HK1170407B - Dynamic vertebral column plate system - Google Patents

Description

Dynamic spinal plate system

Cross Reference to Related Applications

This application claims the benefit of priority from U.S. patent application serial No. 61/160,154 filed on 3/13/2009, which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to implantable orthopedic devices. In particular, the present invention relates to a plating system for post-operatively supporting a portion of the spinal column to facilitate spinal fusion.

Background

A variety of implantable orthopedic devices for assisting recovery following trauma or injury are known in the art. Among these devices, many involve relatively rigid devices that facilitate the transfer of substantial loads from the anatomy, such as from the spine. The applicant has realised that such load transfer prevents the desired loading of the anatomical structure. In the case of bone tissue, insufficient load will prevent, reduce or prevent ossification of the above-described structure, the concept of which is described by and known as "Wolff's law".

Accordingly, the applicant has recognized that it would be desirable to provide an orthopedic device that provides controlled load distribution while providing the necessary support to prevent damage to bone grafts and/or other anatomical structures to allow healing. The applicant has also realised that it is desirable to provide an orthopaedic device which is versatile and which can be adapted to a wide variety of situations. Applicants have further recognized that it is desirable to provide at least one locking feature to prevent inadvertent withdrawal of a fastener, such as a bone screw. The present invention provides a solution to the aforementioned problems.

Disclosure of Invention

According to one aspect of the present invention, a spinal construct for stabilizing spinal segments is provided having a first plate segment, a second plate segment connected to the first plate segment, and a spring connected between adjacent plate segments. A joining member may also be provided that is connected between the first and second plate segments. Alternatively, a separate engagement member may be omitted if sufficient stability is provided in other ways, e.g. by a spring or another element.

The spring may be adapted and configured to provide a predetermined preload between the first and second plate segments. Thus, the spring may be adapted-in combination with other components of the structure-to be shaped, dimensioned and formed from a material that achieves a predetermined preload. Such a preload may advantageously enhance fusion across the bone graft.

Alternatively, the spring may be adapted and configured to resist loading between the first and second plate segments to a predetermined extent.

A cam may be provided on one of the first and second plate segments, the cam being movable between engagement and disengagement with a cam surface associated with the other of the first and second plate segments, wherein engagement between the cam and the cam surface prevents dynamic loading of the spinal segment between the first and second plates.

The cam may be configured such that the position of the cam determines whether the preload applied by the spring is transferred through the construct, or to the spinal segment to which the construct is attached.

The cam may be adapted and configured to adjust the preload applied between the segments by adjusting the tension in the spring.

The spring may be an arcuately curved rod or bar. The spring may be made of a shape memory alloy.

The spring may engage a groove in one of the plate segments, the groove being configured such that outward application of the spring force is resolved into an axial contractive force between the first plate segment and the second plate segment.

A common upper plate may be disposed and connected to the first plate segment and the second plate segment. At least one of the first and second plate segments and the upper plate may be adapted and configured such that there is a substantially linearly translatable connection therebetween. The upper plate and the slidably connected lower plate segments may be connected by a mechanical interlocking device. The mechanical interlock may comprise a dovetail or pin and slot arrangement.

The third plate segment may be provided and connected to at least one of the first and second plate segments by a spring and optionally an engagement member. A fourth, fifth, sixth and subsequent number of plate segments may also be provided.

According to the invention, at least two segments may be provided and the structure may be adapted and configured such that a connection across the first and second segments is selectable between a static configuration and a dynamic configuration.

According to the invention, at least three segments may be provided spanning two connections respectively, and the structure may be adapted and configured such that each of the two connections spanned is selectable between a static configuration and a dynamic configuration.

According to another aspect of the present invention, there is provided a spinal plate system construct for stabilizing spinal column segments having: a first plate section; a second plate segment connected to the first plate segment; a spring element connected between adjacent plate segments adapted and configured to provide a predetermined preload between the adjacent plate segments to enhance spinal fusion; an upper plate connected to the first plate segment and the second plate segment; and a cam disposed on one of the first and second plate segments, the cam being movable between engaging and disengaging with a cam surface of the other of the first and second plate segments, wherein engagement between the cam and the cam surface prevents dynamic loading of the spinal segment between the first and second plate segments. Further, a joint member may be provided that connects between the first and second plate segments.

According to the invention, the cam surface may be provided on the other of the first and second plate segments. Alternatively, the cam surface may be on the upper plate. In such a configuration, the other of the first and second plate segments and the upper plate may be substantially rigidly connected to each other.

According to another aspect of the present invention, there is provided a method of implanting a spinal structure over a spinal column segment, the method comprising the steps, performed in any order, of: the method includes securing each of a plurality of plates of the spinal construct to a respective vertebra, determining whether to apply a preload between a first and second level of vertebrae, and applying a first preload between the first and second level of vertebrae.

The step of applying the first preload may include rotating a first cam of the dynamic spine structure in a first direction.

The method may further comprise the steps of: estimating the efficacy of the first preload and applying a second preload between said first and second sections of the vertebrae in place of the first preload, the second preload being different from the first preload. The second preload is greater than the first preload. Alternatively, the second preload may be less than the first preload.

The step of applying the second preload may include rotating the first cam in a second direction different from the first direction.

The method may further comprise the steps of: determining whether a preload is applied between the first and second levels of vertebrae and a third preload is applied between said second and third levels of vertebrae.

The step of applying the third preload may include rotating a second cam of the dynamic spine structure in the first direction.

The method may further comprise the steps of: estimating the efficacy of the third preload and applying a fourth preload between said second and third segments of the vertebrae in place of the third preload, the fourth preload being different from the third preload.

The step of applying the fourth preload may include rotating the second cam in a second direction different from the first direction.

Additionally or alternatively, a construct according to the present invention may be configured to provide a predetermined amount of resistance to contraction and/or bending between adjacent plate segments, thereby allowing a predetermined amount of load distribution between the construct and the spinal column segment.

According to the invention, the engaging members, if provided, may be arranged symmetrically in the structure with respect to the longitudinal axis of the structure. Furthermore, two laterally opposed springs may be disposed in the structure and may be arranged substantially symmetrically with respect to a longitudinal axis of the structure.

