WO2017190236A1

WO2017190236A1 - Vertebral implant

Info

Publication number: WO2017190236A1
Application number: PCT/CA2017/050533
Authority: WO
Inventors: Stephan DU PLESSIS
Original assignee: Spinal Resources Inc.
Priority date: 2016-05-06
Filing date: 2017-05-02
Publication date: 2017-11-09

Abstract

A vertebral implant comprises a plurality of generally planar plates in parallel orientation to one another, and at least one web substantially orthogonal to the plurality of plates when no external force is applied to the implant and resiliently connecting at least two of the plates. At least one of the plurality plates is deflectable toward another plate when the implant is subject to an axial force, and whereby the implant is axially compressible.

Description

VERTEBRAL IMPLANT

TECHNICAL FIELD

[0001] This disclosure relates to the field of spinal implants, and more specifically, to vertebral implants to replace vertebral discs and/or vertebral bodies.

BACKGROUND

[0002] The human spine or vertebral column is made up of several segmented series of bones comprised of vertebrae separated from each other by intervertebral discs forming a flexible arranged column. The spine is curved along its length according to its spinal region (cervical, thoracic, lumbar, and sacral). Some spinal regions are more mobile than other regions; for example, the cervical spine is relatively mobile to allow a person's neck to turn at different angles and directions. To allow for this mobility, the vertebrae (cervical, thoracic, and lumbar) are generally articulating at the levels of the discs. Vertebrae articulate with each other to give structural strength and flexibility to the spinal column. The anatomy of the spine allows the motion (e.g. translation and/or rotation in a positive and negative direction) to take place without much resistance, but as the range of motion reaches physiological limits, the resistance to motion gradually increases as the elastic limits of supporting tissues are being reached, thereby bringing such motion to a gradual and controlled stop.

[0003] Intervertebral discs (or intervertebral fibrocartilages) lie between adjacent vertebrae in the vertebral column to facilitate the movement, and also to absorb shock and to maintain space between adjacent vertebrae. Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together. The intervertebral disc contains the shock-absorbing gel called the nucleus pulposus. The nucleus pulposus is the inner gel-like center of the disc and functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads. Discs also comprise an outer fibrous ring, the annulus fibrosus, which surrounds the nucleus pulposus. The annulus fibrosus comprise several layers (laminae) of fibrocartilage made up of both type I and type II collagen. Type I is concentrated towards the edge of the ring where it provides greater strength. The stiff laminae can withstand compressive forces. The fibrous intervertebral disc together with the nucleus pulposus helps to distribute pressure evenly across the disc. This prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates. The nucleus pulposus contains loose fibers suspended in a protein gel that acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.

[0004] The upper and lower surfaces of the vertebrae or vertebral bodies give attachment to the intervertebral discs. The upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the intervertebral discs. These surfaces are the vertebral endplates which are in direct contact with the intervertebral discs and form the joint. The endplates are formed from a thickened layer of the cancellous bone of the vertebral body, the top layer being more dense. The endplates function to contain the adjacent discs, to evenly spread the applied loads, and to provide anchorage for the collagen fibers of the disc.

[0005] The role of the discs as shock absorbers in the spine is crucial. The discs perform a load or weight bearing function, wherein they transmit loads from one vertebral body to the next while providing a cushion between adjacent bodies. The normal discs also allow movement to occur between adjacent vertebral bodies but within a limited range. In this way, the mobility (e.g., range of motion) of the spine is dependent upon the specific anatomy of the spinal region and stiffness of the discs in a given segment (e.g., a pair of adjacent vertebrae) of the spine. Such stiffness varies depending upon the specific anatomy and the location of the specific spinal segment within the spine. For example, a segment located in the cervical region of the spine may have a lower stiffness and thus be more flexible (e.g., greater range of motion) as compared to a segment located in the thoracic region. Stiffness of a specific segment is highly dependent on the extent of degeneration in the disc. The relative degrees of stiffness of segments also vary from one individual to another depending upon various factors (such as degeneration and age) that may affect the physical limits of each segment.

[0006] A certain amount of stiffness in spinal segments is needed for normal optimal or symptom-free functioning. The amount of stiffness in a spinal segment can be defined as the ratio of an applied load to the induced displacement with translation or rotation. A loss of stiffness results in exaggerated movement of the associated spinal segment such as, for example, when torque is applied. From a biomechanical perspective, an excessive loss of stiffness indicates spinal instability or hypermobility which results in abnormal or exaggerated motion. Exaggerated motion caused by instability or loss of physiological stiffness may result in greater stress in adjacent innervated connective tissue resulting in pain, and may also lead to a greater risk of nerve-root compression and irritation in the foramina.

[0007] Neck pain is commonly associated with degenerative changes that occur in the intervertebral discs of the cervical spine and around the supporting joints in each vertebra. These degenerative changes commonly take place as a natural part of aging, from disease, injury or trauma, and from daily wear and tear on parts of the spine. These changes can lead to compression of the spinal cord or nerve roots, putting neurological function at risk. Spine fusions done in conjunction with decompressive procedures such as a discectomy or corpectomy, as described below, is done to remove pressure from the spinal cord or nerve roots caused by bone spurs or to treat various pathological conditions and to eliminate abnormal motion between the vertebrae that cause pain, neurological deficit, or spinal deformity. The treatment is typically done by means of decompression of the neural structures followed by a reconstruction of the spine through techniques using fusion of bone with or without instrumentation.

[0008] Decompression or removal of the pressure on the spinal cord and/or nerve roots is typically achieved by discectomy or corpectomy. A discectomy is the surgical removal of herniated disc material and involves also removing the remaining central portion of the intervertebral disc. A partial or complete vertebrectomy or corpectomy involves removing the degenerative vertebrae including the adjacent discs and/or parts or the whole of a vertebral body and replacing them with a bone graft (strut graft). A corpectomy involves removing the corpus or vertebral body and the discs between each vertebra. This can alleviate compression of the nerves and spinal cord caused by bone growth or spurs behind the vertebra.

[0009] Once the vertebral disc, and/or body or bodies have been removed, a spinal fusion is performed to fill the space or gap left after the vertebral disc and/or body or bodies has been removed. Spinal fusion is a surgical technique that attempts to join two or more vertebrae together by placing grafted bone and existing bone together. Placing a bone graft or strut in the empty space between remaining intact vertebrae holds the remaining vertebrae apart. Some type of internal fixation is usually required to hold the vertebra and the bone graft or strut in place, which is usually done by placing a metal plate on the front of the spine and attaching the plate to both the remaining vertebrae and the strut graft with metal screws or rods, or other types of hardware. When bone or bone containing products are implanted, it encourages the patient's natural bone osteoblasts to unite across the vertebrae and become fused, similar to the way a bone fracture heals. As such, as the bone graft heals, it causes the vertebrae to grow together or fuse and become one solid piece eliminating motion across the fused segment.

[0010] Other stabilizing mechanical constructs can be implanted to prevent motion between vertebrae, such as a cage. A cage is a rigid but hollow non biologic structure that is packed with bone. A cage provides structural support and is used to replace and fill a disc space or a corpectomy defect. Replacement of vertebral bodies with cages and the like can provide the required distraction between intact and healthy vertebrae, for fusion of the intact and healthy vertebrae on either end of the distracted channel, thereby preventing any relational movement there between.

[0011] The fusion process uses bone or bone substitute to eliminate motion across a disc space or a mobile section. The fused segment is rigid and stiff with the aim of eliminating all motion in the segment or segments of the spine and thus provide stability to the spine. However, fusion has many drawbacks, especially when one considers the elimination of motion in order to guarantee stability. For example, fusion not only eliminates motion but also accelerates the degeneration process at spinal levels adjacent to the fusion. When motion is eliminated at one level or segment of the spine, it is common to develop adjacent segment disease because the load of the fused segment is transferred to the adjacent segments, which must carry more load.

[0012] As a result, some recently developed technologies avoid fusion and attempt to preserve spinal motion. For example, some newly introduced technologies include artificial discs that can be placed into the disc space thereby allowing for disc space decompression with the added advantage of preserving the motion as the artificial discs do not result in a primary fusion. Surgeons thus now have the option to fuse the affected spine segment or to perform a disc arthroplasty to preserve motion and potentially to minimize the negative effect of fusion.

[0013] While procedures such as artificial disc replacement are welcome alternatives to fusion in the spine, disc degeneration presents as a spectrum of severity and the current treatment options only address the ends of the spectrum. Unfortunately, the available technology of fusion and disc replacement only covers the extremes of the mobility and stiffness ranges, meaning the treated segment of the spine can have full motion with a disc replacement or will be fused and will have no motion. There are variations in the degrees of motion at different segments of the spine based on the degree of stiffness normally present at the specific level and based on the extent of degeneration of the motion segment. Patients vary significantly from each other, with younger patients generally having less degeneration and thus being better candidates for disc replacement, while older patients might have more degeneration and might be better candidates for fusion, and furthermore while patients in their middle ages might be candidates for fusion or disc replacement. The extent of degeneration can vary significantly even between different levels within the same patient. For example, a patient might have severe degeneration at the C5/6 level but very mild degeneration at the C4/5 level. This patient could potentially be a candidate for fusion at C5/6 and disc replacement at C4/5.

[0014] It would be advantageous to have a device that allows for the management of disc levels demonstrating varying degrees of spondylosis, for example disc levels demonstrating moderate spondylosis, which might not be bad enough for fusion or good enough for disc replacement. These levels could likely benefit from a device that provides for dynamic stabilization, where the segment is stabilized but not fused, so there is still a certain limited amount of motion allowed to enable some physiological motion but not enough to stress the adjacent segments. SUMMARY

[0015] It would be advantageous to have device that allows for the reconstruction of spinal structures while preserving motion by taking into consideration the unique and physiological function of the spine, including restricted range of motion to the normal physiological range of motion of the spine, in various motion planes so as not to place additional stresses on neighboring spinal segments.

[0016] In an aspect, a vertebral implant comprises a plurality of generally planar plates in parallel orientation to one another, and at least one web substantially orthogonal to the plurality of plates when no external force is applied to the implant and resiliently connecting at least two of the plates, wherein at least one of the plurality plates is deflectable toward another plate when the implant is subject to an axial force, and whereby the implant is axially compressible.

[0017] The design of the implant device can provide structural support for the spine and intervertebral distraction, as well as provide dynamic stabilization without unduly restricting motion. The implant can accurately replace the height of the excised material, result in acceptable tension levels in the spine, maintain proper curvature of the spine, obtain balance through the spinal segments, allow compressive forces to be absorbed, and restore normal load- bearing characteristics throughout the spine.

[0018] In an aspect, there is provided a vertebral implant with a superior surface and an inferior surface that may comprise: a plurality of plates alongside one another; at least one web transverse to the plates when the implant is in a neutral position and resiliently connecting at least two of the plates; and wherein at least one of the plurality of plates deflects toward another plate upon an axial force applied to the implant, whereby the implant is axially compressible. [0019] In further aspects, the vertebral implant may comprise a one-piece construction. Each plate may be supported by only one of the at least one webs disposed outboard below the supported plate, whereby the plurality of plates and the at least one web function as a cantilever. Each plate may be supported by only one of the at least one webs disposed inboard below the supported plate. The only one web may be disposed in the center below the supported plate. The vertebral implant may further comprise a plurality of webs. The plurality of webs may be disposed in an alternating manner from top to bottom of the implant outboard of the plurality of plates.

[0020] In even further aspects, the stiffness of the implant may progressively increase from a top to a bottom of the implant. The implant may flex in at least one direction. The implant may expand from a compressive state to bias apart opposing vertebral bodies when placed therebetween. An axial length of the implant in the neutral position may exceed a height of a defect. The implant may comprise a thermoplastic.

[0021] In more aspects, a bone-packing bore may extend along a central axis. An osteoconductive preparation may be applied to at least one of the superior surface and the inferior surface. A physical protuberance may be present on at least one of the superior surface and the inferior surface. A fixation flange may extend vertically from at least one of the superior surface and the inferior surface and comprising at least one attachment aperture therethrough. [0022] An artificial endplate may engage at least one of the superior surface and the inferior surface. The artificial endplate may comprise a longitudinal slot receiving and retaining at least a portion of a retained plate. The retained plate may be loosely retained in the longitudinal slot, whereby the implant and the retained plate articulate therebetween. The retained plate may friction fit within the longitudinal slot. The retained plate may comprise at least one of an uppermost plate of the implant and a lowermost plate of the implant.

[0023] In another aspect, there is provided a vertebral implant that may comprise: a plurality of plates alongside one another; means for resiliently connecting the plurality of plates wherein at least one of the plurality of plates deflects towards another plate when the implant is subject to an axial force, where by the implant is axially compressible.

DESCRIPTION OF THE DRAWINGS

[0024] Example embodiments of concepts presented herein are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:

[0025] Fig. 1 A is a perspective view of a vertebral implant in an aspect; [0026] Fig. IB is a side elevation view of the vertebral implant shown in Fig. 1 A; [0027] Fig. 2A is a rear perspective view of a vertebral implant in a further aspect; [0028] Fig. 2B is a front perspective view of the vertebral implant shown in Fig. 2A; [0029] Fig. 2C is a side elevation view of the vertebral implant shown in Fig. 2A;; [0030] Fig. 3 A is a perspective view of a vertebral implant in a further aspect; [0031] Fig. 3B is a side elevation view of the vertebral implant shown in Fig. 3 A; [0032] Fig. 4A is a perspective view of a vertebral implant in a further aspect;

[0033] Fig. 4B is a side elevation view of the vertebral implant shown in Fig. 4A;

[0034] Fig. 4C is a rear elevation view of the vertebral implant shown in Fig. 4A;

[0035] Fig. 5A is a perspective view of a vertebral implant in a further aspect;

[0036] Fig. 5B is a side elevation view of the vertebral implant shown in Fig. 5A;

[0037] Fig. 6A is a perspective view of a vertebral implant in a further aspect;

[0038] Fig. 6B is a side elevation view of the vertebral implant shown in Fig. 6A;

