Degenerative spondylolisthesis. Pathophysiology and results of anterior interbody fusion.

With special attention to the articular facets, an inspection of dry human spinal columns, microradiographic studies of cadaveric specimens, and animal experiments revealed that development of degenerative spondylolisthesis is attributable to rotational strain on the facetal joints at the level of involvement. Disc degeneration predisposes to intersegmental instability and rotational strain, which result in secondary osteoarthritic change of the articular processes and segmental canal stenosis. Thirty-six patients with degenerative spondylolisthesis were treated with anterior interbody fusion (AIF) for segmental canal stenosis at the authors' hospital during 1958-1985. The surgical results of these patients reveal that AIF corrects malalignment of the lumbar spine by complete discectomy, reduces the slip and restores the disc height, and resolves nerve compression, both from the front and from behind, by enlargement of the stenosing canal. In addition, AIF has consistent and satisfactory clinical results at long-term follow-up evaluation because it resolves intersegmental instability, an important problem of degenerative spondylolisthesis. AIF is a reasonable and reliable treatment for patients younger than 60 years of age with segmental stenosis.