According to the invention, a plurality of screws for engaging the structure to the spinal column segment may be provided. The screw may include a slot or other configuration for receiving an engagement member for preventing inadvertent withdrawal of the screw.

According to the invention, one or more of the plate sections may be implemented to comprise respective upper and lower portions.

A plurality of spring elements may be provided for assembly with the plate sections, if so implemented, the spring elements being provided within a range of stiffnesses allowing for a selectivity of the contraction force or preload of the structure, and/or a selectivity of the resistance to contraction of the structure and/or the bending stiffness.

The engagement elements may be received in respective grooves provided in each of the plate sections connected by the engagement members.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to illustrate and provide a further understanding of the systems, devices, kits, and related methods of the invention. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention:

FIGS. 1A and 1B are isometric and isometric views, respectively, illustrating the internal structure of a representative embodiment of a dynamic spinal plate system and accompanying screws according to the present invention, with the spinal plate system shown in an expanded state;

FIGS. 1C and 1D are isometric perspective and isometric line views, respectively, illustrating the internal structure of a representative embodiment of a dynamic spinal plate system and accompanying screws according to the present invention, with the spinal plate system shown in a collapsed condition;

fig. 2A and 2B are isometric and isometric perspective views, respectively, illustrating the internal structure of the dynamic spinal plate system of fig. 1A and 1B, shown without accompanying screws, in accordance with the present invention;

FIGS. 3A and 3B are a top line drawing and a top perspective view, respectively, illustrating the internal structure of the dynamic spinal plate system of FIGS. 1A and 1B shown with accompanying screws;

fig. 3C is a top line drawing of the dynamic spinal plate system of fig. 1A and 1B shown without accompanying screws;

FIGS. 4A and 4B are an end line drawing and an end perspective view, respectively, illustrating the internal structure of the dynamic spinal plate system of FIGS. 1A and 1B shown with accompanying screws;

FIGS. 5A and 5B are a side line drawing and a side perspective view, respectively, illustrating the internal structure of the dynamic spinal plate system of FIGS. 1A and 1B, shown with accompanying screws;

fig. 6A is a bottom line drawing of the dynamic spinal plate system of fig. 1A and 1B shown with accompanying screws;

fig. 6B is a bottom line drawing of the dynamic spinal plate system of fig. 1A and 1B shown without the accompanying screws;

FIGS. 7A and 7B are a line drawing and perspective view, respectively, illustrating a detailed view of a portion of the dynamic spinal plate system of FIGS. 1A and 1B shown with accompanying screws;

FIGS. 8A and 8B are isometric line views of the top and bottom surfaces of the upper plate segment of the dynamic spinal plate system of FIGS. 1A and 1B, respectively;

fig. 9 is an isometric line drawing showing a lower surface of an upper plate segment of the dynamic spinal plate system of fig. 1A and 1B;

FIG. 10 is an isometric line drawing illustrating the upper surface of the lower segment of the dynamic spinal plate system of FIGS. 1A and 1B;

FIGS. 11A and 11B are a line drawing and perspective view, respectively, illustrating a screw and retaining clip according to the present invention for use on the dynamic spinal plate system of FIGS. 1A and 1B;

FIG. 11C is a line drawing of the screw of FIGS. 11A and 11B shown without a retaining clip;

FIG. 12 is a top isometric view of the screw of FIGS. 11A and 11B shown without the retaining clip and showing the socket portion therein;

fig. 13 is an isometric line drawing illustrating engagement members for connecting adjacent plate segments of the dynamic spinal plate system of fig. 1A and 1B;

FIG. 14 is an isometric line drawing illustrating spring members used to connect adjacent plate segments of the dynamic spinal plate system of FIGS. 1A and 1B;

FIG. 15A is a top view of the spring member of FIG. 14;

FIG. 15B is a bottom view of the spring member of FIG. 15A;

FIG. 15C is a front isometric view of the spring member of FIG. 15A;

FIG. 15D is an enlarged partial view of the spring member of FIG. 15A showing a central bend in the spring member;

FIG. 15E is a left side view of the spring member of FIG. 15A;

FIG. 15F is a right side view of the spring member of FIG. 15A;

16-29 illustrate various views of another exemplary embodiment of a dynamic spinal plate system having arcuately curved rods or bar springs and an integral cam member in accordance with the present invention;

FIG. 16 is an isometric view of the plate structure shown in an expanded state according to this embodiment;

FIG. 17 is a side view of the plate structure shown in an expanded state;

FIG. 18 is an isometric view of the plate structure shown in a collapsed condition;

FIG. 19 is a side view of the plate structure shown in a collapsed condition;

FIG. 20 is a bottom isometric view of the plate structure shown in an expanded state;

FIG. 21 is a bottom isometric view of the plate structure shown in a collapsed condition;

FIGS. 22A-C are end views of the plate structure showing the joining step between the upper plate and the lower plate segment;

FIG. 23 is a partially exploded isometric view of the plate structure showing the internal components of the plate structure and the tools used to operate the cams of the plate structure;

FIG. 24 is a bottom isometric view of an upper plate of the plate structure;

FIG. 25 is an exploded view of the internal components of the plate structure;

FIG. 26 is an isometric view of the plate structure shown in an expanded condition with the two cams rotated out of engagement with the opposed grooves for this purpose, and showing the upper plate removed for clarity;

FIG. 27 is a top view of the end of the plate structure with the cams shown retained in the opposed grooves, maintaining the expanded state of the plate, and showing the upper plate removed for clarity;

FIG. 28 is an isometric view of the plate structure shown in the contracted condition with the two cams rotated out of engagement with the opposing grooves for this purpose, and showing the upper plate removed for clarity;

FIG. 29 is a top view of the end of the plate structure shown in the contracted condition, with the cam shown rotated out of engagement with the opposing groove for this purpose, maintaining the expanded condition of the plate, and showing the upper plate removed for clarity;