[0039] Fig. 6C is a rear elevation view of the vertebral implant shown in Fig. 6A;

[0040] Fig. 6D is a top plan view of the vertebral implant shown in Fig. 6A;

[0041] Fig. 7A is a perspective view of a vertebral implant in a further aspect;

[0042] Fig. 7B is a side elevation view of the vertebral implant shown in Fig. 7A;

[0043] Fig. 7C is a rear elevation view of the vertebral implant shown in Fig. 7A;

[0044] Fig. 8A is a top perspective view of an artificial endplate for use with a vertebral implant in an aspect;

[0045] Fig. 8B is a bottom perspective view of the artificial endplate shown in Fig. 8A;

[0046] Fig. 8C is a front elevation view of the artificial endplate shown in Fig. 8A;

[0047] Fig. 8D is a side elevation view of the artificial endplate shown in Fig. 8A; [0048] Fig. 9A is a perspective view of a vertebral implant and artificial endplate assembly in an aspect;

[0049] Fig. 9B is a side elevation view of the vertebral implant and artificial endplate assembly shown in Fig. 9A;

[0050] Fig. 9C is a front elevation view of the vertebral implant and artificial endplate assembly shown in Fig. 9A;

[0051] Fig. 9D is a rear elevation view of the vertebral implant and artificial endplate assembly shown in Fig. 9A;

[0052] Fig. 1 OA is a perspective view of a vertebral implant in a further aspect;

[0053] Fig. 10B is a side elevation view of the vertebral implant shown in Fig. 10A;

[0054] Fig. 11 A is a top perspective of a vertebral implant in a further aspect;

[0055] Fig. 1 IB is a bottom perspective view of the vertebral implant shown in Fig. 11 A;

[0056] Fig. 11C is a rear elevation view of the vertebral implant shown in Fig. 11 A;

[0057] Fig. 1 ID is a side elevation view of the vertebral implant shown in Fig. 11 A;

[0058] Fig. 12A is a perspective view of a vertebral implant and artificial endplate assembly in a further aspect;

[0059] Fig. 12B is a side elevation view of the vertebral implant and artificial endplate assembly shown in Fig. 12 A; [0060] Fig. 12C is a front elevation view of the vertebral implant and artificial endplate assembly shown in Fig. 12 A;

[0061] Fig. 13 A is a perspective view of a vertebral implant in a further aspect; [0062] Fig. 13B is a side elevation view of the vertebral implant shown in Fig. 13 A; [0063] Fig. 14A is a perspective view of a vertebral implant in a further aspect;

[0064] Fig. 14B is a side elevation view of the vertebral implant shown in Fig. 14A [0065] Fig. 15A is a perspective view of a vertebral implant in a further aspect; and [0066] Fig. 15B is a side elevation view of the vertebral implant shown in Fig. 15 A. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS [0067] In the following description, the terms "superior", "inferior", "anterior", "posterior" and "lateral" will be used. These terms are meant to describe the orientation of the implants described herein when positioned in the spine and are not intended to limit the scope of the invention in any way. Thus, "superior" refers to a top portion and "posterior" refers to that portion of the implant (or other spinal components) facing the rear of the patient's body when the spine is in the upright position. Similarly, the term "inferior" will be used to refer to the bottom portions of the implant while "anterior" will be used to refer to those portions that face the front of the patient's body when the spine is in the upright position. The term "coronal" will be understood to indicate a plane extending between lateral ends thereby separating the body into anterior and posterior portions. Similarly, the term "laterally" will be understood to mean a position parallel to a coronal plane. The term "sagittal" will be understood to indicate a plane extending anteroposterior thereby separating the body into lateral portions. The term "axial" will be understood to indicate a plane separating the body into superior and inferior portions. It will be appreciated that these positional and orientation terms are not intended to limit the invention to any particular orientation but are used to facilitate the following description.

[0068] In addition, the term "vertical" is used herein to refer to the "Y", or longitudinal axis of the spine. It will be understood that the longitudinal axis may be referred to generally as "vertical" in the context where the individual is upright. It will also be appreciated that the spine is normally not linear and that a number of curved regions exist. As such, the term "vertical" will be understood to mean a relative orientation of structures in a spinal segment and is not intended to mean orientation with respect to an external reference point.

[0069] In the normal range of physiological motion, vertebrae extend between a "neutral zone" and an "elastic zone". The neutral zone is a zone within the total range of motion where ligaments supporting the spinal bony structures are relatively non-stressed; that is, the ligaments offer relatively little resistance to movement. The elastic zone is encountered when the movement occurs at or near the limit of the range of motion. In this zone, the visco-elastic nature of the ligaments begins to provide resistance to the motion thereby limiting same. The majority of "everyday" or typical movements occurs within the neutral zone and only occasionally continues into the elastic zone. Motion contained within the neutral zone does not stress soft tissue structures, whereas motion into the elastic zone may cause various degrees of elastic responses. Therefore, a spinal prosthetic implant would ideally restrict motion of the vertebrae adjacent thereto to the neutral zone. Such restriction would minimize stresses to adjacent osseous and soft tissue structures. For example, such limitation of movement would reduce facet joint degeneration. [0070] A vertebral implant that may act as either a disc replacement (discectomy implant) or a replacement for one or more discs and one or more adjacent vertebral bodies (corpectomy implant) is provided. The implant may be easily manufactured with characteristics specific to the individual pathology and anatomical condition of the patient so as to preserve motion between adjacent vertebral bodies and permit smooth, continuous expansion and flexion of the vertebral implant in situ, while restoring normal spinal alignment and segmental stiffness. The vertebral implant may expand and compress in the vertical direction, and/or may also flex in response to various loads and forces.

[0071] Figs. 1A and IB illustrate a vertebral implant 10 in an aspect. The vertebral implant 10 may comprise a customizable unitary body 12. The body 12 may be formed in a single unit, one- piece construction. This single piece construction may confer durability on the flexible implant 10, as there are no connections, fractures or points of weakness in the implant 10 that could be prone to cracking or breaking apart, and which would require an additional surgery to correct or replace. In some aspects, the body 12 may be machined out of a single piece of material, while in other aspects the body 12 may be printed by a 3 -dimensional (3D) printer.

[0072] Vertebral implant 10 may have a plurality of interconnected plates 14 in a transverse or substantially orthogonal arrangement with at least one substantially vertical web 16 when the implant 10 is in a neutral position and not subject to external forces (e.g. other than gravity). The plates 14 may run alongside or substantially parallel together in a stacked fashion when not subjected to any external forces. In general, when positioned in a spine, the implant 10 may be oriented vertically with the uppermost plate 14 being referred to as the superior plate 15 and the lowermost plate 14 being referred to as the inferior plate 17. The top-facing surface of the superior plate 15 may be referred to as the superior surface 18 of the implant 10 and the bottom - facing surface of the inferior plate 17 may be referred to as the inferior surface 19 of the implant 10.

