Lumbar spinal instability (olisthesis) after extensive posterior spinal decompression.

Twenty-seven patients who underwent extensive posterior spinal decompression procedures were reviewed to investigate the incidence, the clinical significance and contributing factors of the postdecompression olisthesis, and indication for spinal fusion at the time of extensive decompression. Eleven patients were female and 16 were male. The mean age was 49.4 years. Twenty-two patients were treated with extensive decompression and spinal fusion, and five patients were treated with decompression alone without spinal fusion. The average follow-up time was 2 1/2 years (1-4 1/2). The incidence of newly developed postdecompression olisthesis was 3.7% (1/27) and all four patients with preoperative spondylolisthesis progressed further postoperatively. The author was neither able to identify definitive contributing factors for olisthesis, nor able to confirm the previously reported factors: young age, normal disc heights, and multiple level decompression in this review study. The incidence rate of pseudarthrosis was high (27.3%) after the extensive posterior decompression and fusion. The concomitant spinal fusion is not routinely indicated to patients with extensive posterior spinal decompression. Furthermore, it does not appear to be effective in prevention of olisthesis. The concomitant spinal fusion should be exceptional rather than routine.