FIGS. 30A-C illustrate implantation steps of the dynamic spinal plating system configuration of FIGS. 16-29, but the steps are broadly applicable to other embodiments of the present invention;

FIG. 30A shows the construct during insertion of the last screw for engaging the connected spinal segment;

fig. 30B shows the structure during rotation of the cam by means of the tool for the cam;

FIG. 30C shows the construct after attachment to a spinal segment and rotation of the two cams away from the opposing grooves for the cams, with the upper plate removed for clarity;

FIGS. 31A-H are side and cross-sectional views of various screw configurations for use in the dynamic spinal plate system of the present invention;

FIG. 32A is an isometric view of a dynamic spinal plating system in accordance with the invention having a two-segment plate segment;

FIG. 32B is an isometric view of a dynamic spinal plating system in accordance with the invention having four-segment plate segments;

fig. 33-39 are various views of another exemplary embodiment of a dynamic spinal plate system construct having a ribbon spring and an integral cam member configured to accommodate multiple selectable preloads in accordance with the present invention;

FIG. 33 is an isometric view of the structure of this embodiment shown in an expanded state;

FIG. 34 is an isometric view of the structure of this embodiment shown in a contracted state;

FIG. 35 is an isometric view of the structure of the embodiment shown in an expanded state and showing the upper plate removed for clarity;

FIG. 36 is a bottom isometric view of the upper plate of this embodiment of the structure;

FIG. 37 is a top view of the structure of the embodiment shown in the expanded condition and showing the upper plate removed for clarity;

FIG. 38 is a top view of the structure of this embodiment shown in the contracted condition with the cam in one position for applying a corresponding preload to the spinal segment and showing the upper plate removed for clarity; and

fig. 39 is a top view of the structure of this embodiment shown in the contracted condition with the cam in another position (as compared to fig. 38) for applying a different corresponding preload to the spinal segments and with the upper plate removed for clarity.

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

The devices and methods presented herein may be used to stabilize segments of the spine during post-operative spinal fusion.

Referring to the drawings and as seen in, for example, fig. 1A and 1B, a dynamic spinal plate system for stabilizing spinal segments is assemblable into a plate structure 100 for connection to spinal segments. For example, such structures may be provided to a user (e.g., a physician) after they have been assembled, or may be assembled by the user. The plate system includes a first end plate segment having an upper portion 110a and a lower portion 120a, a second end plate segment having an upper portion 110c and a lower portion 120c connected to and disposed opposite the first plate segment. As illustrated, a middle plate segment having an upper portion 110b and a lower portion 120b may be provided. According to further aspects of the present invention, additional intermediate plate segments may additionally be provided, resulting in a total of 3, 4, 5, 6, 7, 8 or more plate segments in the structure 100 formed by the components of the subject system.

In the illustrated embodiment, the engagement members 140 and spring elements 130 are disposed between and connect adjacent plate segments to form the plate structure 100. While one engagement member 140 and two springs 130 are shown between each pair of adjacent plate segments, it will be appreciated that any suitable number of such elements may be provided. It is specifically contemplated that two laterally opposing engagement members 140 may additionally or alternatively be disposed laterally at the distal end of the spring 130. In such embodiments, it is contemplated that providing additional material along the lateral edges of the plate segments 110, 120 to provide structural support and/or simply provide space for accommodating additional joining members may prove necessary.

The spring 130 is adapted and configured to provide a predetermined amount of retraction force or preload to the structure 100. According to an alternative embodiment, the spring 130 may be adapted and configured to provide a predetermined amount of bending stiffness between adjacent plate segments, thereby allowing a predetermined amount of load distribution between the structure 100 and the spinal segment to which the structure 100 is connected.

As can be seen in fig. 1A and 1B, a plurality of screws 150 are provided to anchor the construct 100 into bone. Holes 113a-c are provided in each upper plate portion 110a, 110b, 110c, in which holes 113a-c the heads of the screws 150 rest. A groove 155 is provided in the head of the screw 150 for receiving a locking element, such as a retaining clip 159 best seen in fig. 11A and 11B. The locking element may be any suitable element, including but not limited to a resilient O-ring, a circlip, or other suitable element, such as a locking ring coil available from Bal Seal Engineering, inc. The locking element may be formed, for example, from any suitable material, such as a metal, metal alloy, elastomeric material, silicone, Neoprene (e.g., Neoprene), or a plastic material such as Polyetheretherketone (PEEK). A locking element, which may be supported by a screw, may be disposed in a groove provided in the structure in use.

As seen in fig. 1B and in fig. 1C, 8B, 9 and 10, spring engaging members or projections 115, 125 may be connected to or integrally provided with a plate segment, such as upper plate portion 110a or lower plate portion 120a, respectively, for engaging spring 130. Similarly, the engagement members 140 are secured to adjacent plates by grooves 117, 127 provided in each respective upper plate portion 110a-c and lower plate portion 120 a-c. The grooves 117, 127 are formed with respective partial "I" shapes to receive the engagement member 140 and permit axial movement between the plate portions 110, 120 and the engagement member 140. Thus, the lateral portions of the grooves 117, 127 may be deeper than the lateral portions of the engagement member 140 to allow for axial movement. Also, it is understood that a variety of shapes of engagement members 140 may be used and are not limited to only the shapes shown.

Although shown as separate components, it will be appreciated that in alternative embodiments, the engagement members 140 may be integrally formed with one plate, fitting into corresponding recesses 117, 127 in an adjacent plate. Thus, relative movement between the plate segments is permitted without the need to manufacture and assemble separate components. Consistent with such embodiments, it is specifically contemplated that permutations of the configuration of separate or integral joining members 140 are possible with any suitable number of joining members 140 disposed between adjacent panels.

The circular spring engaging members or protrusions 115, 125 allow relative movement of the springs when the structure 100 is subjected to different loading conditions, such as axial tensile or compressive forces or transverse bending (e.g., in a plane generally parallel to the plate surfaces and parallel to the longitudinal axis of the structure). Alternatively, the protrusions 115, 125 may be any suitable shape, including but not limited to oval, oblong, polygonal (e.g., square, hexagonal). The shape of the projections 115, 125, which resists rotation about the projections 115, 125, may enhance the lateral stability of the structure 100. Relatively shallow recesses 119 are provided in one or more of the upper plate portions 110a-c and the lower plate portions 120 a-c. The recess 119 is configured to provide space for elastic deformation of the spring 130 under the aforementioned axially compressed and/or bent conditions.

