referring now to fig1 - 4 , there is provided an interspinous process device , comprising : a ) a first body 1 , the first body comprising i ) a first hook - shaped portion 3 adapted for contacting a superior spinous process , and ii ) a first curved track portion 5 having a first face 6 and a second face ( not shown ), the first face 6 having a groove 8 therein and a rail 7 thereon running parallel to the groove , the second face having a groove therein running parallel to the groove of the first face ; b ) a second body 11 , the second body comprising i ) a second hook - shaped portion 13 adapted for contacting an inferior spinous process , ii ) a second curved track portion 15 having a first face 16 and a second face ( not shown ), the first face 16 having a groove 17 therein , the second face having a groove therein and a rail thereon , c ) a housing 21 having i ) a slot 23 therethrough slidably receiving the curved track portions , ii ) a threaded throughhole 26 extending in a direction transverse to the slot , and a containing pin ( not shown ) extending into the slot d ) a set screw 25 adapted for compressing the curved track portions of the first and second bodies , the set screw having i ) a peripheral thread threadably received in the throughhole of the housing , and ii ) an end face ( not shown ) having a constraining feature ( such as a pin ) adapted to constrain the curved track portions , wherein the rail and groove of the second face of the second body respectively slidingly engage the groove and rail of the first face of the first body , wherein the groove of the first face of the second body slidingly engages the constraining feature of the set screw , and wherein the groove of the second face of the first body slidingly engages the containing pin of the housing . in some embodiments , each hook has an acutely angled face to more closely match the angle of the posterior - most portion of the spinous process it contacts . in contrast , the hooks of some conventional spinous process implants have a face that is perpendicular to the distraction path . in the present invention , a first mating face 31 forms an acute angle α which is less than 90 degrees with respect to the tips , while the second mating face 33 forms an obtuse angle β which is more than 90 degrees with respect to the tips . therefore , in accordance with the present invention , there is provided an interspinous process device , comprising : a ) a first hook - shaped portion adapted for contacting a first spinous process , b ) a second hook - shaped portion adapted for contacting a second spinous process , c ) a connector portion adapted to adjustably connect the first and second hook - shaped portions , wherein the first hook - shaped portions has acutely angled contact surface , and wherein the second hook - shaped portion has an obtusely angled contact surface . in some embodiments , each track has an arc shape , which allows for increasing the hook depth as distraction increases . therefore , in accordance with the present invention , there is provided an interspinous process device , comprising : a ) a first hook - shaped portion adapted for contacting a superior spinous process , b ) a second hook - shaped portion adapted for contacting an inferior spinous process , c ) an arced connector portion adapted to adjustably connect the first and second hook - shaped portions . in one arced embodiment , the arc forms a convex surface facing the hooked - shaped portions . in a second arced embodiment , the arc forms a concave surface facing the hooked - shaped portions . in preferred embodiments , the arc defines a radius of between about 2 cm and about 5 cm . in preferred embodiments , the implant has a single locking mechanism . the requirement of only a single locking mechanism minimizes the amount of time the surgeon must spend stabilizing the device . therefore , in accordance with the present invention , there is provided an interspinous process device , comprising : a ) a first hook - shaped portion adapted for contacting a superior spinous process , b ) a second hook - shaped portion adapted for contacting an inferior spinous process , c ) a adjustable connector portion adapted to adjustably connect the first and second hook - shaped portions , d ) a single lock ( such as a set screw ) adapted to lock the adjustable connector portion . in some embodiments , the set screw tightens upon an outer end portion of each track to produce an expanded hook state . in some embodiments , the inner end portion of each track is received in the housing to produce a collapsed hook state . in some embodiments , each hook - shaped portion has an inflection point 35 in each outer end portion . the inflection point allows the concave side 37 of the hook tip 39 ( i . e ., the side of the tip associated with the concave face 41 of the hook ) to contact the spinous process during insertion . the geometry of these hooks allows their insertion between the spinous processes without distracting the spinous processes . the hooks &# 39 ; subsequent distraction ( upon actuation of the inserter ) produces similar distraction in the spinous processes . in contrast , in other conventional interspinous process spacers ( which do not contain an inflection point ), the convex portion of the hook tip ( i . e ., the side of the tip associated with the convex portion of the hook ) distracts the spinous processes as the implant is being inserted . therefore , the inflection point provides an advantage in that both hooks are passed between the spinous processes at the same time , thus insuring full capture of the spinous processes before