PATENT ABSTRACT
Systems for trauma and/or joint fusion implants and instruments include transarticular screw and intra-articular washer, polyaxial screw and plate, single- and multi-level polyaxial bone clamps, and minimally invasive adaptations.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of: 
         [0002]    pending prior U.S. Provisional Patent Application No. 61/477,966, filed Apr. 21, 2011, Attorney&#39;s Docket No. OSM-7 PROV, entitled BONE PLATE, SCREW, AND INSTRUMENT; and 
         [0003]    This application is a continuation-in-part of: 
         [0004]    U.S. patent application Ser. No. 13/188,325, filed Jul. 21, 2011, entitled SPINOUS PROCESS FUSION IMPLANTS AND INSERTION COMPRESSION AND LOCKING INSTRUMENTATION, Attorney&#39;s Docket No. OSM-1 CIP 1. 
         [0005]    U.S. patent application Ser. No. 13/188,325 is a continuation-in-part of: 
         [0006]    U.S. patent application Ser. No. 12/853,689, filed Aug. 10, 2010, entitled SPINOUS PROCESS FUSION IMPLANTS, Attorney&#39;s Docket No. OSM-1. 
         [0007]    U.S. patent application Ser. No. 12/853,689 claims the benefit of: 
         [0008]    U.S. Provisional Patent Application No. 61/232,692, filed Aug. 10, 2009, entitled SPINOUS PROCESS FUSION IMPLANTS, Attorney&#39;s docket no. OSM-1 PROV; and 
         [0009]    U.S. Provisional Patent Application No. 61/366,755, filed Jul. 22, 2010, entitled INSERTION, COMPRESSION AND LOCKING INSTRUMENTATION, Attorney&#39;s docket no. OSM-5 PROV.; and is a continuation-in-part of: 
         [0010]    U.S. patent application Ser. No. 12/820,575, filed Jun. 22, 2010, entitled BONE TISSUE CLAMP, Attorney&#39;s Docket No. OSM-3. 
         [0011]    U.S. patent application Ser. No. 12/820,575 claims the benefit of: 
         [0012]    U.S. Provisional Patent Application Ser. No. 61/219,687, filed Jun. 23, 2009, entitled BONE TISSUE CLAMP, Attorney&#39;s Docket No. OSTE — 004USP1. 
         [0013]    All of the above named documents are incorporated herein by reference in their entirety. 
         [0014]    The following document is incorporated herein by reference: 
         [0015]    U.S. patent application Ser. No. 12/957,056, filed Nov. 30, 2010, entitled POLYAXIAL FACET FIXATION SCREW SYSTEM, Attorney&#39;s docket no. OSM-2. 
     
    
     BACKGROUND 
       [0016]    The present disclosure relates to bone plates, screws and other fasteners, and related instruments. Examples include a screw and washer system with instruments, polyaxial screw and plate systems, bone clamp systems with spacers, sleeves, and/or cages, multi-level bone clamp systems, minimally invasive bone clamp systems, motion preserving systems, and instruments for handling plates, applying compression, and applying locking forces. More specifically, the present disclosure is set forth in the context of spinal surgery, such as spine fusion or motion preservation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Various embodiments of the disclosed technology will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. 
           [0018]      FIG. 1  is a transverse cross sectional view of a facet washer fixation system implanted in a facet joint, taken parallel to articular surfaces of the facet joint; 
           [0019]      FIG. 2  is a longitudinal cross sectional view of the facet washer fixation system and facet joint of  FIG. 1 , taken along a center longitudinal axis of a screw of the system; 
           [0020]      FIG. 3  is an end view of a washer of the system of  FIG. 1  with a portion of a cannula; 
           [0021]      FIG. 4  is a side view of the washer and cannula of  FIG. 3 ; 
           [0022]      FIG. 5  is a side view of a rasp; 
           [0023]      FIG. 6  is a longitudinal cross sectional view of a polyaxial taper lock screw and plate system, taken along a center longitudinal axis of a screw of the system; 
           [0024]      FIG. 7  is a longitudinal cross sectional view of another polyaxial taper lock screw and plate system, taken along a center longitudinal axis of a screw of the system; 
           [0025]      FIG. 8  is a top cross sectional view of a modular spinous process clamp system; 
           [0026]      FIG. 9  is a longitudinal cross sectional view of a sleeve for use with the system of  FIG. 8 ; 
           [0027]      FIG. 10  is a transverse cross sectional view of the sleeve of  FIG. 9 ; 
           [0028]      FIG. 11  is a transverse cross sectional view of another sleeve for use with the system of  FIG. 8 ; 
           [0029]      FIG. 12  is a transverse cross sectional view of yet another sleeve for use with the system of  FIG. 8 ; 
           [0030]      FIG. 13  is a transverse cross sectional view of yet another sleeve for use with the system of  FIG. 8 ; 
           [0031]      FIG. 14  is a side cross sectional view of another spinous process clamp system; 
           [0032]      FIG. 15  is a top cross sectional view of the system of  FIG. 14 ; 
           [0033]      FIG. 16  is a top cross sectional view of a multi-level bone plate system; 
           [0034]      FIG. 17  is a side cross sectional view of the system of  FIG. 16 ; 
           [0035]      FIG. 18  is an exploded top view of yet another bone plate system; 
           [0036]      FIG. 19  is an isometric view of a cage for use with the system of  FIG. 18 ; 
           [0037]      FIG. 20  is a top view of another cage for use with the system of  FIG. 18 ; 
           [0038]      FIG. 21  is a top view of yet another cage for use with the system of  FIG. 18 ; 
           [0039]      FIG. 22  is a top exploded view of yet another bone plate system; 
           [0040]      FIG. 23  is an isometric view of a cage for use with the system of  FIG. 22 ; 
           [0041]      FIG. 24  is an isometric view of another cage for use with the system of  FIG. 22 ; 
           [0042]      FIG. 25  is a side view of the bone plate system of  FIG. 22  with spinous processes; 
           [0043]      FIG. 26  is an end view of yet another bone plate system; 
           [0044]      FIG. 27  is a transverse cross sectional view of the bone plate system of  FIG. 26 ; 
           [0045]      FIG. 28  is a top view of the bone plate system of  FIG. 26 ; 
           [0046]      FIG. 29  is a transverse cross sectional view of the bone plate system of  FIG. 26  after introduction of a plate and a post to a surgical site; 
           [0047]      FIG. 30  is a transverse cross sectional view of the bone plate system of  FIG. 26  after introduction of another plate and locking components to the surgical site; 
           [0048]      FIG. 31  is a transverse cross sectional view of the bone plate system of  FIG. 26  after final locking; 
           [0049]      FIG. 32  is a top cross sectional view of an interspinous process system; 
           [0050]      FIG. 33  is a top view of an extension plate coupled to an instrument; 
           [0051]      FIG. 34  is a side view of another instrument; 
           [0052]      FIG. 35  is a side view of yet another instrument; 
           [0053]      FIG. 36  is a side view of yet another instrument; 
           [0054]      FIG. 37  is an end view of an extension plate coupled to yet another instrument; 
           [0055]      FIG. 38  is a side view of a plate with non-spherical pads; 
           [0056]      FIG. 39  is a side view of a segmental multi-level spinous process plating system; 
           [0057]      FIG. 40  is a side view of another segmental multi-level spinous process plating system; 
           [0058]      FIG. 41  is a side view of a plate with an adjustable locking mechanism; 
           [0059]      FIG. 42  is a transverse cross sectional view of the plate and locking mechanism of  FIG. 41 ; 
           [0060]      FIG. 43  is a side view of yet another segmental multi-level spinous process plating system; 
           [0061]      FIG. 44  is an isometric view of yet another cage for use with the system of  FIG. 18 ; 
           [0062]      FIG. 45  is a cross sectional detail view of a plate and an instrument; 
           [0063]      FIG. 46  is a side view of another bone plate system; 
           [0064]      FIG. 47  is another side view of the bone plate system of  FIG. 46 ; 
           [0065]      FIG. 48  is an exploded view of portions of the system of  FIG. 46 ; 
           [0066]      FIG. 49  is a side view of a plate compressor instrument; 
           [0067]      FIG. 50  is a side view of a provisional locking arm for use with the compressor of  FIG. 49 ; 
           [0068]      FIG. 51  is a side view of a final locking arm for use with the compressor of  FIG. 49 ; 
           [0069]      FIG. 52  is a side view of a jaw portion of the compressor, provisional locking arm, and final locking arm of  FIGS. 49-51 ; and 
           [0070]      FIG. 53  is another side view of the jaw portion of the compressor, provisional locking arm, and final locking arm of  FIG. 52 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0071]    The disclosed technology relates to bone plates, fasteners, and related instruments. The disclosure is made in the context of spine procedures, such as fusion or motion preservation. Those of skill in the art will recognize that the systems and methods described herein may be readily adapted to similar anatomy elsewhere in the body. Those of skill in the art will also recognize that the following description is merely illustrative of the principles of the technology, which may be applied in various ways to provide many different alternative embodiments. This description is made for the purpose of illustrating the general principles of this technology and is not meant to limit the inventive concepts in the appended claims. 
         [0072]    Referring to  FIGS. 1-2 , a facet washer fixation system  10  may include a screw  12  and a washer  14 . 
         [0073]    The screw  12  may include a proximal head portion  16  and a distal shaft  18 . The proximal head portion  16  may have a larger diameter than the rest of the screw  12 . The proximal head portion  16  may include a torque transmission feature  20 . The torque transmission feature  20  may be an internal feature, such as a straight slot, cruciform slot, square socket, hex socket, or the like. The torque transmission feature  20  may also be an external feature, such as a tab, cruciate key, square key, hex key, or the like. The distal shaft  18  may include a threaded portion  22  to thread into bone. The entire length of the shaft may be threaded, or some portion or portions thereof. The screw  12  may be similar or identical to the facet fixation screw system  10  disclosed in U.S. patent application Ser. No. 12/957,056. 
         [0074]    The screw  12  may be made of a biocompatible material or a combination of biocompatible materials. For example, the screw  12  may be made of metal, polymer, ceramic, glass, carbon, composite, bone, or a combination of these materials. 
         [0075]    The washer  14  may be generally annular, curved, polygonal, asymmetric, or irregular. The washer  14  may have an aperture  24  through which at least a portion of the screw  12  may pass. The distal shaft  18  of the screw  12  may pass through the aperture  24  with clearance. 
         [0076]    The washer  14  may be made of a biocompatible material or a combination of biocompatible materials. For example, the washer  14  may be made of metal, polymer, ceramic, glass, carbon, bone, composite, or a combination of these materials. The material may stimulate bone formation on or in the washer. The material may include pores which communicate between the surface and the interior of the material. The pore morphology may be conducive to bone ingrowth. 
         [0077]    The screw  12  may be implanted so that it passes across a joint or discontinuity between two bones or bone fragments. The washer  14  may be implanted so that it lies in the joint, or between the two bones or fragments. Some bone may extend between the screw  16  and the washer  14 . 
         [0078]      FIGS. 1-2  illustrate an arrangement in which the screw  12  and washer  14  are implanted in a facet joint of a spine. The facet joint includes an inferior articular process  2  of a superior vertebra and a superior articular process  4  of an inferior vertebra. The screw  12  is oriented generally perpendicular to the articular surfaces of the facet joint. The screw head  16  rests against the inferior articular process  2 . The washer  14  is oriented generally parallel to, and between, the articular surfaces so that the inferior articular process  2  is between the screw head  16  and the washer. The inferior articular process  2  may fully encircle the distal shaft  18 . The aperture  24  receives the distal shaft  18  of the screw  12 . 
         [0079]    Referring to  FIGS. 2-4 , the facet washer fixation system  10  may include a cannula  26 . The cannula  26  may include a proximal portion  28  and a distal portion  30 . The cannula  26  may also include an intermediate portion  32  which couples the proximal and distal portions  28 ,  30  together. The cannula  26  may be a tubular structure with a longitudinal aperture  34 . The proximal portion  28  may include a grip feature  36 , which may be a flange, ear, tab, handle, or the like. The grip feature  36  may be textured, such as by knurling, grooves, roughening, or by the use of a high friction material such as silicone or rubber. The distal portion  30  may carry a washer holding feature  38  which holds the washer  14  in a desired orientation and at a particular distance from the distal portion  30  of the cannula  26 . The desired orientation may be influenced by the natural orientation of joint articular surfaces with respect to a selected screw trajectory. The washer holding feature  38  may include an arm  40  and a mount  42 , as shown in  FIGS. 2-4 . The arm  40  may extend longitudinally from the distal portion  30 . The arm  40  may extend from one side of the distal portion  30 , and may include one or more bends along its length. More than one arm  40  may be included in the grip feature  36 . The mount  42  may extend from the free end of the arm  40 , and may be forked or bifurcated to receive the washer  14  within the fork. In the example shown, the mount  42  lies in a plane which is approximately perpendicular to a center longitudinal axis of the cannula  26 , although angles greater than or less than  90  degrees are contemplated. The mount  42  may be rigidly fixed to the arm  40 , flexibly coupled to the arm for resilient deflection, or hinged to the arm for free rotation. The mount  42  may include prongs  44  which mate with corresponding indentations  46  on the periphery of the washer  14 . The prongs  44  may slide, spring, snap, roll, or plunge into the indentations  46 . The mount  42  itself may flex or articulate to enable the prongs  44  to engage the indentations  46 . Other interconnections are contemplated, such as a skewer mount which spikes into the washer  14 . 
         [0080]    A method of using the screw  12 , washer  14 , and cannula  26  will now be described in the context of a facet joint fusion procedure. The washer  14  may be inserted into the mount  42  so that the prongs  44  engage the indentations  46  to hold the washer securely in the mount. The cannula may be positioned with the distal portion  30  resting against the inferior articular process  2  of the superior vertebra and the washer  14  and mount  42  within the joint space between the inferior articular process  2  and the superior articular process  4  of the inferior vertebra. The torque transmission feature  20  of the screw  12  may be coupled to a screw driver (not shown). The screw  12  and screw driver may be advanced through the aperture  34  of the cannula  26  until the distal shaft  18  of the screw rests against the inferior articular process  2 . The screw  12  may be driven through the inferior articular process  2 , through the aperture  24  of the washer  14 , and through the superior articular process  4 . Optional additional steps may include placing a guide wire through the cannula, articular processes  2 ,  4 , and aperture  24  to establish a trajectory for the screw  12  to follow; drilling a pilot hole for the screw  12  through the inferior articular process  2  and/or the superior articular process  4 ; tapping a hole for the screw  12  through the inferior articular process  2  and/or the superior articular process  4 ; or using medical imaging to verify instrument and/or implant position. 
         [0081]    Referring to  FIG. 5 , the facet washer fixation system  10  may include a rasp  48 . The rasp  48  may include a proximal portion  50  and a distal portion  52 . The proximal portion  50  may include an elongated shaft  54 . A grip feature (not shown) may be present on the proximal portion  50 . The distal portion  52  may include an aim  56  which carries a rasp head  58  in a particular orientation and at a particular distance from the distal portion  52  of the rasp  48 . The rasp head orientation and distance may be comparable to those for the mount  42 . The arm  56  may extend longitudinally from the distal portion  52 . The arm  56  may extend from one side of the distal portion  52 , and may include one or more bends along its length. More than one arm  56  may be included. The rasp head  58  may extend from the free end of the arm  56 . In the example shown, the rasp head  58  lies in a plane which is approximately perpendicular to a center longitudinal axis of the shaft  54 , although angles greater than or less than  90  degrees are contemplated. The rasp head  58  may be rigidly fixed to the arm  56 , flexibly coupled for resilient deflection, or hinged for free rotation. The rasp head  58  may be generally disc shaped, curved, polygonal, asymmetric, or irregular, and may include cutting features  60  on at least one surface. The cutting features may be blades, teeth, ridges, serrations, points, or other projecting asperities. The cutting features may instead be grooves, channels, or declivities. The rasp head  58  may be a hollow grater structure. The distal portion  52  may resemble the washer holding feature  38  of the cannula  26 . 
