WO2011028575A2

WO2011028575A2 - Flexible intervertebral spacers and associated methods

Info

Publication number: WO2011028575A2
Application number: PCT/US2010/046650
Authority: WO
Inventors: Daniel H. Kim; Joey Camia Reglos; Moti Altarac
Original assignee: Exactech, Inc.
Priority date: 2009-08-26
Filing date: 2010-08-25
Publication date: 2011-03-10
Also published as: WO2011028575A3

Abstract

Flexible intervertebral spacers and associated methods are disclosed herein. In one embodiment, an intervertebral spacer includes a first support member configured to engage a superior vertebra of a spine, a second support member configured to engage an inferior vertebra of the spine, and a joint coupling the first support member to the second support member. The joint is adapted to limit the transverse relationship between the first and second support members while allowing relative movement between the first and second support members relative to each other during flexion, extension, bending, and rotation of the spine.

Description

FLEXIBLE INTERVERTEBRAL SPACERS AND ASSOCIATED

METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/237,032, titled FLEXIBLE INTERVERTEBRAL SPACERS AND ASSOCIATED METHODS and filed August 26, 2009, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present technology generally relates to intervertebral spacers and associated methods of spinal support.

BACKGROUND

[0003] Spine fusion (arthrodesis) is a procedure in which a support device is inserted between two adjacent vertebral bodies to fuse the vertebrae together to stabilize the spine of a patient for relieving pain, and/or other purposes. Figures 1A and 1 B illustrate a portion of a human spine having a superior vertebra 2, an inferior vertebra 4, and an intervertebral disc 6 between the two vertebral bodies. The superior vertebra 2 has superior facet joints 8a and 8b, inferior facet joints 10a and 10b, a posterior arch 16, and a spinous process 18. Pedicles 3a and 3b interconnect the respective superior facet joints 8a and 8b to the superior vertebra 2. Extending laterally from superior facet joints 8a and 8b are transverse processes 7a and 7b, respectively. Extending between inferior facet joints 10a and 10b and the spinous process 18 are lamina 5a and 5b, respectively. Similarly, inferior vertebra 4 has superior facet joints 12a and 12b, superior pedicles 9a and 9b, transverse processes 11a and 11b, inferior facet joints 14a and 14b, lamina 15a and 15b, a posterior arch 20, and a spinous process 22.

[0004] The superior vertebra with its inferior facets, the inferior vertebra with its superior facets, the intervertebral disc, and seven spinal ligaments (not shown) extending between the superior and inferior vertebrae together comprise a spinal motion segment or functional spine unit. Referring to Figures 1C-1 E, each spinal motion segment enables rotational and translational motion relative to each of the three orthogonal axes. In particular, Figure 1C illustrates flexion and extension, anterior translation, and axial loading; Figure 1 D illustrates lateral bending and lateral translation; and Figure 1 E illustrates rotation.

[0005] A normally functioning spinal motion segment provides physiological limits and stiffness in each rotational and translational direction to create a stable and strong column structure to support physiological loads. However, various spinal disorders can produce debilitating pain that can affect the proper function of a spinal motion segment. The specific location or source of spinal pain is most often an affected intervertebral disc or facet joint. Additionally, a disorder in one location or in one spinal component can lead to an eventual deterioration or a disorder, and ultimately, pain in another. Although spine fusion can reduce or eliminate certain types of pain, the resulting fused vertebrae can have limited range of motion in flexion, extension, rotation, and/or lateral bending. Furthermore, spine fusion is believed to increase the stress placed on adjacent non-fused motion segments and may accelerate their degeneration. Accordingly, intervertebral spacers that allow improved spinal motion after spine fusion may be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS [0006] Figure 1A is a perspective view of two vertebral segments of a human spine.

[0007] Figure 1 B is a perspective view of the two vertebral segments of the human spine with the spinous processes and lamina of the superior vertebral segment resected.

[0008] Figures C, 1 D, and 1 E illustrate left, dorsal, and top views of the two spinal segments of Figures 1A and 1 B undergoing various motions.

[0009] Figure 2A is a perspective view of an assembled intervertebral spacer in accordance with an embodiment of the technology.

