[Risk of instability following decompression surgery for lumbar spinal stenosis].

46 patients with lumbar stenosis and neurogenic claudication underwent laminectomy at least over 2 and in 17 cases over 3 segments with removal of the medial half of the facets. 30 patients had a straight spine and 16 a rotation scoliosis. The patients were followed-up regularly 3-10 years after operation, the pre- and postoperative dynamic X-ray views were compared and the symptoms of the patients assessed. In total, 14 or 30% of the spine were unstable. Most commonly, translational instabilities occurred, less frequently retrolisthetic and rotational ones. A significant correlation between low back pain and instability was not found. We are of the opinion that the main cause of an instability is based on the natural history of the disease and is not originated in the extent of surgery.