         [0082]    A method of using the rasp  48  will now be described in the context of the facet joint fusion procedure described above. The rasp  48  may be positioned with the rasp head  58  within the joint space between the inferior articular process  2  and the superior articular process  4 . The rasp  48  may be manipulated to move the rasp head  58  against one or both articular surfaces to roughen or remove articular cartilage, subchondral bone, and the like to prepare a space to receive the washer  14 . The rasp head  58  may be moved in a plane generally parallel to the articulating surfaces, although movement in other directions is contemplated. The rasp head motion may be reciprocating, oscillating, circular, oval, elliptical, figure-eight, or irregular. The rasp  48  may be in the cannula aperture  34  during use. A set or kit of variously sized and shaped rasps or rasp heads may be provided. The rasp or rasp head may be replaceable and/or disposable. 
         [0083]    Referring to  FIG. 6 , a polyaxial taper lock screw and plate system  70  may include a washer  72 , a taper component  74 , a plate  76 , a pad  78 , and a fastener  80 . 
         [0084]    The washer  72  may be a generally annular component with a plate-facing surface  82 , or obverse, and an opposite reverse surface  84 . A threaded hole  86  may extend through the washer between the obverse and reverse surfaces  82 ,  84 . The plate-facing surface  82  may include an indentation  88  or concavity around the hole  86 . The reverse surface  84  may be convex. The washer may include a torque transmission feature (not shown). For example, a hex key may be formed in an outer periphery of the washer. 
         [0085]    The taper component  74  may include a round, generally tubular body  90  with a flange  92  at one end and a full length central longitudinal hole  94 . The flange  92  may be at least partially received within the indentation  88  of the washer  72 . 
         [0086]    The plate  76  may include a bone-facing surface  94 , or obverse, and an opposite reverse surface  96 . A hole  98  may extend through the plate  76  between the obverse and reverse surfaces  94 ,  96 . The hole  98  may receive the body  90  of the taper component  74  with clearance, line to line fit, interference fit, or taper fit. The bone-facing surface  94  may include an indentation  100  around the hole  98 . The indentation  100  may be spherical, conical, parabolic, elliptical, asymmetric, or irregular. The plate  76  may include a rim  102 , or lip, that encircles the indentation  100 . The internal diameter of the indentation  100  may be larger than the internal diameter of the rim  102 , so that the rim  102  forms a constriction around the indentation  100 . 
         [0087]    The pad  78  may be described as a polyaxial foot. The pad  78  may include a spherical plate-facing surface  104  and an opposite bone-facing surface  106 . The spherical plate-facing surface  104  may fit within the indentation  100  with clearance, line to line fit, or interference fit. The spherical surface  104  may have an external diameter that is larger than the internal diameter of the rim  102 , so that the pad  78  is retained with the plate  76  after initial assembly of the pad  78  to the plate  76 . The bone-facing surface  106  may include one or more spikes  108 . The pad  78  may include a central hole  110 . In the example of  FIG. 6 , the hole  110  may extend perpendicular to the bone-facing surface  106 . In other examples, the hole  110  may extend at an acute angle to the bone-facing surface  106 . The hole  110  may receive a portion of the body  90  of the taper component  74  with clearance, line to line fit, interference fit, or taper fit. Alternately, the hole  110  may be the same size as the hole  94  in the taper component  74 , in which case, the taper component  74  may be integrally formed with the pad  78 . The pad  78  may share some or all of the characteristics of the pad  106  disclosed in U.S. patent application Ser. Nos. 12/853,689 and 13/188,325, which are incorporated by reference herein in their entirety. 
         [0088]    The fastener  80  may include a proximal head portion  112  and a distal shaft  114 . The proximal head portion  112  may be threaded, and may include a torque transmission feature  116 . The distal shaft  114  may include a threaded portion  118  to thread into bone. The fastener  80  may include an unthreaded shank portion  120  between the head portion  112  and the threaded portion  118 . The shank portion  120  may fit within the hole  110  of the pad  78  and/or the hole  94  of the taper component  74  with clearance, line to line fit, or interference fit. The proximal head portion  112  may thread together with the threaded hole  86  of the washer  72 . The threaded portion  118  of the distal shaft  114  may thread into bone. 
