Abstract:
Dynamic, rigid, and convertible dynamic-to-rigid devices and methods of using such devices to treat spinal instability conditions of the cervical spine are provided. The devices may include an interspinous, interlaminar stabilization device configured for interlaminar placement between the spinous processes of adjacent cervical vertebrae and optionally secured to the lamina using bone screws or crimped or rigidly fixed to the spinous process. Multiple devices may be used to enable treatment of multiple levels at the same time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 based on U.S. Provisional Application No. 62/079,427, filed Nov. 13, 2014, the complete disclosure of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to devices and methods for treating spine instability, in particular the cervical spine, and includes interlaminar, interspinous stabilization devices and methods of using such devices for segmental stabilization of vertebrae of the cervical spine. 
       BACKGROUND 
       [0003]    Spinal instability is often attributed to undesirable excessive motion between vertebrae and can cause significant pain and neurological deficits leading to significant morbidity and mortality. The instability may result from a number of causes, including abnormalities of the vertebrae, the intervertebral discs, the facet joints, and connective tissue around the spine. These abnormalities may arise from congenital abnormalities, diseases, disorders or defects of the spine from trauma or bone degradation, such as osteoarthritis, cancer, or degenerative disc disease. When the spine becomes unstable, the vertebral column becomes misaligned and may produce micromotion between adjacent vertebrae. Vertebral misalignment and micromotion may result in wear to the vertebral bone surfaces and ultimately generate severe pain. These conditions are often chronic and create progressive problems for the sufferer. 
         [0004]    Known treatments for spinal instability can include long-term medical management, rehabilitation strategies, interventional (needle-based) approaches, or open surgery. Medical management is generally directed at controlling the symptoms, such as pain reduction, rather than correcting the underlying problem. For some patients, this may require chronic use of pain medications, which may alter patient mental state or cause other negative side effects. Rehabilitation strategies often focus on muscle strengthening and spinal alignment. Interventional approaches may include facet, disc, and/or nerve root injections of analgesics and/or anti-inflammatory medications. Surgical treatment typically includes neural decompression with and without spinal fusion. Procedures are often designed to decompress the nerve roots and/or spinal cord as well as restore vertebral alignment and orientation, replace or repair failing components (e.g. discs), and alleviate the pain. 
         [0005]    Recently, a variety of interspinous stabilization devices have become available. These devices are typically implanted between the spinous processes of two or more adjacent vertebrae. By stabilizing the spinous processes in this way, significant stress may be taken off the intervertebral discs to prevent disease progression or to improve conditions such as spinal or neuroforaminal stenosis. In addition, vertebral motion may be controlled without severely altering the anatomy of the spine. 
         [0006]    These devices, along with other interspinous stabilization systems, can be secured between adjacent spinous processes using a number of different mechanisms. For example, such devices can include sharp barbs or other surface projections that engage the bony surface of a spinous process. In addition, flexible ligaments or sutures can be placed around the implants and adjacent bone. In some cases, the devices may be rigidly attached to the spinous process using a bone screw or other suitable bone anchor to prevent the interspinous device from migrating or slipping out of position. 
         [0007]    Fusion of the spine is a well-known and widely practiced medical procedure to alleviate symptoms and potential problems related to spinal instability such as severe back and/or neck pain due to misaligned, damaged or otherwise diseased spines. In many cases, spinal fusion is carried out by removing mobile interfaces (e.g. failing discs, facet joints, bone) followed by implantation of bone material and/or fusion-promoting adjuncts. Bony fusion can be significantly promoted by decreasing micromotion within the treated segments through orthosis or bracing. External orthosis (e.g. back brace) was the primary means of reducing micromotion and promoting fusion prior to the advent of internal spinal fixation systems. These systems initially employed wires to hold spinal segments firmly together. The wiring systems evolved to more rigid, durable implants including pedicle and lateral mass screws, rods, and intervertebral cages. These rigid spinal fixation systems are often designed to maintain or restore spinal alignment and spacing while enabling bone healing and fusion. 
         [0008]    Where it is difficult to maneuver and insert rigid implantable device(s) due to the size limitations or delicate anatomical site (i.e., closeness to facet joints, nerves or spinal cord, for example) of the area to be implanted, it is desirable to provide an implant that inserts along the midline structures and may be converted from a flexible implant into a rigid one that can promote fusion as the spinal condition evolves. 
