Extension-flexion radiographs for motion studies of the lumbar spine. A comparison of two methods.

Since abnormal motion is a quantitative phenomenon and present primarily in the two lowest vertebral spaces, a roentgen examination method yielding the maximum mobility would appear to be suitable. When performing extension-flexion radiographs of the lumbar spine, positioning of patients varies considerably. The present study describes a new examination method, yielding better mobility of the spine than any method earlier described. For the two lowest vertebral spaces, L4-5 and L5-S1, the new method implied significantly greater angular mobility and total angular mobility between L2-S1 than a previous method. Intra- and interobserver errors accounted for were acceptable and the accuracy of the measurements sufficient for clinical work.