Degenerative lumbar spondylolisthesis. Part I: Etiology, pathogenesis, pathomorphology, and clinical features.

The authors analyze the clinical features and the results of various imaging studies in 77 patients with degenerative lumbar spondylolisthesis. The most commonly olisthetic vertebra was L-4, followed by L-3. The extent of the olisthesis ranged from 8-43%. Forty-two percent of the patients with L-3 or L-4 olisthesis had reduced mobility of the underlying vertebra. Five different clinical pictures were present: no symptoms except occasional low back pain; chronic low back pain with no radicular symptoms; radicular symptoms and no signs of nerve root compression, with or without low back pain; radicular symptoms with neurologic deficit; intermittent claudication. Various pathological conditions were identified: slight narrowing of the central spinal canal without compression of neural structures; isolated stenosis of the nerve root canal; stenosis of both the nerve root canal and the central spinal canal. The onset of degenerative spondylolisthesis seems to be connected to excessive shear forces on the olisthetic vertebra. The extent of neural structure compression, and thus the clinical picture, depends on three factors: the primitive size of the spinal canal, the extent of degenerative changes in the zygapophyseal joints, and the extent of olisthesis.