Purpose of the study Degenerative spondylolisthesis of the osteoarthritic spine can lead to severe invalidating back pain, decompensating a clinical situation previously well controlled with drugs. Hypothesizing that such invalidating spinal pain might be related to the unstable olisthy, we treated our patients with isolated intersomatic arthrodesis without reducing the displacement. We present here our results in a retrospective analysis of 39 patients who underwent surgery between 1981 and 1992. Material and methods Mean age of the 39 patients, 11 men and 28 women, was 62 years (mean, range 37-89). Lumbar spine pain had been well controlled for a mean 10 years. The development of important lumbalgia despite adequate drug treatment led to the indication for surgery in all cases. Thirty-four patients experienced radicular claudication which was severe in 16 cases with a walking distance of less than 100 m. Invalidating radiculalgia occurred in a territory compatible with the olisthy: 33 L4-L5, 2 L5-S1, 4 L2-L3. Twelve patients had a neurological deficit in the L5 territory. Myelography, performed in 26 patients, demonstrated complete interruption of the opaque column in 10 facing the superior surface of the oisthy and radicular amputation in 13; compression over several levels was observed in 13 cases. Anterior intersomatic arthrodesis was done with an iliac tricortical corticospongious graft, associated with en bloc cement insertion in 13 cases. A strut plate screwed on the adjacent vertebral bodies was adapted to the vertebral displacement that was not modified. The upright position was authorized on day 20-45 with a corset worn until day 90. No procedure was attempted on adjacent levels. Postoperative myelography or MRI was obtained for 30 patients. Results Mean follow-up was 4 years (range 1-10 years). Transient postoperative paresis (L5) occurred after L4-L5 arthrodesis in 2 patients and phlebitis in 3 patients (one complicated with pulmonary embolism without sequelae). Fusion of the arthrodesis was achieved in all cases. The degree of displacement and the height of the "intersomatic space" was modified little compared with the preoperative situation. Radicular claudication regressed totally in 29 cases (85%) and partially in 5 (15%). Radiculalgia regressed totally in 29 (74%) and partially but substantially in 7 (18%). Lumbalgia regressed totally in 20 cases (54%) and partially in 15 (40%). Function, as assessed wth the Beaujon scale, improved from 8 to 17/20 points. There was one case of secondary degradation with development of radiculalgia related to the level above the arthrodesis in one case. No cause could be identified to explain the failure to relieve preoperative radiculalgia in 8% of the patients. Conclusion Strut plates screwed onto the vertebral bodies enabled intersomatic fusion in all cases. Stabilization of the olisthy alone, without correction of the displacement nor release of the canal, successfully relieved pain in all cases of severe radiculalgia due to osteoarthritic spondylolisthesis and even provided improvement of lumbar pain in patients with various levels of discopathy. Unstable olisthy would thus be the major cause of invalidating pain, particularly radiculalgia in these patients.