         [0089]    The polyaxial taper lock screw and plate system  70  may be assembled by forcing the spherical surface  104  of the pad  78  past the rim  102  and into the indentation  100  of the plate  76 , after which the pad remains captive to the plate; receiving the body  90  of the taper component  74  in the hole  98  of the plate, with the flange  92  adjacent to the reverse surface  96  of the plate; coupling the taper component to the pad, with the hole  94  of the taper component coaxial with the hole  110  of the pad and the bone-facing surface  106  of the pad faces outward from the indentation  100 ; receiving the head portion  112  and shank portion  120  of the fastener  80  through the holes  94 ,  110  so that the distal threaded portion  118  of the fastener extends outwardly from the bone-facing surface  106  of the pad; and threading the proximal head portion of the fastener into the threaded hole of the washer  72 , with the obverse of the washer facing the plate. At first, the fastener  80  and washer  72  may be threaded together with fingertips. The fastener, polyaxial pad  78 , and taper component  74  may polyaxially pivot as a unit about the center of the spherical surface  104  within the indentation  100 . As the fastener and washer are threaded together, the fastener, polyaxial pad  78 , and taper component  74  may be drawn as a unit toward the washer until the polyaxial pad binds within the indentation  100  to lock the system  70  components rigidly together. 
         [0090]    In one method of use, the washer  72 , taper component  74 , plate  76 , pad  78 , and fastener  80  may be pre-assembled but not locked together. A first tool (not shown) may engage the torque transmission feature  116  of the fastener  80 , a second tool (not shown) may engage the torque transmission feature of the washer  72 , and a third tool (not shown) may stabilize the plate  76 . The three tools may nest, although this is not essential. In one example of a nested arrangement, the first tool is a hex driver which is received within the second tool, which is a hex socket. The second tool is received within the third tool, which is a tube terminating in a fork that fits over the width of the plate  76 . The first and second tools may be operated together to turn, or drive, the fastener  80  and washer  72  together to thread the fastener  80  into a bone without locking the system  70  components together. During this step, the bone-facing surface  106  of the pad  72  is brought into contact with the bone and the spikes  108  may penetrate the surface of the bone. The first tool may then be held in a fixed position while the second tool is operated to drive the washer  72  relative to the fastener  80  to lock the system  70  components together. During both steps, the third tool may hold the plate  76  in a fixed position. Tools which hold components in a fixed position while torque is applied elsewhere in the system  70  may be referred to as counter torque tools. 
         [0091]    In another method of use, the fastener  80  alone may be driven into bone, after which the pad  78 , plate  76 , taper component  74 , and washer  72  may be assembled to the installed fastener  80 . The washer  72  may be driven relative to the fastener  80  to lock the system  70  components together as described above. 
         [0092]    While the foregoing description describes a single instance of a fastener, pad, taper component, and washer assembled to a plate, multiple instances of these components are contemplated. For example, a plate may include two instances of the described components, such as one instance at each end of the plate. Additional intermediate instances may also be provided. The instances may lie along a straight line, or along any other geometric construct, or they may be randomly positioned on the plate. 
         [0093]    Referring to  FIG. 7 , another polyaxial taper lock screw and plate system  130  may include a taper component  132 , a plate  134 , and a fastener  136 . 
         [0094]    The taper component  132  may include a threaded shaft  138  with a flange  140  at one end. The flange  140  may include a torque transmission feature  142 , such as a perimeter hex key, central hex socket, slot, or the like. 
         [0095]    The plate  134  may include a bone-facing surface  144 , or obverse, and an opposite reverse surface  146 . A hole  148  may extend through the plate  134  between the obverse and reverse surfaces  144 ,  146 . The hole  148  may receive the shaft  138  of the taper component  132  with clearance, line to line fit, interference fit, or taper fit. The bone-facing surface  144  may include an indentation  150  around the hole  148 . The indentation  150  may be spherical, conical, parabolic, elliptical, asymmetric, or irregular. In this example, the indentation  150  is a frustoconical socket. The plate  134  is shown to have two instances of the hole  148  and indentation  150 , one at each end of the plate. 
         [0096]    The fastener  136  may include a proximal head portion  152 , a distal threaded shaft  154 , and an unthreaded shank  156  between the head portion  152  and the threaded shaft  154 . The head portion  152  may have a spherical outer surface  158  and a central threaded hole  160 . The spherical outer surface  158  may be at least partially received in the indentation  150 . The threaded hole  160  may thread onto the threaded shaft  138  of the taper component  132 . 
         [0097]    The polyaxial taper lock screw and plate system  130  may be assembled by seating the head portion  152  of the fastener  136  in the indentation  150  with the distal threaded shaft  154  extending outwardly from the obverse  144  of the plate  134  and threading the shaft  138  of the taper component  132  into the threaded hole  160 . At first, the fastener  136  and taper component  132  may be threaded together with fingertips. The fastener  136  and taper component  132  may polyaxially pivot as a unit about the center of the spherical surface  158  within the indentation  150 . As the fastener  136  and taper component  132  are threaded together, the fastener and taper component may be drawn toward the plate  134  until the spherical surface  158  binds within the indentation  150  to lock the system  130  components rigidly together. 
         [0098]    Referring to  FIG. 8 , a modular spinous process clamp system  170  may include two plates  172 ,  174 , a plurality of pads  176 , a locking mechanism  178 , and a sleeve  180 , or spacer. Plate  172  may be a first plate and plate  174  may be a second plate. The locking mechanism  178  may include a post  182 , a collet  184 , and a ring  186 . 
         [0099]    At least some of the components of system  170  may share characteristics of corresponding components disclosed in spinal fusion implant  100  of U.S. patent application Ser. No. 12/853,689 and 13/188,325. However, at least the following characteristics may differ from those disclosed in U.S. patent application Ser. Nos. 12/853,689 and 13/188,325. 
         [0100]    The plate  172  may include a spherical or conical socket  188 . The post  182  may include a complementary spherical enlargement  190 , or head, which fits into the socket  188  to form a polyaxial joint. However, a rigid plate-to-post interconnection may be substituted for the polyaxial joint in some examples. 
         [0101]    The plate  174  may lack extension walls. 
         [0102]    The sleeve  180  may at least partially encircle the post  182  and may be between the plates  172 ,  174  when the system  170  is operatively assembled. The sleeve  180  may be an annular or tubular structure with a central longitudinal through hole  192  and an outer surface  194 . The sleeve  180  may be made from bone, ceramic, mineral, plastic, metal, glass, elastomer, or other biocompatible materials. 
         [0103]    Referring to  FIG. 9 , another sleeve  200  may have a central longitudinal hole  192  and an outer surface  202  with a larger outer diameter at each end and a smaller outer diameter in the middle. This sleeve  200  may be described as having a waist or an hourglass figure, particularly when viewed in a longitudinal cross section. This sleeve  200  may also be described as having a concave outer profile when viewed in a longitudinal cross section through the center axis of the hole  192 . 
         [0104]    Referring to  FIG. 10 , sleeve  180  may have a substantially annular transverse cross section. 
         [0105]    Referring to  FIG. 11 , yet another sleeve  210  may have a central longitudinal hole  192  and a polygonal transverse cross section which is generally centered about the hole  192 . Sleeve  210  is shown with a parallelogram cross section, but other shapes are contemplated. 
         [0106]    Referring to  FIG. 12 , yet another sleeve  220  may have a central longitudinal hole  192  and a polygonal transverse cross section which is asymmetrically disposed about the hole  192 . A polygonal cross section, such as the illustrated parallelograms of sleeves  210 ,  220 , may complement the shape of an interspinous process gap. 
         [0107]    Referring to  FIG. 13 , yet another sleeve  230  may have a central longitudinal hole  192  and an H-shaped longitudinal cross section. Sleeve  230  may also resemble a spool. Sleeve  230  may include enlarged flanges  232 ,  234 , or rims, at each end and a reduced diameter midsection  236 . Sleeve  230  may be described as having a concave outer profile in longitudinal cross section. 
         [0108]    Any of the sleeves  200 ,  210 ,  220 ,  230  may take the place of sleeve  180  in the system  170 . A kit of sleeves may be provided. The kit may contain several sleeve morphologies, and several sizes in each morphology. 
         [0109]    Referring to  FIGS. 14-15 , another spinous process clamp system  250  may include curved plates  252 ,  254  which may complement a spinal lordotic or kyphotic curve. The plates  252 ,  254  may include slots  256 , or other arcuate guides such as grooves or rails, to permit longitudinal adjustment of pads  258 , locking mechanism  260 , or both. The system  250  may also include additional grips  262  between the plates  252 ,  254 . While  FIG. 15  shows two opposing grips  262  with the locking mechanism  260 , the grips  262  may be any number, and may be positioned anywhere between the plates. The grips may be static or movable relative to the plates  262 ,  264 . 
         [0110]    Referring to  FIGS. 16-17 , a multi-level bone plate system  270  may include a primary system  272  with a first locking mechanism  274 , and an augmentation system  276  with a second locking mechanism  278 . A locking mechanism  280  on each side of the construct links the primary and augmentation plates together. The locking mechanism  280  may include an arcuate or spherical mechanically locking interface  282 . While  FIGS. 16-17  show one augmentation system  276 , other examples of this technology may include more augmentation systems mechanically linked in daisy chain fashion to address any number of spinal levels. Yet other examples may include augmentation systems linked to each end of the primary system  272 . 
         [0111]    Referring to  FIG. 18 , an expandable interspinous plate system  300  may include plates  302 ,  304 , pads  306 , a locking mechanism  308 , and a cage  310 . The locking mechanism may include a post  312 , a collet  314 , and a ring  316 . 
         [0112]    The cage  310  may occupy a position around the post  312  and between the plates  302 ,  304  when the system  300  is operatively assembled. The cage  310  may reside in an interspinous process space when implanted as part of the system  300 . Referring to  FIG. 19 , the cage  310  may be divided into two portions  318 ,  320  which nest, or telescope, so that a width  322  of the cage may be increased or decreased as desired. In this arrangement, the cage  310  can adjust parallel to the post to fit precisely between plates  302 ,  304 , and it may provide good exposure for loading materials into the cage. The cage  310  may be said to reversibly expand and contract. Each portion  318 ,  320  may have a square channel shape. Nesting may be accomplished by making one channel narrower than the other so that the narrow channel is received within the wider channel, or by staggering two identical channels. Each end of each channel may be open or closed. The portions  318 ,  320  include slots  324 ,  326 , or openings, sized to accept the post  312 . The slots  324 ,  326  may permit the cage  310  to pivot around the post  312 , therefore the cage  310  may assume an angled orientation relative to one or both of the plates  302 ,  304 . 
         [0113]    Referring to  FIG. 20 , another cage  330  may present an overall trapezoidal shape when its two portions  332 ,  334  are nested. A first width  336  may be greater than an opposite second width  338  of the trapezoid. 