[0010] Figure 2B is a perspective and exploded view of the intervertebral spacer of Figure 2A. [0011] Figures 3A and 3B are lateral perspective views of vertebral segments of a human spine during implantation of the intervertebral spacer of Figure 2A.

[0012] Figures 4A, 4B, and 4C are side elevation views of the intervertebral spacer of Figure 2A implanted between vertebral segments of a human spine during various movements.

[0013] Figures 4D, 4E, 4F, 4G, and 4H are anterior elevation views of the intervertebral spacer of Figure 2A during various movements.

[0014] Figures 5A and 5B are side elevation views of the vertebral segments of a human spine with a supplemental stabilization system incorporating the intervertebral spacer of Figure 2A.

[0015] Figures 5C, 5D, and 5E are posterior perspective views of vertebral segments of a human spine during implantation of the spinal stabilization system of Figure 5B.

[0016] Figure 6A is a perspective view of an intervertebral spacer as assembled in accordance with another embodiment of the disclosure.

[0017] Figure 6B is a perspective and exploded view of the intervertebral spacer of Figure 6A.

[0018] Figure 7A is a perspective view of an intervertebral spacer as assembled in accordance with yet another embodiment of the disclosure.

[0019] Figure 7B is a side elevation view of the intervertebral spacer of Figure 7A.

[0020] Figures 8A and 8B are lateral perspective views of vertebral segments of a human spine during implantation of the intervertebral spacer of Figures 7A and 7B.

[0021] Figures 9A and 9B are lateral perspective views of vertebral segments of a human spine during implantation of the intervertebral spacer of Figures 7A and 7B with the supplemental stabilization system of Figure 5A. DETAILED DESCRIPTION

[0022] Various embodiments of intervertebral spacers, systems, and associated methods are described below. The term "intervertebral" generally refers a positional relationship between two vertebral bodies of a human spine. A person skilled in the relevant art will also understand that the devices, systems, and/or methods disclosed herein may have additional embodiments and that the systems and methods disclosed herein may be practiced without several details of the embodiments described below with reference to Figures 2A-9B.

[0023] Figure 2A is a perspective view of an intervertebral spacer 100 in accordance with one embodiment of the technology, and Figure 2B is an exploded view of the intervertebral spacer 100. Referring to both Figures 2A and 2B, the intervertebral spacer 100 can include a first support member 102a, a second support member 102b, and a joint 104 between the first and second support members 102a and 102b. As described in more detail below, the joint 104 can allow relative motion between the first and second support members 102a and 102b during flexion, extension, bending, and rotation of a patient's spine.

[0024] The first and second support members 102a and 102b can have many similar features. As such, the features of the first support member 102a are described below with reference symbols followed by an "a," and the corresponding features of the second support member 102b are shown and noted by the same reference symbol followed by a "b." Common acts and structures are identified by the same reference numbers.

[0025] The first support member 02a can include a first endplate 106a, a first fixation member 112a projecting from a first surface 105a of the first endplate 106a, and a first lever 108a flexibly attached to the first endplate 06a. In the illustrated embodiment, the first endplate 106a is configured to contact the prepared portion of an endplate of an adjacent vertebral body (not shown). The first endplate 106a and the first lever 108a can flex relative to each other at a second surface 105b opposite the first surface 105a. In other embodiments, the first endplate 106a can have a circular, cylindrical and/or other shapes that conform to the shape of the vertebral body and/or the prepared area of the vertebral endplate. The first endplate 106a can be constructed of metals such as surgical steel and titanium, ceramics, polymers, and/or other suitable biocompatible materials.

[0026] In certain embodiments, the first endplate 106a can itself be at least partially flexible. For example, a first end 107a of the first endplate 106a may bend, twist, and/or otherwise flex relative to a second end 107b opposite the first end 107a. In another example, a first longitudinal portion 109a on one side of the first fixation member 112a may bend, twist, and/or otherwise flex relative to a second longitudinal portion 109b on the other side of the first fixation member 112a. In other embodiments, the first endplate 106a may be substantially rigid. In further embodiments, a portion of the first endplate 106a may be rigid while the other portions of the first endplate 106a may be at least partially flexible.