The upper and lower portions of the plate segments, such as upper plate portion 110a and lower plate portion 120a, may be secured to one another in any suitable manner, including but not limited to, welding, mechanical fasteners, solder, adhesives, epoxy materials, mechanical interlocking structures, and the like.

As noted above, fig. 2A and 2B are isometric and isometric views, respectively, illustrating the internal structure of the dynamic spinal plate system of fig. 1A and 1B, shown without accompanying screws, in accordance with the present invention. Fig. 3A and 3B are a top line drawing and a top perspective view, respectively, illustrating the internal structure of the dynamic spinal plate system of fig. 1A and 1B shown with accompanying screws. Fig. 3C is a top line drawing of the dynamic spinal plate system of fig. 1A and 1B shown without accompanying screws. Fig. 4A and 4B are an end line drawing and an end perspective view, respectively, illustrating the internal structure of the dynamic spinal plate system of fig. 1A and 1B shown with accompanying screws. Fig. 5A and 5B are a side line drawing and a side perspective view, respectively, illustrating the internal structure of the dynamic spinal plate system of fig. 1A and 1B shown with accompanying screws. Fig. 6A is a bottom line drawing of the dynamic spinal plate system of fig. 1A and 1B shown with accompanying screws. Fig. 6B is a bottom line drawing of the dynamic spinal plate system of fig. 1A and 1B shown without the accompanying screws. Fig. 7A and 7B are a line drawing and perspective view, respectively, showing a detailed view of a portion of the dynamic spinal plate system of fig. 1A and 1B shown with accompanying screws. Fig. 8A and 8B are isometric line views of the top and bottom surfaces of the upper plate segment of the dynamic spinal plate system of fig. 1A and 1B, respectively. Fig. 9 is an isometric line drawing illustrating a lower surface of an upper plate segment of the dynamic spinal plate system of fig. 1A and 1B, and fig. 10 is an isometric line drawing illustrating an upper surface of a lower plate segment of the dynamic spinal plate system of fig. 1A and 1B.

As best seen in FIG. 3C, for example, the lower plate portion 120a-C of each segment includes a smaller hole 123a, b, or C, respectively, for a screw 150 than the holes 130a-C, respectively, provided in the upper plate portions 110a-C, respectively. This allows the construct 100 to be securely engaged to the spine and the larger holes 113a-c allow space for insertion of the retaining clip 159.

As best seen in fig. 11A and 11D, the illustrated screw 150 may include external threads 151 thereon for securely engaging bone. The proximal groove 155 receives a retaining clip 159 for facilitating engagement with the structure 100. As seen in fig. 12, screw 150 may include a slot 153 and internal threads 152 disposed therein to facilitate removal of screw 150 from bone, if necessary or desired. Such threads 152 are preferably opposite in direction to the threads 151 of the screw 150 so that when the screw is removed, the removal tool does not itself disengage from the screw 150.

As best seen in fig. 13, the engagement member 140 is shaped in this embodiment as a substantially solid "I-beam". Any of a variety of materials may be used, including, for example, but not limited to, stainless steel, titanium alloys, nickel alloys such as nitinol, polymeric materials, ceramic materials, or composite materials. The shape of the engagement member 140, and in particular the web portion 143 thereof, provides resistance to the consequent predetermined amount of bending of the structure, but may also allow a predetermined amount of bending of the structure if so implemented.

According to a preferred embodiment, the plate segments are moved in an axial direction (parallel to the longitudinal axis of the structure 100) guided by the engagement members 140. The spring 130 applies a compressive force between the segments of the structure 100 while the engagement members 140 help stabilize the structure 100. In such embodiments, the engagement member 140 is preferably relatively strong (i.e., resistant to bending forces).

Alternatively, if the structure 100 is implemented to allow bending due to the placement of the spring 130 relative to the engagement member 140, the lateral bending (generally in the plane of the plate segments 110, 120, but parallel to their longitudinal axes) will generally be less than it would be in the vertical direction (out of the plane of the plate segments 110, 120 (but still in a plane parallel to the longitudinal axes of the structure)). In such embodiments, the stiffness of the engaging member 140 may be selected by changing the material properties of the engaging member 140, by changing the composition of the material, by treating the material, or by changing its shape, particularly its cross-sectional shape, to change its cross-sectional moment.

As seen in fig. 14 and 15A-15F, the spring element 130 includes engagement holes 135, the engagement holes 135 for mating with the spring engagement members 115 formed on the upper plate portions 110a-c and the spring engagement members 125 formed on the lower plate portions 120 a-c. The spring element 130 may be formed from any suitable material, including, for example, but not limited to, stainless steel, titanium alloys, nickel alloys such as nitinol, polymeric materials, ceramic materials, or composite materials. The stiffness of the spring element 130 may be selected by changing its material properties, by changing the composition of the material, by processing the material, or by changing its shape. The nature of the overall bend and the cross-section of the component in this region can be varied to increase or decrease its stiffness relative to the spring 130.

As illustrated, the spring 130 narrows to a relatively small cross-sectional area. When axial compression is the primary loading mode, the spring 130 may be set to be pre-stressed, wherein the relaxed state of the spring results in a shorter length of the structure 100 than in the pre-stressed state. In such embodiments, the structure 100 may be provided with removable spacers 160 (fig. 1C) between the plate segments, the removable spacers 160 being removed after connection to the spine segments. Thus, the spring 130 exerts a constant axial compressive force on the spine segment.

In accordance with the present invention, the stiffness of the engagement member 140, the spring 130, and the materials of the plate segments 110, 120 are selected to provide a desired amount of bending of the construct when connected to the spinal column segment. According to one aspect, the device according to the invention allows an axial contraction at each level of between about 0 and 5.0mm, and preferably between about 1.0mm and 3.0mm, across each intervertebral space. According to another preferred aspect, the subject devices tolerate an axial contraction of about 2.0mm at each segment. If desired, the characteristics of the structure may be varied at different segments, providing a greater preload force at one segment than at another segment, or alternatively resistance to axial contraction and/or bending, if desired.

The shapes of plate segments 110 and 120, engagement member 140, and spring 130 preferably, when combined with a corresponding spinal segment, produce a curvature that closely approximates the natural curvature of the spinal segment. In addition to providing a bias to maintain pressure across the intervertebral space to promote fusion of the bone graft, the curvature is preferably very close to the curvature of the spinal column segment to which it is attached.

In addition, the spacing between adjacent plate segments may be selected as desired, and may vary between adjacent segments, for example, throughout a continuous intervertebral space. Such flexibility allows for greater versatility when used with individual bones of a patient.

Moreover, devices according to the present invention may be configured to provide a preload throughout the intervertebral space to facilitate spinal fusion. This is accomplished, for example, by providing a curvature offset of the assembled structure 100. This may be accomplished by providing a preformed bend to the engagement member 140 and/or the spring 130. Such bending need only be slight to result in an effective bias.

Screws used in conjunction with devices according to the present invention, such as screw 150, may comprise any desired structure known in the art. Such screws may be adapted for fixed angle insertion or variable angle insertion with arcuate lower surfaces at the junction of the plate segments 110, 120. Such screws may be self-tapping or self-drilling. Exemplary screw configurations for use in devices according to the present invention are described below in association with fig. 31A-H.

Fig. 16-29 illustrate various views of another exemplary embodiment of a dynamic spinal plate system, generally indicated by the reference numeral 200, in accordance with the present invention. Among other structures, the construct 200 has an arcuately curved rod or bar spring 230 and an integral cam element 261 that allows the construct 200 to be used as a static or dynamic plate to provide preload at one or more segments of a spinal column segment. In short, if the cam 261 is placed in a locked position after implantation (e.g., as shown in fig. 23), or alternatively is unlocked prior to implantation, no preload will be applied to the respective segments. However, if the cam 261 is locked during implantation and unlocked after attachment to the spinal segment, the preload provided by the respective spring 230 will be applied to that segment.

The structure 200 includes many portions similar to the structure 100 discussed in association with fig. 1-15F. For example, construct 200 includes a plurality of holes 223a-c for receiving screws for connection with respective vertebrae, a plurality of lower plate portions 220a-c, engagement members or guides 240, and springs 230 for applying a preload at respective levels, although the configuration of these portions may differ substantially slightly from the components of construct 100, as will be described in greater detail below.

The significant differences between the structure 100 discussed in association with fig. 1-15F and the structure 200 in fig. 16-29 include different configurations of the single upper plate 210, the integral cam 261, and the associated portion, spring 230, which applies a preload if desired.

The unitary upper plate 210 of the structure 200 differs in configuration from the individual upper plate portions 110a-c of the structure 100 in fig. 1-15F. The single upper plate advantageously enhances the stability of the construct 200, and thus also of any attached spinal segments, while permitting linear translation of the adjacent lower plate segments 220a, 220b, 220c, and thus also permitting axial loading to be applied across the attached spinal segments to promote fusion.

As can be seen particularly in fig. 22A, 22B and 22C, the end plate segments 220a, 220C engage the upper plate 210 through a female dovetail 228 formed in the lower plate segments 220a, 220C and a male dovetail 218 formed on the upper plate 210. The dovetails 218, 228 constrain relative motion between the end plate segments 220a, 220c and the upper plate 210 along each axis, except along the longitudinal axis, which motion is constrained by the engagement member 240 and spring 230 when expanded, and constrained by interference with an adjacent plate, such as the intermediate plate 220b, when contracted. The engagement of the dovetail 218 of the upper plate 210 allows for the provision of the cut-out 212, which allows for the resulting deflection of the fork 214 of the upper plate 210 about the cut-out 212, the dovetail 218 being formed on the fork 214.

As with the structure 100, an engagement member 240 is provided for promoting stability of the structure 200 and limiting expansion of the structure 200 beyond a predetermined amount. The lower plate segments 220a-c include recesses 227 to receive the engagement members 240, while the upper plate 210 includes corresponding recesses 217 for this purpose. The upper plate 210 includes a tail portion 216, the tail portion 216 partially defining a recess 217 therein for the engagement member 240 and permitting a tight engagement between the upper plate 210 and the lower plate segments 220a, 220b, 220c at the lateral edges of the structure 200.

Different holes 211a, 211b, 211c are provided in the upper plate 210 for respective purposes. The central hole 211c is configured to allow the lower middle plate segment 220b to be pinned to the upper plate 210 during assembly. Such pins may be peened, welded or otherwise attached to the upper and lower plates in another suitable manner. Such pins may be integrally formed, such as by casting and/or machining, with one of lower middle plate segment 220b and upper plate 210. Alternatively, any intermediate plate, such as plate 220b, may be connected to upper plate 210 in another manner, such as by being connected to upper plate 210 by a dovetail as discussed in association with, for example, end plate segments 220a, 220 c.

Corresponding holes 211a are provided to enable access to each cam 261 to rotate the cam 261 between the locked and unlocked positions as shown, for example, in fig. 30B. An aperture 211b is also provided in line with the gaps 291a, 291b between the lower plate segments 220a, 220b, 220c, the aperture 211b providing a viewing window through the construct 200 to allow the physician to view the relative spacing between the lower plate segments 220a, 220b, 220c, and also the condition of the bone graft (of the vertebrae and any fusion device or material), during or after attachment of the construct 220 to the spinal segments. The physician may thus determine from his or her experience whether the segment of the construct should remain static, or whether the cam 261 should be unlocked to provide dynamic loading application at that segment. The physician may consider a number of factors, including any gaps that he or she may observe, for example, in the intervertebral space, between the vertebrae and any fusion material.