         [0009]    It may be desirable in some situations, such as where the spinous process is damaged, weakened, brittle or insufficient in size to serve as a bearing surface, to provide an interspinous stabilization device that can support the spinal segment independent of the failing element(s). It is further desirable to provide an interspinous stabilization system that can be configured to provide either dynamic or rigid stability to the affected vertebral segment of the spinal column. For instance, it would be desirable to provide such a system whereby the dynamic stability allows for controlled motion of the adjacent vertebrae being affected for example following posterior cervical foraminotomy. It would be even more desirable to provide the same system having the ability to allow for rigid, fusion-promoting securement if so desired or needed. Further still, it would be desirable to provide a system that can provide the option of either dynamic or rigid stability at different levels of the vertebral segment, while also allowing for multi-level vertebral stabilization. 
         [0010]    Whereas there are a number of options for the lumbar spine, very few such options exist for the cervical spine. Due to the limited space afforded the surgeon, and the biomechanical considerations of the highly-mobile cervical spine, the much desired option of a dynamic stabilization device is rarely available. Even more desirable are convertible devices that allow the option of either dynamic or rigid fixation at the spinal segment of the cervical spine to be treated. Accordingly, it is desirable to provide dynamic, rigid, and convertible dynamic to rigid devices and methods of using such devices for interlaminar, interspinous stabilization of the cervical spine. 
       SUMMARY 
       [0011]    The present disclosure provides dynamic, rigid, and convertible dynamic-to-rigid devices and methods of using such devices to treat spinal instability conditions of the cervical spine. The devices may include an interspinous, interlaminar stabilization device configured for interlaminar placement between the spinous processes of adjacent cervical vertebrae and optionally secured to the lamina using bone screws or crimped or rigidly fixed to the spinous process. Multiple devices may be used to enable treatment of multiple levels at the same time. 
         [0012]    In one aspect of the present disclosure, interlaminar, interspinous spinal stabilization devices configured for rigid fixation are provided. These devices may comprise a unitary body having a contour suitable for placement between adjacent cervical vertebrae. In one embodiment, the unitary body may include screw holes to accommodate bone screws such as lateral mass screws. In another embodiment, the body may include brackets for receiving a spinous process of the cervical spine. These brackets may be crimped onto the spinous process. Alternatively, or in addition to the crimping, the brackets may include through-holes for receiving a rivet therethrough. In another embodiment, the body may include extended wings and/or brackets. These devices are configured for rigid fixation of the spinal segment, thereby enabling fusion at that level. 
         [0013]    In another aspect of the present disclosure, interlaminar, interspinous spinal stabilization devices configured for dynamic fixation are provided. These devices may comprise a unitary body having a contour suitable for placement between adjacent cervical vertebrae. In one embodiment, the unitary body may include upper and lower plates connected by a flexible hinge or midsection. The unitary body may include one or more pair of brackets for receiving a spinous process of the cervical spine. These brackets may be crimped onto the spinous process. Alternatively, or in addition to the crimping, the brackets may include through-holes for receiving a rivet therethrough. In still another embodiment, the body may include straps for securing around the spinous process. These devices are configured for dynamic fixation of the spinal segment. 
         [0014]    In still another aspect of the present disclosure, modular, two-part interlaminar, interspinous spinal stabilization devices are provided. These two-part devices are configured for conversion from a dynamic-to-rigid segmental stabilization of the cervical spine. In one embodiment, a dynamic fixation device may be provided with screw holes for fixation with bone screws. The dynamic fixation device may include an opening for receiving a complementary rigid fixation device. The rigid fixation device may act to block the dynamic fixation device, thereby hindering movement and promoting fusion. In one embodiment, the rigid fixation device may comprise one or more brackets for receiving a spinous process. These brackets may be crimped onto the spinous process. Alternatively, or in addition to the crimping, the brackets may include through-holes for receiving a rivet therethrough. 
         [0015]    In further aspect of the present disclosure, various locking screws and mechanisms are provided for use with the devices of the present disclosure. In one embodiment, a retaining plate or locking plate may be provided for use with the devices to prevent backout of screws from the screw holes. In another embodiment, the screw may be provided with self-cutting threads to embed the screw into the screw hole during insertion, thereby preventing backout. In still another embodiment, the screw may be provided with spring tongues to embed the screw into the screw hole during insertion, thereby preventing backout. 
         [0016]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. Additional features of the disclosure will be set forth in part in the description which follows or may be learned by practice of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure. 
           [0018]      FIG. 1A  shows a top-down view of an exemplary embodiment of an interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0019]      FIG. 1B  shows an exploded perspective view of the device of  FIG. 1A  along with an optional retaining or locking plate of the present disclosure. 
           [0020]      FIGS. 2A-2C  show perspective views of the device of  FIG. 1A  in use in a cervical spine. 
           [0021]      FIG. 3A  shows a perspective view of another exemplary embodiment of an interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0022]      FIG. 3B  shows the device of  FIG. 3A  in use with bone screws. 
