AU2013206420B2 - Dynamic cervical plate - Google Patents

Abstract

A dynamic plate system for providing dynamic subsidence between at least first and second bodies, the system comprising: a first plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; a second plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; and a clip member having top and bottom surfaces, wherein the first and second plate members are slidably engaged to one another when the sliding portions of the first and second plate members are in sliding engagement with respect to each other, and wherein the first and second plate members are in a loaded assembled position when the first and second plate members are slidably engaged to one another and the top surface of the clip member contacts the inner mating surface of the first plate member and the bottom surface of the clip member contacts the inner surface of the second plate member.

Description

DYNAMIC CERVICAL PLATE CROSS REFERENCE [0001] This Application claims the benefit of U.S. Application No. 11/900,914, filed September 13, 2007, the disclosure of which is hereby incorporated by reference. This application is a divisional application of Australian Patent Application No. 2008299882, the contents of which are hereby incorporated by reference. FIELD OF THE TECHNOLOGY [0002] The present invention relates to a bone plate, and more particularly it relates to such a dynamic bone plate for use in spine. BACKGROUND OF THE INVENTION [0003] Spinal fixation plates can be used for a variety of conditions, including for example, providing added strength and rigidity after fusion of adjacent vertebral bodies for securing vertebrae together where an intervening vertebral body has been removed and replaced. Generally, a spinal fixation plate is applied to the anterior side of affected vertebrae to span at least one affected disc space. For example, a spinal fixation plate may be applied to adjacent vertebral bodies where at least a portion of a disc has been removed and a spinal fusion spacer has been inserted. [0004] Generally, a spinal plate may be attached to the anterior of two or more vertebral bodies for the purpose of immobilizing, stabilizing, and/or aligning those vertebrae. Additionally, such a plate may be used, for example, to supplement the function of an intervertebral spacer or artificial disc, to prevent an intervertebral spacer from being expelled from an intervertebral disc space and/or to act as a support for biocompatible bone graft material that is implanted in the disc space. [0005] Orthopedic fixation devices such as spinal plates may be coupled to bone with fasteners inserted through openings in the plates. The fasteners may or may not be -1secured to the plate. It is known to secure such fasteners to a bone plate, for example, through the use of threads on the fastener and matching threads on the plate, though other means of securement are available. Such a screw-plate interface may decrease the incidence of loosening of the fixation assembly post-operatively. It is also known that a bushing may preferably be disposed in each plate hole to receive the fastener to permit polyaxial movement so that the fastener may be angulated at a surgeon-selected angle. While polyaxial movement of fasteners through set plate hole locations may increase attachment alternatives of the fasteners themselves, the plate holes remain fixed in relation to each other and to the longitudinal axis of the plate. Consequently, undesirable loads may be imposed on the plate fasteners as vertebral bodies subside after a spacer and/or bone graft material is implanted in the intervertebral disc space of adjacent vertebrae. [0006] Further, screw blocking systems are generally provided in a bone plate to keep the fasteners from backing out of the plate. In the present invention, each opening in the plate preferably has a groove or recess for receiving a split ring, though any other suitable screw locking systems may be used in connection with the present invention. [0007] Split rings may be pre-assembled to the bone plate. A split-ring can be sized to expand upon insertion of a bone screw into an opening in the bone plate. Once the head of the screw has passed through the split ring, the split ring can contract under its natural spring tension. When the ring relaxes to its unexpanded state, it prevents the bone screw from backing out of the plate by the engagement of an undersurface of the split-ring and an upwardly facing surface on the bone screw. U.S. Pat. No. 6,602,255, titled "BONE SCREW RETAINING SYSTEM" and issued on August 5, 2003 and U.S. Patent No. 6,261,291, titled "Orthopedic Implant Assembly" and issued on July 17, 2001, both disclose devices used for securing bone screws to a bone plate and are