OBJECTIVESTo find out the radiologic factors predicting the outcomes of reduction of lumbar spondylolisthesis.

METHODSForty two patients were treated with pedicle screw fixation with posterolateral fusion because of lumbar spondylolisthesis, with the average age of 56.0 years. There were 11 males and 31 females; 20 degenerative spondylolisthesis cases, and 22 isthmic spondylolisthesis cases; 1 L(3,4) case, 26 L(4,5) cases and 25 L(5)S(1) cases; 23 grade I patients and 19 grade II ones. All patients were taken the X-ray examination before operation and one week after operation. Measurements of slip ratio, percentage disc height, slip angle, lumbar lordosis angle and sacral slope angle were based on pre-operation X-rays. Measurements of the post-operation slip ratio were based on post-operation X-rays. Multivariate regression analysis was used to analysis the correlation between reduction ratio and pre-operation slip ratio, slip angle, percentage of disc height, lumbar lordosis angle and sacral slope angle.

RESULTSThe average pre-operation slip ratio was (22.5 +/- 10.6)%. The pre-operation percentage disc height was 0.23 +/- 0.10, the slip angle was 4.4 degrees +/- 5.4 degrees , the lumbar lordosis angle was 43 degrees +/- 13 degrees and the sacral slope angle was 34 degrees +/- 10 degrees . The reduction ratio was (63.2 +/- 27.9)%. No correlation was found among reduction ratio with pre-operation slip ratio, slip angle and sacral slope angle, but a positive correlation between reduction ratio and the pre-operation percentage of disc height (P < 0.05), a positive correlation between reduction ratio and the pre-operation lumbar lordosis angle (P < 0.05) was found.

CONCLUSIONThe percentage disc height and the lumbar lordosis angle can predict the outcomes of reduction of lumbar spondylolisthesis.