[0073] In the aspect shown in Figs. 1A and IB, the plates 14 may be resiliently connected with webs 16 and the plates 14 and webs 16 together function as a dynamic and flexible cantilever system, with the plates 14 functioning as a series of horizontal cantilevers stacked on one another and supported by at most only one web 16, and with the vertically-oriented webs 16 connecting the plates 14 and each supporting one end of a plate 14. The plurality of interconnected plates 14 may form a multi-layer dynamic cage unit that may allow for compression, distraction (axial expansion), and flex to various degrees and directions based upon the stiffness of the body 12. [0074] The various characteristics of the plates 14 and at least one web 16, as will be described below, may allow for the various directional movements of the implant 10, including flexion (posterior to anterior direction), extension (anterior to posterior direction), lateral rotation (when the superior section may be axially rotated with respect to the inferior section about a vertical axis), and lateral bending (side to side or lateral flexion motion), as well as combinations of the above named motions simultaneously. By side to side or lateral flexion, it is meant a direction of the motion wherein the superior section is moved laterally toward the right side or left side of the implant 10. The implant 10 may be manufactured so as to be directionally flexed based upon the stiffness of the body 12, and may also move up and down in a spring-like movement. The vertical dimensions of the implant 10 may be uni directionally expandable and compressible, such as in a spring, which does not have a moment, but may be customized to be multi directionally expandable and compressible based on the body 12 stiffness. [0075] As the implant 10 is subjected to a directional moment and/or is placed under an axial load, it may undergo compression, tension, and bi-axial bending. This may be achieved by manufacturing the implant 10 so as to be dynamic and resiliently flexible. The implant 10 may flex as a result of its specific material properties and design, including the geometry of the plates 14 and configuration of the plates 14 with the webs 16. The implant 10 may be designed so that the stiffness, and therefore its motion, may be tailored to the individual motion segment. The flexibility and direction movement of the implant 10 may be customized so that it is appropriate for a segment of the spine matching the age of the patient. The stiffness of the spinal segment may be measured, for example, by using a stain gauge, and the correct stiffness chosen. Alternatively, the disc height of the disc to be replaced by the implant 10 may be measured to approximate the stiffness of the artificial vertebral replacement to be used. The flexibility and height of the implant 10 may then be tailored to vary the stiffness of the implant 10 and thus allow for customization of the device 10 for the patient being treated. For example, variable stiffness may be required for customization of the implant 10 for the purposes of replacing a disc (in which case, the implant 10 may be more flexible) or a vertebral body (in which case, the implant 10 may be less flexible). Variability in stiffness also may allow for the customization of implant stiffness to be adjusted to the extent or severity of the stiffness and degeneration at the treated segment and/or the entire segment. A surgeon may then be able to select an implant for implantation that might be of low stiffness (e.g. more motion), medium stiffness (e.g. balanced motion) or high stiffness (e.g. less motion) depending on the specific need of the patient. This may allow for functional customization based on demands of the individual patient and the level or levels to be treated. [0076] The cantilever system of implant 10 shown in Figs. 1A and IB may be made up of a plurality of plates 14 that may function in a spring-like manner, but which may be directionally stable to the direction of where the webs 16 are placed. With the plates 14 connected adjacent their ends by the webs 16 in an alternating manner, such as shown in Figs. 1A and IB, the structure of the implant 10 may flex and extend similarly to a normal spine, yet would be more resistant to left and right lateral bending.

[0077] The compression of the plates 14 against each other develops rigidity of the implant 10 to thus support spinal loads. While the system of cantilevered plates 14 is compressible, movement of a segment of the implant 10 may be restricted when an unsupported end of a plate 14 abuts an adjacent plate 14 below it.

[0078] Furthermore, as an axial force is applied to the implant 10, the force may be transferred from one plate 14 to another as deflection takes place. Any such axial expansion or compression may be uniform in some cases, but in others may be non-uniform. As the amount of compressive force on implant 10 increases, the distal ends of plates 14 adjacent the same web may be displaced towards each other and the resistance to such displacement gradually increases due to the tensile strength of the material forming the implant 10 and the elasticity offered by the cantilevered structure. Once the force is removed or reduced, the elastic properties of the cantilevered system of plates 14 may result in a return to the original uncompressed state. As the implant 10 may be resiliently flexible, it may have an inherent tendency to return to this uncompressed state. In such uncompressed state, implant 10 may have the capability of being compressed upon application of a sufficient load. Thus, the system may be compressed and as a result may generate a reactive force in the opposite direction countering the compressive force. The implant 10 may be self-expanding when in a compressive state and may have the ability to resist, transfer and absorb forces applied to it.

[0079] The implant 10 may be also axially expandable and compressible to allow it to fit within an intervertebral channel and for automatic sizing for in situ securement within the intervertebral channel. The implant 10 may also be manufactured and arranged so as to engage opposing vertebrae on either end of the intervertebral channel. When compressed, the implant 10 may generate lift. When the implant 10 is inserted into the intervertebral channel, the implant 10 may decompress and may bias the superior plate 15 against the surface of the superior vertebra and may bias the inferior plate 17 against the surface of the inferior vertebra, elastically biasing apart the superior and inferior vertebral bodies and achieving a balance with the spine. Such elastic biasing may allow the vertebrae to move axially with respect to one another in various planes. This relational movement between vertebrae on either end of the distracted channel (e.g., the superior vertebral plate and inferior vertebral plate) may allow for greater freedom of movement by retaining mobility of the spine without placing additional stresses on neighbouring spinal segments. The implant 10 may be manufactured so as to generate greater lift by increasing the vertical length of the implant 10 such that it may need to be compressed further prior to insertion into the intervertebral channel. By compressing the implant 10 further or maximizing compression, the implant 10 may rebound with more force, generating the lift required for the specific circumstance. [0080] The flexibility and the response to compression of the implant 10 may provide the ability to dynamically respond to loading forces and loading moments applied thereto. This dynamic response of a vertebral implant may be altered by altering the basic structure of the vertebral implant. While the vertebral implant 10 shown in Figs. 1A and IB is an open-loop vertebral implant 10, with distances between adjacent plates 14 of 1-mm, varying designs and distances between adjacent plates may be possible.

[0081] Vertebral implants may be provided in any size, various shapes, and configurations. For example, the implant 10 shown in Figs. 1A and IB may be used for replacing one or more intervertebral bodies given the large number of plates 14 and relatively large height, while the implants 20, 50 shown in Figs. 2A-2C and 5A-5B may be used for replacing one disc at a time, given their relatively small height and small number of plates 24, 54. Depending on the anatomical and pathological requirements of the patient spine to be treated, an implant may be manufactured to replace a single disc or one or more adjacent vertebral bodies, while maintaining range of motion and conferring stability to the spine.