incorporated -2herein by reference in their entirety as if fully set forth herein. [0008] Generally, after implanting the spacer between a pair of vertebrae, there is a compression of the spacer between the adjacent vertebral bodies. This compression ensures a good engagement between the spacer and the endplates, increasing the chances that fusion will occur. Often, particularly in the period immediately following surgery, the spacer may subside slightly into the endplates. In the case of allograft spacers, the space between the vertebral endplates may decrease due to graft resorption. [0009] Where a rigid fixation plate is used to connect vertebral bodies, this subsidence may tend to shift more of the spinal load to the plate than is desirable. Such load shifting can also occur due to inaccuracies in installing the plate to the vertebrae. In extreme circumstances, this load shifting can result in non-fusion or incomplete fusion between the adjacent vertebral bodies. [0010] One form of prior art spinal plate may be adjusted along the longitudinal axis between a plurality of positions. These plates may generally be described as incremental locking plates. Such plates only allow for a first plate and a second plate to be assembled in a finite number of fixed positions with respect to one another by a surgeon or through natural subsidence after implantation. Moreover, many of the plates cannot be extended once locked in a fixed position, and this restricts flexibility during surgery and in revisions. SUMMARY OF THE INVENTION [0011] A first aspect of the present invention provides a dynamic plate system for providing dynamic subsidence between at least first and second bodies, the system comprising: a first plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; a second plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving -3apertures and an inner mating surface; and a clip member having top and bottom surfaces, wherein the first and second plate members are slidably engaged to one another when the sliding portions of the first and second plate members are in sliding engagement with respect to each other, wherein the first and second plate members are in a loaded assembled position when the first and second plate members are slidably engaged to one another and the top surface of the clip member contacts the inner mating surface of the first plate member and the bottom surface of the clip member contacts the inner surface of the second plate member, and wherein the clip member has a substantially straight portion flanked by two curved portions, wherein each of the two curved portions are configured to contact the inner mating surfaces of the first and second plate members adjacent a side, front and back surface of each of the first and second plate members. [0012] A second aspect of the present invention provides a dynamic plate system for providing dynamic subsidence between at least first and second bodies, the system comprising: a first plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; a second plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; and a clip member having top and bottom surfaces separated by a width of the clip member, wherein the first and second plate members are adapted to slidably engage one another, wherein the first and second plate members are in a loaded assembled position when the first and second plate members are slidably engaged to one another and the top surface of the clip member contacts the inner mating surface of the first plate member and the bottom surface of the clip member contacts the inner surface of the second plate member, and wherein the clip member has a -4 substantially straight portion flanked by two curved portions, wherein each of the two curved portions are configured to contact the inner mating surfaces of the first and second plate members adjacent a side, front and back surface of each of the first and second plate members. [0013] Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps. [0014] The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context - 4a for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. BRIEF DESCRIPTION OF THE DRAWINGS [0015] A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description in which reference is made to the accompanying drawings in which: [0016] Figure 1 is an exploded front view of a dynamic subsidence plate according to a first embodiment of the present invention. [0017] Figure 2 is an exploded rear view of the dynamic subsidence plate of Figure 1. [0018] Figure 3 is a top view of the second member of the dynamic subsidence plate of Figure 1. [0019] Figure 4 is a top view of the second member of the dynamic subsidence plate of Figure 1. [0020] Figure 5 is a front assembled view of an exemplary embodiment of a first member, a second member, and a clip, the clip used to maintain the first member and the second member in a first assembled position. [0021] Figure 6 is a back assembled view of the assembly of Figure 5. [0022] Figure 7 is a front assembled view of the plate of Figure 1 showing the vertical slot of the first member situated between the at least two apertures of the second member and a pin placed through the at least two apertures of the second member and the vertical slot of the first member. [0023] Figure 8 is a back assembled view of the plat of Figure 1 showing an instrument inserted into the keyhole of the first member. [0024] Figure 9 is a cross-sectional view taken along line 3-3 of the lock assembly of the dynamic subsidence plate of -5- Figure 1 when the first member and the second member are in an exemplary first assembled position. [0025] Figure 10 is a cross-sectional view taken along line 4-4 of the lock assembly of the dynamic subsidence plate of Figure 1 when the first member and the second member are in a locked position. [0026] Figure 11 is a cross-sectional view taken along line 5-5 of the lock assembly of the dynamic subsidence plate of Figure 1 when the first member and the second member are in an exemplary second assembled position. [0027] Figure 12 is a cross-sectional view of an alternative dynamic subsidence plate showing the ramp portion of the lock assembly when the first member and the second member are in an exemplary first assembled position, the ramp portion shown as an inclined plane. [0028] Figure 13 is a cross-sectional view of the plate of Figure 12 showing the ramp portion of the lock assembly when the first member and the second member are in a locked position, the ramp portion shown as an inclined plane. [0029] Figure 14 is a cross-sectional view of the plate of Figure 12 showing the lock assembly when the first member and the second member are in an exemplary second assembled position, the ramp portion shown as an inclined plane. DETAILED DESCRIPTION [0030] As used herein, when referring to bones or other parts of the body, the term "proximal" means closer to the heart and the term "distal" means more distant from the heart. The term "inferior" means lower or bottom and the term "superior"! means upper or top. The term "anterior"! means towards the front part of the body or the face and the term "posterior"! means towards the back of the body. The term "medial" means toward the midline of the body and the term "lateral"! means away from the midline of the body. [0031] Referring to the drawings, wherein like reference numerals refer to like elements, there is shown in Figures 1-11, an embodiment of the dynamic cervical plate of the -6present invention designated generally by reference numeral 10. As shown in those figures, plate 10 includes a first plate member 12, a second plate member 14, and a lock assembly 16. Preferably, first member 12 and second member 14 are slidably engagable. [0032] Preferably, lock assembly 16 includes a ramp portion 18 on first member 12, an interference portion 20 on second member 14, and a bearing member 19 situated between ramp portion 18 of first member 12 and interference portion 20 of second member 14. Alternatively, ramp portion 18 may be adapted to second member 14 and interference portion 20 may be adapted to first member 12. Preferably, ramp portion 18 is either an inclined plane or a curved ramp, while it is contemplated ramp portion 18 may be other geometric or non geometric configurations. [0033] Preferably, lock assembly 16 is configured to allow movement of first member 12 with respect to second member 14 in a first direction in an infinite number of positions between a first assembled position and a second assembled position. Preferably, lock assembly 16 substantially prevents movement of first member 12 with respect to second member 14 in an opposite second direction between the first and second assembled positions. [0034] Preferably, first member 12 includes a mating surface 22 configured to substantially engage a mating surface 24 of second member 14. The sliding engagement of first member 12 and second member 14 in the first direction can no longer occur after surfaces 22, 24 mate. [0035] Preferably, when plate 10 is in the first assembled position, first member 12 and second member 14 are in sliding engagement. Further, bearing member 19 is preferably freely seated between ramp portion 18 and interference portion 20 in the first assembled position. Preferably, a surgeon preoperatively decides the amount of subsidence between first member 12 and second member 14 of plate 10 that is needed for a particular patient. -7- [0036] Depending on the particular patient, plate 10 is generally configured to subside 1mm to 