PATENT ABSTRACT
Surgical implants are configured for placement posteriorly to a spinal canal between vertebral bodies to distract the spine and enlarge the spinal canal. In the preferred embodiments the device permits spinal flexion while limiting spinal extension, thereby providing an effective treatment for treating spinal stenosis without the need for laminectomy. The invention may be used in the cervical, thoracic, or lumbar spine. Numerous embodiments are disclosed, including elongated, length-adjustable components coupled to adjacent vertebral bodies using pedicle screws. The preferred embodiments, however, teach a device configured for placement between adjacent vertebral bodies and adapted to fuse to the lamina, facet, spinous process or other posterior elements of a single vertebra. Various mechanisms, including shape, porosity, tethers, and bone-growth promoting substances may be used to enhance fusion. The tether may be a wire, cable, suture, or other single or multi-filament member. Preferably, the device forms a pseudo-joint in conjunction with the non-fused vertebra. Alternatively, the device could be fused to the caudal vertebra or both the cranial and caudal vertebrae.

PATENT DESCRIPTION
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Application Ser. No. 60/629,018, filed Nov. 18, 2004, the entire content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to spine surgery and, in particular, to methods and apparatus for treating spinal stenosis. 
       BACKGROUND OF THE INVENTION 
       [0003]    Spinal stenosis is a narrowing of spaces in the spine, results in pressure on the spinal cord and/or nerve roots. This disorder usually involves the narrowing of one or more of the following: (1) the canal in the center of the vertebral column through which the spinal cord and nerve roots run, (2) the canals at the base or roots of nerves branching out from the spinal cord, or (3) the openings between vertebrae through which nerves leave the spine and go to other parts of the body. 
         [0004]    Pressure on the lower part of the spinal cord, or on nerve roots branching out from that area, may give rise to pain or numbness in the legs. Pressure on the upper part of the spinal cord (that is, the neck area) may produce similar symptoms in the shoulders, or even the legs. The condition generally occurs in patients who are in their last decade or decades of life. 
         [0005]    Laminectomy, which involves removing bone, the lamina, from the vertebrae, is the most common surgical treatment for spinal stenosis. Laminectomy enlarges the spinal canal, thus relieving the pressure on compressed nerves. Surgical burs, drills, punches, and chisels are used during the procedure. 
         [0006]    Surgeons risk injuring the nerves or the spinal cord as they enlarge the spinal canal. In addition, elderly patients frequently have co-morbidities that increase the risk of laminectomy. Complications of laminectomy include increased back pain, infection, nerve injury, blood clots, paralysis, prolonged recovery, and death. 
         [0007]    Lumbar fusion is frequently preformed in-conjunction with laminectomy. Current fusion techniques require abrasion of large surfaces of bone. Bone bleeds during and after abrasion. Current fusion techniques increase the risk of spinal stenosis procedures. Fusion also prolongs patient recovery following spinal stenosis surgery. 
         [0008]    Patients and surgeons would welcome less invasive treatments for spinal stenosis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  is a lateral view of a novel device of the invention; 
           [0010]      FIG. 1B  is a lateral view of the embodiment of the invention shown in  FIG. 1A ; 
           [0011]      FIG. 1C  is an end view of a novel vertebral screw and a cross-section of the threaded portion of the rod shown in  FIG. 1A ; 
           [0012]      FIG. 1D  is an end view of the screw shown in  FIG. 1C  and a cross-section of the threaded end component shown in  FIG. 1A ; 
           [0013]      FIG. 1E  is an end view of an alternative embodiment of the screw shown in  FIG. 1C ; 
           [0014]      FIG. 1F  is a lateral view of the device shown in  FIG. 1A  and the screws of the embodiment shown in  FIG. 1C ; 
           [0015]      FIG. 1G  is a lateral view of the embodiment of the device shown in  FIG. 1F ; 
           [0016]      FIG. 1H  is a lateral view of the device shown in  FIG. 1G ; 
           [0017]      FIG. 1I  is a sagittal cross-section of the device shown in  FIG. 1H ; 
           [0018]      FIG. 2A  is a lateral view of an alternative embodiment of the invention; 
           [0019]      FIG. 2B  is an exploded view of the device shown in  FIG. 2A  and an alternative embodiment of the vertebral screws; 
           [0020]      FIG. 2C  is a lateral view of the device shown in  FIG. 2B ; 
           [0021]      FIG. 2D  is an exploded end view of the screw and fastening component shown in  FIG. 2C ; 
           [0022]      FIG. 2E  is end view of the screw and fastening component shown in  FIG. 2D  and a cross-section of the rod-like device shown in  FIG. 2C ; 
           [0023]      FIG. 3A  is a lateral view of an alternative embodiment of the device shown in  FIG. 2A ; 
           [0024]      FIG. 3B  is a lateral view of the embodiment of the device shown in  FIG. 3A ; 
           [0025]      FIG. 3C  is a view of the top of the device shown in  FIG. 3B ; 
           [0026]      FIG. 3D  is an enlarged view of the top of the hinge joint shown in  FIG. 3C ; 
           [0027]      FIG. 3E  is an enlarged view of the top of an alternative embodiment of the hinge joint shown in  FIG. 3D ; 
           [0028]      FIG. 3F  is a lateral view of the device shown in  FIG. 3B  and vertebral screws; 
           [0029]      FIG. 4A  is an exploded lateral view of an alternative embodiment of a vertebral screw and a portion of the device shown in  FIG. 3B ; 
           [0030]      FIG. 4B  is a lateral view of the embodiment of the device shown in  FIG. 4A ; 
           [0031]      FIG. 4C  is a lateral view of the embodiment of the device shown in  FIG. 4B ; 
           [0032]      FIG. 5A  is a lateral view of an alternative embodiment of the device shown in  FIG. 2A ; 
           [0033]      FIG. 5B  is a lateral view of the device shown in  FIG. 5A . The device is shown in its contracted position; 
           [0034]      FIG. 5C  is an exploded view of the device shown in  FIG. 5A  and vertebral screws; 
           [0035]      FIG. 5D  is a lateral view of the assembled device shown in  FIG. 5C ; 
           [0036]      FIG. 6A  is an oblique view of an alternative embodiment of the invention; 
           [0037]      FIG. 6B  is a lateral view of a portion of the spine; 
           [0038]      FIG. 6C  is a lateral view of a portion of the spine and the embodiment of the invention shown in  FIG. 6A ; 
           [0039]      FIG. 6D  is a lateral view of a portion of the spine and the device shown in  FIG. 6A ; 
           [0040]      FIG. 6E  is an oblique view of a cancellous bone block; 
           [0041]      FIG. 6F  is an oblique view of a section of the shaft of a long bone; 
           [0042]      FIG. 6G  is an oblique view of a section of the shaft of a long bone and a cancellous bone block; 
           [0043]      FIG. 6H  is an oblique view of the embodiment of the invention shown in  FIG. 6G ; 
           [0044]      FIG. 6I  is lateral view of a portion of the spine and a sagittal cross-section of the embodiment of the device shown in  FIG. 6A ; 
           [0045]      FIG. 7A  is an oblique view of a portion of a shaft of a long bone; 
           [0046]      FIG. 7B  is an oblique view of portion of a shaft of a shaped long bone; 
           [0047]      FIG. 7C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 7B ; 
           [0048]      FIG. 7D  is an oblique view of a piece of bone; 
           [0049]      FIG. 7E  is an end view of the device shown in  FIG. 7A  and the bone shown in  FIG. 7D ; 
           [0050]      FIG. 7F  is a lateral view of a portion of the spine and a sagittal cross-section of the embodiment of the device shown in  FIG. 7E ; 
           [0051]      FIG. 8A  is an end view of an alternative shape of the device shown in  FIG. 7B ; 
           [0052]      FIG. 8B  is an end view of an alternative shape of the device shown in  FIG. 8A ; 
           [0053]      FIG. 8C  is an end view of an alternative shape of the device shown in  FIG. 8B ; 
           [0054]      FIG. 9A  is an oblique view of an alternative embodiment of the device shown in  FIG. 6A ; 
           [0055]      FIG. 9B  is a view of the top of the embodiment of the invention shown in  FIG. 8A ; 
           [0056]      FIG. 9C  is a lateral view of a portion of the spine and the embodiment of the invention shown in  FIG. 9A ; 
           [0057]      FIG. 10A  is an oblique drawing of an alternative embodiment of the invention related to that shown in  FIG. 6A ; 
           [0058]      FIG. 10B  is a lateral view of a portion of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0059]      FIG. 10C  is a dorsal view of a portion of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0060]      FIG. 10D  is a sagittal cross-section of the embodiment of the invention shown in  FIG. 10B  and a lateral view of the spine; 
           [0061]      FIG. 10E  is a sagittal cross-section of the embodiment of the invention shown in  FIG. 10D  and a lateral view of the spine; 
           [0062]      FIG. 10F  is a coronal cross section of the embodiment of the invention shown in  FIG. 10E  and the spine; 
           [0063]      FIG. 11A  is a dorsal view of the embodiment of the invention shown in  FIG. 10F  and the spine; 
           [0064]      FIG. 11B  is a dorsal view of the embodiment of the invention shown in  FIG. 11A  and the spine; 
           [0065]      FIG. 12A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 11A ; 
           [0066]      FIG. 12B  is a dorsal view of the embodiment of the invention shown in  FIG. 12A  and the spine; 
           [0067]      FIG. 12C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 12A ; 
           [0068]      FIG. 12D  is a lateral view of, the spine and the embodiment of the invention shown in  FIG. 12C ; 
           [0069]      FIG. 13A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10B ; 
           [0070]      FIG. 13B  is a dorsal view of the embodiment of the invention shown in  FIG. 13A  and the spine; 
           [0071]      FIG. 14A  is a lateral view of the spine and an alternative embodiment of the invention shown in  FIG. 13A ; 
           [0072]      FIG. 14B  is a dorsal view of the embodiment of the invention shown in  FIG. 14A  and the spine; 
           [0073]      FIG. 14C  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 14B ; 
           [0074]      FIG. 14D  is a dorsal view of the spine and an alternative embodiment of the invention shown in  FIG. 14C ; 
           [0075]      FIG. 15  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0076]      FIG. 16  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0077]      FIG. 17  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0078]      FIG. 18  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0079]      FIG. 19  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0080]      FIG. 20A  is a dorsal view of the spine and an alternative embodiment of a device related to that shown in  FIG. 17 ; 
           [0081]      FIG. 20B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 20A ; 
           [0082]      FIG. 21A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 20A ; 
           [0083]      FIG. 21B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 21A ; 
           [0084]      FIG. 22  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A ; 
           [0085]      FIG. 23A  is a lateral view of the spine and an alternative embodiment of the invention shown in  FIG. 22 ; 
           [0086]      FIG. 23B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 23A ; 
           [0087]      FIG. 24A  is an exploded dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 23B ; 
           [0088]      FIG. 24B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 24A ; 
           [0089]      FIG. 25A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A ; 
           [0090]      FIG. 25B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 25A ; 
           [0091]      FIG. 26A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 25A ; 
           [0092]      FIG. 26B  is dorsal view of the spine and the embodiment of the invention shown in  FIG. 26A ; 
           [0093]      FIG. 26C  is a sagittal cross-section of an alternative embodiment of the invention related to that shown in  FIG. 26B ; 
           [0094]      FIG. 27A  is a lateral view of an alternative embodiment of the device related to that shown in  FIG. 26A ; 
           [0095]      FIG. 27B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 27A ; 
           [0096]      FIG. 28A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0097]      FIG. 28B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 28A ; 
           [0098]      FIG. 28C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 28B ; 
           [0099]      FIG. 29  is a lateral view of the spine, the embodiment of the invention shown in  FIG. 12A , and a device to help prevent extrusion of the spinous process spacer; 
           [0100]      FIG. 30  is a view of the caudal aspect of the cranial vertebra shown in  FIG. 28C ; 
           [0101]      FIG. 31  shows a dorsal view of the spine; 
           [0102]      FIG. 32A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 12A ; 
           [0103]      FIG. 32B  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 32A ; 
           [0104]      FIG. 32C  is a lateral view of the spine and an alternative multilevel embodiment of the invention related to that shown in  FIG. 32B ; 
           [0105]      FIG. 33  is a lateral view of the spine and an alternative multilevel embodiment of the invention related to that shown in  FIG. 32C ; 