After implantation, the physician may choose to hold one or more of the cams 261 in the locked position, or alternatively, may unlock one or more of the cams prior to implantation, causing the respective gaps (e.g., 291a, 291b) to close. In either case, the segment of the structure 200 will behave essentially as a static plate. More typically, however, each cam 261 will be unlocked by rotating the cam 261 away from its position in the groove 265, as shown in fig. 26, for example, after implantation. At this point, even if no visible contraction occurs, the spring 230 begins to exert a force across the corresponding gap (e.g., 291a) at that segment, and thus against the spinal segment, which would typically be a fusion between the vertebrae.

According to an alternative embodiment, the cam 261 may be configured similar to the cam 561 discussed below in connection with the embodiments of fig. 33-39. Still alternatively, the cam 261 may be configured and adapted to engage the pin in a position to stretch the respective spring 230, thereby achieving an increased preload after implantation.

The spring 230 is configured as an arcuate rod or bar. As illustrated, the ends of the spring 230 are retained in a pin 231, the pin 231 being translatable relative to grooves 215 and 225, the grooves 215 and 225 being formed in the upper and lower plates 210 and 220a, 220c, respectively (see fig. 23 and 24).

At the maximum extent of expansion of the structure 200, such as shown in fig. 16, 17, 20 and 23, the gaps 291a, 291b between adjacent lower plate segments 220a, 220b and 220c are also at their maximum, as limited by the central spring 230 and the laterally disposed U-shaped engagement members 240, which engagement members 240 engage in the grooves 117, 127 formed in the upper plate 110 and each of the lower plate segments 220a-c, respectively. The cams 261 rotate on the respective projections 267 and engage, in their locking positions, the grooves 265 formed on the facing surfaces of the adjacent plates, thereby maintaining a predetermined interval. In addition to the hole in the cam 261 for receiving the projection 267, a hole 269 may be provided in the cam to engage with a tool for rotating the cam 261.

The dimensions of these components may be selected to vary the amount of spacing between adjacent plates, however, according to a preferred embodiment, the maximum spacing of the gaps 291a, 291b is about 2.0mm, such as is used in cervical vertebral segments. The spacing may be selected to be larger or smaller, for example between 1.0mm and 3.0mm of translation, depending on the placement of the structure 200 (or any other structure according to the present invention). That is, if used on lumbar vertebral segments, the construct may be configured to provide a greater maximum spacing between plate segments, such as 3.0mm, or perhaps greater if indicated for a particular application. The maximum spacing 291a, 291b between the segments 220a-c determines the maximum range of travel that the spring 230 can apply a preload to a segment of the spine, e.g., over the entire fusion.

A piece of bone, cage or other fusion material is typically inserted between the vertebrae to be fused together in place of the disc and carries most of the load carried by the spine. The construct 200 then provides stability to the spinal segment to which it is attached while minimizing load transfer to the construct, which promotes proper fusion. The spring 230 maintains the load on the segment even in the absence of an external load. In this manner, the construct 200 (and other constructs according to the present invention) advantageously allows for subsidence (nesting) of the fusion material while minimizing any space between the adjacent vertebrae and the fusion material, thereby further enhancing fusion.

In the embodiment of the structure 200 of fig. 16-29, implantation of the structure 200 is shown in fig. 30A, 30B, and 30C, with the spring 230 being an arcuately shaped rod or bar member formed of a resilient material. According to a preferred aspect, the spring 230 is formed from a shape memory alloy, such as nitinol. According to one aspect, the spring 230 is linear in its natural state and bends into the arcuate configuration shown when the structure 200 is assembled. The diameter of the spring 230 is selected according to the desired amount of force to be applied. Thus, the spring 230 rotates in an outward arc when attempting to return to its natural configuration, initially applying a generally laterally outward force to the outer plate segments 220a, 220c via the slots 225 formed in the outer plate segments 220a, 220c via the pins 231 at the ends of the spring 230.

The groove 215 formed in the underside of the upper plate follows the arc of the pin 231 caused by the spring 230. The slot 225 in the lower end plate segment 220a, 220b is a linear structure and provides an arcuate longitudinal component of travel of the pin 231 in translation of the plate segment 220a, 220b itself when closing the gap 291a, 291 b. The linear configuration of the slots 225 of the lower endplate segments 220a, 220b within which the pins 231 pass facilitates converting the generally arcuate application of spring force into an axial force parallel to the translation of the endplate segments 220a, 220 c. As can be appreciated, any lateral component of the force exerted by the spring will be symmetrically exerted by each pin 231, so these forces cancel each other out within the outer plate segments 220a, 220c, and no net external force is generated.

As configured, the slot 225 is not completely parallel to the edges of the plates 220a, 220 c. The angle of the slot 225 is set to increase the translational distance of the outer plate segments 220a, 220c that provides sufficient force application thereon.

According to the present invention, the target force application may be between about 0N and 90N (between about 0 to 20 pounds-force). According to one embodiment of the present invention, the target force is applied between about 13N and 44N (between about 3 to 10 pounds-force) for application to the cervical vertebral segments. Alternatively, the targeted force application may be greater or lesser depending on the spinal segment. According to another embodiment of the present invention, the target force for application is between about 44N and 89N (between about 10 to 20 pounds-force) for a thoracic or lumbar vertebral segment. As discussed herein, if resistance to compressive forces is desired, and it is not desired to apply a preload through any of the structures described herein, then such a target force is 0N. Any application of force sufficient to safely achieve the desired effect is possible according to the present invention.

Fig. 26 shows the structure 200 in an expanded state just after the cam 261 disengages from the opposing groove 265. As shown in fig. 28 and 29, in the absence of the attached spine segments, the outer plate segments 210a, 210c are pulled inward by the action of the springs 230 as the cams 261 disengage from the opposing grooves 265.

