in its preferred embodiment device consists of a screw , screw clamp , rod receiver , compression spacer , rod and nut ( fig1 ). screw has a long threaded portion placed into the bone and a protruding cylindrical shaft with a spherical head ( fig2 ). a compressible cylindrically shaped screw clamp of substantial thickness ( fig3 ) has a spherical cut - out at one end such that it fits precisely over the screw head ( fig4 ). it pivots about the screw head with angle of deflection greater then ninety degrees and 360 degrees of revolution through the entire range of deflection . screw clamp ( fig6 ) tightly fits into cylindrical assembly consisting of the rod receiver and compression spacer ( fig7 ). rod receiver has a travel tube with a tapered end which fits over the screw clamp . the other end forms the seat for the rod bounded by threaded walls ( fig8 ). up and down movement of the screw clamp within the rod receiver allows for a vertical adjustment . compression clamp is a deformable component fitting within the travel tube of the rod receiver ( fig5 ). it has a contact dome extending into the seat of the rod receiver . pressure from the rod locked into the seat by a threaded nut , displaces the compression spacer into the tapered end of the travel tube . the resulting deformation of the compression spacer transfers compressive force onto the screw clamp . this fixes the screw head within the screw clamp and prevents any travel of the screw clamp within the travel tube . this process is repeated for each screw in the assembly . alternative embodiments of the screw shaft and screw clamp articulation which enable pivoting and rotational motion are possible . fig1 preferred embodiment of the invention showing screw ( 1 ), screw clamp ( 6 ), compression spacer ( 9 ), rod ( 17 ) and nut ( 18 ) fig1 a different orientation of the preferred embodiment of the invention showing screw ( 1 ), screw clamp ( 6 ), compression spacer ( 9 ), rod ( 17 ) and nut ( 18 ). fig2 bone screw consisting of threaded portion ( 2 ), protruding shaft ( 3 ) and spherical head ( 4 ). please notice the channel ( 5 ) through the center of the screw . fig3 preferred embodiment of the screw clamp consisting of a cylindrical compressible shaft ( 8 ) and articulating end ( 7 ). fig4 articulation between screw head ( 4 ) and articulating end ( 7 ) of the screw clamp . notice that this articulation allows only pivoting motion and is not a ball - socket joint . fig5 one of the embodiments of the compression spacer ( 9 ) with contact dome ( 10 ) which is depressed by the rod ( 17 ) when its locked , and constricting tube ( 11 ) deformed by the tapered section of the rod receiver ( 16 ). fig6 preferred embodiment of the rod receiver ( 12 ) consisting of the seat ( 13 ) for the rod , threaded extensions ( 14 ) which accept a nut ( 18 ), travel tube ( 15 ) and tapered end ( 16 ). fig7 assembly consists of screw clamp ( 6 ), compression spacer ( 9 ) and rod receiver ( 12 ). fig8 preferred embodiment of the invention with compression spacer ( 9 ) and rod receiver ( 12 ) rendered transparent to demonstrate the entire assembly . also note the screw clamp ( 6 ) and the screw ( 1 ). note that if deformable compression spacer ( 9 ) is pressed into the rod receiver ( 12 ) the tapered configuration at the bottom of the rod receiver will constrict corresponding area of the compression spacer , which in turn will transmit compressive forces to the articulation between screw clamp ( 6 ) and a screw ( 1 ). demonstrates 90 degrees deflection angle ( potentially & gt ; 90 degrees ) between screw ( 1 ) and screw clamp ( 6 ). fig1 assembly demonstrates vertical travel of screw clamp ( 6 ) within the rod receiver ( 12 ). please compare to pic 8 . please note that compression by compression spacer ( 9 ) will be transferred to screw clamp ( 6 ) over a wide range of vertical travel . fig1 bone screw ( 1 ) with central channel ( 5 ). fig1 . bone screw ( 1 ) with off - center channel ( 5 ). fig1 alternative embodiment of the screw ( 1 ) and screw clamp ( 6 ) articulation with compressible spherical spacer ( 19 ) threaded over the cylindrical screw shaft ( 3 ). fig1 alternative embodiment of the screw ( 1 ) and screw clamp articulation . screw clamp would be modified to fit over the projections ( 20 ) of the compressible t - spacer ( 21 ).
an apparatus for rigid fixation of individual vertebra to the stabilizing rod . it consists of an anchor secured to the vertebra and a connector with multiple degrees of freedom linking each anchor to a rod . pressure from the rod against a connector engages internal constricting mechanism and eliminates movement within the connection . this results in rigid fixation between individual anchors and the rod .