spinal prostheses. In an exemplary embodiment, a distractor is disclosed that maintains the empty space between adjacent vertebrae following a discectomy, and that can removably mate with other surgical instruments, such as, for example, a filler bar, an implanting tool, or a funnel. In other embodiments of the present invention a distractor is disclosed having various features to assist in implanting a spinal prosthesis, such as, for example, an angled distal end and/or an expandable paddle. In another embodiment of the present invention, an articulating inserter is disclosed. Moreover, various implants and funnels are also disclosed herein.

Abstract: A device for facilitating implantation of an intramedullary nail includes a coupling portion extending from a first end configured to couple to a proximal end of an intramedullary nail to a joint portion and a radiolucent handle coupled to the joint portion and extending distally therefrom along a path which, when the coupling portion is coupled to an intramedullary nail in a desired orientation, extends substantially parallel to a longitudinal axis of a proximal portion of the nail, the radiolucent part including first and second radiopaque markers positioned and oriented so that, when the nail is coupled to the coupling portion in the desired orientation, the first and second markers align with edges of the proximal portion of the nail.

Abstract: Instruments are provided for shifting elongate members, such as spinal rods, with respect to coupling members of spinal fixation systems. The instruments include a low friction drive mechanism having one or more rolling elements that ride along a helical groove or track in order to transform rotational movement of a drive member into linear shifting of a reducer member that shifts the elongate member. A one-way locking mechanism may be provided to selectively prevent unwanted counter-rotation of the low friction drive mechanism. The one-way locking mechanism may include annular ratchet teeth arranged on the exterior of the drive member and a ratchet pawl located adjacent to the teeth and selectively engageable therewith.

Abstract: An annulus repair system is provided. This repair system may cover a hole or opening in the annulus or repair a defect or damage to the annulus. In one embodiment, the annulus repair system comprises a blocking component that covers a hole in the annulus, a stabilizing component that helps stabilize the blocking component and a suturing material that connects the two components together. In certain embodiments, the annulus repair system may further comprise a cannula for guiding the blocking component, the stabilizing component and at least a portion of the suturing material through body tissue and into the disc space. Methods for utilizing the annulus repair system of the present invention also are provided.

Abstract: An intervertebral implant includes a first endplate having a first surface configured to substantially engage with a first vertebral body and a second surface having an extension with a concave contact surface, the concave contact surface being spaced apart from the second surface. The implant further includes a second endplate having a first surface configured to substantially engage with a second vertebral body and a second surface comprising a convex contact surface, and the second endplate having first and second side rails positioned along and above the second surface defining a first and second arcuate slots on opposing sides of the second surface. A plate connecting the first and second endplates is also provided.

Abstract: An insertion tool for positioning intervertebral spacers into disc spaces. The insertion tool has a proximal end and a distal end, a T-handle secured to the proximal end and a pair of alignment rails extending to the distal end. The insertion tool includes a handle secured to the proximal end of the guide rails, and a shaft that extends through the handle, whereby the shaft has a threaded portion that extends to the T-handle. The insertion tool also includes a blocker that is secured to the distal end of the shaft. The blocker includes stop arms that guide the blocker through the guide rails and toward the distal end of the shaft. The blocker may be provided in a plurality of different sizes corresponding to the sizes of the implants to be inserted into a disc space. A lock is provided for locking the implant to the shaft.

Abstract: A combination of a bone fixation plate for fixation of fractures having a small terminal bone fragment, such as fractures of the distal radius and a holder/impactor for gripping the bone plate and for facilitating impacting the bone plate, with or without predrilled holes. The bone plate includes hook members configured to provide subchondral support to a distal bone fragment, without causing shortening of the fragment into the metaphyseal bone, and without providing a bending torque directed to the base of the plate. The holder/impactor is securely attachable to the bone plate, and includes a striking surface and a distal surface contour overlying and resting adjacent an apex of the hook member. The tooth members of the hook plate are preferably sharpened at their tips and edges to facilitate their impaction.

Abstract: A trial implant system including a trial implant configured to be temporarily inserted into an intervertebral space defined by a superior vertebral body and an inferior vertebral body is disclosed. The trial implant may include a superior plate and an inferior plate coupled to the superior plate. The superior plate may have a first mating portion that defines a first articulating interface and the inferior plate may have a second mating portion that defines a second articulating interface. The second articulating interface may be configured to interact with the first articulating interface of the superior plate such that at least one of the superior plate and the inferior plate is capable of movement relative to the other. The first and second articulating interfaces may be primary or auxiliary articulating interfaces. For example, the first and second articulating interfaces may be corresponding curved surfaces or they may be corresponding engagement features.