Compression-traction radiography of lumbar segmental instability.

Compression-traction radiography was used to assess movements in the sagittal plane of the lumbosacral joint in a control group of asymptomatic normal individuals and in a patient group with a symptomatic lytic spondylolisthesis. Sagittal translatory movements were found in both groups, but the amount of displacement was significantly larger (P less than 0.001) in the patient group as compared with the controls. The average displacement in the patient group, using a relative measurement technique, was 5.2%, ranging from 0.2 to 15.4%; and the corresponding values in the controls resulted in a mean of 0.8% and a range of -2.3% to 3.6%. Eighteen of the 29 patients (62%) exhibited translations of the lytic vertebra exceeding the largest displacement (greater than 3.6%) detected in the control group. The translatory movements in the patients were composed of a predominant anterior displacement in the compression view and a smaller posterior movement in the traction view. Analysis of sagittal rotation, ie, angulatory movements in the L5-S1 segment, resulted in no significant difference between the two groups. Compression-traction radiography may detect pathologic translatory movements, indicative of lumbar segmental instability.