Clinical study on stability of combined distraction and compression rod instrumentation with posterolateral fusion for unstable degenerative spondylolisthesis.

The authors examined the stability of combined distraction and compression rod instrumentation with posterolateral fusion in 40 consecutive patients with unstable degenerative spondylolisthesis. All operations were performed by floating fusion of L3-4 or L4-5 after decompression procedures. Mobility at the fused level was checked every 4 weeks after operation by the disc space angle on the functional radiographic films without brace. The average period of postoperative follow-up was 26 months. In 30 patients, no mobility was found at any time. In six patients, any mobility disappeared within 24 weeks, and in three patients, within 1 year. Pseudoarthrosis was found in one patient. The solid fusion rate was 97.5%. The values of percent slippage and slip angle were slightly improved. Lumbar lordosis was in the normal range at follow-up.