           [0023]      FIGS. 4A and 4B  show perspective views of the device of  FIG. 3B  in use in a cervical spine. 
           [0024]      FIG. 5A  shows a front view of still another exemplary embodiment of an interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0025]      FIG. 5B  shows a perspective view of the device of  FIG. 5A . 
           [0026]      FIG. 6  shows a front view of the device of  FIGS. 5A and 5B  with optional rivets. 
           [0027]      FIGS. 7A and 7B  show perspective views of the device of  FIGS. 5A and 5B  in use in a cervical spine. 
           [0028]      FIGS. 8A and 8B  show perspective views of yet another exemplary embodiment of an interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0029]      FIGS. 9A and 9B  show perspective views of the device of  FIGS. 8A and 8B  in use in a cervical spine. 
           [0030]      FIG. 10A  shows a perspective view of even still another exemplary embodiment of an interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0031]      FIG. 10B  shows the device of  FIG. 10A  in use with optional bone screws and optional rivet. 
           [0032]      FIG. 11A  shows a perspective view of yet another exemplary embodiment of an interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0033]      FIG. 11B  shows the device of  FIG. 11A  in use with optional rivet. 
           [0034]      FIG. 12A  shows a perspective view of an exemplary embodiment of a modular, two-part interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0035]      FIG. 12B  shows a top-down view of the device of  FIG. 12A . 
           [0036]      FIG. 13A  shows an exploded view of another exemplary embodiment of a modular, two-part interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0037]      FIG. 13B  shows a top-down view of the fully assembled device of  FIG. 13A . 
           [0038]      FIG. 14  shows an exploded view of still other exemplary embodiment of a modular, two-part interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0039]      FIGS. 15A and 15B  show perspective views of the device of  FIG. 14  in use in a cervical spine. 
           [0040]      FIGS. 16A-16C  show perspective exploded views of even still another exemplary embodiment of a modular, two-part interlaminar, interspinous spinal stabilization device of the present disclosure. 
           [0041]      FIG. 16D  shows a front view of the fully assembled device of  FIGS. 16A-16C . 
           [0042]      FIG. 17A  shows a perspective view of an exemplary embodiment of a bone screw suitable for use with the interlaminar, interspinous spinal stabilization devices of the present disclosure. 
           [0043]      FIG. 17B  shows a partial cross-sectional view of the bone screw of  FIG. 17A  in use with a device of the present disclosure. 
           [0044]      FIG. 18A  shows a perspective view of an exemplary embodiment of a bone screw suitable for use with the interlaminar, interspinous spinal stabilization devices of the present disclosure. 
           [0045]      FIG. 18B  shows a partial cross-sectional view of the bone screw of  FIG. 18A  in use with a device of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]      FIG. 1A  illustrates an exemplary embodiment of an interlaminar, interspinous spinal stabilization device  10  of the present disclosure. The device  10  may comprise a main body  12  having an upper surface  14 , a lower surface  16 , an anterior portion  18 , and a posterior portion  20 . The main body  12  may be formed as a solid body, and as such, the upper and lower surfaces  14 ,  16  and the anterior and posterior portions  18 ,  20  may be interconnected, as illustrated. The main body  12  itself may also be shaped to conform to the anatomy of the spine, and in particular, the cervical spine  2 . For instance, the posterior portion  20  may be slightly curved, as shown, as can be the sides  26  of the main body  12 . 
         [0047]    As further illustrated, the four corners  22  of the main body  12  at the anterior portion  18  can be enlarged to accommodate screw holes  24 . The screw holes  24  may be angled to allow the insertion of screws  40  through the holes and towards the upper or lower vertebrae  4 ,  6 ,  8  of the cervical spine  2 , as shown in  FIGS. 2A to 2C . In one embodiment, these screws  40  may diverge and extend upwardly or downwardly. These screws  40  may be, for example, lateral mass screws and may include an elongated shaft  42  with a threaded tip  44  at one end and a screw head  46  at an opposite end. Such use of lateral mass screws  40  along with the implantable device  10  would enable a rigid, secure fixation of the device  10  in between the cervical vertebrae and consequently stabilize that vertebral segment of the spine  2  being treated. 
         [0048]    The implantable devices  10  of  FIGS. 1A and 1B  may be contoured to allow ease of insertion in between the vertebrae, such as for example, by providing a main body  12  having a wedge shape. For instance, the sides  26  and posterior portion  20  may be tapered or narrowed to provide a leading edge. Additionally, the main body  12  may have a low profile to allow stacking of devices  10  at multiple levels. This stacking is illustrated in  FIGS. 2A to 2C  in which multiple devices  10  may be used in adjacent levels of the cervical spine  2 , without abutting one another or crowding the area. The contours of the main body  12  enable the device  10  to have a closely matched fit within the interspinous space of the cervical spine  2 . Thus, when in use, the device  10  provides sufficient interlaminar support of the cervical vertebrae  4 ,  6 ,  8 , as shown in  FIGS. 2B and 2C . Accordingly, the device  10  may be appropriately considered an interspinous, interlaminar spinal stabilization device  10  for the cervical spine. 
