THE ROLE OF PEDICULOLAMINAR FIXATION IN COMPROMISED PEDICLE BONE

Study Design. This in vitro study analyzed the effects of a supralamin ar hook on pedicle screw fixation in compromised pedicle bone. Objecti ves. To determine the ability of pediculolaminar fixation to restore p edicle screw pull-out strength after stripping of senile pedicle bone. Summary of Background Data. Despite improvements in pedicle screw des ign, the bone-screw interface remains the ''weakest link'' in pedicle screw fixation. This interface is especially vulnerable in osteoporoti c bone, previously instrumented pedicles, and at the ends of long inst rumentation constructs. Methods. Side-to-side testing between a pedicl e screw and a pedicle screw supplemented with a supralaminar hook (ped iculolaminar fixation) was performed in human cadaveric lumbar vertebr ae. Comparisons were made for intact and compromised pedicle bone. Res ults. Pediculolaminar fixation restored 89% of intact pedicle screw pu ll-out strength, whereas the pedicle screw alone restored only 19% of intact pull-out strength. The role of pediculolaminar fixation was gre atest in weaker bone. Significant differences were noted in energy to failure and post-failure energy. In intact bone, the pediculolaminar c onstruct did not increase pull-out strength or energy to failure, alth ough it did have a greater post-failure energy. Conclusion. Pediculola minar fixation can augment pedicle screw fixation in pedicle bone comp romised by previous stripping or significant osteoporosis or both.