         [0114]    Referring to  FIG. 21 , yet another cage  340  illustrates a narrow channel portion  342  nesting inside a wide channel portion  344 . 
         [0115]    Any of the cages  310 ,  330 ,  340  may enclose or support a bone graft, a scaffold for bone growth, or the like. The enclosed material may be a solid block or morselized pieces. Cages may be fenestrated or otherwise open to provide pathways for a bone fusion mass to develop. Cages may be load-bearing or load-sharing with the rest of the system  300 . For example, the cages may be open at cephalad and caudal faces for spinal fusions. 
         [0116]    Referring to  FIG. 22 , another expandable interspinous plate system  360  may include a cage  370  which is adjustable in a direction generally parallel to the plates  362 ,  364 , or generally perpendicular to the post. The cage  370  may include two portions  372 ,  374  which nest or telescope so that a length  376  of the cage  370  may be adjusted as desired. The two portions  372 ,  374  may be square channels, and may include open ended slots  378 ,  380  which accept a post  382  and enable the cage  370  to pivot around the post  382 . The cage  370  may be rotated to an orientation in which the adjustment direction is substantially parallel to a physiologic load direction, which may subject a contained graft to compressive and/or tensile loads after implantation. Cage  370  may be fenestrated or otherwise open to provide pathways for a bone fusion mass to develop. 
         [0117]    Referring to  FIG. 24 , another cage  390  may include at least a partial anterior wall  392  on one or both portions  394 ,  396 . 
         [0118]    Referring to  FIG. 25 , system  360  is shown implanted adjacent to spinous processes  384 ,  386 . It can be seen that cage  370  rests between the spinous processes and at an acute angle relative to plate  362 . 
         [0119]    Referring to  FIGS. 26-28 , a minimally invasive bone plate system  400  may include a curved post  402 , which may facilitate insertion of the post after placement of plates  404 ,  406 .  FIGS. 29-31  illustrate three steps in an example method of use. In  FIG. 29 , plate  404  and post  402  may be inserted as a unit on one side of a series of spinous processes  384 ,  386 , along direction arrow  401 . In  FIG. 30 , plate  406  is attached over post  402  on the other side of the spinous processes. In  FIG. 31 , the system  400  has been fully locked together around the spinous processes. 
         [0120]    Referring to  FIG. 32 , an extension limiting interspinous process spacer system  420  may include plates  422 ,  424  and locking mechanism  428 . The locking mechanism  428  may include a post  432 , a collet  434 , and a ring  436 . Each plate  422 ,  424  may couple to the locking mechanism  428  at a polyaxial joint. The plates  422 ,  424  may have smooth bone-facing or obverse sides  438 ,  440  to permit the adjacent spinous processes to separate during spinal flexion. Spinal extension may be limited by the outside diameter of the post  432 . 
         [0121]    Referring to  FIG. 33 , an instrument  450  provides three-point positive locking to an extension plate  460 . The instrument  450  includes two lateral connections  452 ,  454  and a medial connection  456 . More specifically, the instrument may engage lateral cups  458 , or sockets, and a medial inner lip  461 , or edge, of a window  462  in an extension wall  464 . The lateral cups  458  may share some or all of the characteristics of the instrument connection feature  150  disclosed in U.S. patent application Ser. Nos. 12/853,689 and 13/188,325. 
         [0122]    Referring to  FIGS. 34-35 , instruments  470 ,  480  include positive locking through the lateral cups  458 . Instrument  470  includes an enlarged tip  472  which is received in the lateral cup  458 . Protruding from the tip  472  are forked tongues  474  which may be stored in a retracted position within the tip  472  or deployed to an extended flared position outside the tip. When the tip  472  is in the lateral cup  458 , the tongues  474  may be extended through the lateral cup to grapple with the obverse surface  466  of the plate  460 . Instrument  480  includes an enlarged tip  482  with a protruding deployable lever  484  that also grapples with the obverse  466  of the plate  460 . 
         [0123]    Referring to  FIG. 36 , instrument  490  includes a fork  492  which grips an exposed lip  463  of the window  462 . 
         [0124]    Referring to  FIG. 37 , instrument  500  includes a spherical expanding tip  502  which is received in the lateral cup  458 . The tip  502  expands when a shaft is driven through the tip  502  along its length. The tip  502  may be described as an expanding collet.  FIG. 45  shows another example of an instrument  600  with a similar structure and function. 
         [0125]    Referring to  FIG. 38 , a bone plate system  520  may include non-spherical or non-circular swiveling grips  522 , or pads. The range of motion of the non-spherical grips  522  may be selectively limited by the grip geometry. 
         [0126]    Referring to  FIG. 39 , another multi-level bone plate system  540  may include chevron shaped plates  542 . Each plate  542  may include three pads  544  arranged in a triangle pattern complementary to the chevron shape. Each plate may also include a locking mechanism  546 . Consecutive plates  542  nest together as shown so that two plates may be secured to a single spinous process. The nesting shapes have sufficient clearance to permit angulation of consecutive plates to adapt to spinal lordotic, kyphotic, or scoliotic curves. 
         [0127]    Referring to  FIG. 40 , yet another segmental multi-level bone plate system  550  includes S-bend plates  552 . Consecutive plates partially bypass each other so that two plates may be secured to a single spinous process. Although only two consecutive plates are shown in  FIGS. 39-40 , more plates may be included depending on the number of spinal levels to be treated. 
