To verify the changes of segmental motion after posterolateral lumbar fusion.

Thirty-eight cases of lumbar posterolateral fusion with good postoperative results and full range of motion, followed up for at least one year were reviewed. We measured the translation and angulation by the Dupuis method on flexion extension radiographs.

1) The motion at adjacent segments was 0.75 mm translation and 6.5 degree angulation at L1-2, 0.75 mm and 8.62 degree at L2-3, 0.95 mm and 9.67 degree at L3-4, 1.17 mm and 10.67 degree at L4-5 and 0.41 mm and 7.41 degree at L5-S1. The motion at L5-S1 was less than that in the control group, but at other levels it was not different. 2) The total range of motion of lumbar spine in the control group was 47.8 degree. In one-segment fusion the range of motion was 31.1 degree(64.9%), in two-segment fusion was 26.8 degree(56.1%) and in three-segment fusion was 14.3 degree(29.8%). The longer the fusion level was, the smaller the total range of motion of lumbar spine was. 3) The percentage of motion at adjacent mobile segments in the fusion group increased more significantly than that in the control group.

Segmental motion at adjacent segment in the fusion group was similar to the motion in the control group. The compensatory increased motion at adjacent mobile segment was not definite, however, the percentage of motion at adjacent segment increased after spinal fusion.