         [0049]      FIG. 1B  illustrates the interlaminar, interspinous spinal stabilization device  10  of  FIG. 1A  with an optional retaining or locking plate  50 . Retaining plates, also known as locking plates,  50  are known in the industry for use in blocking the opening of screw holes  24  and the associated screw heads  46  within these screw holes  24  to prevent undesired screw backout, or the loosening of the screws out of the device  10 , over time and with repeated micromotion. As shown in  FIG. 1B , an exemplary embodiment of a locking plate  50  may be provided along with the interlaminar, interspinous spinal stabilization device  10  of  FIG. 1A . The locking plate  50  may have a similar, complementary shape as the anterior portion of device  10 , with a narrowed midsection flanked by enlarged arms  52 . The plate  50  may include a screw hole  54  for insertion of a fixation screw (not shown) into a receiving hole  32  in the anterior portion  18  of the device  10 , to securely lock the locking plate  50  onto the main body  12 . Once fixed to the main body  12 , the locking plate  50  should rest firmly against the anterior portion, while the arms  52  should cover or block at least a portion of the screw holes  24  and screw heads  46 . 
         [0050]      FIGS. 3A and 3B  illustrate another exemplary embodiment of an interspinous, interlaminar spinal stabilization device  110  of the present disclosure, while  FIGS. 4A and 4B  illustrate the device  110  in situ in a cervical spine  2 . The device  110  of  FIGS. 3A and 3B  share similar features to the device  10  of  FIGS. 1A and 1B . As such, these similar features are designated by the same reference number following the prefix “1”. Like device  10 , device  110  may comprise a main body  112  having an upper surface  114 , a lower surface  116 , an anterior portion  118 , and a posterior portion  120 . The main body  112  may be formed as a solid body, and as such, the upper and lower surfaces  114 ,  116  and the anterior and posterior portions  118 ,  120  may be interconnected, as illustrated. The main body  112  may also be shaped to conform to the anatomy of the spine, and in particular, the cervical spine  2 . For instance, the posterior portion  120  may be slightly curved, as can be the sides  126  of the main body  112 . Such curvature enables the form-fitting adherence of the device  110  to the anatomical region of the intervertebral space of the cervical spine  2 , as previously described above. 
         [0051]    Also like device  10 , the two corners  122  of the main body  112  at the anterior portion  118  can be enlarged to accommodate screw holes  124 . The screw holes  124  may be angled to allow the insertion of screws  40  such as those previously described through the holes and towards the upper or lower vertebrae  4 ,  6 ,  8  of the cervical spine  2 , as shown in  FIGS. 4A and 4B . In one embodiment, these screws  40  may diverge and extend upwardly or downwardly. Use of the screws  40  would enable a rigid, secure fixation of the device  110  in between the cervical vertebrae and consequently stabilize that vertebral segment of the spine  2 . 
         [0052]    In addition, device  110  may further include a surface modification such as a protrusion or fin  128  on the upper surface  114  of the main body  112 , as illustrated. This protrusion or fin  128  may further enhance stabilization and anchorage within the interspinous space. In addition, device  110  may be configured to have a pair of brackets  134  extending from the lower surface  116  of the main body  112 . These brackets  134  may collectively form a stirrup, or bone-receiving region  136 . As illustrated in  FIGS. 4A and 4B , these brackets  134  allow the device  110  to receive a spinous process of the lower vertebra. The brackets  134  may be configured to be malleable, and allow crimping onto the spinous process. Teeth, spikes, barbs, ridges, or other similarly sharp bone-piercing protrusions or surface roughening features  138  may be provided on the brackets  134  to further enhance bone contact with the spinous process. 
         [0053]    Like device  10  above, the interlaminar, interspinous spinal stabilization device  110  of  FIGS. 3A and 3B  may utilize one or two different types of fixation mechanisms: screw fixation, such as for example with lateral mass screws  40 , may be utilized for securing the device  110  to the upper vertebra, while crimping to the spinous process of the lower vertebra may also be utilized. The device  110  is configured such that either one or both mechanisms may be implemented, without affecting the other mechanism. And similar to device  10 , the present device  110  also allows stacking or multiple devices  110  to be used at one time at different levels of the cervical spine  2 .  FIGS. 4A and 4B  illustrate the use of the devices  110  whereby one level utilizes screw fixation while the other level utilizes crimping. 