           [0106]      FIG. 34  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A ; 
           [0107]      FIG. 35A  is a lateral view of the spine and an alternative multilevel embodiment of the invention related to that shown in  FIG. 20B ; 
           [0108]      FIG. 35B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 35A ; 
           [0109]      FIG. 35C  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 20B ; 
           [0110]      FIG. 35D  is a dorsal view of the spine and a three-level version of the device shown in  FIG. 35B ; 
           [0111]      FIG. 36A  is a dorsal exploded view of the spine and an alternative embodiment of the device related to that shown in  FIG. 35B ; 
           [0112]      FIG. 36B  is dorsal view of the spine and the embodiment of the invention shown in  FIG. 36A ; 
           [0113]      FIG. 37  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 33 ; 
           [0114]      FIG. 38A  is an exploded lateral view of spine and an alternative embodiment of the invention related to that shown in  FIG. 12A ; 
           [0115]      FIG. 38B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 38A ; 
           [0116]      FIG. 38C  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 38B ; 
           [0117]      FIG. 39A  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 38C ; 
           [0118]      FIG. 39B  is a dorsal view of the embodiment of the invention shown in  FIG. 39A ; 
           [0119]      FIG. 40A  is a dorsal view of an alternative embodiment of the device related to that shown in  FIG. 39A ; 
           [0120]      FIG. 40B  is a dorsal view of the embodiment of the invention shown in  FIG. 40A ; 
           [0121]      FIG. 40C  is a lateral view of the spine and the embodiment of the device shown in  FIG. 40B ; 
           [0122]      FIG. 41A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0123]      FIG. 41B  is a lateral view of the embodiment of the device shown in  FIG. 41A ; 
           [0124]      FIG. 41C  is a dorsal view of the embodiment of the invention shown in  FIG. 41B ; 
           [0125]      FIG. 42  is an oblique view of an alternative embodiment of the invention related to that shown in  FIG. 41C ; 
           [0126]      FIG. 43A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 41A ; 
           [0127]      FIG. 43B  is an oblique view of the device shown in  FIG. 43B ; 
           [0128]      FIG. 44A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 43A ; 
           [0129]      FIG. 44B  is an oblique view of the invention shown in  FIG. 44A ; 
           [0130]      FIG. 45  is an oblique view of an alternative embodiment of the invention related to that shown in  FIG. 44B ; 
           [0131]      FIG. 46  is an oblique view of an alternative embodiment of the invention related to that shown in  FIG. 45 ; 
           [0132]      FIG. 47A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 46 ; 
           [0133]      FIG. 47B  is an oblique view of the embodiment of the invention shown in  FIG. 47A ; 
           [0134]      FIG. 48A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 47A ; 
           [0135]      FIG. 48B  is an oblique view of the embodiment of the invention shown in  FIG. 48A ; 
           [0136]      FIG. 49A  is lateral view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0137]      FIG. 49B  is an exploded lateral view of the embodiment of the device shown in  FIG. 49A ; 
           [0138]      FIG. 49C  is a lateral view of an alternative embodiment of the invention related to that shown in  FIG. 49A ; 
           [0139]      FIG. 50A  is lateral view of an alternative embodiment of the device related to that shown in  FIG. 49C ; 
           [0140]      FIG. 50B  is a dorsal view of the embodiment of the invention shown in  FIG. 50A ; 
           [0141]      FIG. 50C  is an oblique view of bones shaped to be connected in an alternative method according to the invention; 
           [0142]      FIG. 50D  is a lateral view of an alternative embodiment of the device related to that shown in  FIG. 49C ; 
           [0143]      FIG. 51A  is an oblique view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0144]      FIG. 51B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 51A ; 
           [0145]      FIG. 51C  is a caudal view of the embodiment of the device shown in  FIG. 51A ; 
           [0146]      FIG. 52  is dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 51B ; 
           [0147]      FIG. 53  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 52 ; 
           [0148]      FIG. 54A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 53 ; 
           [0149]      FIG. 54B  is a dorsal view of the spine and the device shown in  FIG. 54A ; 
           [0150]      FIG. 55  is a dorsal view of the spine and an alternative embodiment of the device shown in  FIG. 54B ; 
           [0151]      FIG. 56A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0152]      FIG. 56B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 56A ; 
           [0153]      FIG. 57  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 56A ; 
           [0154]      FIG. 58  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0155]      FIG. 59  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10A ; 
           [0156]      FIG. 60A  is a lateral view of the spine and an exploded lateral view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0157]      FIG. 60B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 60A ; 
           [0158]      FIG. 61  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0159]      FIG. 62A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10C ; 
           [0160]      FIG. 62B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 62A ; 
           [0161]      FIG. 63A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 62A ; 
           [0162]      FIG. 63B  is a lateral view of the spine and the embodiment of the device shown in  FIG. 63A ; 
           [0163]      FIG. 64A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 63B ; 
           [0164]      FIG. 64B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 64A ; 
           [0165]      FIG. 65A  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0166]      FIG. 65B  is a dorsal view of the embodiment of the device shown in  FIG. 65A ; 
           [0167]      FIG. 66A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 41A ; 
           [0168]      FIG. 66B  is an oblique view of the device shown in  FIG. 66A ; 
           [0169]      FIG. 67  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0170]      FIG. 68  is a lateral view of the spine and an alternative embodiment of the device related to that shown in  FIG. 12A ; 
           [0171]      FIG. 69A  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0172]      FIG. 69B  is a dorsal view of the device shown in  FIG. 69A ; 
           [0173]      FIG. 70A  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 69A ; 
           [0174]      FIG. 70B  is a dorsal view of the device shown in  FIG. 70A ; 
           [0175]      FIG. 71  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 45 ; 
           [0176]      FIG. 72A  is lateral view of a knife-like instrument; 
           [0177]      FIG. 72B  is a lateral view of the spine and the cutting tool shown in  FIG. 72A ; 
           [0178]      FIG. 73A  is a lateral view of a tool used to distract the spinous processes; 
           [0179]      FIG. 73B  is a view of the one end of the distracting tool shown in  FIG. 73A ; 
           [0180]      FIG. 73C  is a lateral view of the tool shown in  FIG. 72A ; 
           [0181]      FIG. 73D  is a view of the dorsal aspect of two adjacent spinous processes and the end of the tool shown in  FIG. 73C ; 
           [0182]      FIG. 73E  is a dorsal view of two adjacent spinous processes and the tips of the tool shown in  FIG. 73D ; 
           [0183]      FIG. 74A  is a lateral view of a measuring tool; 
           [0184]      FIG. 74B  is a view of a gauge that may be used on the handle of the instrument shown in  FIG. 74A ; 
           [0185]      FIG. 75  is an oblique view of a sleeve; 
           [0186]      FIG. 76A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 12A ; 
           [0187]      FIG. 76B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 76A ; 
           [0188]      FIG. 77A  is a lateral view of the tip of an instrument; 
           [0189]      FIG. 77B  is a lateral view of the tip of the instrument shown in  FIG. 77A ; 
           [0190]      FIG. 77C  is a lateral view of the tip of the tool shown in  FIG. 77A  and a device according to the invention; 
           [0191]      FIG. 78A  is a lateral view of the tip of a distractor tool; 
           [0192]      FIG. 78B  is a dorsal view of the tips of two spinous processes and the tip of the distractor tool shown in  FIG. 78A ; 
           [0193]      FIG. 79A  is a dorsal view of the tip of a spinous process, a cross-section of a tool, and a cable; 
           [0194]      FIG. 79B  is a dorsal view of the tip of a spinous process, the cross-section of the tool shown in  FIG. 79A  and a cable; 
           [0195]      FIG. 80A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A ; 
           [0196]      FIG. 80B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 80A ; 
           [0197]      FIG. 80C  is a cranial view of the embodiment of the invention shown in  FIG. 80A ; 
           [0198]      FIG. 81  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 80A ; 
           [0199]      FIG. 82  is a caudal view including an alternative embodiment of the invention related to that shown in  FIG. 81 ; 
           [0200]      FIG. 83  is a caudal view including an alternative embodiment of the invention related to that shown in  FIG. 82 ; 
           [0201]      FIG. 84  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 37 ; 
           [0202]      FIG. 85  is a dorsal view of the spine and an alternative embodiment of the invention shown in  FIG. 80A ; 
           [0203]      FIG. 86  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 85 ; 
           [0204]      FIG. 87A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 85 ; 
           [0205]      FIG. 87B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 87A ; 
           [0206]      FIG. 88A  is a lateral view of the spine an alternative embodiment of the invention related to that shown in  FIG. 20A ; 
           [0207]      FIG. 88B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 88A ; 
           [0208]      FIG. 89A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 88A ; 
           [0209]      FIG. 89B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 89A   
           [0210]      FIG. 90A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 10A ; 
           [0211]      FIG. 90B  is a lateral view of the assembled device shown in  FIG. 90A ; 
           [0212]      FIG. 90C  is an anterior view of the assembled device shown in  FIG. 90B ; 
           [0213]      FIG. 90D  is coronal cross section of the assembled device shown in  FIG. 90C ; 
           [0214]      FIG. 91A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A ; 
           [0215]      FIG. 91B  is a coronal cross-section of the spine and the embodiment of the device shown in  FIG. 91A ; 
           [0216]      FIG. 92A  is an oblique view of a shim-like device; 
           [0217]      FIG. 92B  is an exploded lateral view of the spine, shims, and an alternative embodiment of the invention related to that shown in  FIG. 89A ; 
           [0218]      FIG. 92C  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 92B ; 
           [0219]      FIG. 93A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 61 ; 
           [0220]      FIG. 93B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 93A ; 
           [0221]      FIG. 93C  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 93B ; 
           [0222]      FIG. 94A  is a view of the cranial side of the embodiment of the invention shown  FIG. 10A  and a novel insertion tool; 
           [0223]      FIG. 94B  is a side view of the embodiment of the invention shown in  FIG. 94A ; 
           [0224]      FIG. 94C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 94B ; 
           [0225]      FIG. 94D  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 94C ; 
           [0226]      FIG. 94E  is an exploded lateral view of the spine and the embodiment of the invention shown in  FIG. 94D ; 
           [0227]      FIG. 94F  is an exploded view of the caudal end of a vertebra, and the embodiment of the tool shown in  FIG. 94E ; 
           [0228]      FIG. 94G  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 94F ; 
           [0229]      FIG. 94H  is a cross section of the embodiment of the invention shown in  FIG. 94A ; 
           [0230]      FIG. 95A  is a lateral view of the spine, the embodiment of the SPS shown in  FIG. 10A , and a second impactor tool; 
           [0231]      FIG. 95B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 95A ; 
           [0232]      FIG. 95C  is a lateral view of the tool shown in  FIG. 95A ; 
           [0233]      FIG. 95D  is a view of the cranial side of the tool shown in  FIG. 95C ; 
           [0234]      FIG. 96A  is a cranial view of an alternative embodiment of the invention related to that shown in  FIG. 94A ; 
           [0235]      FIG. 96B  is a lateral view of the embodiment of the invention shown in  FIG. 96B ; 
           [0236]      FIG. 97A  is a lateral view of an alternative embodiment of the invention related to that shown in  FIG. 73A ; 
           [0237]      FIG. 97B  is an exploded cranial view of the embodiment of the invention shown in  FIG. 97A ; 
           [0238]      FIG. 97C  is an oblique view of the embodiment of the invention shown in  FIG. 97A  and one arm of a McCulloch retractor; 
           [0239]      FIG. 98A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 20A ; 
           [0240]      FIG. 98B  is an oblique view of an assembled device of the embodiment shown in  FIG. 98A ; and 
           [0241]      FIG. 98C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 98A . 
