BIOMECHANICAL EVALUATION OF CASPAR AND CERVICAL-SPINE LOCKING PLATE SYSTEMS IN A CADAVERIC MODEL

There exist two markedly different instrumentation systems for the ant erior cervical spine: the Cervical Spine Locking Plate (CSLP) system, which uses unicortical screws with a locking hub mechanism for attachm ent, and the Caspar Trapezial Plate System, which is secured with unlo cked bicortical screws. The biomechanical stability of these two syste ms was evaluated in a cadaveric model of complete C5-6 instability. Th e immediate stability was determined in six loading modalities: flexio n, extension, right and left lateral bending, and right and left axial rotation. Biomechanical stability was reassessed following fatigue wi th 5000 cycles of flexion-extension, and finally, the spines were load ed in flexion until the instrumentation failed. The Caspar system stab ilized significantly in flexion before (p < 0.05) but not after fatigu e, and it stabilized significantly in extension before (p < 0.01) and after fatigue (p < 0.01). The CSLP system stabilized significantly in flexion before (p < 0.01) but not after fatigue, and it did not stabil ize in extension before or after fatigue. The moment needed to produce failure in flexion did not differ substantially between the two plati ng systems. The discrepancy in the biomechanical stability of these tw o systems may be due to differences in bone screw fixation.