10mm. Generally, surface 22 of first member 12 and surface 24 of second member 14 are slidably engaged and distanced approximately 1mm to 4mm apart in the first assembled position. A surgeon may decide based on the type of operation performed or the particular patient's anatomy and/or deformity to have surface 22 of first member 12 and surface 24 of second member 14 in the first assembled position at a greater distance than 4mm. The second assembled position is defined as the position where sliding engagement of first member 12 and second member 14 in the first direction is prevented, generally, after surfaces 22, 24 mate. [0037] In a preferred embodiment, first member 12 may translate freely with respect to second member 14 in a first direction Dl without engaging lock assembly 16. Preferably, lock assembly 16 is configured to allow first member 12 and second member 14 to slide freely with respect to one another in first direction Dl. Generally, first direction Dl is a downward direction as surface 22 of first member 12 translates toward second member 14. Movement in the first direction may only occur for first member 12 if second member 14 is in a fixed position. However, because of the anatomical structure and function of the spine, first and second members 12, 14 will generally both translate with respect to one another as subsidence occurs. Therefore, first member 12 and second member 14 both generally define movement in first direction Dl and second direction D2. It is also contemplated that the present invention is applicable to implants other than plates and further, other than plates moving in directly opposite directions. [0038] As shown in FIGS. 9-11, lock assembly 16 preferably provides a locking mechanism to allow movement or translation of members 12, 14 freely in first direction Dl, while preventing backward movement or translation of members 12, 14 in reference to one another in second direction D2. -8- Preferably, bearing member 19 is located in the deeper part of ramp portion 18 when first member 12 and second member 14 are in sliding engagement at an exemplary first assembled or at rest position as shown in FIG.9. [0039] As first member 12 and second member 14 begin to subside, bearing member 19 is preferably static and will rotate in place in the deeper area of the pocket. As shown in FIG. 10, if first member 12 and second member 14 begin to move or translate in opposite second direction D2 and members 12, 14 therefore start to pull apart, bearing member 19 will be forced to rotate up ramp portion 18 due to the friction created between ramp portion 18 and interference portion 20 of members 12, 14. [0040] Preferably, bearing member 19 will rotate up ramp portion 18 until the amount of point loading of bearing member 19 with respect to ramp portion 18 and interference portion 20 of members 12, 14 is sufficient enough to stop the movement or translation of members 12, 14 in second direction D2. Preferably, this point loading occurs instantaneously as the movement of members 12, 14 change from first direction Dl to second direction D2. [0041] Preferably, movement of members 12, 14 in second direction D2 is less than 1mm. Preferably, lock assembly 16 is further configured such that if first member 12 and second member 14 have stopped moving apart in direction D2, and start moving towards each other again in direction Dl, bearing member 19 may go back down ramp portion 18, thus releasing lock assembly 16. [0042] The depth and shape of ramp portion 18, interference portion 20, and the size of bearing 22 are all critical features for performance and design intent of dynamic plate 10. If the dimensions of ramp portion 18 and interference portion 20 are constant among several different plates, the distance between the first and second assembled positions of plate 10 may be affected by the size of bearing member 19. -9- [0043] Further, the locking forces imparted by ramp portion 18 and interference portion 20 on bearing member 19 may be affected by the size of bearing member 19. One skilled in the art would easily understand that a larger bearing between similarly sized ramp portions 18 and interference portions 20 of different plates 10 would place a greater force on bearing member 19 as well as limit the distance that the plates may translate in the first and/or second directions between the first and second assembled positions. [0044] FIGS. 12-14 show an alternative embodiment of a lock assembly 16' for a dynamic plate 10'. Preferably, lock assembly 16' includes an inclined plane ramp portion 18'. Lock assembly 16' preferably provides a locking mechanism to allow movement or translation of a plate member 12' and a plate member 14' freely in first direction Dl, while preventing backward movement or translation