[0082] The characteristics of the implant may be selected so as to confer proper biomechanical properties to the device that may depend on, among other things, the amount of bone that is removed from the patient, the age of the patient, and/or the location of the removed bone. The implants may be used in any region of the spine, and particularly in regions with articulating vertebrae including regions of the cervical spine, thoracic spine, and lumbar spine. The implant may be designed taking into account various architectural abnormalities of the patient's spine and thus correct and stabilize many types of deformities. For example, the implant may be custom fitted to the desired degree of bending to correct and stabilize any deformities in the spine and may be sized to fit the curve to be corrected. [0083] Tailor-ability of the implant in terms of stiffness, and therefore compressibility and rotational and bending directions, may be achieved through modifications of the cantilever structure of plates, which may result in the system having different properties that may vary from layer to layer within the system. The implant may be varied in regard to various characteristics, including implant height, position and thickness of webs, thickness of plates, geometry of plates, and materials. It will also be understood that one or more of these modifications may be used in conjunction to achieve the desired effect for a given patient.

[0084] Implant height

[0085] The size of the vertebrae may vary according to placement in the vertebral column, spinal loading, posture and pathology. Along the length of the spine, the vertebrae changes to accommodate different needs related to stress and mobility. As such, different vertebral segments may require different vertical lengths of vertebral implants. Furthermore, the implants may be used in the reconstruction of an individual disc or one or more adjacent vertebral bodies, which may also affect the required vertical length of implant.

[0086] The implant may replace one or a plurality of vertebrae by varying its height. Depending on the height of the implant, the implant may replace 1 to 4 vertebrae. In some aspects, the implant may replace more than 4 vertebrae. For example, Figs. 1A and IB illustrate a vertebral implant 10 that may allow for additional implant height and may be used in cases where increased height is required such as for a corpectomy. Figs. 2A-2C and 5A-5B illustrate implants 20, 50 with shorter heights, which may be used in cases where lower height is required such as for a discectomy.

[0087] As a person gets older, their discs get stiffer and height of a vertebral segment may get shorter. Younger people generally have original vertebral height that has not yet decreased in vertical length. By customizing the vertical length of the implant to be used to a specific person, one may be able to match the implant size with the extent of degeneration (and other characteristics) of the patient to keep the same height as the vertebral segment being replaced when the implant is in position in the intervertebral channel so as to keep the spine from collapsing. The implant height, when expanded, should exceed the height of the defect, including the amount of anchorage, so as to confer the desired amount of distraction between the superior and inferior vertebral bodies. Generally, the axial length or height of the implant in its neutral position may also slightly exceed the height of the defect.

[0088] The vertebral implant height may be modified by adjusting the thickness of the plates (as will be described in more detail below), adjusting the distance between adjacent plates and thus the length of the webs, and/or adjusting the total number of plates in the implant. All such modifications may affect the mechanical and compressive properties of the implant structure. As an example, adjusting the height of a web may affect the height of the gap or the distance between adjacent plates, which may substantially influence the distance a plate may deflect under a force, and thus the structure stiffness.

[0089] Position and thickness of webs [0090] The length and width of the webs may also affect the flexion and compressibility of the implant such that the length and width of the webs may be adjusted in order to provide a target stiffness or distractive force. For example, the webs may have a wider width as shown, for example, in the webs 36 of Figs. 3 A and 3B, or could have a more narrow width as shown, for example, in the webs 56, 76, 156 of Figs. 5A-5B, 7A-7C, Figs. 15A-15B, respectively. The shape of the webs may also affect the flexion and compressibility of the implant. For example, the axial cross-section of the webs 36 shown in Figs. 3A-3B may be rectangular in shape, while the axial cross-section of the webs 56 shown in Figs. 5A-5B may be circular in shape. In some aspects, the webs may also be hollow to allow for greater flexibility, while in other aspects, the webs may be solid to provide greater structure and support, depending on the particular needs of the patient.

[0091] The webs may support and allow the plates to be moveable relative to each other. Such relative movement includes varying degrees of freedom, but may be limited by not only the thickness and shape of the webs, but also the placement of the webs.

[0092] The webs may be disposed about the plates to allow the plates to be displaced at varying angles and to varying degrees relative to one another. The webs may allow for spacing of the plates horizontally and the said webs provide support for the plates. The webs may be positioned anywhere along the plates. The placement position and the number of webs between the plates may affect the extent of deflection of the plates with respect to each other when a force is applied to the system of plates, thereby creating a flexible and compressible cantilever system made up of plates and beams connected to each other.

[0093] The properties (stiffness, resistance to compression, distraction, bending of the implant) of the system of cantilevers may be controlled and manipulated by the strategical positioning of one or more webs between the plates. For example, by placing a single web adjacent the end between two beams, a more flexible layer may be produced if a force were to act on the opposite end of the plate. This can be seen, for example, in the implant 30 shown in Figs. 3A-3B, where the webs 36 may be disposed outboard of the plates 34 to confer a greater amount of compressibility to the implant 30.

[0094] By placing a single web 132 in the middle of the plate 134, such as shown in Figs. 13A- 13B, or by placing a web at both ends of a plate, as shown in Figs. 14A-14B, a less flexible layer may be created. For example, the webs 132 may be placed inboard into the center of the implant such that there may be less deflection of the plates 134 they support, so that some of the flexibility may be removed in terms of compression because the implant 130 may be stiffer axially, but the device may still flex. Additionally, by adding webs 142 on either side of a given plate 144, the point of deflection of the implant 140 may be changed. This would result in a closed loop design and may, for example, allow the implant 140 to deflect more to the anterior than the posterior.

[0095] The implant 30 may be manufactured in any variety of angles, including a vertically straight implant, or one with lordotic, kyphotic, or scoliotic curvature. This may also be achieved through strategic positioning of the webs at desired locations along the width of the implant. For example, more or less angle may be created on a given side of an implant by increasing the number of vertical webs on one side compared to the other (e.g. having an odd number of vertical webs on each side). In some aspects, there may be more vertical webs on the anterior of the implant than on the posterior of the implant, thus generating a greater separating force in the anterior intervertebral space as compared to the posterior space and so as to increase lordosis of the spine when the implant is in place. In some aspects, there may be vertical webs alternating all the way around the device, rather than alternating from one side to the other.

[0096] Thus, the stiffness or amount of deflection of an individual plate may be adjusted by manipulating the positioning of the webs and may impact the flexibility of the system of plates. The positioning of the webs at various locations along a plate may also restore the contour of the spine by allowing for the adjustment or optimization of the amount or degree of lordosis that may be provided to the spine after insertion of the implant. [0097] Thickness of plates

[0098] Plates may be adjusted in length, width, or in thickness, all of which may affect the movement of the overall implant. For example, the thickness of the plates and spaces between the plates may allow for more or less movement of the implant. The thickness of the horizontal plates may be altered to alter the flexibility of the overall device. Thickening of a plate may provide increased stiffness as compared to a relatively thinner plate. The spaces between adjacent plates may also be altered to alter the stiffness of the implant, with smaller spaces between adjacent plates providing more opportunity for deflection between the plates.

[0099] By isolating one or more of the layers in the cantilever structure and eliminating deflection in selected layers, the mechanical properties of an implant may be changed. Figs. 4A- 4C demonstrate the ability to have different layers in the same implant structure. By combining different layers of different stiffness, a variable stiffness system may be produced. In the implant 40 shown in Figs. 4A-4C, deflection in selected layers of plates 44 may be increased or decreased by respectively increasing or decreasing the height of the web 46 in the superior and inferior sections, as compared to the mid sections, so that deflection may then be less likely to take place at the layers in the mid-section. This type of structure may allow for increased flexibility of the superior and inferior sections, as compared to the mid-section of the implant 40.

