FLEXIBILITY AND DISTRACTION AFTER MONOSEGMENTAL AND BISEGMENTAL LUMBOSACRAL FIXATION WITH ANGULAR STABLE FIXATORS

Study Design. In human lumbosacral spines, the flexibility and interse gmental distraction allowed by four monosegmental and bisegmental intr apedicular devices during compression and flexion/compression loading were investigated. Objectives. To compare the flexibility and interseg mental distraction allowed by four monosegmental and bisegmental intra pedicular, lumbosacral fixation devices applied to destabilized cadave ric spines, and to determine the effect of each device on the flexibil ity and intersegmental distraction of the motion segment above each fu sed segment. Summary of Background Data. The lumbosacral segment is th e most mobile region in the lumbar spine, exhibiting the highest range of motion in both flexion and extension. Therefore, the fixation of t his and the adjacent segment is of special clinical interest. Methods. L5-S1 facetectomy of L5 laminectomy procedures were performed on cada veric human lumbosacral spines. Fixation devices then were applied acr oss one or two levels, and intersegmental motion under flexion/compres sion or under pure compression loads was monitored. Results. The flexi bility and posterior strain allowed by the four implants did not diffe r significantly between implants. The strain across the stabilized sit e (monosegmental and bisegmental) was below 10% for all devices tested . The flexibility and distraction were reduced to levels below intact after the fixators were applied. The distraction across the segment ab ove the fusion was not increased because of fixation with these four f ixators. Conclusion. Angular stable fixation devices, such as those de scribed here, provide adequate stabilization of the posteriorly destab ilized spine.