of members 12', 14' in reference to one another in second direction D2. Preferably, bearing member 19' is located in the deeper part of ramp portion 18' when first member 12' and second member 14' are in sliding engagement at an exemplary first assembled or at rest position as shown in FIG. 12. [0045] As first member 12' and second member 14' begin to subside, bearing member 19' is preferably static and will rotate in place in the deeper area of the pocket. As shown in FIG. 13, if first member 12' and second member 14' begin to move or translate in opposite second direction D2 and members 12', 14' therefore start to pull apart, bearing member 19' will be forced to rotate up ramp portion 18' due to the friction created between ramp portion 18' and interference portion 20' of members 12', 14'. [0046] Preferably, bearing member 19' will be forced to rotate up ramp portion 18', until the amount of point loading of bearing member 19' with respect to ramp portion 18' and interference portion 20' of members 12', 14' is sufficient enough to stop the movement or translation of members 12', 14' in second direction D2. Preferably, this point loading occurs -10instantaneously as the movement of members 12', 14' change from first direction Dl to second direction D2. [0047] Preferably, movement of members 12', 14' in second direction D2 is less than 1mm. Preferably, lock assembly 16' is further configured such that if first member 12' and second member 14' have stopped moving apart in direction D2, and start moving towards each other again in direction Dl, bearing member 19' may go back down ramp portion 18', thus releasing lock assembly 16'. [0048] In FIG. 2, an exploded rear view of first member 12 and second member 14 of plate 10 is shown. Interference portion 20 is shown, while ramp portion 18 is now hidden on the other side of first member 18. Preferably, a slight protrusion 21 extends outwardly from interference portion 20. Preferably, first member 12 further includes a recessed portion 23 as shown in FIG. 1. Protrusion 21 is preferably configured to engage recessed portion 23. The engagement of protrusion 21 and recessed portion 23 acts to further secure first member 12 and second member 14 in an exemplary second assembled position as shown in FIG. 11. Further, protrusion 21 and recessed portion 23 may act to guide the sliding engagement of members 12, 14 between the first and second assembled positions. [0049] In one embodiment, first member 12 further includes at least one vertical slot 26. Preferably, second member 14 further includes at least two apertures 28, wherein first and second member 12, 14 are prevented from disengaging when vertical slot 26 of first member 12 is situated between at least two apertures 28. Further, a pin 17 is preferably placed through at least two apertures 28 of second member 14 and vertical slot 26 of first member 12 as shown for example, in FIGS. 5 and 6. Preferably, pin 17 is a deformable rivet that may be inserted into a first aperture 28 as shown in FIGS. 5 and 7, and later be deformed to engage and be fixed within second aperture 28 as shown in FIG. 8. -11- [0050] Alternatively, second member 14 may include at least one vertical slot 26 and first member 12 may include at least two apertures 28 wherein first and second members 12, 14 are prevented from disengaging when vertical slot 26 of second member 14 is situated between at least two apertures 28. In this alternative embodiment, pin 17 is placed through at least two apertures 28 of first member 12 and vertical slot 26 of second member 14. [0051] Preferably, the function of vertical slot 26 is to aid in limiting the translation of first and second members 12, 14 with respect to one another between the first and second assembled positions. Further, apertures 28 in first and second members 12, 14 preferably act to secure pin 17 therein. Preferably, pin 17 is configured to slidably engage the slot of first and second members 12, 14. Further still, the slot 26 and pin 17 configuration preferably acts to add further security to the slidable engagement of first and second members 12, 14. [0052] Preferably, vertical slot 26 includes a top portion 25 and a bottom portion 27. When the first and second members 12, 14 are in the first assembled position, pin 17 is preferably through slot 26 and apertures 28 and is adjacent to bottom portion 27 of slot 26. Alternatively, when the first and second members 12, 14 are in the second assembled position, pin 17 is preferable through slot 26 and apertures 28 and is adjacent to top portion 25 of slot 26. [0053] Openings 38 in plate 10 for receiving bone screws may be seen in plate 10. Typically, spinal plates are secured to adjacent vertebrae by bone screws which pass through openings in the plates. Screw