[0027] The first fixation member 112a can be configured to penetrate into or otherwise interface with the vertebral endplate of an adjacent vertebral body. In the illustrated embodiment, the first fixation member 112a includes an elongated structure with a generally triangular cross section. The elongated structure has a base 114a attached to the first surface 105a of the first endplate 106a and a pointed edge 116a extending away from the base 114a. In operation, the pointed edge 116a would at least partially cut into the adjacent vertebral body and thus fix the relative position between the vertebral body and the first endplate 106a. In other embodiments, the first fixation member 112a can also include elongated or discrete structures with rectangular, trapezoidal, conical and/or other suitable cross sections. The first fixation member 112a can alternatively be a plurality of barbs or spikes. In further embodiments, the first fixation member 112a may be omitted, and the first endplate 106a may interface directly with the adjacent vertebra via the first surface 105a.

[0028] The first lever 108a can allow the first endplate 106a to be compressed, twisted, bent, laterally translated, and/or otherwise flexed relative to the joint 104. As shown in Figures 2A and 2B, the first lever 108a forms an oblique angle a with the first endplate 106a. The oblique angle a can range from about 5° to about 45° and/or other suitable angles. In the illustrated embodiment, the lever 108 includes a plate-like structure with a first lever end 118a and a second lever end 118b. The first lever end 118a is flexibly attached to the first endplate 106a and the second endplate 106b at junctions 110a and 110b, respectively. The second lever end 118b is spaced apart from the first lever end 118a and from second surface 105b of the first endplate 106a. The lever 108 can be constructed of titanium, stainless steel, and/or another suitable material with sufficient flexibility and mechanical strength. Even though Figures 2A and 2B show that the lever 108 has the same width W as the first endplate 106a, in certain embodiments, the lever 108 may have a different width and/or may have other suitable structural features.

[0029] The second support member 102b can include a second endplate 106b, a second fixation member 112b carried by the second endplate 106b, and a second lever 108b flexibly attached to the second endplate 106b. The second endplate 106b, the second fixation member 112b, and the second lever 108b can be generally similar in structure and function as the corresponding components of the first support member 102a excepting the difference between the first and second levers 108a and 108b discussed below.

[0030] As shown in Figure 2B, the joint 104 can include a protrusion 120 projecting from the second lever end 118b of the first lever 108a and a corresponding depression 130 in the second lever end 118b of the second lever 108b. The depression 130 can be configured to receive the protrusion 120 and form the joint 104. In the illustrated embodiment, the joint 104 is a ball joint in which the protrusion 120 includes a generally semi-spherical dome extending away from the first lever 108a and a pin 124 projecting from the apex of the dome. Correspondingly, the depression 130 includes a generally semi-spherical recess extending into the second lever 108b and an aperture 134 that receives the pin 124. In other embodiments, the pin 124 and the aperture 134 may be omitted from the protrusion 120 and the depression 130, respectively. In further embodiments, the protrusion 120 and the corresponding depression 130 may include cubic, pyramidal, cylindrical, and/or other suitable shapes to form other types of joints.

[0031] In certain embodiments, the protrusion 120 simply contacts the depression 130 without any adhesive and/or fastener to fixedly attach the first lever 108a to the second lever 108b. As such, the combination of the protrusion 120 and the depression 130 can limit the positional shift between the first and second support members 102a and 102b along the X-axis and the Y-axis while allowing these components to rotate (as indicated by the arrow R), twist (as indicated by the arrow T), or extend/contract along the Z-axis. In other embodiments, the protrusion 120 of the first lever 108a may be in contact and fixedly attached to the second lever 108b in the depression 130.