           [0242]      FIG. 99A  is a dorsal view of the spine and an alternative embodiment of the invention including rods that connect components placed between spinous processes; 
           [0243]      FIG. 99B  is an exploded dorsal view of the embodiment of the invention drawn in  FIG. 99B ; 
           [0244]      FIG. 99C  is a lateral view of the spine and the embodiment of the invention drawn in  FIG. 99B ; 
           [0245]      FIG. 100A  is an oblique view of an alternative embodiment of the invention related to that drawn in  FIG. 97A ; 
           [0246]      FIG. 100B  is a dorsal view of the embodiment of the invention drawn in  FIG. 100A ; 
           [0247]      FIG. 100C  is a lateral view of the embodiment of the device drawn in  FIG. 100B ; 
           [0248]      FIG. 101A  is a coronal cross section of an alternative embodiment of the invention drawn in  FIG. 93B ; 
           [0249]      FIG. 101B  is sagittal cross section of the embodiment of the device drawn in  FIG. 101A ; and 
           [0250]      FIG. 101C  is a lateral view of the spine and the embodiment of the device drawn in  FIG. 101A . 
       
    
    
     SUMMARY OF THE INVENTION 
       [0251]    This invention is directed to surgical apparatus for treating spinal stenosis, without the need for laminectomy. Broadly the invention resides in a device configured for placement posteriorly to a spinal canal between vertebral bodies to distract the spine and enlarge the spinal canal. In the preferred embodiments the device permits spinal flexion while limiting spinal extension, thereby providing an effective treatment for treating spinal stenosis. The invention may be used in the cervical, thoracic, or lumbar spine. 
         [0252]    Numerous embodiments are disclosed, including elongated, length-adjustable components coupled to adjacent vertebral bodies using pedicle screws. The preferred embodiments, however, teach a device configured for placement between adjacent vertebrae and adapted to fuse to the lamina, facet, spinous process or other posterior elements of a single vertebra. Various mechanisms, including shape, porosity, tethers, and bone-growth promoting substances may be used to enhance fusion. The tether may be a wire, cable, suture, allograft tissue, or other single or multi-filament member. Preferably, the device forms a pseudo-joint in conjunction with the non-fused vertebra. Alternatively, the device could be fused to the caudal vertebra or both the cranial and caudal vertebrae. 
         [0253]    In certain embodiments at least a portion of the device is constructed from bone. For example, the device may be constructed from the shaft of the clavicle, rib, humerus, radius, ulna, metacarpal, phalanx, femur, tibia, fibula, or metatarsal bone. The device includes a slot or indent to receive a portion of a spinous process or other vertebral feature to enhance fusion. The device may contain one or more bone-growth promoting substances such as BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 . . . n, demineralized bone matrix, allograft cancellous bone, autograft bone, hydroxy appetite, coral or other highly porous substance. 
         [0254]    An elastic, synthetic ligament or allograft ligament may me provided as part of the invention. The device may be configured to surround or clamp to a single spinous process, or include optional projections extending along the sides of a spinous process. The device may include spring-like or shape-memory properties. The device may have an asymmetric cross section or other shape to wedge or distract the spinous processes upon insertion. The may include a generally V-, U-, or C-shaped device configured to fit between the lamina of one vertebra and the spinous process and or lamina of an adjacent vertebra, and my be customized at the time of surgery. 
         [0255]    The devices according to this invention may be made of any suitable material, including titanium, chrome-cobalt, stainless steel, polymers, liquid metals, shape-memory materials, ceramics, or human tissue. The device may be made of an in-situ curing material. The device could be customized to fit between the spinous processes. Bone or bone-growth material could be added top the device after the device cures. 
         [0256]    Devices according to the invention may be constructed of bone, including allograft bone, PEEK (polyaryletherketone), or ceramic. Devices according to the invention may also me made of other biocompatible materials such as Polyphenolsulfone, Polysulfone, Acetal (Delrin), UHMW Polyethylene, and composites of these materials and carbon fibers. Alternative materials include bioresorbable materials such as polylactic acid (PLA), polyglycolic acid (PGA), poly (ortho esters), poly(glycolide-co-trimethylene carbonate), poly-L-lactide-co-6-caprolactone, polyanhydrides, poly-n-dioxanone, and poly(PHB-hydroxyvaleric acid). 
         [0257]    Certain devices according to the invention are designed to withstand loads of at least 90 N, and are preferably provided in a number of sizes. For example, the cranial-to-caudal dimensions could vary from 6 mm-24 mm in 2 mm increments. The ventral-to-dorsal dimensions could also vary from 6 mm-24 mm, also in 2 mm increments. The left-to-right dimensions could vary from 10-50 mm, again in 2 mm increments. Multi-level devices, similar to the embodiment shown in  FIG. 35D  would be supplied in larger dimensions. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0258]      FIG. 1A  is a lateral view of a three-component device used to treat spinal stenosis, drawn in its extended position. The central rod component  102  is threaded  104 ,  106  on both ends. One end of the component has left-handed threads. The other end of the rod component has right-handed threads. Bolt-like components  108 ,  110  are threaded onto the ends of the rod component. As discussed in further detail below, the rod component is coupled to pedicle screws then adjusted to force the screws apart. This permits spinal flexion, but limits spinal extension, thereby distracting the spine and enlarging the spinal canal. 
         [0259]      FIG. 1B  is a lateral view of the device of  FIG. 1A  drawn in its contracted position. Tools are used to prevent rotation of the end components. A wrench may be used to rotate the rod component placed on flats  112 . Rotating the rod component, while preventing rotation of the end components, causes the end components to advance along the treaded portions of the rod, simultaneously. 
         [0260]      FIG. 1C  is an end view of a vertebral screw  120  and a cross section of the threaded portion  104  of the rod, which passes through an opening  122  in the screw.  FIG. 1D  is an end view of the screw drawn in  FIG. 1C  and a cross section of the threaded end component  110  drawn in  FIG. 1A . The larger diameter of the end component prevents the component from passing through the opening in the screw. 
         [0261]      FIG. 1E  is an end view of an alternative embodiment of a screw having a mechanism  130  that permits a connector ring  132  to swivel about a shaft  134  of the screw. 
         [0262]      FIG. 1F  is a lateral view of the device drawn in  FIG. 1A  and the screws of the embodiment drawn in  FIG. 1C . The device is drawn in its extended position. The narrow diameters of the treaded portions of the rod component permit the device to be inserted through the openings in the screws.  FIG. 1G  is a lateral view of the embodiment of the device drawn in  FIG. 1F . The rod-like device has been inserted into the screws.  FIG. 1H  is a lateral view of the device drawn in  FIG. 1G . The device is drawn in its contracted position. Rotation of the rod-like component advances the end bolt-like components into the screws. The large diameter of the end components prevents the tightened rod component from passing through the slot-like openings in the screws. 
         [0263]      FIG. 1I  is a sagittal cross section of the device drawn in  FIG. 1H . The hemispherical ends  140 ,  142  of the rod component  102  articulate with the donut-like opening of the screws. The drawing illustrates the spherical cross section of the connector portion of the screws. The cooperation between the rod component and the screws prevent the heads of the screws from approaching one another. The enlargements at the ends of the assembled device may also be used to limit spinal flexion. The devices according to this invention may be made of any suitable material, including titanium, chrome-cobalt, stainless steel, polymers, liquid metals, shape-memory materials, ceramics, or human tissue. The device may also include a spring component. For example, a coil spring could be placed around the rod component. 
         [0264]    The following disclosure describes how the device may be used to enlarge the spinal canal. The screws are placed into the pedicles of adjacent vertebrae, or into vertebrae spaced apart by at least one intermediate vertebra. The rod component is installed, and the enlargements at the ends of the bolt-like end components prevent the assembled rod from dissociating from the screws. A rod component of the appropriate length is selected to force the screws apart. This distracts the spine and enlarges the spinal canal as the heads of the screws separate. The circular openings in the screws enable the screws to slide along the end components. This permits spinal flexion, but limits spinal extension, which enlarges the spinal canal. Spinal flexion occurs as the screws advance along the end components. Spinal extension decreases the diameter of the spinal canal and decreases the size of the neuroforamina. 
         [0265]      FIG. 2A  is a lateral view of an alternative embodiment of the invention which has two rod-like components  202 ,  204 . The rod components have a turnbuckle to allow lengthening and shortening of the rods. Each turnbuckle further includes a nut  206 ,  208  that permits the rod to be locked in a particular length. One end of the rod component is shaped somewhat like the end component drawn in  FIG. 1F . The rods are connected to one another by a cable  210 . 
         [0266]      FIG. 2B  is an exploded view of the device drawn in  FIG. 2A  and an alternative embodiment of the vertebral screws, each using a ring-like closure mechanism  220 ,  222 ,  224 .  FIG. 2C  is a lateral view of the device drawn in  FIG. 2B . The device has been drawn in an assembled configuration.  FIG. 2D  is an exploded end view of the screw  219  and a fastening component  220 . 
         [0267]      FIG. 2E  is end view of the screw and fastening component drawn in  FIG. 2D  and a cross section of the rod-like device drawn in  FIG. 2C . The fastening component may be made of a shape memory material. Alternatively, the fastening component may be made of an elastic material that is stretched prior to inserting the component. The fastening ring contracts after it is placed over the head of the screw. 
         [0268]      FIG. 3A  is a lateral view of an alternative embodiment of the invention, wherein the rod-like components are connected by a hinge joint  302 .  FIG. 3B  is a lateral view of the embodiment of the device drawn in  FIG. 3A . The rods are drawn in a different position than drawn in  FIG. 3A .  FIG. 3C  is a view of the top of the device drawn in  FIG. 3B .  FIG. 3D  is an enlarged view of the top of the hinge joint drawn in  FIG. 3C . 
         [0269]      FIG. 3E  is an enlarged view of the top of an alternative hinge joint  310  oriented in a direction  312  that is not perpendicular to the axis  314  of the rod components.  FIG. 3F  is a lateral view of the device drawn in  FIG. 3B  and vertebral screws  320 ,  322 ,  324 . 
         [0270]      FIG. 4A  is an exploded lateral view of an alternative vertebral screw and a hinged device that passes through an angled slot  402  in the screw when the rods  404 ,  406  are angled properly.  FIG. 4B  is a lateral view of the device with the rods area angled to pass the rods through the slot in the screw.  FIG. 4C  is a lateral view of the device with the rods oriented such that they will not pass through the slot in the screw. 
         [0271]      FIG. 5A  is a lateral view of an alternative embodiment wherein rod-like components  502 ,  504  are threaded over an elastic cord  506 . The end components  508 ,  510  are connected to the elastic cord. The device is drawn in its extended position. The elastic cord is stretched in the extended position.  FIG. 5B  is a lateral view of the device drawn in its contracted position.  FIG. 5C  is an exploded view of the device drawn in  FIG. 5A  and vertebral screws  512 ,  514 ,  516 . The elastic cord passes through the slots in the vertebral screws.  FIG. 5D  is a lateral view of the assembled device drawn in  FIG. 5C . 
         [0272]      FIG. 6A  is an oblique view of an alternative embodiment of the invention in the form of a cylindrical device  602  having two slots  604 ,  606  in sides of the device. The ends of the tube shaped device may by open.  FIG. 6B  is a lateral view of a portion of the spine. The supraspinous ligament  610  is attached to the dorsal surface of the spinous processes  612 ,  614  of two consecutive vertebrae. The interspinous ligament  620  courses between the spinous processes of the vertebrae. The intervertebral disc is depicted at  622  and the neuroforamina at  624 . 
         [0273]      FIG. 6C  is a lateral view of a portion of the spine and the device of  FIG. 6A , which has been wedged between the spinous processes. The supraspinous and interspinous ligaments have been removed. The device forces the spinous processes apart. The spine flexes as the spinous processes are forced apart. The neuroforamina and the spinal canal are enlarged as the spine is flexed. The device holds the vertebrae in a flexed position. The device may be made of any suitable materials, including bone, metals, ceramics, or polymers. For example, the device may be made from an allograft shaft of a long bone such as the humerus, tibia, fibula, radius, ulna, or femur. Alternatively, the device may be made of material known as PEEK. 
