The significance of residual stenosis after decompression for lumbar spinal stenosis.

Thirty-one patients with degenerative or combined degenerative and developmental lumbar spinal stenosis diagnosed by myelography and at subsequent surgery were thoroughly examined by computed tomography (CT) to reveal the completeness of the decompression and its correlation with the outcome. Complete elimination of the stenosis was achieved in 10 cases (32%) of whom 9 (90%) showed improvement. Various combinations of residual stenosis (some type of stenosis of the lateral part of vertebral canal at the laminectomy sites and also central stenosis outside the laminectomy field) were observed in 21 cases (68%). Of these, 14 (67%) had nearly complete, subtotal decompression with minimal or some residual stenosis, 7 (33%) had only minor decompression of the most constricted part of the spinal canal with a considerable amount of residual stenosis. The latter groups showed improvement in 8 cases (57%) and 6 cases (86%), respectively. Three patients (10%) with increased postoperative symptoms had only minimal or some residual stenosis. The significance of these findings is discussed.