         [0054]    Turning now to  FIGS. 5A, 5B, 6, 7A, 7B, 8A, 8B, 9A, and 9B , the present disclosure also provides exemplary embodiments of interlaminar, interspinous spinal stabilization devices  200  that are flexible and allow some motion of the cervical vertebrae while simultaneously stabilizing the vertebral level.  FIGS. 5A and 5B  illustrate one such exemplary embodiment. Device  200  as shown in  FIGS. 5A and 5B  may comprise an upper plate  202  and a lower plate  204  connected by a flexible midsection  206 , allowing the plates  202 ,  204  to move relative to one another. The plates  202 ,  204  create an open free end  208 , as illustrated. The device  200  may be configured to nest securely in between the cervical vertebrae, as illustrated in  FIGS. 7A and 7B . 
         [0055]    Due to the unique anatomy of the cervical spine  2 , the upper plate  202  may be shorter in length than the lower plate  204 , as can be seen in  FIGS. 5B and 7B . In addition, the plates  202 ,  204  may also be contoured, or curved, in order to matingly fit and interlaminarly support the cervical vertebra at that level. The upper plate  202  may further include a surface modification such as a protrusion or fin  228 , as illustrated. This protrusion or fin  228  may further enhance stabilization and anchorage within the interspinous space, similar to previously described protrusion or fin  128  above. 
         [0056]    Brackets  214  may be provided on the upper and lower plates  202 ,  204 . Each pair of brackets  214  may create a stirrup, or bone-receiving area  216 , for receiving a spinous process, as can be seen in  FIG. 7A . The brackets  214  may be malleable, to allow crimping onto the spinous process, as previously described with bracket  134  of device  110 . Additionally, brackets  214  may include teeth, spikes, barbs, ridges, or other similarly sharp bone-piercing protrusions or surface roughening features  218  to further enhance bone contact with the spinous process. These brackets  214  may be angled relative to the upper and lower surfaces  202 ,  204 , as illustrated in  FIGS. 5B and 7B , in order to conform to the unique anatomy of the cervical spine, and allow stacking or multi-level stabilization, as shown in  FIGS. 7A and 7B . 
         [0057]      FIG. 6  illustrates another exemplary embodiment in which interspinous, interlaminar spinal stabilization device  200  may optionally utilize a fixation element through the brackets  214 . As shown, the device  200  of the present disclosure may be provided with through-holes  226  at each of the brackets  214  for receiving a rivet  230  therethrough. As used herein, it is to be understood that the term rivet is intended to broadly encompass a nut and bolt assembly, without limitation. The rivet  230  may comprise a threaded bolt  232  that threadingly engages a threaded nut  240  at threaded end  234 . Either one or both of the pair of brackets  214  of the device  200  may utilize this additional fixation mechanism. 
         [0058]    It is contemplated that the user may elect to crimp the brackets first  214 , then place the rivet  230  through the brackets  214  to secure them onto the spinous process, or merely use the rivet  230  without first crimping, as the rivet  230  would effectively move the brackets  214  together in a crimping manner during installation. Furthermore, the user has the option of utilizing crimping and/or rivet installation in either one or both of the pair of brackets  214 . Accordingly, it is possible to crimp at the upper level, and use a rivet  230  at the lower level, or vice versa, without affecting the stability of the device  200 . Such flexibility enables the user to customize the level of rigidity, fixation, and flexibility of the device at a single level. For example, while not shown, it is contemplated that any one or more of the devices  200  of  FIGS. 7A and 7B  may also include a rivet  230  through the pair of brackets  214  of the upper or the lower plates  202 ,  204 , as desired. 
         [0059]      FIGS. 8A and 8B  illustrate yet another exemplary embodiment of the interspinous, interlaminar spinal stabilization device  200 ′ of the present disclosure. The device  200 ′ shares all of the same features of device  200  of  FIGS. 5A and 5B , with the exception that, in this embodiment, the brackets  214  are replaced with bars  244 . These bars  244  may include a slot  246  for receiving a fastening element such as a tie, belt, or strap  250 , such as illustrated. The straps  250  may be configured to securely wrap around the upper or lower spinous processes of the level of the cervical spine being stabilized. As shown, the straps  250  may be connected to a housing unit  260  that allows length-wise adjustment by a mechanism such as a rotating knob or dial  262 . In one embodiment, the adjustment mechanism may comprise a screw that, when rotated, tightens the straps  250  around the spinous process. This housing unit  260  may be located at the side of the device  200 ′. Use of the strap  250  would thus enable fixation without the need to drill a hole through the spinous process.  FIGS. 9A and 9B  illustrate the use of this embodiment in situ, at a single level. Of course, it is contemplated that multiple devices  200 ′ may be stacked and therefore multiple levels may be stabilized at the same time, as previously described. 
         [0060]      FIGS. 10A and 10B  illustrate even still another exemplary embodiment of the interspinous, interlaminar spinal stabilization device  300  of the present disclosure. The device  300  may comprise a main body  302  having two different pairs of extensions for attachment to bone: a pair of wings or arms  304  that extend upwardly from the main body  302 , and a pair of brackets  314  extending downwardly from the main body  302 . Each of these extensions will be described in greater detail now. 
         [0061]    As shown, wings or arms  304  may extend from the main body  302  in an upwardly direction. The ends of the wings or arms  304  may include screw holes  306  for receiving a bone screw such as, for example, the lateral mass screws  40  previously described. The screw holes  306  may be angled to allow the screws  40  to be inserted into the body of the vertebra of the upper level where stabilization is taking place. 
         [0062]    A pair of brackets  314  may extend downwardly from the main body  302  to create a stirrup or bone-receiving area  316  for receiving a spinous process. The brackets  314  may further include teeth, barbs, spikes, ridges, or other similarly sharp bone-piercing protrusions or surface roughening features  318  to further enhance bone contact with the spinous process. These brackets  314  may be angled relative to the main body  302 , in order to conform to the unique anatomy of the cervical spine, and allow stacking or multi-level stabilization, as previously described and shown. Also similar to the devices previously described, the brackets  314  may optionally utilize a fixation element through the brackets  314 . As shown, the device  300  of the present disclosure may be provided with through-holes  326  at each of the brackets  314  for receiving a rivet  230  therethrough. The rivet  230  may comprise a threaded bolt  232  that threadingly engages a threaded nut  240 , similar to the rivet  230  previously described. 
         [0063]    The main body  302  may further include a central opening  310  which may be used to hold a fusion enhancing material or therapeutic agent, such as for example, bone substitute material, bone morphogenic protein, bone graft material including demineralized bone matrix, bone chips, autograft, allograft, xenograft, medical agents, stem cells, proteins, or other biological agents that promote bone fusion or provide therapeutic benefits, including antibiotics or antimicrobial agents and the like. The main body  302  may additionally include a surface modification such as a protrusion or fin  328 , as illustrated. This protrusion or fin  328  may further enhance stabilization and anchorage within the interspinous space, similar to previously described protrusion or fin  128 ,  228  above. 
         [0064]      FIGS. 11A and 11B  show a variation of device  300 ′ in which all of the features of device  300  are present, along with an additional pair of brackets  314 . As illustrated, the device  300 ′ provides yet an additional extension comprising an upwardly extending pair of brackets  314 . The upwardly extending pair of brackets  314  is identical to those extending downwardly, and are angled and shaped to match the anatomy of the cervical spine  2 .  FIG. 11B  shows the device  300 ′ in use with a rivet  230  through the upwardly extending brackets  314 . It is understood, of course, that the rivet  230  may be utilized by the lower brackets  314 , or both upper and lower brackets  314 , with optional lateral mass screws  40  extending through the wings  304 . At the same time, the user may optionally crimp the brackets  314  in addition to, or instead of, using the rivet  230 . Accordingly, this type of unitary body  302  provides several different rigid fixation options at different locations, thereby promoting fusion. 
         [0065]      FIGS. 12A, 12B, 13A, 13B, 14, 15A, 15B, and 16A-16D  show various exemplary embodiments of a modular, two-part interspinous spinal stabilization device of the present disclosure. Turning now to  FIGS. 12A and 12B , a two-part modular design for an interlaminar, interspinous spinal stabilization device  400  is illustrated. The device  400  may comprise a main frame  402  having a sleeve-receiving opening  410  for receiving a sleeve or insert  450 . The main frame  402  may further include upwardly extending arms or wings  404 , similar to the wings or arms  304  previously described above. The wings or arms  404  may include angled screw holes  406  similar to the screw holes  306  previously described above. 
         [0066]    Within the main frame  402  is an insert or sleeve  450  comprising a main body  452 . A pair of brackets  454  extends upwardly from the main body  452 , while another pair of brackets  454  extends downwardly from the main body  452  in a fashion similar to that shown in  FIGS. 11A and 11B  of device  300 ′. Like device  300 ′, the pair of brackets  454  creates a stirrup or bone-receiving area  456  for receiving a spinous process. The brackets  454  may further include teeth, spikes, barbs, ridges, or other similarly sharp bone-piercing protrusions or surface roughening features  458  to further enhance bone contact with the spinous process. These brackets  454  may be angled relative to the main body  452 , in order to conform to the unique anatomy of the cervical spine, and allow stacking or multi-level stabilization, as previously described and shown. Also similar to the devices previously described, the brackets  454  may optionally utilize a fixation element through the brackets  454 . Accordingly, the brackets  454  may be provided with through-holes  464  for receiving a rivet  230  therethrough. The rivet  230  may comprise a threaded bolt  232  that threadingly engages a threaded nut  240 , similar to the rivet  230  previously described. 