         [0274]      FIG. 6D  is a lateral view of a portion of the spine and the device drawn in  FIG. 6A . The device has been filled with a material that promotes bone growth. For example, the device may be filled with bone, BMP soaked collagen sponges, or demineralized bone matrix. The device may fuse with one or both of the spinous processes. The device does not fuse with other portions of the vertebrae. For example, the device does not fuse across to the lamina of the vertebrae. The lamina of the vertebrae remain their normal size and shape. The lack of fusion across the lamina facilitates future surgical “decompression” procedures. The interspinous has been reconstructed. The area of the drawing at  630  represents the reconstructed interspinous ligament. Allograft tendon may be used to reconstruct the interspinous ligament. Other materials such as Gortex, Dacron, Marlex or other non-absorbable material may be used to reconstruct the interspinous ligament. 
         [0275]      FIG. 6E  is an oblique view of a cancellous bone block  640  which may be placed into the device drawn of  FIG. 5A .  FIG. 6F  is an oblique view of a section of the shaft  642  of a long bone.  FIG. 6G  is an oblique view of a section of the shaft of a long bone and a cancellous bone block. The cancellous bone block has been placed into the cortical bone ring.  FIG. 6H  is an oblique view showing two slots machined into the sides of the cortical bone ring. As with the embodiment of  FIG. 6A , the slots are shaped to fit over at least a portion of the spinous processes. 
         [0276]      FIG. 6I  is lateral view of a portion of the spine and a sagittal cross section of the embodiment of the device drawn in  FIG. 6A  or  6 H. The dotted lines represent the outline of the cortical ring. The drawing illustrates holes  660 ,  662  in the spinous processes receive an allograft tendon. Allograft tissue could also be wrapped around the cranial aspect of the cranial spinous process and the caudal aspect of the caudal spinous process. 
         [0277]      FIG. 7A  is an oblique view of a portion of a shaft of a long bone.  FIG. 7B  is an oblique view of portion of a shaft of a long bone that has been machined to fit between two spinous processes. The bone has been machined to insert the device at an orientation ninety degrees to the orientation drawn in  FIG. 6I .  FIG. 7C  is a lateral view of the spine and the device of  FIG. 7B  which has been inserted between the spinous processes. 
         [0278]      FIG. 7D  is an oblique view of a piece of bone with teeth machined or otherwise formed to facilitate insertion in a first direction and resist extrusion in a direction 180 degrees from the first direction.  FIG. 7E  is an end view of the device drawn in  FIG. 7A  and the bone drawn in  FIG. 7D  which has been inserted into the device drawn in  FIG. 7B . The bone of  FIG. 7D  may be fastened to the device of  FIG. 7B . 
         [0279]      FIG. 7F  is a lateral view of a portion of the spine and a sagittal cross section of the embodiment of the device drawn in  FIG. 7E . The dotted lines represent the outline of the periphery of the device. 
         [0280]      FIG. 8A  is an end view of an alternative shape of the device drawn in  FIG. 7B .  FIG. 8B  is an end view of an alternative shape of the device drawn in  FIG. 8A .  FIG. 8C  is an end view of an alternative shape of the device drawn in  FIG. 8B . Alternative shapes are possible, including solid forms. 
         [0281]      FIG. 9A  is an oblique view of an alternative embodiment of the invention which has a single slot  902  on one side of the device  900 .  FIG. 9B  is a view of the top of the embodiment of the invention drawn in  FIG. 8A .  FIG. 9C  is a lateral view of a portion of the spine and the embodiment of the invention drawn in  FIG. 9A . The device straddles a single spinous process  920 . This embodiment of the device is designed to fuse to a single spinous process. Fusion to a single spinous process allows spinal flexion, but limits spinal extension. The invention anticipates embodiments of the device that do not fuse to either spinous process. 
         [0282]      FIG. 10A  is an oblique drawing of an alternative embodiment of the invention related to that shown in  FIG. 6A . The device has chambers  1002 ,  1004  in the left and right sides of the cranial portion which may be filled with a material that promotes the growth of bone into the device. One or more openings may connect the two chambers. The cranial end of the device also has openings that extend into the chambers. The openings provide a path for cells to migrate into the chambers. 
         [0283]    The device has a notch  1010  on its cranial side which may or may not have teeth. The notch accommodates the Spinous Process (SP) of the cranial vertebra. The caudal end  1012  of the device preferably includes a concavity. As with the embodiment of  FIG. 6C , the device may be made of bone including allograft bone, metal such as titanium, PEEK (polyaryletherketone), or ceramic. Devices according to the invention may also me made of other biocompatible materials such as Polyphenolsulfone, Polysulfone, Acetal (Delrin), UHMW Polyethylene, and composites of these materials and carbon fibers. Alternative materials include bioresorbable materials such as polylactic acid (PLA), polyglycolic acid (PGA), poly (ortho esters), poly(glycolide-co-trimethylene carbonate), poly-L-lactide-co-6-caprolactone, polyanhydrides, poly-n-dioxanone, and poly(PHB-hydroxyvaleric acid). 
         [0284]    Devices according to the invention are designed to withstand loads of at least 90 N, and are preferably provided in a number of sizes. For example, the cranial-to-caudal dimensions could vary from 6 mm-24 mm in 2 mm increments. The ventral-to-dorsal dimensions could also vary from 6 mm-24 mm, also in 2 mm increments. The left-to-right dimensions could vary from 10-50 mm, again in 2 mm increments. Multi-level devices, similar to the embodiment shown in  FIG. 35D  would be supplied in larger dimensions. 
         [0285]      FIG. 10B  is a lateral view of a portion of the spine and the embodiment of the invention shown in  FIG. 10A . The device fits between the SP of two adjacent vertebrae  1020 ,  1022 . The device distracts the spinous processes  1024 ,  1026 . The device also causes relative flexion of the spine at the area of the spine treated with the device. The device has been filled with a bone growth promoting substance  1030 . The bone growth material has also been applied to the lamina  1032  of the cranial vertebra  1020 . A portion of the lamina of the cranial vertebra has been decorticated to facilitate migration of cells from the patient&#39;s bone to the bone growth material. The device is designed to fuse to the cranial vertebra. The lack of bone growth material at the caudal end of the device inhibits fusion to the caudal vertebra. 
         [0286]      FIG. 10C  is a dorsal view of a portion of the spine and the embodiment of the invention shown in  FIG. 10A . The SP  1026  of the caudal vertebra  1022  fits into the concavity  1012  on the caudal end of the device. The SP  1024  of the cranial vertebra  1020  fits into the notch  1010  on the cranial end of the device. Bone growth material  1032  is shown in the cranial aspect of the device and the lamina, SP, and facets of the cranial vertebra. 
         [0287]      FIG. 10D  is a sagittal cross section of the embodiment of the invention shown in  FIG. 10B  and a lateral view of the spine. The bone growth material  1032  can be seen extending from the lamina and SP of the cranial vertebra into one of the chambers in the device. The bone growth material extends through the slots in the cranial aspect of the device and through the openings on the left and the right sides of the device. 
         [0288]      FIG. 10E  is a sagittal cross section of the embodiment of the invention shown in  FIG. 10D  and a lateral view of the spine. The spine has been flexed. A gap  1040  can be seen between the SP of the caudal vertebra and the caudal end of the device. 
         [0289]      FIG. 10F  is a coronal cross section of the embodiment of the invention shown in  FIG. 10E  and the spine. The device is seated between the spinous processes of the cranial and caudal vertebrae. The chambers that house the bone growth material can be seen on the left and right sides of the device. Bone growth material  1032  can be seen passing through the slots on the cranial aspect of the device. An opening could connect the chambers in the left and the right sides of the device. 
         [0290]      FIG. 11A  is a dorsal view of the embodiment of the invention shown in  FIG. 10F  and the spine.  FIG. 11B  is a dorsal view of the embodiment of the invention shown in  FIG. 11A  and the spine. The spine has been flexed beyond the flexion caused by the device. A gap  1040  forms between the device and the caudal SP. The device is fused to the cranial vertebra. Alternatively, the device could be fused to the caudal vertebra or both the cranial and caudal vertebrae. 
         [0291]      FIG. 12A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 10A . The device has been connected to the SP of the cranial vertebra. A cable, strap, cable tie, wire, cord, suture or other member  1202  has been wrapped around the base or waist of the SP. Second and third strap members  1204 ,  1206  pass between the SP and the loop around the SP. The second and third strap members are looped through holes  1208 ,  1210  on the left and right sides of the cranial aspect of the device. The device is forced into the SP, lamina, and/or facet joints of the cranial vertebra. The strapping method prevents migration of the device. The strapping method also prevents or restricts movement between the device and the cranial vertebrae. Reducing movement between the device and the cranial vertebra facilitates fusion to the cranial vertebra. The caudal end of embodiments of the device that are made of allograft bone could be treated to discourage fusion between the device and the caudal vertebra. For example, bone wax could be applied to the caudal end of the allograft device. Alternatively, the caudal end of the device could be covered with an allograft soft tissue, such as fascia, to inhibit bone growth to the device. Synthetic materials could also be used to inhibit bone growth to a portion of the device. 
         [0292]      FIG. 12B  is a dorsal view of the embodiment of the invention shown in  FIG. 12A  and the spine. A cable  1202  has been wrapped around the SP  1224  of the cranial vertebra. The second and third cables  1204 ,  1206  can be seen passing through the left and right sides of the device. The second and third cables also pass between the SP and the first cable. The cable that is looped around the SP of the cranial vertebra is preferably passed between the interspinous ligament and the cranial aspect of the SP. 
         [0293]      FIG. 12C  is a lateral view of the spine and the embodiment of the invention wherein a fourth cable, strap, cable tie, wire, cord, suture or other member  1242  has been passed around the SP  1224  of the cranial vertebra and through the device. The fastening devices are preferably made of non-absorbable material. Alternatively, fastening member  1242  could pass through a set of holes in the ventral portion of the device. 
         [0294]      FIG. 12D  is a lateral view of the spine and an embodiment of the invention wherein a fourth member  1252  has been passed around the SP  1226  of the caudal vertebra and through the device. The fourth cable may be tightly tied or loosely tied to permit movement between the caudal vertebra and the device. 
         [0295]      FIG. 13A  is a lateral view of the spine and an embodiment of the invention wherein a screw, nail, or pin  1302  has been passed through the SP  1326  of the caudal vertebra. A member  1304  has been passed through the device and around the SP  1326  of the caudal vertebra. The cable and the pin prevent migration of the device. The cable and the pin also prevent or restrict movement between the device and the caudal vertebra. The device and the fastening method are designed to fuse the device to only the caudal vertebra. The caudal aspect of the device has holes that extend from the lamina and SP of the caudal vertebra to the chambers inside the device. Bone growth material is placed into the device and over the caudal vertebra. The lamina and/or the SP of the caudal vertebra could be decorticated to promote fusion.  FIG. 13B  is a dorsal view of the embodiment of the invention shown in  FIG. 13A  and the spine. 
         [0296]      FIG. 14A  is a lateral view of the spine and an alternative embodiment of the invention wherein screws  1402 ,  1404  pass through the caudal aspect of the device. A screw, pin, or nail  1406  also passes through the SP  1426  of the caudal vertebra. Note that transverse pin  1406  passes dorsal to one of the screws and ventral to the other screw.  FIG. 14B  is a dorsal view of the embodiment of the invention shown in  FIG. 14A  and the spine. 
         [0297]      FIG. 14C  is a dorsal view of the spine and an embodiment of the invention wherein optional cables, sutures, wires, cable ties or like members  1420 ,  1422  have been wrapped around the screws and the pin. Bone growth material has been placed over the caudal aspect of the device and the SP and lamina of the caudal vertebra. 
