Mechanical instability as a cause of gait disturbance in high-grade spondylolisthesis: a pre- and postoperative three-dimensional gait analysis.

Mechanical instability of the spinopelvic junction is a suspected cause of abnormal gait in high-grade spondylolisthesis. Computerized three-dimensional gait analysis was performed on a 10-year-old with grade III spondylolisthesis at L-5. Preoperatively, the gait pattern was characterized by posterior pelvic tilt, decreased hip flexion, increased knee flexion, and decreased stride length and walking speed. All temporal and kinematic parameters of gait normalized after laminectomy and instrumented, in situ arthrodesis (L-4-S-1). The absence of any neurologic abnormalities on preoperative imaging, intraoperative somatosensory-evoked potentials (SSEP) monitoring, and nerve-root exploration, together with the observed improvement after stabilization of the spinopelvic junction, suggests a mechanical basis for the gait changes in high-grade spondylolisthesis.