Effects of back pain on the correlation between hip and lumbar spine movements

Abstract

The aim of this experimental study was to examine the effects of low back pain and limitation in straight leg raise on the kinematics of the lumbar spine and hips. