Abstract
The purpose of this study was to investigate the biomechanical stability of unilateral pedicle screw and rod system fixation (unilateral PS fixation) using the Tadpole system fixation for an unstable lumbar spine. We used 5 lumbar spines (L3/4) of a functional spinal unit (FSU) obtained from wild boar cadaver specimens. Damage or instrumentation was sequentially administered to each specimen, and 6 models were prepared: (1) an intact model, (2) an injury model with facet joint resection, (3) a unilateral PS fixation model, (4) a bilateral PS fixation model, (5) a Tadpole system fixation model, and (6) a combination of the unilateral PS and Tadpole system fixation models. We conducted a bending test in 8 directions by using a 6-axis material tester, and the range of motion (ROM) of each model in all directions was measured. The ROM of the combined fixation model of the unilateral PS and Tadpole system was considerably decreased in all directions. These findings indicate that the combination unilateral PS and Tadpole system fixation is a minimally invasive method that has the same stability as bilateral PS fixation.
