Abstract: A secondary cover plate that contacts a stand-alone fusion cage without rigidly connecting to the cage, and instead only docks against the cage (or passes through a fixation cage) and is secured into the adjacent bone. The secondary cover plate is the last item that would be added to the fixation cage construct and would at least partially cover the head of one or more angled screws. The secondary cover plate could slidably engage the fixation cage without permanently snapping into any features of the cage itself. The secondary cover plate would then be final positioned by advancing into one or more adjacent vertebral bodies. The secondary cover plate advancing step could be achieved by tapping it into place (into bone) so that it is finally secured into the bone.

Abstract: Intervertebral devices and systems, and methods of their use, are disclosed having configurations suitable for placement between two adjacent vertebrae, replacing the functionality of the disc therebetween. Intervertebral devices and systems contemplated herein are implantable devices intended for replacement of a vertebral disc, which may have deteriorated due to disease for example. The intervertebral devices and systems are configured to allow for ample placement of therapeutic agents therein, including bone growth enhancement material, which may lead to better fusion between adjacent vertebral bones. The intervertebral devices and systems are configured for use in minimally invasive procedures, if desired.

Abstract: An insertion instrument for expandable spinal implants includes an elongate member, a shuttle, and a worm gear. The elongate member includes a handle portion of a proximal end and an end effector on a distal end, wherein the end effector is configured to be releasably engaged to an expandable spinal implant. The shuttle is slidably disposed within a cavity defined within the end effector and includes a wedged shaped distal end configured to engage an expandable spinal implant. The worm gear is rotatably disposed within the cavity defined in the end effector and is in mechanical communication with the shuttle, such that rotation of the worm gear effectuates movement of the shuttle. Distal movement of the shuttle effectuates articulation of an expandable spinal implant. A method of performing surgery is also disclosed.

Abstract: The present invention provides an expandable fusion device capable of being installed inside an intervertebral disc space to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion. In one embodiment, the fusion device includes body, a first endplate, and a second endplate, a middle ramp piece, a stem, and two ramp pins. The middle ramped piece is operable to move to generate lordotic expansion of the first and second endplates followed by parallel expansion. The fusion device is operable to be deployed down an endoscopic tube.

Abstract: A spinal implant for placement between first and second vertebrae includes a housing having first and second axial end surfaces and a bore extending along an axis through the housing and between the end surfaces. A first projection extends at least partially about the axis and including a channel. A lift is slidably received in the bore and includes threads along its length. A collar is threadably engaged with the lift and extends into the channel on the housing such that the projection prevents axial movement of the collar relative to the housing. Rotation of the collar about the axis causes the lift to move axially relative to the collar and the housing for adjusting the height of the implant.

Abstract: An expandable housing for an interbody fusion system has movable tapered external helical threaded members that travel along tracking to operably engage against the top and bottom shell members, urging them apart to cause expansion in the height of the housing. In an embodiment, the tapered members are disposed in a dual arrangement such that independent engagement of the tapered members along lateral portions of the top and bottom shells cause an angular tilt to the exterior surface of the housing when the tapered members are moved to different degrees. This function permits adjustment in the angular relationship between adjacent vertebrae and assists the lordotic adjustment of the patient's spine. When the functions of the device are used in combination by the surgeon, the device provides an effective tool for in situ adjustment when performing lateral lumbar interbody fusion.

Abstract: The present invention provides an expandable fusion device capable of being inserted between adjacent vertebrae to facilitate the fusion process. The expandable fusion device may include first and second endplates, a translation member configured to expand an anterior side and/or posterior side of the device, a plurality of joists configured to connect the first and second endplates to the translation member, and first and second actuation members disposed internally to the device such that openings on a back side of the device can be used to expand or compress the anterior side, the posterior side, or both and such openings may also be used to introduce graft material into the device.

Abstract: A motion preserving spinal implant is presented for use in placement between intervertebral space for total replacement of a degenerated spinal disc The motion preserving spinal implant has a pair of end plates sandwiched around an inner core and an outer core, with the inner core being concentrically positioned within the outer core. The outer core encapsulates the inner core and provides adequate sealing of the inner core while maintaining flexibility and elasticity to advantageously support physiological movements. The inner core is constructed of an elastomeric material and acts as a solid diaphragm in order to resist and withstand localized compression and other forces. The end plates provide anchoring and fusion with adjoining vertebra and hold the inner and outer cores in place. The motion preserving spinal implant restores the normal height and natural function of the degenerated spinal disc and preserves the natural motion of the spine.