[0032] The intervertebral spacer 00 may be implanted into a patient with any known interbody fusion techniques. For example, Figures 3A and 3B show a lateral insertion technique for implanting the intervertebral spacer 100 between the superior vertebra 2 and the inferior vertebra 4 of a patient's spine 1. The spine 1 has an anterior side 1a and a posterior side 1 b. As shown in Figure 3A, the intervertebral disc 6 between the superior and inferior vertebrae 2 and 4 has been removed. An expander and/or other suitable instrument distracts the superior and inferior vertebrae 2 and 4 before the intervertebral spacer 100 is inserted laterally between the anterior and posterior sides 1a and 1b of the spine 1. The first and second fixation members 112a and 112b are then implanted between the superior and inferior vertebrae 2 and 4. In other embodiments, the intervertebral spacer 100 may be implanted using an anterior lumbar interbody fusion (ALIF) technique in which an anterior abdominal incision is used to reach the lumbar spine, a posterior lumbar interbody fusion (PLIF) technique in which a posterior incision is used to reach the lumbar spine, and/or other suitable interbody fusion techniques.

[0033] Several examples of movement of the patient's spine 1 facilitated by the intervertebral spacer 100 are illustrated in Figures 4A-4H. Figures 4A-4C are side views of the patient's spine 1 during various movements. Figure 4A shows the spine 1 in a neutral position with the intervertebral spacer 100 between the superior and inferior vertebrae 2 and 4. Figure 4B shows the spine 1 under flexion when the superior vertebra 2 tilts toward the anterior side 1a of the spine 1 (as indicated by the arrow F). Figure 4C shows the spine under extension when the superior vertebra 2 tilts toward the posterior side 1 b of the spine 1 (as indicated by the arrow E). Figures 4D-4H are anterior views of the patient's spine 1 during other movements of the spine 1. Figure 4D shows the spine 1 in a neutral position with the intervertebral spacer 100 between the superior and inferior vertebrae 2 and 4. Figure 4E shows the spine 1 under lateral compression to the left (as indicated by the arrow LCL). Figure 4F shows the spine 1 under lateral compression to the right (as indicated by the arrow LCR). Figure 4G shows the spine under lateral extension to the left (as indicated by the arrow LEL). Figure 4H shows the spine under lateral extension to the right (as indicated by the arrow LER). The intervertebral spacer 100 also enables combinations of any of the spinal movements shown in Figures 4A-4H. Also, even though Figures 4A-4H only illustrate certain types of movement, several embodiments of the intervertebral spacer 100 can also facilitate axial compression/extension, anterior translation, rotation, and/or other types of movement in the spine 1.

[0034] Several embodiments of the intervertebral spacer 100 can allow greater degrees of movement of the patient's spine 1 when compared to conventional interbody fusion devices. Conventional interbody fusion devices typically include a rigid cage-like structure or a cancellous bone graft (i.e., allograft) from the patient. As a result, such interbody fusion devices cannot flex and thus may limit the degrees of various motions of the spine 1. In contrast, as shown in Figures 4A-4H, the structural and/or material flexibility of the intervertebral spacer 100 enables it to shift, bend, twist, and/or otherwise flex in response to the natural movement of the spine 1. Several embodiments of the intervertebral spacer 100 accordingly accommodate the degrees of flexion and extension of the spine 1 by compressing, tilting, and/or twisting the first and second support members 102a and 102b relative to the joint 104 (Figures 2A and 2B) via flexing the first and second levers 108a and 108b. As a result, the intervertebral spacer 100 can at least reduce the limitation on the movement of the patient's spine 1.

[0035] In certain embodiments, the intervertebral spacer 100 can form one component of a system for stabilizing the patient's spine. For example, Figure 5A shows a spinal stabilization system 140 that includes the intervertebral spacer 100 and a screw system 142, and Figure 5B shows another spinal stabilization system 141 that includes two screw systems 142 arranged side by side. In further embodiments, three, four, or any other desired number of screw systems 142 may be implanted into suitable locations in the superior and inferior vertebrae 2 and 4.