Fig. 30A-C illustrate implantation of the dynamic spinal plating system construct 200 of fig. 16-29 in various stages of attachment to a spinal segment 90. Fig. 30A shows the construct 200 in an expanded state attached to three vertebral bodies 91, 93 and 95 and spanning two intervertebral spaces 92 and 94 of a spinal segment 90, with screws 150 inserted using an insertion tool 81. Fig. 30B shows the structure 200 during disengagement of the lower cam 261 using the tool 83. Fig. 30C is a plan view of the structure 200 after each cam 261 has disengaged from its respective opposing groove 265, with the upper plate removed for clarity. The force exerted by the spring 230 is indicated by the arrows, and the resulting force applied to the spinal segment is shown by the arrows parallel to its longitudinal axis. As illustrated, after disengagement, the cam 261 cannot be rotated completely away from the adjacent plate due to the positioning of the pin 231. However, as settling occurs and the pins 231 move laterally outward, the cam 261 may continue to rotate away from the adjacent plate.

Fig. 31A-H are side and cross-sectional views of various screw configurations used in the dynamic spinal plate system of the present invention. Fig. 31A and 31B show a screw 250 having a self-tapping end 254 and a head 258 that allows variable angular engagement with the attached panel. A groove 255 is provided in the head 258 of the screw 250 for receiving a locking element, which may be any suitable element, including but not limited to a resilient O-ring, a circlip, or may be another suitable element, such as a locking ring coil commercially available from Bal Seal Engineering, inc. The locking element may be formed of any suitable material, such as a metal, metal alloy, elastomeric material, silicone, Neoprene (e.g., Neoprene), or a plastic material such as Polyetheretherketone (PEEK), for example. A locking element, which may be carried by a screw, may be disposed in a groove provided in the structure being used.

As with screw 150 discussed in connection with the embodiment of fig. 1-15F, screw 250 includes a socket 153 for engaging an insertion tool for implantation, if necessary, and internal threads 153 are preferably provided to facilitate removal of screw 250. Fig. 31C and 31D are side and cross-sectional views of a screw 350 having a self-drilling end 356 and a head 258 allowing engagement at variable angles. Fig. 31E and 31F are side and cross-sectional views of a screw 450 having a head 459 that, due to its trapezoidal cross-section, only permits engagement with an attached plate at a fixed angle, as compared to the more rounded cross-section of the head 258 of the screws 250 and 350. The screw 450 also includes a self-drilling end 356. Fig. 31G and 31H show a screw 550 having a self-tapping end 254 and a head 459 for engagement at a fixed angle.

Fig. 32A is an isometric view of a dynamic spinal plate system construct 300 having two-segment plate segments 320a, 320b and a single superior plate 310 according to the present invention. The internal component may be any of the components shown herein, but as illustrated, the structure 300 is provided with a spring configuration similar to that of the structure 200 described in association with fig. 16-29.

Fig. 32B is an isometric view of a dynamic spinal plate system structure 400 having four-segment plate segments 420a, 420B, 420c, and 420d and a single superior plate 410 according to the present invention. The internal component may be any of the components shown herein, but as illustrated, the structure 400 is provided with a spring configuration similar to that of the structure 200 described in association with fig. 16-29. As described above, the intermediate plates 420a, 420b may be connected by means of pins or in an alternative manner.

In any event, it is generally preferred, but not required, that no more than one lower plate segment (e.g., 420a-d) be non-translatably secured to the upper plate 410. In the case of a two-segment construction, one segment may be pinned to the upper plate, or alternatively, both may be slidable relative to the upper plate. In the case of a three segment configuration, as shown in fig. 16-29, the intermediate plate may be non-translatably secured by pins or other structures. Although a dovetail structure may be applied to the intermediate plate, the use of one or more pin connections may make the structure 400 easier to assemble. Thus, in a four-segment configuration, as in the configuration 400, one of the intermediate plates, e.g., 420b, may be pinned in a non-translatable manner, while the other of the intermediate plates, e.g., 420c, may be pinned through a slot 411 in the upper plate 410. This pin and slot 411 arrangement may additionally be applied to, or alternatively replace, any of the dovetail arrangements described herein, if desired.

The number of lower plates can be selected as desired according to the invention. In practice, the number of lower plate segments that can generally be used can range between 2 and 6. Thus, any structure according to the present invention may comprise five or six segments, even those not explicitly described herein.

Fig. 33-39 are various views of another exemplary embodiment of a dynamic spinal plate system construct 500 according to the present invention, the construct 500 having a ribbon spring 530 and an integral cam member 561 adapted and configured to accommodate a plurality of selectable preloads. The spring 530 may be formed of any suitable material, but according to a preferred embodiment is a shape memory alloy, such as nitinol.

As with the structure 200 shown in fig. 16-29, a single upper plate 510 is provided. However, unlike the embodiment shown in fig. 16-29, the upper plate 510 of the structure 500 of fig. 33-39 includes a cam surface 512 on its underside, as best seen in fig. 36. When the cams 561 are rotated in line with the central axis of the structure 500, as shown in fig. 33, 35 and 37, they engage the cam surfaces 512, the cam surfaces 512 then serve to push the outer plate segments 520a, 520c outwardly away from the intermediate plate 520b because the cams 561 are rotatably connected to the outer plate segments 520a, 520c and the upper plate 510 is fixed to the intermediate plate 520 b. Thus, the structure 500 can be implanted by means of the cam 561 directed along this.

After the construct 500 is attached to the spinal segment, the cams can be rotated clockwise or counterclockwise. The cam 561 is generally oblong in shape, having a tab 562 extending therefrom, and a slot 569 that engages a tool for actuating the cam 561. The protrusion 562 includes a stopper 564 on an outer end thereof for catching the slidable pin 531 when the cam 561 is rotated clockwise and an inner hook 566 for catching the slidable pin 531 when the cam is rotated counterclockwise. These two positions of each cam 561 allow for a selectable level of tension of the spring 530, and thus a selectable level of preload applied to the spinal segment. This cam configuration may be applied to other embodiments of the structures described herein, including but not limited to the structure 200 described in association with fig. 16-29.

As with the structure 200 described above, the slidable pin 531 is retained in the track 525, the track 525 as implemented being substantially parallel to the inner edges of the end plate segments 520a, 520 c.