Abstract: The present invention provides an expandable fusion device capable of being installed inside an intervertebral disc space to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion. In one embodiment, the fusion device includes a body portion, a first endplate, and a second endplate, the first and second endplates capable of being moved in a direction away from the body portion into an expanded configuration or capable of being moved towards the body portion into an unexpanded configuration. The fusion device is capable of being deployed and installed in both configurations.

Abstract: A bone fusion device for insertion between bones that are to be fused together, such as, for example, the vertebrae of a spinal column. The bone fusion device comprises at least one extendable tab and one or more tab extension assemblies. Each tab extension assembly is able to be adjusted in order to individually control the extension or contraction of a side of the tab thereby enabling adjustment of the height and/or angle of the tab with respect to the body of the bone fusion device. Each tab extension assembly is able to be individually adjusted such that the side controlled by each assembly is raised or lowered until the desired tab angle is achieved. The tab is advantageously positioned and angled to correspond to the vertebrae to help brace the device until the bone has fused.

Abstract: An expandable intervertebral cage device includes a first base plate and a second base plate, a proximal block with internal threading that mechanically couples the first base plate and the second base plate, and a distal block comprising an internal passage. The device has exactly two arm assemblies, one on each side. Each arm assembly includes a first arm mechanically coupled to the first base plate and the distal block, and a second arm is mechanically coupled to the second base plate and the distal block. A screw is arranged partially within the internal threading of the proximal block and passes through the internal passage of the distal block, such that rotation of the screw relative to the proximal block causes a change in distance between the proximal block and the distal block, and a corresponding change in the spacing and lordosis of the device.

Abstract: Disclosed herein is a spinal interbody cage, comprising an upper plate, a lower plate, a screw arbor and two slide blocks. The screw arbor includes a first section with an outer thread and a second section with an outer thread. The outer threads of the first and second sections have opposite directions. The upper plate respectively has a pair of upper plate slanted surfaces proximate to the first and second sections of the screw rod. The lower plate respectively has a pair of lower plate slanted surfaces proximate to the first and second sections. The screw rod is disposed in and cooperates with the inner threads of the slide blocks. The screw rod and slide blocks are arranged between the upper and lower plates.

Abstract: Embodiments of a composite interbody system 10 for treating mammalian bony segments including various materials to encourage bony fusion while enabling radiographic visualization where the composite interbody system 10 may be employed between two, adjacent mammalian bony segments to stabilize, maintain spacing between, or couple the bony segments. Other embodiments may be described and claimed.

Abstract: A bone trabecular fusion cage for implanting into an intervertebral disc is disclosed. The fusion cage includes a bone trabecular housing made of titanium alloy powder material with trabecular housing accommodation space therein. A side wall of the bone trabecular housing is provided with a plurality of pores, and sclerotin can grow into the bone trabecular housing through the pores to securely fix the bone trabecular fusion cage in the intervertebral disc; and a liner made of polyether-ether-ketone material and fixed in the accommodating space of the bone trabecular housing, wherein the polyether-ether-ketone liner gpores can provide good elastic modulus of bone. With the product of the present disclosure, bone implantation is not required, the patient recovers fast, and excellent fusion effect can be obtained.

Abstract: A prosthetic device for replacing at least part of one vertebral body, the prosthetic device being expandable from a fully collapsed state to a fully expanded state and comprising an upper endplate, a lower endplate and an expandable support structure extending between the two endplates, said expandable support structure being configured to displace the two endplates relative to one another along a longitudinal axis of the prosthetic device and to hold the two endplates at a minimum axial distance that corresponds to the height of at least one intervertebral disc and half a vertebral body, wherein the expandable support structure includes an anterior post and a posterior post, wherein the length (L1/L2) of each post is individually adjustable and is lockable independently from one another to hold the two endplates with an inclination of 0° to 40° relative to each other.

Abstract: An expandable vertebral body device, system, instrument, and methods of assembly and using the device, system, and instrument are disclosed. The vertebral body device includes a body with a first end and a second end, a first rotating member rotatably coupled to the first end, a second rotating member rotatably coupled to the second end, a first extension member moveably coupled to the first end, and a second extension member moveably coupled to the second end. The expandable cage system comprises a vertebral body device and an insertion instrument. Methods for assembling and using the vertebral body device and instrument are also disclosed.

