The role of pediculolaminar fixation in compromised pedicle bone.

Abstract

This in vitro study analyzed the effects of a supralaminar hook on pedicle screw fixation in compromised pedicle bone. To determine the ability of pediculolaminar fixation to restore pedicle screw pull-out strength after stripping of senile pedicle bone. 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. 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. 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. Pediculolaminar fixation can augment pedicle screw fixation in pedicle bone compromised by previous stripping or significant osteoporosis or both.