         [0067]    The main body  452  may further include a central opening  460  which may be used to hold a bone graft or other fusion enhancing material. The main body  452  may additionally include a surface modification such as a protrusion or fin  462 , as illustrated. This protrusion or fin  462  may further enhance stabilization and anchorage within the interspinous space, similar to previously described protrusion or fin  128 ,  228 ,  328  above. 
         [0068]    Although not shown, it is contemplated that bone screws such as, for example, lateral mass screws  40  may be used to fix the wings  404  of the main frame  402  to a vertebra. Optional rivets  230  may be used for fixing either or both of the pair of brackets  454  to a spinous process. Additionally, each of the pair of brackets may be configured to be crimped onto the spinous process, either instead of, or in addition to, the use of the rivets for rigid fixation. 
         [0069]    In one embodiment, the two components of the device  400  may comprise different materials for different properties. For example, the main frame  402  may be formed of a polyetheretherketone (PEEK) material to facilitate fixation with lateral mass screws  40 , while the sleeve or insert  450  may be formed of a metal such as, for example, titanium to allow optional crimping and/or fixation with a rivet  230 . 
         [0070]      FIGS. 13A and 13B  illustrate still another exemplary embodiment of a two-part modular interlaminar, interspinous spinal stabilization device  500 . The device  500  shares similar features to device  400  previously described, and may comprise a main frame  502  having an insert-receiving slot  510  for receiving an insert  550 . The main frame  502  may further include upwardly extending arms or wings  504 , similar to the wings or arms  304 ,  404  previously described above. The wings or arms  504  may include angled screw holes  506  similar to the screw holes  306 ,  406  previously described above for use with a bone screw such as, for example, the lateral mass screws  40  previously described. However, unlike the opening  410  of device  400 , the insert-receiving slot  510  of device  500  is partially open and contains a rail  512  for sliding engagement with the insert  550 , as shown by the arrow in  FIG. 13A . 
         [0071]    The insert  550  may comprise a main body  552 , and a pair of brackets  554  extending downwardly from the main body  552  in a fashion similar to that shown in  FIGS. 11A and 11B  of device  300 ′. Like device  300 ′, the pair of brackets  554  creates a stirrup or bone-receiving area  556  for receiving a spinous process. The brackets  554  may further include teeth, spikes, barbs, ridges, or other similarly sharp bone-piercing protrusions or surface roughening features  558  to further enhance bone contact with the spinous process. These brackets  554  may be angled relative to the main body  552 , in order to conform to the unique anatomy of the cervical spine, and allow stacking or multi-level stabilization, as previously described and shown. Also similar to the devices previously described, the brackets  554  may optionally utilize a fixation element through the brackets  554 . Accordingly, the brackets  554  may be provided with through-holes  564  for receiving a rivet  230  therethrough. The rivet  230  may comprise a threaded bolt  232  that threadingly engages a threaded nut  240 , similar to the rivet  230  previously described. 
         [0072]    The main body  552  may further include a central opening  560  which may be used to hold a fusion enhancing material or therapeutic agent such as described above. The main body  552  may additionally include a surface modification such as a protrusion or fin  562 , as illustrated. This protrusion or fin  562  may further enhance stabilization and anchorage within the interspinous space, similar to previously described protrusion or fin  128 ,  228 ,  328 ,  462  above. In addition, the main body  552  may include a groove  566  that allows the body  552  to be slidingly inserted into the insert-receiving opening  510  of the main frame  502  along the rails  512 .  FIG. 13B  shows a fully assembled device  500  in which the insert  550  is nested securely within the frame  502  of device  500 . 
         [0073]    Although not shown, it is contemplated that bone screws such as, for example, lateral mass screws  40  may be used to fix the wings  504  of the main frame  502  to a vertebra. Optional rivet  230  may be used for fixing the pair of brackets  554  to a spinous process. Additionally, the pair of brackets may be configured to be crimped onto the spinous process, either instead of, or in addition to, the use of the rivet for rigid fixation. 
         [0074]    As previously described for device  400 , the two components of the device  500  may comprise different materials for different properties. For example, the main frame  502  may be formed of a polyetheretherketone (PEEK) material to facilitate fixation with lateral mass screws  40 , while the insert  550  may be formed of a metal such as, for example, titanium to allow optional crimping and/or fixation with a rivet  230 . 