Abstract: This disclosure relates to intervertebral disc prostheses which may have an upper plate, a lower plate, and a mobile core, with the upper surface of the core being in contact with at least a part of the lower surface of the upper plate. In some configurations, limit stops reduce friction while limiting or preventing the movements of the core relative to the lower plate, in translation and in rotation, respectively, along an axis substantially parallel to the lower plate and about an axis substantially perpendicular to the lower plate. Instrumentation for insertion of the prostheses into intervertebral spaces is also described.

Abstract: Systems and methods for treating musculo skeletal disorders of the spinopelvic anatomy including treating spinal deformities by spinopelvic fixation including fusion of the sacroiliac joint at the base of long spinal fusion construct cases. The system may include implants designed to be used as an adjunct to long spinal fusions to further the immobilization and stabilization of the sacroiliac joint. The implants may be designed to augment an S2AI screw and an S1 screw in order to improve durability of the foundation of the spinal construct. The implants may have a triangular cross section.

Abstract: An adjustable spinal fusion intervertebral implant is provided that can comprise upper and lower body portions that can each have proximal and distal wedge surf aces disposed at proximal and distal ends thereof. An actuator shaft disposed intermediate the upper and lower body portions can be actuated to cause proximal and distal protrusions to converge towards each other and contact the respective ones of the proximal and distal wedge surfaces. Such contact can thereby transfer the longitudinal movement of the proximal and distal protrusions against the proximal and distal wedge surfaces to cause the separation of the upper and lower body portions, thereby expanding the intervertebral implant. The upper and lower body portions can have side portions that help facilitate linear translational movement of the upper body portion relative to the lower body portion.

Abstract: An expandable, adjustable inter-body fusion device is presented. The inter-body fusion device can have a first plate, a second plate, and an insert positioned substantially therebetween the first plate and the second plate. The first plate, the second plate, and the insert define an interior cavity. Moving the insert longitudinally with respect to the first and second plates increases or decreases the distance of the first plate with respect to the second plate, effectively expanding the inter-body fusion device and increasing the volume of the interior cavity. The angle between the first plate and the second plate is selectively adjustable.

Abstract: Exemplary embodiments of apparatuses and methods of an expandable fusion device are provided. In one embodiment, an intervertebral implant can be provided, having a first endplate having an upper surface and a lower surface, a second endplate having an upper surface and a lower surface. A first side wall extends from the first endplate and a second side wall extends from the second endplate and are configured to engage one another to provide a selective variable height between the first endplate and the second endplate. The first side wall and the second side wall form a substantially hollow portion substantially enclosed by the first endplate, second endplate and the side walls. The substantially hollow portion is configured to receive bone growth inducing material.

Abstract: Disclosed is an implantable artificial intervertebral disc joint replacement device for implantation between adjacent vertebral bodies. The device allows selective positioning of a disc implant element and comprises translatable surfaces, a mechanism for translation, a means for bone attachment, and an integrated disc implant. The device can be used in the lumbar, thoracic, and cervical regions of the spine in single or multi-level configurations. When implanted in a patient, the device includes an upper (cranial) component and a lower (caudal) component attached to the vertebral body above and below the replaced intervertebral disc respectively, with the joint implant integrated into the translatable surfaces. Following implantation, precise positioning of the joint implant within the intervertebral space with respect to the spinal axis is then adjusted based upon the particular anatomical and functional needs of the individual patient to satisfy spinal range of motion and stability requirements.

Abstract: Various spinal implants and methods for stabilizing the spine are provided. In one exemplary embodiment, a spinal implant is provided having an expandable container with an interior volume that is selectively expandable between a compressed condition and an expanded condition. The expandable container is coupled to a superior endplate member having a bone-contacting surface and an engagement surface effective to mate with a superior surface of the expandable container, and an inferior endplate member having a bone-contacting surface and an engagement surface effective to mate with an inferior surface of the expandable container. In addition, at least one inlet port is formed in the expandable container and is effective to communicate a fluid to at least one cavity disposed within the interior volume of the expandable container.