[0100] The implant 40 shown in Figs. 4A-4C may be also progressive, meaning that the stiffness increases as the plates 44 become thicker near the mid-section since more force may be required to compress as the plates 44 become thicker.

[0101] In some aspects, even a given plate may have varying thickness between the end attached to the web and the free deflecting end. [0102] Geometry of plates

[0103] The relative movement of the plates may be limited to a predetermined specified range depending on the anatomy and functional requirements of the disc and/or vertebral bodies the implant may replace. This may be accomplished, at least partially, by varying the plates with respect to width or diameter, length, and shape.

[0104] In some aspects, the width of the plates may remain substantially constant across its surface. However, in other aspects, the width of the plates may be gradually reduced from the distal deflecting end to the proximal end attached to the web, or vice versa. For example, by tapering the width of the plates from the distal deflecting end to the proximal end attached to the web, the implant may be allowed to move in other planes. In some aspects, the plates in the superior section of the implant may be wider than the plates in the inferior section of the implant to provide a stiffer implant than having narrow or narrowing superior plates for the same thickness. Such an implant may allow for a gradual change in stiffness characteristics along its length. [0105] The length of the plates from the distal deflecting end to the proximal end attached to the web may be modified to adjust the stiffness of the implant. For example, shortening the length of a given plate may result in increased stiffness while lengthening the plate may decrease stiffness.

[0106] The shape of the plates may also be varied to adjust the mechanical properties of the implant. For example, Figs. 2A-2C illustrate an implant 20 with square plates 24 with right corners and rounded edges, while Figs. 3A and 3B illustrate an implant 30 with square plates 34 with right corners and square edges. The plates may also be rounded at the corners in some aspects, rather than being at right angles. Further still, Figs. 5A and 5B illustrate an implant 50 with rounded-edged plates 54 with both square and rounded edges. Figs. 6A-6D illustrate an implant 60 with round plates 64 with rounded edges. The shape of the plates may generally be rectangular, square, oval, round, square with round corners, or even irregular shaped.

[0107] If the shape of the plates is round giving the implant a cylindrical shape, as is the case, for example, with the implant 60 of Figs. 6A-6D, the implant 60 may have freedom to bend more from side to side, as compared to implants having square-shaped plates, such as is shown in Figs. 2A-2C. Adjusting the diameter and radii of curvature of the plates 60 may allow for an increase or decrease in the permitted range of relative motion of the plates 64, as well.

[0108] The geometry of the plates may be customized for the specific intervertebral bodies to be replaced. For example, for cervical bodies, one may be more interested in front and back movement and so one may select plate geometry that provides for this movement.

[0109] Materials

[0110] The material of the implant body may be chosen so that the implant may be flexible and may experience compression and flexion without permanently having its structure deformed. The material may be generally biocompatible and resilient, although some more rigid materials may be used in some cases, depending on needs of the specific patient.

[0111] Implant 10, for example, may be generally formed of a resilient material that may allow the implant to handle axial loading and may provide the required distracting force to keep adjacent vertebrae separated by the desired distance while also allowing a desired amount of compression. Once the compressive force on implant 10 is removed, the device may be designed to return to its non-compressed shape, while still restricted within the intervertebral space. The implant 10 may be made from various known materials known in the art such as, for example, carbon fiber, simple or advanced plastics such as a crystalline thermoplastic such as polyether- etherketone (PEEK), shape metal alloys such as Nitinol™, steel, or more commonly used materials such as cobalt chrome, stainless steel or titanium alloys. In general, implant 10 may be formed from one or more materials having a tensile strength sufficient to provide an elastic force allowing the implant 10 to have a spring-like functionality.

[0112] The material properties of the implant body 12 may allow the plates 14 and webs 16 to be flexible to varying degrees. Materials which permit smaller deflections mean that the deflection may be shared among the plates 14. In some aspects, the implant body 12 may be made out of thermoplastic due to deflection fatigue. While thermoplastics may crack, they may be likely to stay in place in the implant 10 rather than getting dislodged and needing to be surgically removed and replaced. Additionally, depending on the material, height, and mechanical properties of the implant 10, the implant body 12 may be made out of different alloys, plastics, and combinations of titanium and plastics.

[0113] These modifications to implant height, position and thickness of webs, thickness of plates, geometry of plates, and materials taken individually or in a combination may allow for a variety of stiffness characteristics to be provided for the implant. It will be understood that a variety of stiffness characteristics may be required along the spine of a single individual. That is, the motion requirements and restrictions of vertebral segments along the spine may vary from one segment to the next. For example, the motion and forces within a cervical spinal segment may be considerably different from those of a lumbar segment. As such, the ability of the structure of the implant to be modified in numerous ways may allow it to be customized to be used in various spinal locations. [0114] Bore

[0115] In some aspects, the implant may flex about its central axis. However, in the aspects shown in Figs 6A-6D, 7A-7C, and 15A-15B, a bore 61, 71, 151 may extend along the central axis through one or all of the plates 64, 74, 154. This bore 61, 71, 151 may allow for packing fusing material such as bone to ensure solid bone growth between the intact vertebrae and so the implant 60, 70, 150 may be used as a fusion device to stop all deflection. Bone graft may be packed inside to allow the bone graft to fuse to the implant 60, 70, 150 then grow outward between the plates into the patient's body after implantation and connect with healthy bone adjacent the implant 60, 70, 150, improving fixation of the implant 60, 70, 150 within the patient's body.

[0116] Attachment/Fixation system

[0117] In some embodiments, the superior and inferior external surfaces of the implants may be provided with a surface structure or coating to promote bone in-growth, and thereby, allow anchoring of the implant in the intervertebral space as a means of initial fixation and long-term stability of the implant. These attachment means may be used for stabilization and to resist rotation and/or migration of the implant.

[0118] For example, the implant 10 of Figs. 1A-1B may have superior surface 18 and inferior surface 19 which may be contact surfaces prepared with chemical or biological treatments through commercially available means including titanium, plasma spray, and hydroxyapatite coating, and the like to encourage fixing to adjacent bone structures. The surface preparation may enhance the osteoconductive properties of the implant for solid integration with adjacent bone. [0119] Initial fixation may be achieved through screw fixation through the inferior plate 17 into the superior endplate of the inferior vertebra or through the superior plate 15 into the inferior endplate of the superior vertebra. Fixation may also be achieved using features that encourage fusion of the implant to the bone, such as physical protuberance such as spikes, ridges, keels, knurling, engagement teeth, fins, or the like added to the superior surface 18 and/or inferior surface 19, which may allow for fusion with bone. These may be engageable with the vertebral endplates. The engagement may be provided through patterns, dimensions, shapes, smooth surfaces, grooved surfaces, rough surfaces, or mobility.

[0120] Bone anchors may also be used to ensure that the implant is properly secured to the intact vertebrae on either side of the intervertebral channel. The bone anchors may include slotted screws, staples, bolts, hooks, or clamps. The bone anchors may be used through the intact vertebrae on either side of the intervertebral channel and above and below the implant to hold the implant in place and keep the implant from slipping.

