Differences in repositioning error among patients with low back pain compared with control subjects

Study Design. Trunk repositioning error was measured in 20 patients with chronic low back pain and 20 control subjects. Objectives. To measure trunk repositioning error as a method of measuring proprioception of the low back and to compare trunk repositioning error in patients with low back pain and in control subjects. Summary of Background Data. Although many current low back pain rehabilitation programs incorporate proprioceptive training, very little research has been performed on proprioception of the low back. Methods. While standing with the legs and pelvis immobilized, the subject bent the trunk to a predetermined target position and then attempted to replicate the position. Repositioning error was calculated as the absolute difference between the actual target position and the subject-perceived target position. The multiple target positions in the frontal and sagittal planes were tested. Trunk position was measured with a 3Space Tracker, which analyzes the three-dimensional position of the body. Results. Repositioning error in patients with low back pain was significantly higher than that of control subjects in flexion, and significantly lower than that of control subjects in extension. Conclusions. The increase in repositioning error of patients with low back pain during flexion implies that some aspects of proprioception are lost in patients with low back pain. The decrease in repositioning error in patients with low back pain in extension is not as easily explained, but could possibly be caused by increased activation of mechanoreceptors in facet joints.