distraction . therefore , in accordance with the present invention , there is provided an interspinous process device , comprising : a ) a first hook - shaped portion adapted for contacting a superior spinous process , b ) a second hook - shaped portion adapted for contacting an inferior spinous process , c ) a connector portion adapted to adjustably connect the first and second hook - shaped portions , wherein the first and second hook - shaped portions each have an inflection point . in addition , the tips are bulleted to more easily puncture the ligament . in some embodiments , at least one track has a longitudinal groove 7 , 17 therein , and the tracks are oriented in the housing so that the longitudinal grooves nest . thus , each body component has an integrated track with grooves to interface with the opposite body . therefore , in accordance with the present invention , there is provided an interspinous process device , comprising : a ) a first hook - shaped portion adapted for contacting a superior spinous process , b ) a second hook - shaped portion adapted for contacting an inferior spinous process , c ) a connector portion adapted to adjustably connect the first and second hook - shaped portions , wherein the connector portion comprises first and second track portions having mating grooves . in some embodiments , the first and second bodies are oriented so that the hook - shaped portions open in opposite directions in the expanded state . in some embodiments , the housing has a mating feature to constrain the tracks in the housing . in particular , this mating feature is a pin that prevents groove 17 from sliding all the way out of the housing , thereby preventing disassembly . in some embodiments , the set screw has a mating feature to constrain the tracks in the housing . in particular , this mating feature is a pin that prevents groove 17 from sliding all the way out of the housing , thereby preventing disassembly . in some embodiments , the threaded recess extends into the housing in a third direction , and the throughbore extends through the housing in a fourth direction substantially perpendicular to the third direction of the threaded recess . in some embodiments , each body further comprises iii ) an intermediate portion connecting the inner end portion of the first hook - shaped portion to the inner end portion of the first longitudinal track . with correct material selection , the implant can be rigid for fusion , or have a spring - like action for non - fusion applications . therefore , in some embodiments , there is provided a method of using an interspinous spacer having a collapsed condition and an expanded condition , the method comprising the steps of : a ) inserting the spacer in its collapsed condition into an interspinous space of a patient that has been selected for spinal fusion , b ) expanding the spacer . in some embodiments , the site at which the spinal fusion is desired is the intervertebral disc space . preferably , some graft material and an intervertebral fusion cage is inserted into the disc space , preferably by a lateral approach . therefore , the patient receives both the spacer of the present invention within an interspinous space ( preferably with graft ) and an intervertebral fusion cage ( also preferably with graft ) in the disc space ). in some embodiments , the fusion site is an interspinous process site . spinal process fixation on the easily accessible dorsal processes of the spine represents one of the earliest historically acceptable means to accomplish segmental stability in the spine . see bradney i w : repair of a fracture / dislocation of lumbar vertebrae in a french poodle . aust vet j 43 : 421 , 1967 ; harmon h , hugenberg j e : surgical repair of a vertebra in a dog . j am vet med assoc 149 : 46 , 1966 ; hoerlein b f : methods of spinal fusion and vertebral immobilization in the dog . am j vet res 17 : 685 , 1956 ; hurov l : spinal fracture plating . sac 58 : 441 , 1962 ; and lumb w y , brasmer t h : partial vertebral prosthesis in a dog . j am vet med assoc 155 : 1581 , 1969 . posterior interspinous decompression in conjunction of spinous process fixation offers significant immediate stability as it provide resistance to flexion and rotation , however , this stability is limited by the relative strength of the spinous processes and implant stiffness . see neo m , fujibayashi s , yoshida m , nakamura t , spinous process plate fixation as a salvage operation for failed anterior cervical fusion , technical note , j neurosurg spine , 2006 january ; 4 ( 1 ): 78 - 81 ; liu g , zhao j n , dezawa a . “ endoscopic decompression combined with interspinous process implant fusion for lumbar spinal stenosis ”, chin j traumatol . 2008 december ; 11 ( 6 ): 364 - 7 . in one embodiment , a procedure producing posterior interspinous decompression in conjunction of spinous process fixation may be carried out as follows : after surgical exposure of the interspinous process space , the surgical technique begins with removal of the interspinous ligaments and contouring the bone edges of the adjacent segment inferior and superior aspects of the spinous processes . a small amount of distraction is applied , and next the lamina is thinned out with a burr . then , a curette is used to identify the ligamentum flavum . a small rongeurs is used to remove the bone covering the nerves . then , a curette is used to lift the ligaments from the nerve and decompress the dura . a small rongeurs is then used to cut the ligaments and complete the decompression until the dura is seen as shining . then , bone graft can be placed between the spinous processes , and the