Passive reduction of spondylolisthesis on the operating room table: a prospective study.

Translational motion of low-grade spondylolisthesis is traditionally assessed with lateral flexion and extension radiographs. Maximum motion in an unanesthetized patient may be limited by patient cooperation, pain, or muscle spasm. Twenty-four patients with degenerative or isthmic spondylolisthesis were assessed with preoperative lateral flexion and extension radiographs. A lateral radiograph was obtained on the operating room table after administering an anesthetic, exposing the spine, and performing a laminectomy. The percentage slip decreased from 24 to 15 to 6% on flexion, extension, and intraoperative lateral radiographs, respectively (p < 0.001). The amount of reduction did not correlate with disc height, slip angle, slip level, or type of spondylolisthesis. Many low-grade spondylolisthesis deformities reduce almost completely on the operating table. Translational motion of spondylolisthesis is greater than preoperative flexion and extension radiographs indicate.