The role of pediculolaminar fixation in compromised pedicle bone

Study Design. This in vitro study analyzed the effects of a supralaminar hook on pedicle screw fixation in compromised pedicle bone. Objectives. To determine the ability of pediculolaminar fixation to restore pedicle screw pull-out strength after stripping of senile pedicle bone. Summary of Background Data. Despite improvements in pedicle screw design, the bone-screw interface remains the ''weakest link'' in pedicle screw fixation. This interface is especially vulnerable in osteoporotic bone, previously instrumented pedicles, and at the ends of long instrumentation constructs. Methods. Side-to-side testing between a pedicle screw and a pedicle screw supplemented with a supralaminar hook (pediculolaminar fixation) was performed in human cadaveric lumbar vertebrae. Comparisons were made for intact and compromised pedicle bone. Results. Pediculolaminar fixation restored 89% of intact pedicle screw pull-out strength, whereas the pedicle screw alone restored only 19% of intact pull-out strength. The role of pediculolaminar fixation was greatest in weaker bone. Significant differences were noted in energy to failure and post-failure energy. In intact bone, the pediculolaminar construct did not increase pull-out strength or energy to failure, although it did have a greater post-failure energy. Conclusion. Pediculolaminar fixation can augment pedicle screw fixation in pedicle bone compromised by previous stripping or significant osteoporosis or both.