A prospective randomized study of unilateral versus bilateral instrumented posterolateral lumbar fusion in degenerative spondylolisthesis

Study Design. Prospective randomized study on 82 patients with degenerative lumbar spondylolisthesis, having undergone posterolateral fusion with bilateral or unilateral instrumentation. Objective. To determine the effectiveness of unilateral pedicle instrumentation in clinical outcome and rate of union in comparison with the classic bilateral system. Summary of Background Data. Instrumentation has proved to have advantages and disadvantages related to its rigidity. The use of less rigid systems applied to posterior lumbar fusions proved promising according to the results achieved in both experimental and clinical field. Methods. Eighty-two patients were randomized into 2 groups: Group 1 (n = 42) had had bilateral instrumentation, and Group 2 (n = 40) had only had unilateral instrumentation. One case from Group 1, L3-S1 dropped out; only fusions of 1 or 2 levels remained in the study. Length of time spent on operating, blood loss, blood transfusion, hospital stay, complications, clinical results measured by SF-36v2, and radiologic assessment of union and of loss of height of adjacent discs were analyzed and compared by means of chi(2) test, t test, and Fisher exact test. Results. Statistically, there was no significant difference between the 2 groups in relation to demographics, blood loss, need of transfusion, hospital stay, complications, clinical results, rate of union, and effect on adjacent discs. The operating time needed for Group 2 was significantly shorter in than the time needed for Group 1 (P < 0.001). In Group 1, 3 of 186 screws violated the pedicle cortex requiring reoperation because root irritation versus no complication on a total of 90 screws in Group 2. Conclusion. Unilateral instrumentation used for the treatment of degenerative lumbar spondylolisthesis is as effective as bilateral instrumentation when performed in addition to 1- or 2-level posterolateral fusion. The cost of this method is lower, saves time, and reduces possible risk inserting screws in only one side.