Abstract: A vertebral body system and method having a polyaxial fastener receiving member, adjustable width plates and a pedicle screw having a pedicle threaded portion and a threaded portion for fastening to the vertebral body.

Abstract: An intervertebral disc prosthesis is disclosed comprising at least two plates, namely first and second plates, articulated about each other by means of a curved surface, namely articulation, of at least one of the plates, each of the plates comprising a surface known as a contact surface, intended to be in contact with a vertebral plate of one of the vertebrae between which the prosthesis is intended to be inserted, this contact surface for each of the plates comprising a geometrical centre at equal distance from at least two diametrically opposite points located on the periphery of the plate, in which the geometric centres of the plates are not vertically aligned, this off-setting of the geometrical centres of the plates engendering an off-setting of the edges of the plates in at least one direction perpendicular to the vertical axis of the spinal column.

Abstract: An expandable intervertebral fusion implant, including an inferior component, including a first plurality of axial members and a first plurality of cross-members, a superior component, including a second plurality of axial members and a second plurality of cross-members, and at least one locking arm operatively arranged to lock the superior component at a distance from the inferior component.

Abstract: An expandable intervertebral implant (10) includes superior (20) and inferior (30) bone contacting members and at least one vertical wire netting (50) interconnecting the superior and inferior bone contacting members. The superior and inferior bone contacting members include at least two bone contacting components interconnected via one or more lateral wire nettings such that the implant is vertically and laterally expandable in situ from a first insertion configuration to a second expanded configuration. The vertical and lateral wire netting are preferably constructed of a plurality of individual link members. The present invention also preferably relates to an associated method of manufacturing the intervertebral implant such that the intervertebral implant can be manufactured as an integral component or part.

Abstract: Embodiments herein are generally directed to vertebral implants and implant trials for use with vertebral implant assemblies. In some embodiments, these implants and implant trials may be used in conjunction with corpectomy procedures.

Abstract: An expandable cage system for use in spinal surgery includes a top portion having an outwardly extending top arm, and a bottom portion having an outwardly extending bottom arm. The bottom arm is configured to engage with the top arm such that upon engagement, the top portion and the bottom portion are substantially restricted from movement relative to each other in an anterior-posterior direction, and in a medial-lateral direction. The expandable cage system further includes a removable shim configured to be positioned between the top portion and the bottom portion to hold the expandable cage in an expanded position within a spinal cavity.

Abstract: An orthopedic device for implanting between adjacent vertebrae comprising: an arcuate balloon and a hardenable material within said balloon. In some embodiments, the balloon has a footprint that substantially corresponds to a perimeter of a vertebral endplate. An inflatable device is inserted through a cannula into an intervertebral space and oriented so that, upon expansion, a natural angle between vertebrae will be at least partially restored. At least one component selected from the group consisting of a load-bearing component and an osteobiologic component is directed into the inflatable device through a fluid communication means.

Abstract: An intervertebral prosthesis for insertion between adjacent vertebrae includes upper and lower prosthesis plates locatable against respective vertebrae and having opposing, concavely curved recesses therein, and a core located between the plates. The core has opposed, convexly curved surfaces received in the recesses of the plates to allow the plates to slide in articulated manner over the core. The opposed surfaces of the core and the recesses of the plates have cooperating spherical curvatures. The recess of each plate surrounds a locating peg projecting centrally from the base of the recess and is bounded by an annular rim, such that the annular rims of the plates are arranged to contact one another at a predetermined limit of sliding movement of the plates over the core. The peg locates loosely in an opening located centrally in a curved surface of the core, whereby the plates can slide over the core in all directions while the peg holds the core captive.

Abstract: An adjustable spinal fusion intervertebral implant is provided that can comprise upper and lower body portions that can each have proximal and distal wedge surf aces disposed at proximal and distal ends thereof. An actuator shaft disposed intermediate the upper and lower body portions can be actuated to cause proximal and distal protrusions to converge towards each other and contact the respective ones of the proximal and distal wedge surfaces. Such contact can thereby transfer the longitudinal movement of the proximal and distal protrusions against the proximal and distal wedge surfaces to cause the separation of the upper and lower body portions, thereby expanding the intervertebral implant. The upper and lower body portions can have side portions that help facilitate linear translational movement of the upper body portion relative to the lower body portion.