         [0298]      FIG. 14D  is a dorsal view of the spine and an alternative embodiment of the invention wherein crossing screws  1420 ,  1432  pass through the device. 
         [0299]      FIG. 15  is a lateral view of the spine showing an alternative method is used to fasten a device according to the invention to the cranial vertebra. A wire, cable, suture, or other single or multi-filament member  1502  is passed through the device and around or through screws  1504  placed into the pedicles of the cranial vertebra. 
         [0300]      FIG. 16  is a dorsal view of the spine showing an alternative method used to fasten a device according to the invention to the cranial vertebra. A wire, cable, suture, or other single or multi-filament member  1602  is passed through the device and around the transverse processes  1620 ,  1622  of the cranial vertebra. 
         [0301]      FIG. 17  is a dorsal view of the spine showing an alternative method used to fasten a device according to the invention to the cranial vertebra. A screw  1702  is passed through the device and through the cranial SP  1724 . Alternatively, screws could be passed through the SP and the left and right sides of the device. The left and right sides of the device are preferably tapered. 
         [0302]      FIG. 18  is a lateral view of the spine illustrating an alternative method used to fasten a device according to the invention to the cranial vertebra. Member  1802  passes through the left and right sides of the device. The member also passes around the lamina of the cranial vertebra. 
         [0303]      FIG. 19  is a lateral view of the spine showing an alternative method used to fasten a device according to the invention to the cranial vertebra. Members  1902 ,  1904  pass through the left and right sides of the device. The members also pass around the cranial vertebra just cranial to the inferior facet joints  1920 . 
         [0304]      FIG. 20A  is a dorsal view of the spine and an alternative embodiment of the invention including a device  2002  that surrounds the SP of the cranial vertebra. The device impinges against the cranial aspect of the caudal vertebra. The device may be held in place by a pin  2004  that passes through the SP  2024  of the cranial vertebra.  FIG. 20B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 20A . The device is preferably designed to fuse to the cranial vertebra. 
         [0305]      FIG. 21A  is a dorsal view of the spine and an alternative embodiment of the invention  2102  which clamps to the cranial aspect of the SP of the caudal vertebra  2126 . The device may also clamp to the cranial vertebra  2124 , or both the caudal and cranial. The device may have spring properties that clamp the device to the SP. Alternatively, the device could be made of a shape memory material such as a Nitinol. The device could contract as it reacts to temperature change.  FIG. 21B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 21A . The device was shown in its clamped or contracted shape. 
         [0306]      FIG. 22  is a lateral view of the spine and an alternative embodiment of the invention  2202  attached to the SP  2226  of the caudal vertebra. A hinge joint  2204  connects the fastener to the portion of the device that contains the bone growth material. A screw  2206  passes through the fastener component and the SP. 
         [0307]      FIG. 23A  is a lateral view of the spine and an alternative embodiment of the invention  2302  attached to the SP  2326  of the caudal vertebra. The device has a component  2306  that houses the bone growth material and a fastening component  2308 .  FIG. 23B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 23A . A hook  2310  from the fastening component is placed over the caudal aspect of the SP of the caudal vertebra. The fastening component may be connected to the component that contains the bone growth material via a ratchet mechanism. The ratchet mechanism locks the components after the components are compressed together. 
         [0308]      FIG. 24A  is an exploded dorsal view of the spine and an alternative embodiment of the invention including a spring-like clip  2402  that connects the device to the SP of the vertebra.  FIG. 24B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 24A . The spring-like component has been connected to the component  2406  that houses the bone growth material. 
         [0309]      FIG. 25A  is a lateral view of the spine and an alternative embodiment of the invention having projections  2502 ,  2504  that extend from the left and right sides of the cranial portion of the device. The projections have concavities that may receive bone growth promoting substances. The projections lie over the lamina of the cranial vertebra. The lamina may be decorticated to facilitate fusion between the device and the cranial vertebra.  FIG. 25B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 25A . 
         [0310]      FIG. 26A  is a lateral view of the spine and an alternative embodiment of the invention which has projections  2602 ,  2604  that extend from the left and right sides of the cranial portion of the device. Bone growth promoting substance has been packed around the projections. The projections have bristles that help hold the bone growth material.  FIG. 26B  is dorsal view of the spine and the embodiment of the invention shown in  FIG. 26A .  FIG. 26C  is a sagittal cross section of an alternative embodiment of the invention shown in  FIG. 26B . The projections  2602 / 4  swivel in holes on the cranial portion of the device. 
         [0311]      FIG. 27A  is a lateral view of an alternative embodiment of the invention, wherein projections  2702 ,  2704  from the cranial aspect of the device are connected to the component  2706  that houses the bone growth material via hinge joints.  FIG. 27B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 27A . The projections are preferably perforated to promote bone growth for a firmer attachment. Whereas a friction-fit or the use of soft tissues such as ligaments may weaken with time, fusion provides a more permanent attachment mechanism. 
         [0312]      FIG. 28A  is a lateral view of the spine illustrating one method of inserting a device according to the invention, including that shown in  FIG. 10A . The spinous processes  2802 ,  2804  of the cranial and caudal vertebra are distracted as the wedge-shaped device is forced between the spinous processes. In  FIG. 28B  the spinous processes have been distracted by the device. In  FIG. 28C  the device has been rotated 90 degrees. The spinous processes have been further distracted as the device cams open the interspinous space. 
         [0313]      FIG. 29  is a lateral view of the spine along with an embodiment of the invention, such as that shown in  FIG. 12A , including a device  2900  to help prevent extrusion of the spinous process spacer. The accessory device  2902  is strapped at  2904  to the SP of the cranial vertebra. A pin  2906  is placed through the SP dorsal to the strap  2904  of the accessory device  2902 . The accessory device  2902  impinges against the dorsal aspect of the spacer device  2920  if the spacer device  2920  migrates in a dorsal direction. 
         [0314]      FIG. 30  is a view of the caudal aspect of the cranial vertebra shown in  FIG. 28C . The shaded area of the drawing represents possible contact points of the spinous process spacer shown in  FIG. 12A . The spinous process spacer may contact the SP, lamina, and/or inferior facets of the cranial vertebra.  FIG. 31  is a dorsal view of the spine. The shaded areas represent possible contact points of the spinous process spacer (SPS). The areas could be decorticated to promote fusion of the spinous process spacer to either or both vertebrae. 
         [0315]      FIG. 32A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 12A . Spinous process spacers are used to distract two levels of the spine. Three or more spinous process spacers could be used to distract three or more levels of the spine.  FIG. 32B  is a lateral view of the spine and a variation of the embodiment of the invention shown in  FIG. 32A . The caudal aspect of the cranial SPS has a concavity  3202 . The strap  3204  from the caudal SPS  3200  fits in the concavity of the cranial SPS. The concavity avoids impingement of the strap from the caudal SPS between the cranial SPS and the intermediate SP. 
         [0316]      FIG. 32C  is a lateral view of the spine and an alternative, multilevel embodiment of the invention. The cranial strap  3220  from the caudal SPS is passed through an opening in the cranial SPS. The method avoids impingement of the strap from the caudal SPS and the intermediate SP. 
         [0317]      FIG. 33  is a lateral view of the spine and an alternative, multilevel embodiment of the invention wherein SPS devices are connected to the cranial and caudal aspects of the SP of the intermediate vertebra. Both SPS devices  3302 ,  3304  are preferably fused to only the intermediate vertebra  3310 . Cables are passed from the left and right sides of both SPS devices. The cables  3320 ,  3322  from the lateral aspects of the SPSs also pass through a cable  3340  wrapped around the SP of the intermediate vertebra. 
         [0318]      FIG. 34  is a lateral view of the spine and an alternative embodiment of the invention shown in  FIG. 12A . The strap that surrounds the SPS is widened along the cranial aspect of the SP. 
         [0319]      FIG. 35A  is a lateral view of the spine and an alternative, multilevel embodiment of the invention related to that shown in  FIG. 20B . The device distracts two adjacent levels of the spine. Allograft bone embodiments of the device could be treated to prevent fusion to the SP of the cranial and caudal vertebrae. For example, the cranial and caudal aspects of the device could be covered with bone wax, polymer, or other substance that inhibits bone growth to the device. The ends of the device could be constructed of only cortical bone. The center of the device is designed to fuse to the posterior elements of the intermediate vertebra. The center portion of an allograft bone device could include cortical and cancellous bone. Bone-growth-promoting substances could be placed between the device and the posterior elements of the intermediate vertebra. The posterior elements of the intermediate vertebra could be decorticated to facilitate fusion. The posterior elements of the vertebrae caudal and cranial to the device would not be decorticated. 
         [0320]      FIG. 35B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 35A . The device distracts two levels of the spine. The device preferably allows spinal flexion, but limits spinal extension at both levels of the spine. 
         [0321]      FIG. 35C  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 20B . The two-component device is snapped together around a SP. The device may be held together through components  3540 ,  3542  that plastically deform when they area assembled. Alternatively the components could be made of a shape memory material such as Nitinol.  FIG. 35D  is a dorsal view of the spine and a three-level embodiment of the device shown in  FIG. 35B . 
         [0322]      FIG. 36A  is a dorsal, exploded view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 35B . The device has a slot  3602  that accommodates more than one SP.  FIG. 36B  is dorsal view of the spine and the embodiment of the invention shown in  FIG. 36A , wherein a cross member  3604  has been fastened to the device. The cross member  3604  fits between two adjacent spinous processes. 
         [0323]      FIG. 37  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 33 . A SPS  3702  has been connected to the caudal aspect of the cranial vertebra  3704  and a SPS  3710  has been connected to the cranial aspect of the caudal vertebra  3712  in a two-level construct. The cranial SPS is preferably fused to the cranial vertebra and the caudal SPS is preferable fused to the caudal vertebra. The arrangement keeps each SPS from impinging on the strap of an adjacent SPS. 
         [0324]      FIG. 38A  is an exploded lateral view of spine and an alternative embodiment of the invention related to that shown in  FIG. 12A . A component  3802  is attached to the dorsal aspect of the SPS. The two components  3802 ,  3804  have teeth along their mating surfaces. The teeth interdigitate to prevent movement of one component relative to the other component. A screw  3810  is used to connect the two components. The dorsal component  3810  helps prevent the SPS  3804  from rotating about the coronal axis of the spine. Rotation of the SPS about the coronal axis of the spine could reduce the distraction of the vertebrae.  FIG. 38B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 38A . The assembled device has been attached to the SP using the technique taught with reference to  FIG. 12A . 
         [0325]      FIG. 38C  is a lateral view of the spine and an alternative embodiment of the invention including a dorsal component  3830  attached to the SPS with a cable  3832 . The dorsal component has a chamber. Bone or bone-growth promoting substances may be added to the chambers in both components of the device. Holes may pass between the chambers of both components. 
         [0326]      FIG. 39A  is a dorsal view of an alternative embodiment of the invention with components  3902 ,  3904  seen on the left and right sides of the device which slide along a slot  3906  formed across the dorsal surface of the SPS. The lateral locations of the dorsal components prevent the dorsal components from impinging against the spinous processes during rotation of the device. As taught in reference to  FIG. 28C , rotation of the SPS in the coronal axis of the spine cams open the interspace. 
         [0327]      FIG. 39B  is a dorsal view of the embodiment of the invention shown in  FIG. 39A . The components  3902 ,  3904  on the dorsal aspect of the device have been moved to the center of the device  3900 . The dorsal components may be reversibly connected together. The components could snap together via portions of the components that plastically deform. Alternatively, the components could fasten together using shape-memory materials. The dorsal components are snapped together after the SPS is rotated to cam open the interspace. The connected dorsal components strike the spinous processes if the SPS is rotated after the components are connected. The configuration of the device prevents loss of distraction as the SPS is unable to rotate from the “cam” position. 
         [0328]      FIG. 40A  is a dorsal view of an alternative embodiment of the invention which has two projections  4002 ,  4004  on the dorsal aspect of the device  4000 .  FIG. 40B  is a dorsal view of the embodiment of the invention shown in  FIG. 40A . A cord  4010  has been wrapped around the projections on the dorsal aspect of the device. The cord is preferably an elastic band.  FIG. 40C  is a lateral view of the spine and the embodiment of the device shown in  FIG. 40B . The band  4010  controls rotation of the device about the coronal axis of the spine. The band strikes the SP if the SPS is rotated about the coronal axis of the spine. The SPS may be rotated about the coronal aspect of the spine before the band is added to the device. The band is added to the device after the SPS is rotated into place. 
         [0329]      FIG. 41A  is an exploded oblique view of an alternative embodiment of the invention may of allograft bone. The large cylinder  4102  could be made from the shaft of a long bone. The tibia, humerus, femur, radius, ulna, fibula, metatarsal; metacarpal, rib, pelvic bone, phalanges or other bones may be used to construct the device. 
         [0330]      FIG. 41B  is a lateral view of the embodiment of the device shown in  FIG. 41A . A bone dowel  4104  has been placed through holes in the bone components  4110 ,  4112  that project from the cylinder shaped bone. The bone dowel holds the assembled bone SPS together.  FIG. 41C  is a dorsal view of the embodiment of the invention shown in  FIG. 41B . 
         [0331]      FIG. 42  is an oblique view of an alternative embodiment of the invention machined from the shaft of a single long bone. The ventral aspect  4204  of the SPS  4202  is open. The large opening on the ventral aspect of the SPS prevents the SPS from protruding into the spinal canal. Holes such as  4210  are drilled into the sides of the device. The holes can be used attach the SPS to the spine with suture or cables. 
         [0332]      FIG. 43A  is an exploded oblique view of an alternative embodiment of the invention similar to that shown in  FIG. 41A .  FIG. 43B  is an oblique view of the device shown in  FIG. 43B . Bone dowels  4302 ,  4304  are used to hold a rectangular or trapezoid shaped bone piece  4306  within a cylinder shaped bone  4308 . The central bone component acts as a beam or column to strength the cylindrical bone. 
         [0333]      FIG. 44A  is an exploded oblique view of an alternative embodiment of the invention similar to that shown in  FIG. 43A .  FIG. 44B  is an oblique view of the SPS shown in  FIG. 44A . A smaller bone  4402  is placed inside a larger bone  4404 . The bones are held together with a bone dowel, screw, nail, staple, or other component  4406 . For example, a portion of the shaft of a metatarsal bone could be placed inside a portion of the humerus. 
         [0334]      FIG. 45  is an oblique view of an alternative embodiment of the invention shown in  FIG. 44B . The device is manufactured by assembling the shafts of two bones  4502 ,  4504  that have been split along their longitudinal axes. The bones may be held together by bone dowels or other components  4506 . The radius of one side of the assembled SPS is larger than the radius of the other side of the SPS. 
         [0335]      FIG. 46  is an oblique view of an alternative embodiment wherein the shaft of a first bone  4602  has been placed into a portion of the shaft  4604  of a second bone. The larger bone has been split along its longitudinal axis. The smaller one projects through the opening in the larger bone. The assembled SPS can be held together with bone dowels or other fastening mechanism  4706 . 
         [0336]      FIG. 47A  is an exploded, oblique view of an alternative embodiment of the invention.  FIG. 47B  is an oblique view of the embodiment of the invention shown in  FIG. 47A . Projections  4702 ,  4704  from one bone component  4710  fit into slots (not visible) in a second bone component  4720 . Two or three pieces of bone are used to assemble the completed device, as shown in  FIG. 47B . Other shapes of the assembled SPS can be manufactured by assembling more than three bones. 
         [0337]      FIG. 48A  is an exploded oblique view of an alternative embodiment of the invention wherein a first bone component  4802  is inserted into a slot of a second bone component  4804 .  FIG. 48B  is an oblique view of the embodiment of the SPS shown in  FIG. 48A . The bone components may be held together with bone pins  4806  on either slide of the slot within one of the bones. The shape of the SPS manufactured from two bones may be varied by changing the size of the bone components or the location and/or size of the slots within one of the components. Alternatively, the device could be manufactured with more than two bone components. For example a first bone component could be manufactured with two slots to receive two other bone components. A composite device could be constructed with bone and one or more other materials. For example, the device could be assembled from components made of bone and components made of PEEK. 
         [0338]      FIG. 49A  is lateral view of an alternative embodiment of the invention related to that shown in  FIG. 10A .  FIG. 49B  is an exploded lateral view of the embodiment of the device shown in  FIG. 49A . The device is assembled from pieces of bone  4904  that are stacked, machined, and pinned together. The pieces of bone are preferably pinned together with other pieces of bone  4910 .  FIG. 49C  is a lateral view of an alternative embodiment of the invention similar to that shown in  FIG. 49A . The pieces of bone have teeth  4920  on the dorsal and ventral surfaces where the pieces of bone contact with one another. The teeth interdigitate to improve the strength of the assembled bone SPS device. 
         [0339]      FIG. 50A  is lateral view of an alternative embodiment related to the device shown in  FIG. 49C  which is assembled from multiple pieces of bone. The device may be constructed from machined pieces of cortical bone  5002  and pieces of cancellous bone  5004 . Cortical bone is used to enable the device to receive loads from the vertebrae, whereas cancellous bone is used to facilitate fusion of the device to a single vertebra. 
         [0340]      FIG. 50B  is a dorsal view of the embodiment of the invention wherein the bone components are pinned together. Projections  5010  from bones fit into recesses in other bone components. 
         [0341]      FIG. 50C  is an oblique view of bones shaped to be connected in an alternative method than used in the device shown in  FIG. 50A . Rectangular projections  5020  and slots  5022  are machined into the bones. 
         [0342]      FIG. 50D  is a lateral view of an alternative embodiment which has been constructed by assembling bones shaped like the bones in  FIG. 50C . The pieces of bone may be assembled much like the pieces of wood are assembled in Jenga puzzles. The assembled bones could be pinned to hold the bones together. 
         [0343]      FIG. 51A  is an oblique view of an alternative embodiment of the invention related to that shown in  FIG. 10A .  FIG. 51B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 51A . The V- or U-shaped device  5102  is designed to fit between the SP of the L5 vertebra and the sacrum. Screws  5104 ,  5106  connect the device to the sacrum. Bone-growth promoting material is placed over or in the device. Bone-growth material is also preferably placed on to the sacrum. The device is designed to fuse to the sacrum. The device may be made of bone, metal, ceramic, polymers, or other material.  FIG. 51C  is a caudal view of the embodiment of the device shown in  FIG. 51A . Screws  5104 ,  5106  may be seen within the device. The screws may course in different directions. For example, the screws may converge. The device may be used in other levels of the spine. The screws may be placed into the pedicles of the vertebrae. 
         [0344]      FIG. 52  is dorsal view of the spine and an alternative embodiment of the invention  5202  similar to that shown in  FIG. 51B , which is connected to screws  5204 ,  5206  placed into the pedicles of the vertebra. The device may be made of metal, bone, ceramic, or polymers. The device may be fused to one of the vertebrae. Alternatively, the device may be used without promoting fusion to either vertebra. 
         [0345]      FIG. 53  is a dorsal view of the spine and a version of the invention shown in  FIG. 52 . The device  5302  has been connected to screws  5304 ,  5306  placed into the pedicles of one of vertebrae  5310 . The device is designed for use in patients who have undergone removal of one or more spinous processes. A “bumper” component  5312  has been placed over a component that courses from one pedicle screw to the other pedicle screw. The various components may be made of a polymer, metal, or bone. 
         [0346]      FIG. 54A  is a lateral view of the spine and an alternative embodiment of the invention shown in  FIG. 53 . Screws  5404 ,  5406  are placed into the pedicles of vertebrae  5410 . The screws are placed through portions of the superior facets of the caudal vertebra. The inferior facets of the cranial vertebra impinge against the screws. The screws are placed after the spine is flexed. The screws allow spinal flexion but limit spinal extension. 
         [0347]      FIG. 55  is a dorsal view of the spine and an embodiment of the invention  5500  shown in  FIG. 10A  having been placed between the spinous processes  5502 ,  5504  of two vertebrae. The bone growth material extends into the facet joints between the two vertebrae. The bone growth material and the subsequent fusion mass cooperate with the SPS device to limit spinal extension. 
         [0348]      FIG. 56A  is a dorsal view of the spine and an alternative embodiment of the invention wherein paired devices  5602 ,  5604  are placed along the left and right sides of the dorsal aspect of the vertebrae.  FIG. 56B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 56A . The devices fit over the caudal aspect of the lamina of the cranial vertebra and the cranial aspect of the lamina of the caudal vertebra. 
         [0349]      FIG. 57  is a dorsal view of the spine and an alternative embodiment of the invention  5702  adapted to fit over the caudal aspect of the lamina  5704  of the cranial vertebra and the SP and/or lamina of the caudal vertebra  5706 . The device distracts the vertebra and limits extension of the spine. 
         [0350]      FIG. 58  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A . The dorsal and ventral surfaces of the cranial end of the device have concavities  5802 ,  5804  to receive bone-growth-promoting material (not shown). 
         [0351]      FIG. 59  is a lateral view of the spine and the embodiment of the invention related to that shown in  FIG. 10A . A tube  5902  passes from a hole in the pedicle  5904  of the vertebra to the concavity  5906  of the device  5908 . The tube  5902  facilitates the migration of cells from the body or pedicle of the vertebra to the bone growth promoting material. Alternatively, cells obtained from aspirating the vertebra or other bone may be added to the bone growth material in the device. 
         [0352]      FIG. 60A  is a lateral view of the spine and an exploded, lateral view of an alternative embodiment of the invention including a semi-cylindrical component  6002  with a hinge joint  6004  is placed between the spinous processes of two adjacent vertebrae  6010 ,  6012 .  FIG. 60B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 60A . A rod  6020  has been placed into the hinged semi-cylindrical component. The rod component expands the hinged component and distracts the spine. Spring-like properties of the hinged component or shape-memory properties of the components could be used to fasten the components. 
         [0353]      FIG. 61  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A . A component  6102  attached to one SP impinges against a component  6104  attached to a SP of an adjacent vertebra. The components may be attached to the spinous processes using the method taught in FIG.  12 A. The components could be made of metal, polymers, ceramic, bone, fabric or combinations thereof. 
         [0354]      FIG. 62A  is a dorsal view of the spine and a further alternative embodiment of the invention related to that shown in  FIG. 10C . Two wedge-shaped components  6202 ,  6204  are connected and inserted between the spinous processes of two adjacent vertebrae.  FIG. 62B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 62A . The wedge components  6202 ,  6204  have been urged together so as to increase the width of the device in the cranial-to-caudal direction, thereby distracting the vertebra. The components could be drawn together with screws. Alternatively, the components could be forced together with pliers. The components could be locked in the compressed position using screws or other fasteners, plastic deformation technology, or shape-memory technology. 
         [0355]      FIG. 63A  is a lateral view of the spine and a variation of the embodiment of the invention shown in  FIG. 62A .  FIG. 63B  is a lateral view of the spine and the embodiment of the device shown in  FIG. 63A . Two components  6302 ,  6304  are compressed together after placing the device between the spinous processes  6310 ,  6312  of adjacent vertebrae. The device distracts the spine as the components are forced together. The components may be locked in their compressed position. 
         [0356]      FIG. 64A  is a lateral view of the spine and different configuration of the invention shown in  FIG. 63B .  FIG. 64B  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 64A . The device distracts the spine as the components  6402 ,  6404  are forced apart. The components may be locked in their extended position. 
         [0357]      FIG. 65A  is a dorsal view of an alternative embodiment of the invention related to that shown in  FIG. 10A .  FIG. 65B  is a dorsal view of the embodiment of the device shown in  FIG. 65A . The two components  6502 ,  6504  of the device articulate at the joint between the components. The positions of the components may be changed by rotating one component relative to the second component. A screw  6510  may be used to lock the components in a desired position. 