[0036] Each screw system 142 can include two screws 143 (only the screw ends are shown) individually received in seats 146, two screw heads 144, and a cross member 148 extending between the two screws 143. The two screws 143 are individually fixed to the superior and inferior vertebrae 2 and 4. One example of the screws 143 and seats 146 is disclosed in U.S. Patent Application No. 12/079,676, filed March 28, 2008, the disclosure of which is incorporated herein in its entirety. In the illustrated embodiment, the cross member 148 is a dynamic rod that includes a spring with both ends fixed to the seats 146 by the two screws 143. Examples of dynamic rods are disclosed in U.S. Patent Application Nos. 10/970,366, filed on October 20, 2004, 11/006,495, filed on December 6, 2004, 11/033,452, filed on January 10, 2005, 11/436,407, filed on May 17, 2006, 11/427,738, filed on June 29, 2006, 12/154,540, filed on May 23, 2008, 12/233,212, filed on September 18, 2008, 12/366,089, filed February 5, 2009, and 12/540,865, filed on August 13, 2009.

[0037] Without being bound by theory, it is believed that the screw system 142 may cooperate with the intervertebral spacer 100 to further stabilize the superior vertebra relative to the inferior vertebra. As described above, the intervertebral spacer 100 can at least partially stabilize the superior and inferior vertebrae 2 and 4 by engaging the fixation members 112a and 112b (Figures 2A and 2B) with the adjacent vertebral bodies. The screw system 142 can further enhance the stabilization by bracing the two vertebrae with the cross member 148. The cross member 148 can have a sufficient rigidity to provide adequate support to the superior and inferior vertebrae 2 and 4 while also flexing to allow some degree of relative movement between the superior and inferior vertebrae 2 and 4.

[0038] Even though Figures 5A and 5B show that the screw systems 142 are implanted into the vertebral bodies of the superior vertebra and the inferior vertebra at a lateral location, in other embodiments, the screw system 142 may also be implanted in the pedicles and/or other suitable locations in the vertebrae. Figures 5C-5E are posterior views of the spine 1 during implantation of the intervertebral spacer 100 with pedicle screws. As shown in Figure 5C, screws 143 and corresponding seats 146 of a first screw system 142a are initially implanted into the left pedicle 3a of the superior and inferior vertebrae 2 and 4 without installing the cross member 148. The screws 143, seats 146, and the cross member 148 of a second screw system 142b are implanted into the right pedicles 3b of the superior and inferior vertebrae 2 and 4.

[0039] The caregiver can then use an expander and/or other suitable instrument to open the space between the superior and inferior vertebrae 2 and 4 at least proximate the right pedicle 3b. The caregiver can then insert the intervertebral spacer 100 into the space laterally between the superior and inferior vertebrae 2 and 4 (as indicated by the arrow ID). As shown in Figure 5D, the caregiver can then cease to expand the space and plant the first and second fixation members 112a and 112b into the superior and inferior vertebrae 2 and 4. As shown in Figure 5E, the caregiver can then fasten the cross member 148 to the screws 143 with the screw heads 144.

[0040] Figure 6A is a perspective view of an intervertebral spacer 200 as assembled, and Figure 6B is an exploded view of the intervertebral spacer 200 in accordance with another embodiment of the disclosure. The intervertebral spacer 200 can include structural components generally similar to those of the intervertebral spacer 100 of Figures 2A and 2B except that the first support member 02a does not include the first lever 108a (Figure 2A). Instead, the protrusion 120 of the joint 104 projects from the second surface 105b of the first endplate 106a. The intervertebral spacer 200 can operate in generally the same manner as the intervertebral spacer 100 of Figures 2A and 2B. For example, the combination of the protrusion 120 and the depression 130 can limit the positional shift between the first and second support members 102a and 102b along the X-axis and the Y-axis while allowing these components to rotate (as indicated by the arrow R), twist (as indicated by the arrow T), or extend/contract along the Z-axis.

[0041] Figure 7A is a perspective view of an intervertebral spacer 300, and Figure 7B is a side elevation view of the intervertebral spacer 300 in accordance with yet another embodiment of the disclosure. The intervertebral spacer 300 can include structural components generally similar to those of the intervertebral spacer 100 of Figures 2A and 2B except that the first and second support members 102a and 102b individually include a flange 150 (identified as a first flange 150a and a second flange 150b). In the illustrated embodiment, the first flange 150a extends generally perpendicularly from the second end 107b of the first support member 102a, and the second flange 150b extends generally perpendicularly from the second support member 102b and in generally the opposite direction as the first flange 150a. The flange 150 can include an aperture 152 sized and shaped to receive a screw 154. The screw 154 includes a screw head 156 and a threaded section 158 extending therefrom. In other embodiments, the flange 150 can have other suitable structural arrangements and/or accommodate other stabilization components, as described in more detail below with reference to Figures 9A and 9B.