Abstract: An endoscopic pedicle probe for use during spinal surgery to form a hole in a pedicle for reception of a pedicle screw has an enlarged proximal end for cooperation with the hand of the surgeon and an elongate shaft terminating in a distal tip that may be pushed through the pedicle to form the hole. The tip may be detachable for replacement. An endoscope extends through the shaft and is connected with a monitor to enable the surgeon to visually observe the area being treated. In a preferred form a light means extends through the shaft to illuminate the area being treated, and in a further preferred form a conduit extends through the shaft to convey a fluid to flush the area being treated. In a further embodiment, two endoscopes are associated with the probe.

Abstract: An expandable, adjustable inter-body fusion device is presented. The inter-body fusion device can have a first plate, a second plate, and an insert positioned substantially therebetween the first plate and the second plate. The first plate, the second plate, and the insert define an interior cavity. Rotation of the insert relative to the first and second plates increases or decreases the distance of the first plate with respect to the second plate, effectively expanding the inter-body fusion device and increasing the volume of the interior cavity. The angle between the first plate and the second plate is selectively adjustable.

Abstract: The present invention provides an expandable fusion device capable of being installed inside an intervertebral disc space to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion. In one embodiment, the fusion device includes a central ramp, a first endplate, and a second endplate, the central ramp capable of being moved in a first direction to move the first and second endplates outwardly and into an expanded configuration. The fusion device is capable of being deployed down an endoscopic tube.

Abstract: Methods and apparatus for posterior lumbar interbody fusion (PLIF) surgical procedures. The apparatus includes a sleeve assembly for guiding an interbody graft into position between adjacent anatomical structures. The sleeve includes a first piece having a first internal ramp and a second piece having a second internal ramp opposite the first internal ramp, and an elastic band configured to connect the first and second pieces together. The first and second internal ramps comprise a V shape with an opening therebetween through which the interbody graft is urged during the surgical procedure.

Abstract: An oblique expanding fusion cage device including a body with a superior portion and an inferior portion. The superior portion and the inferior portion have a proximal end and a distal end. The fusion cage device also includes a pathway, an opening, and an expanding member. The pathway travels from the proximal end to the distal end of the device between the superior and inferior portions. The opening in the proximal end of the body enables access to the pathway. The expanding member may be removably inserted into the opening and is moveable toward the distal end of the body, wherein the expanding member engages the superior portion and the inferior portion as the expanding member moves distally within the pathway.

Abstract: Medical devices in accordance with various embodiments of the present invention employ one or more coaxial screw gear sleeve mechanisms. In various embodiments, coaxial screw gear sleeve mechanisms include a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post and a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing the device to expand.

Abstract: A spacer for separating bones of a joint, the spacer includes a first endplate configured to engage a first bone of the joint; a second endplate configured to engage a second bone of the joint; and an actuation subassembly comprising a drive nut, a drive screw coupled to the drive nut, and a cam frame coupled to the drive screw, wherein the cam frame is disposed between the first endplate and the second endplate, wherein the cam frame comprises a proximal frame end, a distal frame end, and lateral frame sides, wherein cams disposed on the lateral frame sides selectively engage at least one of the first endplate or the second endplate.

Abstract: A joint spacer therapeutically maintains separation of bones of a joint. A carriage is slideably retained within the frame and has at least one ramped surface. An actuator screw is threadably engaged with the frame, and rotatably connected to the carriage, to cause the carriage to slideably move within the frame when the actuator screw is rotated. First and second endplates engage the bones of the joint, and each has at least one ramped surface that is mateable with the ramped surface of the carriage, whereby when the carriage is slideably moved by rotation of the actuator screw, the endplates ramped surface slides against the carriage ramped surface to cause the endplates to move along an axis transverse to the longitudinal axis of the frame, to increase the height of the spacer. Piercing elements are connected to the carriage to pierce bone of the joint when the carriage is moved.

Abstract: A methodology for grafting together adjacent bony structures is provided using an implant device having an endplate with an inner disc portion and outer ring portion spaced from the inner disc portion by a connecting wall disposed therebetween. An endplate interior surface includes a retaining structure for securing the endplate to one of the bony structures, and endplate an exterior surface has an integrally formed socket. A ball-joint rod has a longitudinally extending body and an end, and at least a portion of the ball-joint rod end is curvilinear in shape. The curvilinear ball-joint rod end is rotatably disposed in the endplate socket to fixedly interconnect the bony structures.