blocking systems are provided to keep the vertebral screws from backing out of the plate. In the present invention, each opening 38 in members 12, 14 preferably has grooves or recesses for receiving a split ring, though any other suitable screw locking systems may be used. [0054] Plate 10 may further include a keyhole 40 associated with either first and/or second members 12, 14. Preferably, -12keyhole 40 is configured to allow an instrument 42 to enter at least some of the space between ramp portion 18 and interference portion 20 as shown generally in FIG. 8. Preferably, instrument 42 is configured to dislodge bearing member 19 from between ramp portion 18 and interference portion 20 and/or hold bearing member 19 in place in the deeper portion of ramp portion 18. Instrument 42 may be used to release bearing member 19 locked between ramp portion 18 and interference portion 20. [0055] Preferably, instrument 42 is configured to impart a force on bearing member 19 sufficient to overcome the frictional forces on bearing member 19 while locked between ramp portion 18 and interference portion 20. Preferably, instrument 42 is further configured to move bearing member 19 back towards the deeper part of ramp portion 18 where bearing member 19 may freely rotate as shown in FIG. 9. [0056] FIGS. 3 and 4 are top views of members 12 and 14 respectively. As shown in FIG. 3, first member 12 preferably includes a first prong 29 and a second prong 31 extending outwardly from surface 22. Preferably, first prong 29 includes a male portion 30 and a receiving portion 32 and second prong 31 includes ramp portion 18. As shown in FIG. 4, second member 14 preferably includes a first prong 33 and a second prong 35. Preferably, first prong 33 includes a female portion 34 and a guidance portion 36. Female portion 34 is preferably configured to receive male portion 30 of first prong 29 of first member 12 and guidance portion 36 is preferably configured to engage receiving portion 32 of first prong 29 of first member 12. Preferably, second prong 35 of second member 14 includes interference portion 20. [0057] FIG. 5 is a view of first and second members 12, 14 of plate 10 in an exemplary first assembled position. Preferably, a clip 50 is used to maintain the spacing between surfaces 22, 24 of first and second members 12, 14 in the first assembled position. Clip 50 preferably includes a top portion 51, a first end 52, a bottom portion 53, and a second -13end 54. Preferably, in the first assembled position, surface 22 of first member 12 rests on top portion 51 of clip 50 and bottom portion 53 of clip 50 rests on surface 24 of second member 14. [0058] As shown in FIG. 6, clip 50 may encompass a portion of the perimeter of members 12, 14 such that a surgeon or medical technician has access to ends 52, 54 after members 12, 14 have been implanted. It is preferred, that clip 50 functions to maintain the spacing of members 12, 14 in the fist assembled position while also being configured to easily be removed from between members 12, 14. Alternatively, clip 50 may encircle the entire perimeter of members 12, 14. Preferably, clip 50 is made of a material strong enough to withstand forces that may be generated between members 12, 14 before and after implantation of members 12, 14 to a respective vertebral body. [0059] One method of implanting plate 10 includes fastening first and second members 12, 14 in the first assembled position to a respective vertebral body, clip 50 used to maintain members 12, 14 of plate 10 in the first assembled position, and removing clip 50 from the assembly such that first member 12 and second member 14 may translate in a first direction Dl. In this exemplary method, plate 10 further includes lock assembly 16 configured to allow first and second members 12, 14 to subside in a first direction in an infinite number of positions between a first assembled position and a second assembled position and alternatively limit the translation of the first member 12 and the second member 14 in an opposite second direction D2. [0060] Behind assembled clip 50 in the first assembled position, bearing member 19 is generally located in the deeper part of ramp portion 18. After clip 50 is removed from between members 12, 14, bearing member 19 is preferably static and will rotate in place in the deeper area of the pocket as surfaces 22, 24 of members 12, 14 slowly come together as natural subsidence occurs. If during subsidence, first member -14- 12 and second member 14 begin to move or translate in second direction D2, bearing member 19 will be forced to rotate up ramp portion 18 due to the friction created between ramp portion 18 and interference portion 20 of members 12, 14. [0061] Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. -15-