[0042] Figures 8A and 8B show a lateral insertion technique for implanting the intervertebral spacer 300 between the superior vertebra 2 and the inferior vertebra 4 of a patient's spine 1. As shown in Figure 8A, the intervertebral disc 6 between the superior and inferior vertebrae 2 and 4 can be first removed. An expander and/or other suitable instrument distracts the superior and inferior vertebrae 2 and 4. The intervertebral spacer 300 is then inserted laterally until the flanges 150 abut the superior and inferior vertebrae 2 and 4 (as indicated by the arrow ID). As shown in Figure 8B, the screws 154 are inserted through the apertures 152 of the first and second flanges 150a and 150b and screwed into the superior and inferior vertebrae 2 and 4 until the screws 154 are fully fastened. The expander is then released so that the first and second fixation members 12a and 112b contact the superior and inferior vertebrae 2 and 4. In other embodiments, the intervertebral spacer 300 can be implanted using an anterior lumbar interbody fusion (ALIF) technique, a posterior lumbar interbody fusion (PLIF), and/or other suitable interbody fusion techniques.

[0043] Several embodiments of the intervertebral spacer 300 can also accommodate other stabilization components. For example, Figures 9A and 9B are lateral perspective views of vertebral segments of a human spine during implantation of the intervertebral spacer 300 of Figures 7A and 7B with the supplemental stabilization system of Figure 5A. As shown in Figures 9A and 9B, the intervertebral spacer 300 can be combined with the screw system 142 of Figure 5A to provide additional stabilization. In other embodiments, the intervertebral spacer 300 may also be combined with other suitable stabilization components.

[0044] From the foregoing, it will be appreciated that specific embodiments of the disclosure have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. For example, certain embodiments of the intervertebral spacer 200 may also include one or more of the flanges 150 as shown in Figures 7A and 7B. Many of the elements of one embodiment may be combined with other embodiments in addition to or in lieu of the elements of the other embodiments. Accordingly, the disclosure is not limited except as by the appended claims.

Claims

CLAIMS I/We claim:

1. An intervertebral spacer, comprising:

a first support member configured to engage an endplate of a superior vertebra of a spine;

a second support member proximate the first support member, the second support member being configured to engage an endplate of an inferior vertebra of the spine; and

a joint coupling the first support member to the second support member, the joint being configured to connect the first and second support members together, and the joint being configured such that the first and second support members move relative to each other during flexion, extension, bending, and rotation of the spine.

2. The intervertebral spacer of claim 1 wherein:

the first support member includes a first endplate and a first lever, the first endplate having a first edge opposite a second edge, the first lever having a first end attached to the first edge of the first endplate and a second end extending away from the first end and spaced apart from the first endplate, the first lever forming an oblique angle from about 5° to about 45° in relation to the first endplate;

the second support member includes a second endplate and a second lever, the second endplate having a first edge opposite a second edge, the second lever having a first end attached to the first edge of the second endplate and a second end extending away from the first end and spaced apart from the second edge of the second endplate, the second lever forming an oblique angle from about 5° to about 45° in relation to the second endplate;

at least one of the first and second levers is at least partially flexible; and the joint includes: a generally semi-spherical protrusion projecting from the second end of the first lever; and

a generally semi-spherical depression in the second end of the second lever, the depression being configured to receive the protrusion at the second end of the first lever.

3. The intervertebral spacer of claim 1 wherein:

the first support member includes a first endplate and a first lever, the first lever having a first end attached to the first endplate and a second end extending at a first oblique angle relative to the first endplate;

the second support member includes a second endplate and a second lever, the second lever having a first end attached to the second endplate and a second end extending at a second oblique angle relative to the second endplate;

at least one of the first and second levers is at least partially flexible; and the joint includes:

a protrusion at the second end of the first lever; and

a depression in the second end of the second lever, the depression being shaped and sized to receive the protrusion at the second end of the first lever.