         [0075]    The main frame  502  as well as the insert  550  may be provided in various other forms to provide ultimate flexibility regarding the amount of fixation to bone that can be provided. For instance,  FIG. 14  shows the main frame  502  of device  500  but with the option of an insert  550 ′ instead of insert  550 . Insert  550 ′ is similar to insert  550 , but has the added feature of a second pair of brackets  554 . The brackets  554  may have the features of bracket  554  of insert  550 . 
         [0076]    As shown in  FIGS. 15A and 15B , it is possible to utilize insert  550 ′ with the upper and lower brackets  554  along with frame  502  at one level, while utilizing insert  550  with a single pair of lower brackets  554  with frame  502  at an adjacent level. Thus, as illustrated, it is possible to stack multiple devices  500  by interchanging the components of the modular device  500  in order to create an ideal configuration that matches the anatomy of the cervical spine and allows multi-level stabilization without crowding. 
         [0077]      FIGS. 16A-16D  show another variation of device  500  in which the main frame  502 ′ now includes two pairs of arms  504 ,  508 . The upper arms  504  and lower arms  508  are similar in feature, and can contain screw holes  506  for receiving a bone screw such as, for example, the lateral mass screws  40  previously described. These arms  504 ,  508  may further be positioned adjacent to one another so as not to add unnecessary bulk to the overall frame  502 ′. The insert-receiving slot  510  of the frame  502 ′ may still contain a rail  512  for mating with the groove  566  of the insert  550 ,  550 ′, and as such, the mechanism of attaching the insert  550 ,  550 ′ to the frame  502 ′ remains the same as described above, and as illustrated in  FIGS. 16C and 16D . 
         [0078]    In the embodiments of  FIGS. 12A, 12B, 13A, 13B, 14, 15A, 15B , and  16 A- 16 D, these modular, two-part interlaminar, interspinous spinal stabilization devices enable an initially dynamic device to be converted into a fusion-enabling device by inserting the insert or sleeve into the dynamic device. The insert or sleeve thus acts to block the dynamic device from movement, thereby allowing subsequent fusion treatment of the spinal segment. 
         [0079]      FIGS. 17A and 17B  show an exemplary embodiment of a locking screw  600  of the present disclosure. The locking screw  600  may comprise a threaded shaft  602  that extends into a leading tip  604  at one end and a screw head  606  at the opposite end. The tip  604  may be self-tapping or self-leading. The screw head  606  may include a tool-engaging opening  608 . In addition, the screw  600  may comprise self-cutting threads  610  adjacent the screw head  606 , as shown. The self-cutting threads  610  enable the screw  600  to embed itself upon insertion into a PEEK screw hole  506 , such as the one for main frame  502  of device  500 , as illustrated in  FIG. 17B . Such a screw  600  would be useful for any number of devices of the present disclosure. 
         [0080]      FIGS. 18A and 18B  show another exemplary embodiment of a locking screw of the present disclosure. The locking screw  700  may comprise a threaded shaft  702  that extends into a leading tip  704  at one end and a screw head  706  at the opposite end. The tip  704  may be self-tapping or self-leading. The screw head  706  may include a tool-engaging opening  708 . In addition, the screw  700  may comprise spring tongues  710  adjacent the screw head  706 , as shown. The spring tongues  710  enable the screw  700  to lodge itself upon insertion into a PEEK screw hole  506 , such as the one for main frame  502  of device  500 , as illustrated in  FIG. 18B . Such a screw  700  would be useful for any number of devices of the present disclosure. 
         [0081]    It is contemplated that the devices described and shown herein are useful for treatment of persistent neck pain and joint stress, such as that experienced following disc replacement surgery. Furthermore, the implant devices and their components may be linked together by fastening elements like screws (including overlapping screws), wire bands, ties, and the like, in order to provide an interconnected construct of multiple devices at multiple levels. Additionally, in some instances, small openings may be provided in the midline aspect of the devices provided herein to allow optional suturing of midline structures (e.g., muscle, fascia) during reconstruction of the soft tissues overlying the region. 
         [0082]    It is understood that the devices of the present disclosure may be formed from a number of biocompatible materials, including the materials previously mentioned. For instance, the devices may be formed of a medical grade metal like titanium or a titanium alloy. The devices may also be formed from a variety of other materials, such as stainless steel, cobalt chrome, ceramics, and/or polymeric materials, such as ultra-high molecular-weight polyethylene (UHMWPE) and polyetheretherketone (PEEK), either alone or in combination with other suitable materials. 
         [0083]    Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiment disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the embodiment being indicated by the following claims.