spacer is finally placed and locked after compressing the graft . the graft is held in place by the compression force applied by the spinous process fixation device . this virtually ensures subsequent bone fusion and offers substantial acute stability . this technique significantly diminishes translational mobility at the unstable segment . it also minimizes hyperextension at the unstable segment via medial compression of the grafts into the interspinous space . the fusion of a minimal number of spinal segments should be emphasized . this substantially diminishes the chance of flexible kyphosis and degenerative changes , both above and below the fusion site . in some embodiments , the site at which the spinal fusion is desired is an interspinous process space . preferably , some graft material and the spacer are inserted into the interspinous space . therefore , the patient receives both the spacer of the present invention within an interspinous space ( preferably with graft ). fig5 discloses a pair of devices 51 of the present invention implanted on a spine . the angled faces of the devices put the devices in an orientation that allows multiple implants to be implanted without contacting each other . fig6 a and 6 b disclose an inserter 61 of the present invention . in particular , the inserter comprises : a ) a longitudinal barrel 63 having a proximal end portion 65 and a distal end portion 67 , b ) a pistol grip 69 formed on the proximal end portion of the barrel , the pistol grip having a lever 71 , and c ) a shaft 73 disposed in the barrel and having a proximal end portion 75 and a distal end portion 78 having a pair of teeth 80 extending therefrom , d ) a knob 77 formed on the proximal end portion of the knob , and e ) a pair of linkages 79 formed on the distal end portion 78 of the shaft , each linkage having a distal pin 81 . actuation of the knob on the inserter serves to actuate the teeth to hold the housing . in use , the pin components of the inserter fits into the insertion features ( holes ) present on each of the bodies of the implant of the present invention . during insertion , the inserter is actuated so that the linkages are in an essentially parallel state and the pins are relatively close together to reflect the collapsed state of the implant . during distraction , the inserter is actuated so that the linkages are in an essentially perpendicular state ( as shown in fig6 a and 6 b ) and the pins are relatively far apart to reflect the expanded state of the implant . the components of the device of the present invention could be metal , plastic , or ceramic . if a metal is chosen as the material of construction for a component , then the metal is preferably selected from the group consisting of nitinol , titanium , titanium alloys ( such as ti - 6a1 - 4v ), chrome alloys ( such as crco or cr — co — mo ) and stainless steel . if a polymer is chosen as a material of construction for a component , then the polymer is preferably selected from the group consisting of polycarbonates , polyesters , ( particularly aromatic esters such as polyalkylene terephthalates , polyamides ; polyalkenes ; poly ( vinyl fluoride ); ptfe ; polyarylethyl ketone paek ; and mixtures thereof . in some embodiments , the components could be made of a stainless steel alloy , preferably biodur ™ ccm plus ™ alloy available from carpenter specialty alloys , carpenter technology corporation of wyomissing , pa . in some embodiments , the component is made from a composite comprising carbon fiber . composites comprising carbon fiber are advantageous in that they typically have a strength and stiffness that is superior to neat polymer materials such as a polyarylethyl ketone paek . in some embodiments , the component is made from a polymer composite such as a pekk - carbon fiber composite . in some embodiments , the composite comprising carbon fiber further comprises a polymer . in some embodiments , the polymer is a polyarylethyl ketone ( paek ). in some embodiments , the paek is selected from the group consisting of polyetherether ketone ( peek ), polyether ketone ketone ( pekk ) and polyether ketone ( pek ). in some embodiments , the paek is peek . in some embodiments , the carbon fiber comprises between 1 vol % and 60 vol % ( more preferably , between 10 vol % and 50 vol %) of the composite . in some embodiments , the polymer and carbon fibers are homogeneously mixed . in others , the material is a laminate . in some embodiments , the carbon fiber is present in a chopped state . in some embodiments , the chopped carbon fibers have a median length of between 1 mm and 12 mm , such as between 4 . 5 mm and 7 . 5 mm . in some embodiments , the carbon fiber is present as continuous strands . a ) 40 - 99 % ( more preferably , 60 - 80 vol %) polyarylethyl ketone ( paek ), and wherein the polyarylethyl ketone ( paek ) is selected from the group consisting of polyetherether ketone ( peek ), polyether ketone ketone ( pekk ) and polyether ketone ( pek ). in some embodiments , the composite consists essentially of paek and carbon fiber . in some embodiments , the composite comprises 60 - 80 wt % paek and 20 - 40 wt % carbon fiber . for example , the composite may comprise 65 - 75 wt % paek and 25 - 35 wt % carbon fiber .
a device intended for the treatment of spinal stenosis . this device is an inter - spinous spacer that is introduced through a single posterior incision . it uses a single piece insertion technique with a unilateral approach . the surgeon does not need to access the opposite side of the spinous process . it allows the user infinite adjustability in distraction height with a single locking mechanism .