         [0358]      FIG. 66A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 41A . The device is preferably made of bone.  FIG. 66B  is an oblique view of the device shown in  FIG. 66A . Projections  6602 ,  6604  from the central component  6610  are forced into holes  6620 ,  6622  in the lateral components  6630 ,  6632 . 
         [0359]      FIG. 67  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 10A . The cranial aspect of the device  6702  is made of a resorbable material designed to resorb after the device fuses to one of the vertebrae. 
         [0360]      FIG. 68  is a lateral view of the spine and an alternative embodiment of the device related to that shown in  FIG. 12A . A compressible, resilient or elastic component  6802  is attached to the caudal end of the device. The component  6802  dampens loads across the device. 
         [0361]      FIG. 69A  is a dorsal view of an alternative embodiment of the invention. Components  6902 ,  6904  on the left and right side of the device are connected with a hinge joint  6906 . The components are also connected with one or more elastic bands. Compression on the caudal end of the device hinge the two components open. The device dampens loads applied by the spinous processes.  FIG. 69B  is a dorsal view of the device shown in  FIG. 69A . The device has been partially opened to show the bands  6910 . 
         [0362]      FIG. 70A  is a dorsal view of an alternative embodiment of the invention similar to that shown in  FIG. 69A .  FIG. 70B  is a dorsal view of the device shown in  FIG. 70A . The components  7002 ,  7004  on the left and right sides of the device are connected with two or more elastic cords  7010 ,  7012 . The device is shown in its opened position. The device may be opened by forces from the spinous process adjacent to the device. The device dampens loads applied by the spinous processes. 
         [0363]      FIG. 71  is a lateral view of the spine and an alternative embodiment of the invention utilizing components preferably made from the shafts of bones. The bone components  7102 ,  7104  may be pinned in the configuration illustrated in the figure. 
         [0364]      FIG. 72A  is lateral view of a knife-like instrument  7202  that may be used to cut the ligaments between the spinous processes. The cutting surface of the knife is shown at  7210 .  FIG. 72B  is a lateral view of the spine and the cutting tool shown in  FIG. 72A . The device  7202  has partially severed the interspinous ligament  7210 . The device cuts the ligament as it is pulled away from the spinal canal. 
         [0365]      FIG. 73A  is a lateral view of a tool  7302  used to distract the spinous processes.  FIG. 73B  is a view of the one end of the distracting tool shown in  FIG. 73A . Fabric or elastic bands  7310 ,  7312  connect the tips  7330 ,  7332 ,  7334 ,  7336  of the tool. 
         [0366]      FIG. 73C  is a lateral view of the tool, and  FIG. 73D  is a view of the dorsal aspect of two adjacent spinous processes and the end of the tool shown in  FIG. 73C . The fabric bands  7310 ,  7312  fit between the spinous processes  7340 ,  7342 . The thin bands conform to the shape of the spinous processes while applying pressure over a large area. The flexibility and the size bands protect the spinous processes from injury during spinal distraction. 
         [0367]      FIG. 73E  is a dorsal view of two adjacent spinous processes and the tips of the tool shown in  FIG. 73D . The drawing illustrates the tool distracting the spinous processes  7340 ,  7342 . The handle of the tool may include a gauge (not shown) that measures the force applied to the tool or the distance the tips of the tools have opened. The method may include distracting the spinous processes a certain distance (for example, 5 mm), a certain percent (for example 20%) or until a certain amount of force is applied (for example, 20 inch/pounds). 
         [0368]      FIG. 74A  is a lateral view of a measuring tool  7400  having tips  7402 ,  7404  that are placed into the interspinous space. The tool may be used to distract the spinous processes and measure the distance between the spinous processes. The information may be used to determine the proper size of the device to be inserted between the spinous processes.  FIG. 74B  is a view of a gauge  7410  used on the handle of the instrument shown in  FIG. 74A . The gauge suggests the proper size of the SPS device to insert between, the spinous processes. 
         [0369]      FIG. 75  is an oblique view of a sleeve  7500  according to the invention that may be placed over the cables used in embodiments of the invention including that shown in  FIG. 12A . 
         [0370]      FIG. 76A  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 12A . A cable  7602  has been looped around the SP of the cranial vertebra. The cable also surrounds cable  7604  loops that attach to the left and right sides of the device  1200 . The cables on the left and right sides of the device are tightened after the device is placed between the spinous processes.  FIG. 76B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 76A . 
         [0371]      FIG. 77A  is a lateral view of the tip of an instrument  7702  that may be used to hold the SPS device.  FIG. 77B  is a lateral view of the tip of the instrument shown in  FIG. 77A . A retractable member  7704  is shown in its retracted position.  FIG. 77C  is a lateral view of the tip of the tool shown in  FIG. 77A  and a SPS device. A projection  7710  from the tool is placed into a hole on the lateral side of the SPS device. The retractable arm  7704  passes over the other side of the SPS, thus holding the SPS device in the tool. 
         [0372]      FIG. 78A  is a lateral view of the tip  7802  of a distractor tool  7804  according to the invention.  FIG. 78B  is a dorsal view of the tips of two spinous processes  7810 ,  7812  and the tip of the distractor tool shown in  FIG. 78A . The wedge shaped distractor tool is forced between adjacent spinous processes to wedge the spinous processes open. 
         [0373]      FIG. 79A  is a dorsal view of the tip of a SP  7902 , a cross section of an inventive tool  7904 , and a cable  7906 . The tool is used to prevent over tightening the lower cable in the embodiment of the invention shown in  FIG. 12D .  FIG. 79B  is a dorsal view of the tip of a SP, the cross section of the tool shown in  FIG. 79A  and a cable. The tool has been rotated 90 degrees. Rotating the tool allows removal of the tool. Removing the tool provides sufficient slack in the cable to allow the SPS device to move away from the caudal vertebra. 
         [0374]      FIG. 80A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A . The SPS  8002  is attached to the dorsal portion of the SP  8004  of the cranial vertebra. A cable, cord, wire suture or other flexible member(s)  8010  pass through a hole  8012  in the SP. The flexible member “bridle”  8020  also attaches to the left and right sides of the SPS. For example, a cable could pass through hole(s)  8030  in the SPS. This dorsal cable and attachment mechanism prevents the SPS from migrating into the spinal canal. The invention may be particularly helpful in patients treated with unilateral or bilateral laminotomies and/or partial facetectomies. A portion of the caudal end of the lamina is removed during laminotomies. The medial portions of the facet area removed during partial facetectomies. Facetectomy and laminotomy enlarge the spinal canal. The invention helps prevent SPSs from falling into the enlarged opening into the spinal canal. A sleeve could be used to increase the surface area of the cable. The sleeve could fit over the cable where the cable passes through the hole in the SP. Alternatively, a grommet could be placed into the hole in the SP. 
         [0375]      FIG. 80B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 80A . The bridle cable  8010  passes from one side of the SPS, through a hole in the SP, to the other side of the SPS. The cables and methods illustrated in  FIG. 12A  were not shown to better illustrate the bridle cable.  FIG. 80C  is a cranial view of the embodiment of the SPS shown in  FIG. 80A . The circles  8040 ,  8042  on the left and right sides of the dorsal portion of the SPS are designed to accept the ends of the bridle cable. 
         [0376]      FIG. 81  is a lateral view of the spine and an alternative embodiment of the invention wherein a portion  8102  of the SPS  8104  extends over the dorsal aspect of the SP. The dorsal aspect of the SP could be notched to help prevent the SPS from sliding off of the SP. Alternatively, the SPS may have a projection that extends over the SP of the caudal vertebra or the spinous processes of the cranial and the caudal vertebrae. Additional embodiments may use a harness, bridle, or mesh that extends from the left and right sides of the SPS and over one or more spinous processes. Alternatively, the invention could use a single member that extends from one side of the SPS to the SP. The unilateral embodiment of the invention is preferably placed on the side of the unilateral “hemi” laminotomy. 
         [0377]      FIG. 82  is a caudal view of a SPS and an alternative embodiment of the invention related to that shown in  FIG. 81 . A projection including a hook  8202  from the SPS  8204  passes through a hole in the SP  8210 . 
         [0378]      FIG. 83  is a caudal view of an alternative embodiment of the invention similar to that shown in  FIG. 82 . Cables or other members  8302 ,  8304  pass from the sides of the SPS  8300  to a member  8310  that was placed into a hole in the SP. The cables or other members that pass through the SP could be made of bone, metal, ceramic, plastic, or other material. The component  8310  that passes through a hole in the SP preferably is made of a material that allows the patient&#39;s bone to grow into the component. 
         [0379]      FIG. 84  is a lateral view of the spine and a variation of the embodiment of the invention shown in  FIG. 37 . The cable that connects the caudal SPS to the SP of the intermediate vertebra passes through a hole  8406  in the SP of the intermediate vertebra  8410 . The hole in the SP is preferably located in the center of the SP. Alternatively, the cable could pass through another portion of the intermediate vertebra. For example, the cable could pass through holes in the lamina. 
         [0380]      FIG. 85  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 80A . The SPS  8502  has a projection  8504  from the cranial portion of the device. The projection extends over a portion of the lamina cranial to laminotomy defect. Projections could extend from the left and right sides of the SPS. A unilateral projection could extend from the SPS on the side of the laminectomy. Alternatively, a unilateral projection could extend from the SPS on the side contralateral to the laminectomy.  FIG. 86  is a dorsal view of the spine and an alternative configuration of the invention shown in  FIG. 85 . The projection  8602  from the cranial portion of the SPS is connected to a screw  8604 . The screw is preferably placed into on of the pedicles of the cranial vertebra. 
         [0381]      FIG. 87A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 85 . The drawing illustrates a retractable projection member  8702  in its retracted position.  FIG. 87B  is a dorsal view of the spine and the embodiment of the SPS shown in  FIG. 87A . The member  8702  is shown in its extended position. The projection member may locked in the extended position. 
         [0382]      FIG. 88A  is a lateral view of the spine an alternative embodiment of the invention related to that shown in  FIG. 20A . The SPS device  8802  has two or more holes or chambers  8810  that may be filled with bone or bone growth promoting material. The device could be attached to the spine in the method taught in reference to  FIG. 12A . As with most other embodiments described herein, the device may be constructed of bone, metal, polymer, ceramic, or other material. The circle with dots represents a chamber in the side of the device.  FIG. 88B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 88A . 
         [0383]      FIG. 89A  is a lateral view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 88A . The device  8800  fits over SP  8802  and distracts two sets of adjacent spinous processes. Pin  8804  may be used to hold the device in place, and holes/apertures  8810  may be provided for bone ingrowth.  FIG. 89B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 89A . 
         [0384]      FIG. 90A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 10A . Openings  9002 ,  9004  on the left and right side of the device  9000  may be optionally closed with additional components  9012 ,  9014 . The additional components may be screwed into the openings in the sides of the device. Alternative mechanisms may be used to fasten the side components to the device. Bone or bone-growth promoting substances may be placed into the device before fastening the side components. Tether fastening components may be passed through the bone in-growth holes on the cranial portion of the device. 
         [0385]    The bone in-growth holes are limited to the cranial portion of the assembled device. Alternatively, the in-growth holes may be limited to the caudal portion of the device, the ventral portion of the device, the dorsal portion of the device, or any combination of two, three, or more portions of the device. The invention may also include one component device that does not have holes on the left and/or the right sides of the device.  FIG. 90B  is a lateral view of the assembled device shown in  FIG. 90A .  FIG. 90C  is an anterior view of the assembled device shown in  FIG. 90B :  FIG. 90D  is coronal cross section of the assembled device shown in  FIG. 90C . 
         [0386]      FIG. 91A  is a dorsal view of the spine and an alternative embodiment of the invention related to that shown in  FIG. 12A . Components  9102 ,  9104  from one end of the device  9100  pass over the cranial end of the cranial SP or the caudal aspect of the SP caudal to the device. The components may be tightened to force the device against the SP or lamina. Forcing the device against the SP, or lamina, eliminates movement between the device and the posterior elements of the spine the device is attached to. 
         [0387]      FIG. 91B  is a coronal cross section of the spine and the embodiment of the device shown in  FIG. 91A . The fixation components may be locked in the tightened position. For example, the fixation components may include nuts  9110 ,  9112  that is threaded onto the component. The loose fit between the fixation component and the device allow the fixation components to swivel within the holes of the device. The device may have spherical recesses to receive the nuts of the fixation components. 
         [0388]      FIG. 92A  is an oblique view of a shim-like device  9200  used to improve the fit between an interspinous device and the SP. The device is preferably made of bone. A portion of the device may be removed after the device is inserted between the interspinous device and the SP. The shim may also be made of metal, polymers (including PEEK), ceramic, or other material. The shims may be supplied in many different sizes and shapes. 
         [0389]      FIG. 92B  is an exploded lateral view of the spine, shims  9200 ,  9200 ′, and an alternative embodiment of the invention similar to that shown in  FIG. 89A . Shims  9200 ,  9200 ′ fit between the SPS and the SP  9210 . The SPS is designed to fuse to the posterior elements of the intermediate vertebra. The cranial and caudal ends of the device are sloped to fit the lamina of the cranial and caudal vertebra, respectively. 
         [0390]      FIG. 92C  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 92B . A shim  9200  can be seen between the lateral aspect of the SP and the SPS and a shim  9200 ′ can be seen between the caudal aspect of the SP and the SPS. Bone or bone growth promoting material may be placed in the openings between the SPS, the SP and the shims. Bone or bone-growth promoting substances may also be placed in the chambers of the SPS, over the SPS, and around the posterior elements of the intermediate vertebra. The hole in the device may be customized at the time of surgery. For example, surgeons could use power burs to enlarge the hole in the device. The enlarged hole would enable surgeons to place the device over abnormally large or deformed spinous processes. 
         [0391]      FIG. 93A  is a lateral view of the spine and an alternative embodiment of the invention (see also  FIG. 61 ). The two components  9300 ,  9302  of the device have chambers  9310 ,  9312 . Bone or bone-growth promoting substances may be placed in the chambers and between each component and the SP the component partially surrounds. The cranial component  9300  is designed to fuse to the SP of the cranial vertebra. The caudal component  9302  is designed to fuse to the SP of the caudal vertebra. 
         [0392]      FIG. 93B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 93A . The components cooperate to limit spinal extension, lateral bending, and/or axial rotation. The components allow spinal flexion. The device decreases the loads across the facet joints. Decreasing the loads may decrease back pain from arthritic facet joints. 
         [0393]    The articulating surfaces of the components may be shaped in many different ways without departing from the spirit of the invention.  FIG. 93C  is a dorsal view of the spine and an alternative embodiment of the invention wherein the articulating surfaces of the components  9330 ,  9332  are shaped differently. 
         [0394]      FIG. 94A  is a view of the cranial side of the embodiment of the SPS shown  FIG. 10A  and a tool  9400  used to facilitate insertion of the SPS. The tool has two components. An impactor component  9402  passes through a cylindrical opening in a second component  9404 . The SPS  9440  fits into a U-shaped opening in the side of the second component  9404 . A projection (not visible) from the tip of the impactor component fits into a hole in the dorsal side of the SPS. A projection (also not visible) from the base of the U of the second component fits into a hole on the side of the SPS. 
         [0395]    The ventral surface of the SPS lies on one of the arms of the U-shaped component. The impactor component pistons inside the second component. The impactor component is advanced into the hole of the SPS to reversibly lock the SPS in the instrument. The impactor component can be reversibly locked in the second component. For example, a spring-loaded ring could be moved from one position to the next to reversibly lock the two components. Alternatively, a nut could be advanced along the impactor component to reversibly lock the impactor component to the second component.  FIG. 94B  is a side view of the embodiment of the invention shown in  FIG. 94A . The ventral arm  9450  of the U-shaped end of the second component is wedge-shaped in cross section. 
         [0396]      FIG. 94C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 94B .  FIG. 94D  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 94C . The tool and the SPS are impacted between adjacent spinous processes. The wedge-shaped end of the tool separates the spinous processes as the tool is advanced between the spinous processes. The impactor component of the tool may be struck with a mallet to advance the tool and the SPS between the spinous processes. 
         [0397]      FIG. 94E  is an exploded lateral view of the spine and the embodiment of the invention shown in  FIG. 94D . The tool has been removed from the SPS. The SPS maintains distraction of the spinous processes. Distraction of the spinous processes by the SPS enables the wedge-shaped end of the tool to be easily removed from between the spinous processes. The impactor component of the tool is withdrawn from the SPS to enable the U-shaped second component to slide off the SPS.  FIG. 94F  is an exploded view of the caudal end of a vertebra, a SPS, and the embodiment of the tool shown in  FIG. 94E . The tool  9400  has been removed from the SPS  9440 . 
         [0398]      FIG. 94G  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 94F . The impactor component of the tool was not shown. Projections  9460 ,  9462  from the cranial and/or caudal sides of the U-shaped component of the tool fit along the sides of the Spinous processes. The projections help center the SPS between the spinous processes. Alternatively, two projections may project from both the cranial and caudal sides of the tool. The projects could straddle both sides of the spinous processes cranial and caudal to the SPS. The notch in the SPS also helps center the SPS relative to the spinous processes. 
         [0399]      FIG. 94H  is a cross section of the embodiment of the invention shown in  FIG. 94A . The impactor component is depicted at  9460 , and the SPS is shown at  9462 . The component with the wedge component is represented at  9400 . 
         [0400]      FIG. 95A  is a lateral view of the spine, the embodiment of the SPS shown in  FIG. 10A , and a second impactor tool  9502  used to advance the SPS  9504  towards the spinal canal. The tool may used after initial placement of the SPS by the tool shown in  FIG. 94A .  FIG. 95B  is a dorsal view of the spine and the embodiment of the invention shown in  FIG. 95A . Like the tool shown in  FIG. 94G , optional projections  9560 ,  9562  help center the SPS in the sagittal plane of the spine.  FIG. 95C  is a lateral view of the tool shown in  FIG. 95A . The projection  9570  from the ventral end of the tool fits into a hole in the dorsal side of the SPS.  FIG. 95D  is a view of the cranial side of the tool shown in  FIG. 95C . 
         [0401]      FIG. 96A  is a cranial view of an alternative configuration of the invention shown in  FIG. 94A , wherein the arm  9602  that connects the wedge component to the shaft of the instrument passes cranial to the SPS. Alternatively, the connecting arm may pass on the caudal side of the SPS. The piston component is threaded into the shaft of the second component. A nut  9620  may used to reversibly lock the components together. The SPS is represented by the area of the drawing with vertical and horizontal lines.  FIG. 96B  is a lateral view of the embodiment of the invention shown in  FIG. 96B . 
         [0402]      FIG. 97A  is a lateral view of an alternative embodiment of the invention related to that shown in  FIG. 73A . L-shaped components  9702 ,  9704  fit over the arms of distraction or retraction devices. For example, the L-shaped components may fit over the arms of a “McCulloch” retractor (V. Mueller Company). Flexible bands are indicated at  9706 ,  9708 . The distraction components could be designed to fit into other instruments such as the “Caspari Distractor”. 
         [0403]      FIG. 97B  is an exploded, cranial view of the embodiment of the invention shown in  FIG. 97A . The flexible band  9706  fits over the arms of the distraction component. Screws  9720 ,  9722  may be used to prevent the flexible band from sliding off the distraction component. Alternatively, a Velcro strap could be placed over the arms of the distraction component.  FIG. 97C  is an oblique view of the embodiment of the invention shown in  FIG. 97A  and one arm  9770  of a McCulloch retractor. The square shaped opening in the instrument fits over the square shaped arm  9770  of the retractor. 
         [0404]      FIG. 98A  is an exploded oblique view of an alternative embodiment of the invention related to that shown in  FIG. 20A . A spacer component is placed over a spinous process. A dowel-like component  9802  is placed through an opening  9804  on the side of the device  9806 , after the device is placed over the spinous process. The dowel component may locked into the spacer component. For example, the dowel component may be oval in cross section. Alternatively the oval dowel component could be cammed to lock the two components together. 
         [0405]      FIG. 98B  is an oblique view of an assembled device of the embodiment shown in  FIG. 98A .  FIG. 98C  is a lateral view of the spine and the embodiment of the invention shown in  FIG. 98A . The dowel component narrows the hole in the spacer component. The tip of the SP  9810  is too large to fit through the narrowed hole in the SPS. The dowel component may also increase apply pressure to the SP. 
         [0406]      FIG. 99A  is a dorsal view of the spine and an alternative embodiment of the invention including rods  9902 ,  9904  that connect components placed between spinous processes. One or more of the interspinous components may prevent spinal extension through the level the interspinous component was placed. 
         [0407]      FIG. 99B  is an exploded dorsal view of the embodiment of the invention drawn in  FIG. 99B . The rods may have spherical enlargements  9906 ,  9908  on one end of the rods. The spherical enlargements of the rods articulate with spherical concavities  9910 ,  9912  in one of the interspinous components. Set screws hold the rods in the interspinous components. The spherical articulation between the rods and the interspinous components allow the rods to be collinear or in a non-collinear alignment. The interspinous components may be tightened over the intermediate SP. 
         [0408]      FIG. 99C  is a lateral view of the spine and the embodiment of the invention drawn in  FIG. 99B . The holes in the interspinous components may be filled with bone or a bone-growth-promoting substance. The interspinous components may fuse to the posterior elements of the intermediate vertebra. 
         [0409]      FIG. 100A  is an oblique view of an alternative embodiment of the invention related to that drawn in  FIG. 97A .  FIG. 100B  is a dorsal view of the embodiment of the invention drawn in  FIG. 100A . A band  9920  has been placed through slots  9922 ,  9924  in the arms  9926 ,  9928  of the device. The band is preferably flexible. The band may be made of plastic, metal, or fibrous material. For example, a plastic cable tie could be used. The large fastening end of the cable would prevent the first end of the cable from passing completely through one arm of the device. The fastening end of a second cable tie could be affixed to the second end of the cable tie, after the second end of the cable tie is passed through the second slot in the device. The large ends cable tie trap the cable tie within the device.  FIG. 100C  is a lateral view of the embodiment of the device drawn in  FIG. 100B . 
         [0410]      FIG. 101A  is a coronal cross section of an alternative embodiment of the invention drawn in  FIG. 93B . Rigid components  9930 ,  9932  are attached to adjacent spinous processes  9940 ,  9942 . The fastening bands were not drawn on the component attached to the caudal SP. A flexible member  9950  is placed between the rigid components. The flexible component is preferably trapped between the rigid components without attaching to either component. The rigid components may have chambers filled with bone or bone-growth-promoting substances. The rigid components could fuse to the spinous processes. The flexible component may be made polymers, including elastomers or hydrogels. Alternatively, the intermediate component could be made of polyethylene. The polyethylene component could be attached to one of the rigid components. The large surface area of the rigid components enables transfer of loads across a larger area of the polymer component than can be transferred by the SP alone. The rigid components also surround a portion of the spinous processes. The configuration of the rigid components permits insertion of a polymer component that is larger than the space between the spinous processes. The device permits load transfer through large portions of large polymer components. The longevity of the polymer component is increased by the use of larger polymer components and by the transfer of loads through large portions of the polymer component. The polymer component could dampen the loads between the rigid components. 
         [0411]      FIG. 101B  is sagittal cross section of the embodiment of the device drawn in  FIG. 101A . The areas of the drawing with closely spaced lines represent the rigid components. The area  9950 ′ represents a portion of the polymer component. The device is configured to allow motion between the rigid components and contain the polymer component. The polymer component could be made of more than one material or of the same material with different durometers. For example, the transverse component of the polymer component may have more tensile strength than the lateral portions of the polymer component.  FIG. 101C  is a lateral view of the spine and the embodiment of the device drawn in  FIG. 101A .