[0121] In some aspects, a fixation plate may stabilize the implant to promote bony fusion. For example, as shown in Figs. 10A-10B and Figs. 1 1A-11D, the implants 100, 110 may be formed with inferior and superior plates 107, 117, 105, 115 integrated with fixation flanges 103, 113 for positioning against the endplate of an adjacent vertebral body when the implant 100, 110 is inserted into a spine. Fixation flanges 103, 113 may be formed with attachment apertures 109, 119 to allow fixation of the implants 100, 110 to the superior and inferior vertebra by driving screws or the like there through. As can be seen in Figs. 10A and 10B, the fixation flange 103 may be straight or as can be seen in Figs. 11A-11D, the fixation flange 113 may be curved or arcuate, depending on the configuration of the spine to be treated and so that the flange 103, 113 may conform more closely with the existing spinal configuration of the patient and may provide a close fit to the vertebrae to which it is attached. In some aspects, the flange 103, 113 may be provided on both the superior and inferior sections of the implants 100, 110, though in other aspects, the flange 103, 113 may be provided on only one or the other of the superior or inferior section of the implants 100, 110.

[0122] As the implant 100, 110 heals into place, the flanges 103, 113 may stabilize the implant 100, 110, allowing the implant 100, 110 to fuse to the intact vertebrae above and below it.

[0123] Assembly

[0124] In some aspects, the superior plate 15 and/or the inferior plate 17 may be provided or associated with an artificial endplate, which may be designed or adapted to be affixed to the inferior surface of the superior vertebral body or the superior surface of the inferior vertebral body once the implant is in place within the intervertebral space. The artificial endplates may be configured to engage the superior surface 18 and/or inferior surface 19 of implant 10.

[0125] Figs. 8A-8D illustrate artificial endplate 80 in an aspect for fixation of the implant 10 to the vertebral bodies above and/or below. The artificial endplate 80 may serve as an end of the implant 10 and may fit against healthy vertebrae adjacent the removed vertebrae and vertebral discs. Artificial endplate 80 may be used to fuse the implant 10 to either or both of the vertebrae on either side of the distracted channel. The artificial endplate 80 may have a vertically- extending flange 82 with at least one fixation aperture 84 to allow screws to be inserted therein and screwed into the healthy intact vertebrae. The screws may be inserted through aperture 84 and secured to the adjacent bone structure of the respective vertebral bodies. [0126] Artificial endplate 80 may have a bone-contacting surface 86 configured and dimensioned to rest against healthy bone adjacent the artificial endplate 80. The bone-contacting surface 86 may be provided with a means for fixing or fusing the artificial endplate 80 to the adjacent vertebral body. For example, the bone-contacting surface 86 may be provided with a surface texture or coating to initiate or encourage bone fusion, as described above in relation to the contact surfaces of superior surface 18 and inferior surface 19.

[0127] Artificial endplate 80 may be connected to superior plate 15 such that artificial endplate 80 may be generally parallel to inferior plate 17 or such that artificial endplate 80 may be angled with respect to inferior plate 17. By providing artificial endplate 80 in a parallel orientation with respect to inferior plate 17 and connected to the superior plate 15, the resulting distractive force may be applied parallel to the middle of the intervertebral space, thereby resulting in symmetrical distraction. Similarly, when artificial endplate 80 is attached to superior plate 15 at its distal deflecting end and where the distal end of implant 10 is positioned anteriorly in the disc space, and endplate 80 is attached at an angle to the inferior plate 17, maximal lordosis may be established as the anterior disc height would be distracted more than the posterior disc height. Artificial endplate 80 may also be varied in terms of height, in addition to its angles, and may be customizable to the specific anatomical requirements of the patient.

[0128] A longitudinal slot 86 may be provided in the artificial endplate 80 where the superior plate 15 and/or inferior plate 17 of the implant 10 may be, but are not necessarily, inserted and retained. The cross-sectional shape and size of the implant 10 may or may not correspond to the cross-sectional shape and size of the artificial endplate 80. In the aspects shown in Figs. 9A-9D and Figs. 12A-12C, the cross-sectional shape and size of the implant 90, 120 may correspond to the cross-sectional shape and size of the artificial endplate 80. [0129] Figs. 12A-12C illustrate a vertebral implant 120 and the artificial endplate 80 in an assembly in an aspect with superior plate 125 and inferior plate 127 contacting, but not inserted, into the artificial endplate 80. In some aspects, an artificial endplate 80 may be provided adjacent only one of the superior section or inferior section of the implant 120; however, in the aspect shown, artificial endplates 80 may be provided adjacent both the superior plate 125 and inferior plate 127. In the aspect shown, the artificial endplates 80 and the respective plates 125, 127 may be capable of articulation therebetween because the artificial endplates 80 may not secured to the implant 120. By not having artificial endplates 80 secured to the implant 120, movements such as flexion and extension may be less restricted since the artificial endplates 80 and superior plate 125 and inferior plate 127 may be in sliding contact. This arrangement therefore may allow for various degrees of articulation between plates 125, 127 and the artificial endplates 80, thus may allow a greater range of motion.

[0130] Alternatively, Figs. 9A-9D illustrate the vertebral implant 90 and artificial endplate 80 in an assembly with superior plate 95 and inferior plate 97 may be inserted into the artificial endplate slots 86 for attachment to the artificial endplates 80. The artificial endplate slots 86 may accommodate at least a portion of the distal deflecting end of the superior plate 95 or inferior plate 97. In some aspects, there may be a locking clip to engage and secure the implant 90 relative to the artificial endplates 80 to prevent or minimize micro movements therebetween.

[0131] In use, the artificial endplate 80 may first be secured to the vertebral endplates to fix the position of the artificial endplates 80 to the intact vertebra, and then the superior plate 95 and inferior plate 97 of implant 90 may be inserted into the respective slots 86 of the upper and lower artificial endplates 80 to retain the implant 90 in place. [0132] The slot 86 and plate 95, 97 interface may be rigid (e.g. friction fit) or mobile (e.g. articulating). With a friction fit between the slots 86 and the plates 95, 97, one may avoid shear stress between the artificial endplates 80 and bone. Alternatively, with a mobile or articulating fit, the slots 86 may be sized to allow superior plate 95 and inferior plate 97 to be moveable there-within. This arrangement with the artificial endplates 80 attaching the plates 95, 97 loosely in slots 86 may allow even more flexibility by allowing for articulation between the artificial endplates 80 and the plates 95, 97, and may thus further reduce shear stress between the artificial endplates 80 and bone. With such arrangement, artificial endplates 80 may be secured to the respective vertebral bodies and prevented from moving with respect to the same. Thus, the movement of the spinal segment may be restricted to articulation between plates 95, 97 and the artificial endplates 80.

[0133] By permitting more motion between the plates 95, 97 and the artificial endplates 80 than between the artificial endplates 80 and bone in this way, one may reduce shear stress between the artificial endplates 80 and bone and minimize the chance of dislocating the implant 90 or otherwise allowing the implant 90 to shift.

