Radiological features of spondylolysis and spondylolisthesis in the adult health study sample

Radiographs made periodically of the lumbosacral spines of 85 spondylolysis and 31 spondylolisthesis patients were studied for interval changes during observation periods as long as 20 years. Five had spondylolysis at multiple levels and four had spondylolysis and spondylolisthesis at different levels; 31% of the spondylolysis was unilateral whereas the previously reported rate was 20%. Four types of isthmic defects occurred. A broad-angular type was observed only at the upper lumbar levels, and this probably develops in a manner different from the other types. Of 40 persons with unilateral defects 25 had elongation of their contralateral intact isthmus, most likely due to repeated fractures and healing, with increase in its length each time. One case of spondylolisthesis developed to double level involvement. A trapezoidal shaped vertebral body, hypermobility of the affected vertebral body, and progressive degenerative disc changes predisposed to anterior displacement, but when intervertebral spaces became markedly narrowed, the anterior displacement ceased. Contrary to earlier reports, this study shows that spondylolysis can develop and progress to spondylolisthesis in middle aged and older persons. (author)