Abstract
The three dimensional intervertebral movements of fourteen patients with lumbar instability were measured. These movements of a group of six normal subjects were also measured. The CT scan in rotation to the left and to the right was used to investigate the axial rotational instability of the lumbar spine. MRI was used to determine the grade of disc degeneration. The relations between the axial rotational instability and other dimensional movements, the grade of disc degeneration and physical signs were analyzed. The facet of the lumbar spine with rotational instability showed hypertrophy, subluxation and joint laxity. The intervertebral disc of the lumbar spine with rotational instability showed the grade 3-4 disc degeneration. When facet degeneration increases in addition to disc degeneration, rotational instability may occur, and then rotational deformity may narrow the lumbar canal.
