Long-term clinical and radiological postoperative outcomes after an interspinous microdecompression of degenerative lumbar spinal stenosis.

STUDY DESIGN: A retrospective study to evaluate the clinical outcome and the risk of postoperative instability 5 years after microsurgical management of lumbar spinal stenosis using the interspinous approach.

OBJECTIVE: To evaluate the long-term outcome and the risk of postoperative instability after the microsurgical interspinous decompression of lumbar spinal stenosis.

SUMMARY OF BACKGROUND DATA: The interspinous approach involves partial resection of the supraspinous ligament followed by resection of the interspinous ligament, partial resection of the caudal aspect of the superior spinous process and resection of the ligamentum flavum, producing a central fenestration through which the decompression of the cauda equina and the nerve roots can be effected with an undercutting technique, with tailored partial resection of the lamina and the medial aspects of the facet joints. In this article, we investigated the long-term clinical outcome and the long-term risk for instability after using this approach.

METHODS: One hundred and 6 patients undergoing decompressive surgery for lumbar spinal stenosis using the interspinous approach, including cases with spondylolisthesis without instability, were included in this study. The long-term outcome was evaluated in a follow-up study, 5 years after surgery. The clinical long-term outcome was evaluated retrospectively using self-rating questionnaires: the Oswestry Disability Index, visual analogue scale (0-10), walking capacity (1-5), progress in walking capacity and global activity, and level of satisfaction. The risk of postoperative instability was evaluated on the basis of dynamic radiographs of the lumbar spine.

RESULTS: The Oswestry Disability Index showed a mean improvement in symptoms from 58.20% to 21.61%, and the visual analogue scale showed that the intensity of leg and back pain decreased from 8.62 and 8.69 points to 2.33 and 3.48 points, respectively. Walking capacity increased from 3.37 (severely restricted) to 1.81 (slightly restricted), and 93.23% of cases indicated that they were moderately satisfied or very satisfied. Dynamic radiographs revealed no postoperative instability after decompression using the interspinous approach.

CONCLUSION: The clinical outcome 5 years postoperatively after using the interspinous approach for lumbar spinal stenosis showed a favorable maintenance of improvement in symptoms. Radiological data showed that this approach does not alter the stability of the spine.

LEVEL OF EVIDENCE: 4.