When the construct 500 is implanted on a spinal segment, the spacing between adjacent plates is thus maintained by the cam 561 engaging the cam surface 512 of the upper plate 510. After connection to the respective vertebrae, one or more cams 561 may remain in an axial position, thus essentially providing a static plate at that segment. If dynamic loading is desired at one or more segments, the respective cam 561 is rotated clockwise or counterclockwise, as described above, to fix the slidable pin 531 at the intermediate position or at its laterally outermost region.

During implantation, the surgeon may apply the lesser of the two selectable preloads by rotating one or both of the cams 561 counterclockwise, thereby maintaining the cams 561 in the position shown in fig. 38. The physician can then assess whether the preload is sufficient to produce the desired effect, for example in reducing the gap between the adjacent vertebrae and the fusion material. If an increased preload is desired, the cam 561 may be rotated clockwise (approximately one and a half of a turn) to hold the cam 561 in the position shown in FIG. 39, or vice versa.

It should be noted that in the closed configuration of the construct 500 shown in fig. 38 and 39, the gaps 591a and 592b are completely closed because the construct is not connected to the spine segment. If the structure is connected to a spinal segment, the gaps 591a and 592b will remain open indefinitely with the respective cam 561 held in the locked position (parallel to the longitudinal axis), and will likely remain open indefinitely to some extent, unless the fusion material is deposited to such an extent that the intervertebral space contracts the total amount of the respective gaps 591a and 592b after implantation.

Materials for the above-presented components including plate segments 110, 120, etc. may include, for example, stainless steel, titanium alloys, memory metals such as nitinol, polymeric materials, ceramic materials such as silicon nitride, or composite materials.

The device according to the invention can be applied to any region of the spinal column, for example from the first cervical vertebra (C1) to the first sacral vertebra (S1). When used in different locations along the spinal column, plate segments 110 and 120, engagement member 140, spring 130, and screw 150 are sized according to the size of the vertebral bodies in that region and the loading conditions to be experienced.

Kits according to the present invention can be provided and include a range of plate sizes, springs 130 having varying stiffnesses, engagement members having varying stiffnesses and/or shapes, bone screws of varying sizes, and can include fixed and/or variable angle (polyaxial) screws. The kit may include a plate having dimensions suitable for cervical and/or thoracic and/or lumbar and/or sacral applications.

The devices, systems and methods of the present invention as described above and illustrated in the drawings provide spinal plate system structures and related systems, methods and kits having superior characteristics and versatility, and adaptively enhance fusion of bone grafts.

In short, the structure according to the invention may be selectively dynamic, the pushing mechanism (dynamism) may be passive or active, and if active, the level of preload may be easily selected. That is, a structure according to the present invention may be used as a completely static (not dynamically active at any one segment), may be used as static at one or more segments and dynamic at the remaining segments, or may be used as dynamic at all segments. Moreover, alternative urging mechanisms may be active, such as where a preload is applied by the structure, or alternatively passive, where forces are managed by load sharing between connected spinal segments and the structure.

In applications of the passive pushing mechanism according to the present invention, the structure may be configured to provide a predetermined amount of resistance to compressive forces in translation and/or bending between adjacent plate segments, thereby allowing a predetermined amount of load distribution between the structure and the spinal column segment. The active urging mechanism may include a selectable preload, for example selectable by varying the tension in one or more members such as one or two springs. Also, it should be noted that while the term "spring" is used herein, it is to be understood that the appearance of such a spring may vary within, and is not limited to, conventional spring concepts.

It is to be understood that the applicant contemplates that a structure described herein in relation to one embodiment may be advantageously applied to any other embodiment described herein, even if such structure is not explicitly described in relation to such embodiment, but does not include the case where such features are mutually exclusive. That is, it is specifically contemplated that elements of one embodiment may be interchanged with elements of another embodiment without limitation, but not including if the structures are not compatible with another structure or if, for example, another structure must be interchanged. It will be apparent to those skilled in the art that further modifications and variations can be made in the apparatus, systems, and methods of the present invention without departing from the spirit or scope of the invention.

Claims (8)

1. A spinal construct for stabilizing a spinal column segment, comprising:

a) a first plate section;

b) a second plate segment connected to the first plate segment;

c) a spring connected between the first and second plate segments, wherein the spring is a U-shaped spring having a first end and a second end both slidably connected to the first plate segment, the U-shaped spring further having a curved portion extending between the first and second ends, the curved portion being captured by the second plate segment such that the U-shaped spring applies a net axial compressive force between the first and second plate segments; and

d) a cam mounted on the first plate segment to selectively rotate between a locked position against a cam surface on the second plate segment to set a space between the first and second plate segments having a static load and an unlocked position such that a U-shaped spring applies a dynamic compressive force.

2. The spinal construct of claim 1, wherein the spring is adapted and configured to provide a predetermined preload between the first and second plate segments.

3. The spinal construct of claim 1, wherein the spring is adapted and configured to resist loading between the first and second plate segments to a predetermined degree.

4. The spinal construct of claim 1, further comprising a common superior plate connected to the first and second plate segments.

5. The spinal construct of claim 4, wherein at least one of the first and second plate segments and the common superior plate are adapted and configured such that there is a substantially linearly translatable connection therebetween.

6. The spinal construct of claim 1, further comprising a third plate segment connected to at least one of the first and second plate segments by a spring.

7. The spinal construct of claim 1, wherein the construct is adapted and configured such that a connection spanning between the first and second plate segments is selectable between a static configuration and a dynamic configuration.

8. A spinal plate system construct for stabilizing spinal column segments, comprising:

a) a first plate section;

b) a second plate segment connected to the first plate segment;

c) a spring element connected between adjacent plate segments, adapted and configured to provide a predetermined preload between adjacent plate segments to enhance spinal fusion;

d) an upper plate connected to the first and second plate segments; and

e) a cam disposed on one of the first and second plate segments, the cam being movable between engagement and disengagement with a cam surface associated with the other of the first and second plate segments, wherein engagement between the cam and the cam surface prevents dynamic loading of the spine segment between the first and second plate segments, and the cam is adapted and configured to adjust a preload applied between the segments by adjusting tension in the spring.