[0134] In Use

[0135] In use, a user may remove a disc and/or one or more vertebra, as well as any disc fragments visible. The gap between the remaining healthy intact vertebrae, or the intervertebral channel where a disc and/or vertebrae are removed, may be measured to determine the necessary properties of the implant. The implant may be customized, constructed and arranged to fit within the intervertebral channel. For example, the correct size of the implant may be determined by measuring the intervertebral channel. The stiffness of the segment may be measured with a strain gauge and the implant may be manufactured with the correct stiffness. Alternatively, the disc height may measure or approximate the stiffness of the segment and may be used as an indicator of the same. The implant may be manufactured with the necessary properties for the individual patient's physiology and pathology. In some aspects, the physical properties of the implant may be customized to provide the spinal segment being treated with a desired degree of curvature in either the anterior or posterior directions thereby allowing the segment to assume a lordotic or kyphotic shape, as needed, and in some cases, may even correct or address scoliotic curvature. The flexibility, compressibility, and overall configuration of the implant as well as its height may be adjusted using the properties described above (such as the number of plates used, the length of the webs, etc.) so as to allow for customization of the implant in order to provide desired degrees and ranges of motion and thus improving or restoring the biomechanics of the spine.

[0136] After the disc and/or vertebrae are removed, the implant may be inserted into the cavity between the remaining opposing vertebrae. Using the implant 10 of Figs. 1A-1B as an example, the implant 10 may be first compressed and then inserted into the intervertebral space between the remaining opposing vertebral bodies. The implant 10 may be inserted into the resected part of the spinal column and aligned in the sagittal and frontal plane.

[0137] In one embodiment, the superior plate 15 and inferior plate 17 of the implant 10 may be designed to abut the endplates of the superior and inferior vertebral bodies. However, the implant 10 may also include or be used with one or more artificial endplates 80 or other prosthetic devices. Once positioned within the intervertebral space, the compressive force on implant 10 may be released and the implant may be allowed to expand to bear against the adjacent vertebral bodies from within the intervertebral space. The degree to which implant 10 generates positive Y-axis translation may be limited by the height of the intervertebral space and by the tension offered by the surrounding ligaments. Continuous and dynamic Y-axis (or vertical) distraction of the spinal segment may be generated by implant 10 due to the elastic force generated by the compressed separation of the plates 14 by the webs 16, thereby applying a separating force against the adjacent vertebrae.

[0138] As the structure of the body 12 of the implant 10 confers the inherent ability to resist or cushion negative Y-axis translation, the implant 10 may be able to preserve intervertebral and disc height. The body 12 also may have the inherent ability to generate positive Y-axis translation (distraction) so as to be able to resist axial or Y-axis compression and may be able to dynamically balance these loading forces acting on the intervertebral space. The implant 10 in this way may not only provide cushioning but also elastic support and balance, thereby restoring normal physiological intervertebral function and mechanics.

[0139] The implant 10 may be allowed to expand in situ between the intact vertebrae above and below the implant 10 with the desired height and anchorage achieved when the implant 10 may be in a neutral state. The implant 10 may then be joined at the top and bottom in the spine, with the implant endplates 15, 17 contacting the vertebral endplates or otherwise making use of one or more artificial endplates 80, as described in more detail above.

[0140] The implant described herein may help support the spine and maintain normal spacing between intact vertebrae following a discectomy or corpectomy. The structure of the implants described herein may allow for motion-preserving spinal fixation wherein a disc and one or more vertebral bodies can be replaced, while still preserving motion. The implant may balance the reconstruction of spinal structures by restoring normal motion segment stiffness and restrain the implant to the normal physiological range of motion in the motion planes through which they move, while at the same time allowing for the preservation of motion. The implant may be manufactured with different heights, shapes, materials, endplate angulations, etc. to allow a user to choose the specific configuration suitable to the individual pathology and anatomical condition of the patient and to restore the normal curvature of the spine when installed. Specifically, the implant may absorb compressive forces to cushion and/or balance loads and may be inserted with as much or as little lift as desired or required, and may furthermore allow for motion of the implant in different axes. In this way, the implant described herein may mimic the natural mobility of the spine or segment(s) of spine.

[0141] The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.

Claims

CLAIMS What is claimed is:

1. A vertebral implant with a superior surface and an inferior surface comprising: a plurality of plates alongside one another; at least one web transverse to the plates when the implant is in a neutral position and resiliently connecting at least two of the plates; and wherein at least one of the plurality of plates deflects toward another plate upon an axial force applied to the implant, whereby the implant is axially compressible.

2. The vertebral implant of claim 1, wherein the vertebral implant comprises a one-piece construction.

3. The vertebral implant of claim 1, wherein each plate is supported by only one of the at least one webs disposed outboard below the supported plate, whereby the plurality of plates and the at least one web function as a cantilever.

4. The vertebral implant of claim 1, wherein each plate is supported by only one of the at least one webs disposed inboard below the supported plate.

5. The vertebral implant of claim 4, wherein the only one web is disposed in the center below the supported plate.

6. The vertebral implant of claim 1, further comprising a plurality of webs.

7. The vertebral implant of claim 6, wherein the plurality of webs are disposed in an alternating manner from top to bottom of the implant outboard of the plurality of plates.

8. The vertebral implant of claim 1, wherein stiffness of the implant progressively increases from a top to a bottom of the implant.

9. The vertebral implant of claim 1, wherein the implant flexes in at least one direction.

10. The vertebral implant of claim 1, wherein the implant expands from a compressive state to bias apart opposing vertebral bodies when placed therebetween.

11. The vertebral implant of claim 10, wherein an axial length of the implant in the neutral position exceeds a height of a defect.

12. The vertebral implant of claim 1, wherein the implant comprises a thermoplastic.

13. The vertebral implant of claim 1, further comprising a bone-packing bore extending along a central axis.

14. The vertebral implant of claim 1, further comprising an osteoconductive preparation applied to at least one of the superior surface and the inferior surface.

15. The vertebral implant of claim 1, further comprising a physical protuberance on at least one of the superior surface and the inferior surface.

16. The vertebral implant of claim 1, further comprising a fixation flange extending vertically from at least one of the superior surface and the inferior surface and comprising at least one attachment aperture therethrough.

17. The vertebral implant of claim 1, further comprising an artificial endplate engaging at least one of the superior surface and the inferior surface.

18. The vertebral implant of claim 17, wherein the artificial endplate comprises a longitudinal slot receiving and retaining at least a portion of a retained plate.

19. The vertebral implant of claim 18, wherein the retained plate is loosely retained in the longitudinal slot, whereby the implant and the retained plate articulate therebetween.

20. The vertebral implant of claim 19, wherein the retained plate friction fits within the longitudinal slot.

21. The vertebral implant of claim 20, wherein the retained plate comprises at least one of an uppermost plate of the implant and a lowermost plate of the implant.

22. A vertebral implant comprising:

a plurality of plates alongside one another;

means for resiliently connecting the plurality of plates wherein at least one of the plurality of plates deflects towards another plate when the implant is subject to an axial force, where by the implant is axially compressible.