Three-dimensional x-ray analysis of normal movement in the lumbar spine.

Biplanar radiography was used to assess the normal three-dimensional movements of the lumbar spine in the erect posture in a group of asymptomatic volunteers. The primary movements investigated were flexion and extension, while the three-dimensional analysis also measured any associated coupled lateral bends and axial rotations. The results showed that each intervertebral joint had a total range of flexion and extension of approximately 14 degrees, the lower levels moving slightly more than the upper levels. All the intervertebral joints had more movement in flexion than extension from the upright position, except for the L5/S1 joint, which showed no consistent pattern, some subjects extending more than flexing. Coupled movements of 4 degrees or more in flexion and 3 degrees or more in extension were shown to be abnormal.