Abstract: A prosthetic disc for insertion between adjacent vertebrae includes upper and lower plates, a core disposed between the plates, and at least one projection extending from at least one of the upper and lower curved surfaces of the core into at least one recess of one of the inner surfaces of the plates. The recess is oversize with respect to the projection to allow sliding movement of the plate over the core while retaining the core between the plates during such sliding movement. The projection(s) may include a rod extending through an axial hole in the core, multiple surface features of the core, or the like.

Abstract: An expandable interspinous spacer implant that is configured to be inserted into an interspinous space that is defined between a spinous process of a superior vertebral body and a spinous process of an inferior vertebral body is provided. The implant may include a superior housing, an inferior housing, and a distracting member. The superior housing may have an outer surface that is configured to engage the spinous process of the superior vertebral body and the inferior housing may have an outer surface that is configured to engage the spinous process of the inferior vertebral body. The distracting member may be disposed between the superior and inferior housings, such that activation of the distracting member distracts the superior and inferior housings apart from each other.

Abstract: The first objective of this paper is to take an existing design for a shape-shifting surface (SSS) and make it waterproof, making it an effective barrier to fluid flow. The second objective is to minimize internal stresses in the device during operation, by optimizing the kinematic geometry of the SSS. The first objective was achieved by adding a waterproof membrane between the layers of the SSS, where the membrane had an origami fold pattern that enables the membrane to mimic the kinematics of the SSS. The second objective was achieved by creating a two objective optimization routine, which determined the kinematic geometry of the SSS which would minimize the internal stresses due to compression/tension of the flexure portion of the SSS during operation. The resulting SSS is easier to operate due to lower stresses, and has a membrane which prevents transverse fluid flow and mimics its motion.

Abstract: A method and system for performing bone fusion and/or securing one or more bones, such as adjacent vertebra, are disclosed.

Abstract: An interspinous implant comprises a first member and a second member. The members define a pathway. A third member is movable along the pathway relative to the first member and the second member. Systems and methods are disclosed.

Abstract: A joint spacer therapeutically maintains separation of bones of a joint. A carriage is slideably retained within the frame and has at least one ramped surface. An actuator screw is threadably engaged with the frame, and rotatably connected to the carriage, to cause the carriage to slideably move within the frame when the actuator screw is rotated. First and second endplates engage the bones of the joint, and each has at least one ramped surface that is mateable with the ramped surface of the carriage, whereby when the carriage is slideably moved by rotation of the actuator screw, the endplates ramped surface slides against the carriage ramped surface to cause the endplates to move along an axis transverse to the longitudinal axis of the frame, to increase the height of the spacer. Piercing elements are connected to the carriage to pierce bone of the joint when the carriage is moved.

Abstract: Expandable spinal implants and drivers connected by a bendable joint are disclosed. The flexible connector allows the implant and driver to move to different angular orientations with respect to each other, and to apply rotational force or torque from the driver to the implant and its expansion mechanism. During insertion of an implant into the desired position, the driver may be oriented in the same or different direction than the long axis of the implant. After the spinal implant is placed in the desired position, the driver is used to expand the implant in selected dimensions.

Abstract: An implant for the application in spinal or trauma surgery is provided that has a variable axial length, the implant including a first member and a second member guided relative to the first member to be movable relative thereto in an axial direction for adjusting an overall length of the implant; and at least one engagement member that is in a first configuration configured to engage the first member and the second member such that the first member and the second member are locked with respect to each other and in a second configuration configured to engage the first member such that the second member is movable with respect to the first member; wherein, in the second configuration, the engagement member is configured to be secured against disengagement from the first member by an abutment, and wherein the engagement member is a monolithic part.

Abstract: Spacerless artificial disc replacements (ADR) are disclosed. One preferred embodiment includes two saddle-shaped components to facilitate more normal spinal flexion, extension, and lateral bending while limit axial rotation, thereby protecting the facet joints and the annulus fibrosus (AF). Either or both of the superior and inferior components are made of a hard material such as chrome cobalt, titanium, or a ceramic including alumina, zirconia, or calcium phosphate. The articulating surfaces of the ADR are also preferably highly polished to reduce friction between the components. Metals, alloys or other materials with shape-memory characteristics may also prove beneficial.