Claims (12)

1. A dynamic plate system for providing dynamic subsidence between at least first and second bodies, the system comprising: a first plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; a second plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; and a clip member having top and bottom surfaces, wherein the first and second plate members are slidably engaged to one another when the sliding portions of the first and second plate members are in sliding engagement with respect to each other, wherein the first and second plate members are in a loaded assembled position when the first and second plate members are slidably engaged to one another and the top surface of the clip member contacts the inner mating surface of the first plate member and the bottom surface of the clip member contacts the inner surface of the second plate member, and wherein the clip member has a substantially straight portion flanked by two curved portions, wherein each of the two curved portions are configured to contact the inner mating surfaces of the first and second plate members adjacent a side, front and back surface of each of the first and second plate members.

2. The dynamic plate system of claim 1, wherein the first plate member further includes a first prong and a second prong, the first prong of the first plate member having a male - 16 - portion and a receiving portion, the second prong of the first plate member including a ramp portion, and wherein the second plate member further includes a first prong and a second prong, the first prong of the second plate member having a female portion configured to receive the male portion of the first prong of the first plate member and a guidance portion configured to engage the receiving portion of the first prong of the first plate member, the second prong of the second plate member including an interference portion.

3. The dynamic plate system of claim 1 or claim 2, wherein the first and second plate members each have male and female sliding portions, the first and second plate members being slidably engaged to one another when a male sliding portion of the first plate member is at least partially received within a female sliding portion of the second plate member and the female sliding portion of the first plate member at least partially receives the male sliding portion of the second plate member.

4. The dynamic plate system of any one of the preceding claims, wherein the first plate member further includes at least one vertical slot.

5. The dynamic plate system of claim 4, wherein the second plate member further includes at least two apertures, wherein the first and second plate members are prevented from being slidably disengaged when the vertical slot is situated between the at least two apertures and a pin is placed through the at least one of the at least two apertures and the vertical slot.

6. The dynamic plate system of any one of the preceding claims, wherein the clip member has a width measured as the distance between the top and bottom surfaces thereof, the - 17 - width of the clip member being the same as a linear distance measured between a first plane of the inner mating surface of the first plate member and a second plate of the inner mating surface of the second plate member when the first and second plate members are in the loaded assembled position.

7. A dynamic plate system for providing dynamic subsidence between at least first and second bodies, the system comprising: a first plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; a second plate member having a body portion and a sliding portion, the body portion having first and second bone screw receiving apertures and an inner mating surface; and a clip member having top and bottom surfaces separated by a width of the clip member, wherein the first and second plate members are adapted to slidably engage one another, wherein the first and second plate members are in a loaded assembled position when the first and second plate members are slidably engaged to one another and the top surface of the clip member contacts the inner mating surface of the first plate member and the bottom surface of the clip member contacts the inner surface of the second plate member, and wherein the clip member has a substantially straight portion flanked by two curved portions, wherein each of the two curved portions are configured to contact the inner mating surfaces of the first and second plate members adjacent a side, front and back surface of each of the first and second plate members. - 18 -

8. The dynamic plate system of claim 7, wherein the first plate member further includes a first prong and a second prong, the first prong of the first plate member having a male portion and a receiving portion, the second prong of the first plate member including a ramp portion, and wherein the second plate member further includes a first prong and a second prong, the first prong of the second plate member having a female portion configured to receive the male portion of the first prong of the first plate member and a guidance portion configured to engage the receiving portion of the first prong of the first plate member, the second prong of the second plate member including an interference portion.

9. The dynamic plate system of claim 7 or claim 8, wherein the first and second plate members each have male and female sliding portions, the first and second plate members being slidably engaged to one another when a male sliding portion of the first plate member is at least partially received within a female sliding portion of the second plate member and the female sliding portion of the first plate member at least partially receives the male sliding portion of the second plate member.

10. The dynamic plate system of any one of claims 7 to 9, wherein the first plate member further includes at least one vertical slot.

11. The dynamic plate system of claim 10, wherein the second plate member further includes at least two apertures, wherein the first and second plate members are prevented from being slidably disengaged when the vertical slot is situated between the at least two apertures and a pin is placed through the at least one of the at least two apertures and the vertical slot. - 19 -

12. The dynamic plate system of any one of claims 7 to 11, wherein the width of the clip member is the same as a linear distance measured between a first plane of the inner mating surface of the first plate member and a second plate of the inner mating surface of the second plate member when the first and second plate members are in the loaded assembled position. - 20 -