4. The intervertebral spacer of claim 1 wherein:

a protrusion at the second end of the first lever; a depression in the second end of the second lever, the depression being shaped and sized to receive the protrusion at the second end of the first lever; and

the depression cooperates with the protrusion to limit transversely shifting between the first endplate and the second endplate.

5. The intervertebral spacer of claim 1 wherein:

a protrusion at the second end of the first lever;

a depression in the second end of the second lever, the depression being shaped and sized to receive the protrusion at the second end of the first lever; and

the depression cooperates with the protrusion to limit transversely shifting between the first endplate and the second endplate while allowing the first endplate to bend, rotate and longitudinally shift relative to the second endplate in response to movement between the superior and inferior vertebrae.

6. The intervertebral spacer of claim 1 wherein:

a protrusion at the second end of the first lever;

the depression cooperates with the protrusion to limit transversely shifting between the first endplate and the second endplate while allowing the first endplate to pivot around the joint relative to the second endplate.

7. The intervertebral spacer of claim 1 wherein:

the first support member includes a first endplate;

the second support member includes a second endplate and a lever, the lever having a first end attached to the second endplate and a second end extending at an oblique angle relative to the second endplate, the lever being at least partially flexible; and

the joint includes:

a protrusion at the first endplate; and

a depression in the second end of the lever, the depression being shaped and sized to receive the protrusion at the first endplate.

8. The intervertebral spacer of claim 1 wherein:

the first support member includes a first endplate and a first lever, the first lever having a first end attached to the first endplate and a second end extending at a first oblique angle relative to the first endplate, the first endplate having a first flange with a first aperture, the first flange extending away from the first lever;

the second support member includes a second endplate and a second lever, the second lever having a first end attached to the second endplate and a second end extending at a second oblique angle relative to the second endplate, the second endplate having a second flange with a second aperture, the second flange extending away from the second lever;

a protrusion at the first endplate; and

a depression in the second end of the second lever, the depression being shaped and sized to receive the protrusion at the first endplate.

9. The intervertebral spacer of claim 1 wherein:

the second support member includes a second endplate and a second lever, the lever having a first end attached to the second endplate and a second end extending at a second oblique angle relative to the second endplate, the second endplate having a second flange with a second aperture, the second flange extending away from the second lever; at least one of the first and second levers is at least partially flexible;

the joint includes:

a protrusion at the first endplate; and

a depression in the second end of the second lever, the depression being shaped and sized to receive the protrusion at the first endplate; and

the intervertebral spacer further includes:

a first screw extending through the first aperture; and

a second screw extending through the second aperture.

10. The intervertebral spacer of claim 1 wherein:

at least one of the first and second levers is at least partially flexible;

the joint includes:

a protrusion at the first endplate; and

the intervertebral spacer further includes:

a first screw extending through the first aperture;

a second screw extending through the second aperture; and

a cross member extending between the first and second screws and fastened to the first and second endplates via the first and second screws.

11. The intervertebral spacer of claim 1 wherein the joint includes a ball

12. An intervertebral spacer, comprising:

a first support member configured to engage a superior vertebra of a spine; a second support member operatively coupled to the first support member, the second support member being configured to engage an inferior vertebra of the spine; and wherein at least one of the first and second support members includes a endplate and a lever attached to and extending away from the support member, the endplate and/or the lever being at least partially flexible.

13. The intervertebral spacer of claim 12 wherein:

the endplate includes a first surface and a second surface;

the intervertebral spacer also includes a fixation member on the first surface of the support member;

the lever has a first end and a second end; and

the first end of the lever is attached to the second surface of the support member.

14. The intervertebral spacer of claim 12 wherein:

the endplate includes the first surface and the second surface;

the intervertebral spacer also includes the fixation member on the first surface of the support member;

the lever has the first end and the second end;

the first end of the lever is attached to the second surface of the support member; and

the lever includes a protrusion or a depression proximate the second end.