         [0128]    Referring to  FIGS. 41-42 , another bone plate system  560  includes a plate  562  with an elongated slot  564  which receives the locking mechanism  566 . In this arrangement, a polyaxial washer  568  may support a collet  570  in the slot  564  so that the locking mechanism  566  may be positioned as desired along the slot. 
         [0129]    Referring to  FIG. 43 , another plate  580  for segmental multi-level fixation may have a generally T-shaped profile. Pads (not shown) may be located in the ends of the crossbar of the T so that two plates may be anchored to each spinous process. 
         [0130]    Referring to  FIG. 44 , another cage  590  is shown. The cage  590  may be a box shape with four pillars  592  supporting two walls  594 . A hole  596  extends through both walls. Windows  598  are defined between the pillars. The hole  596  may receive a post of a locking mechanism, and the cage  590  may rest between two plates in an operative assembly. This cage may contain or support bone graft or other materials, such as osteogenic materials, within the box. 
         [0131]    Referring to  FIG. 45 , a transverse cross sectional exploded view shows an instrument  600  and a portion of a plate  602 . 
         [0132]    Plate  602  includes an instrument connection feature  604 , which has an enlarged middle portion  606  between a first portion  608  and a second portion  610 . 
         [0133]    Instrument  600  includes an enlarged tip  612  and a plunger  614 . The enlarged tip  612  is received in the middle portion  606  of the instrument connection feature  604 . The tip  612  is hollow and includes at least one slit  616  to impart flexibility to the tip. In an extended position, the plunger  614  is received in the tip  612  and forces the tip to spread apart or enlarge for a tight fit in the middle portion  606  of the instrument connection feature  604 . The plunger  614  is actuated by an arm  618  which is coupled to a control (not shown). The plunger  614  moves between a disengaged or retracted position and an engaged, or extended position in response to the control. 
         [0134]    Referring to  FIGS. 46-48 , another curved plate  630  includes a curved trough  632 . The trough may receive one or more pads  636  which may be movably mounted in the trough. For example, the trough  632  may include a spherical cup  634  for engagement with the pad  636 . In another example, a spherical surface  638  of the pad  636  may be directly retained and slidable in the trough  632 . 
         [0135]    Referring to  FIG. 49 , a plate compressor  650  may include opposing jaws  652 ,  654 , a main pivot  656 , opposing handles  658 ,  660 , and an optional ratchet mechanism  662 . The plate compressor  650  may connect to the plates of any of the spinous process systems disclosed herein, and may urge the plates together and automatically maintain a compressive force between the plates until the ratchet bar  662  is released. 
         [0136]    Referring to FIGS.  50  and  52 - 53 , a provisional locking arm  670  may include a jaw  672 , a main pivot receiver  674 , and a handle  676 . The provisional locking arm  670  may be added to the plate compressor  650  by hooking the main pivot receiver  674  onto the main pivot  656 . The jaw  672  terminates in a collet fork  678  which isolates the applied force to push a collet component of a plate locking mechanism toward the plates for provisional locking. The provisional locking arm  670  may include a force indicator  680  which signals when a provisional locking force threshold has been reached. The force indicator  680  may be a beam. The signal provided by the force indicator may be visual, auditory, tactile, or any combination. The signal may be produced by differential deflection between the handle  676  and the force indicator  680 . 
         [0137]    Referring to  FIG. 51 , a final locking arm  690  may include a jaw  692 , a main pivot receiver  694 , and a handle  696 . The final locking arm  690  may be added to the plate compressor  650  by hooking the main pivot receiver  694  onto the main pivot  656 , regardless of the presence or absence of the provisional locking arm  670  on the compressor  650 . The jaw  692  terminates in a ring  698  which isolates its applied force to push a ring component of a plate locking mechanism toward the plates for final locking. The final locking arm  690  may include another force indicator  700  calibrated for a final locking force threshold. 
         [0138]    When the provisional locking arm  670  and final locking arm  690  are coupled to the plate compressor  650 , the combination may have many of the characteristics set forth for the instrument  350  disclosed in U.S. patent application Ser. No. 13/188,325. 
         [0139]    The components of the systems disclosed herein are preferably formed of titanium or titanium alloy. In other embodiments, component parts may comprise cobalt-chrome and its alloys, stainless-steel, titanium and its alloys, titanium carbide, titanium nitride, ion-implantation of titanium, diffusion hardened metals, diamond like coatings, diamond-like carbon, zirconium nitride, niobium, oxinium or oxidized zirconium, ceramics such as alumina and zirconia, polymers, or other biocompatible materials. Any part may comprise a combination of any of the materials listed, and the systems may comprise parts made of differing materials. 
         [0140]    Any of the components disclosed herein may include surface treatments or additives in one or more of the component materials to provide beneficial effects such as anti-microbial, analgesic or anti-inflammatory properties. Any of the components disclosed herein may include coatings or treatments to provide surface roughening, including but not limited to knurling or porous coating, among others. Such treatments may be directionally applied to promote movement between component parts in one direction, and/or increase friction between component parts in another direction. 
         [0141]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. It is appreciated that various features of the above described examples and embodiments may be mixed and matched to form a variety of other combinations and alternatives. It is also appreciated that this system should not be limited simply to facet joint fixation. As such, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.