[Isthmic spondylolisthesis with spontaneous development in adults. Apropos of 8 cases].

Eight cases of progressive deterioration in spondylolisthesis in adults have been observed. In 7 cases, the displacement was between the 4th and 5th lumbar vertebra and only once between the 5th lumbar vertebra and the sacrum. The mean age of the patients was 37 years. Several factors leading to this deterioration are considered - disc degeneration, antero-posterior imbalance of the spine and inadequate fixation of the 4th lumbar vertebra to the ilium.