15. The intervertebral spacer of claim 12 wherein:

the endplate includes the first surface and the second surface;

the lever has the first end and the second end;

the lever includes a protrusion proximate the second end, the protrusion including a generally semi-spherical dome and a generally cylindrical structure extending from a top of the semi-spherical dome.

16. The intervertebral spacer of claim 12 wherein:

the endplate includes the first surface and the second surface;

the lever has the first end and the second end;

the lever includes a depression proximate the second end, the depression including a generally semi-spherical opening and a generally cylindrical aperture extending from a bottom of the semi-spherical opening into the lever.

17. A spinal stabilization system, comprising:

an intervertebral spacer configured to be positioned between a superior vertebra and an inferior vertebra of a spine, the intervertebral spacer including

a first support member configured to engage the superior vertebra of the spine;

a second support member configured to engage the inferior vertebra of the spine;

a joint operatively coupling the first support member to the second support member, the joint including a protrusion and a depression configured to receive the protrusion; and

a screw system including:

a first screw configured to be attached to the superior vertebra;

a second screw configured to be attached to the inferior vertebra; and a cross member extending between the first and second screws.

18. The spinal stabilization system of claim 17 wherein the cross member includes a coil spring.

19. The spinal stabilization system of claim 17 wherein the first and second screws are configured to be attached to vertebral bodies of the superior vertebra and inferior vertebra, respectively.

20. The spinal stabilization system of claim 7 wherein the first and second screws are configured to be attached to pedicles of the superior vertebra and inferior vertebra, respectively.

21. A method for implanting a spinal stabilization system in a patient, comprising:

distracting a superior vertebra and an inferior vertebra of a spine; and positioning an intervertebral spacer between the distracted superior and inferior vertebrae, the intervertebral spacer including:

a first support member proximate the superior vertebra;

a second support member proximate the inferior vertebra; and a joint operatively coupling the first support member to the second support member, the joint including a protrusion and a depression configured to receive the protrusion.

22. The method of claim 21 wherein:

the first support member includes a first endplate and a first fixation member carried by the first endplate;

the second support member includes a second endplate and a second fixation member carried by the second endplate;

the method further includes:

ceasing to force open the space between the superior vertebra and the inferior vertebra; and

allowing the first and second fixation members to be planted into the superior vertebra and the inferior vertebra, respectively.

23. The method of claim 21 wherein positioning the intervertebral spacer includes positioning the intervertebral spacer laterally in the space between an anterior side and a posterior side of the spine.

24. The method of claim 21 , further comprising:

inserting a first screw into the superior vertebra;

inserting a second screw into the inferior vertebra; and

fastening a cross member between the first and second screws of the superior and inferior vertebrae.

25. The method of claim 21 , further comprising:

inserting a first screw into a body of the superior vertebra;

inserting a second screw into a body the inferior vertebra; and

fastening a cross member between the first and second screws of the bodies of the superior and inferior vertebrae.

26. The method of claim 21 , further comprising:

inserting a first screw into a pedicle of the superior vertebra;

inserting a second screw into a pedicle the inferior vertebra; and

fastening a cross member between the first and second screws of the pedicles of the superior and inferior vertebrae.

27. The method of claim 21 , further comprising:

inserting a first screw into a pedicle of the superior vertebra;

inserting a second screw into a pedicle the inferior vertebra; and

after positioning the intervertebral spacer between the space, fastening a cross member between the first and second screws of the pedicles of the superior and inferior vertebrae.

28. An intervertebral spacer, comprising:

a first support member configured to engage a superior vertebra of a spine; a second support member configured to engage an inferior vertebra of the spine; and

means for limiting transverse movement between the first and second support members while allowing non-transverse movement between the first support member relative to the second support member.

29. The intervertebral spacer of claim 28 wherein means for limiting transverse movement between the first and second support members include means for allowing the first support member to bend, twist, rotate, and/or tilt relative to the second support member.

30. The intervertebral spacer of claim 28 wherein means for limiting transverse movement between the first and second support members include means for flexing the first support member relative to the second support member in non- transverse directions.

31. The intervertebral spacer of claim 28, further comprising means for engaging the superior vertebra or the inferior vertebra.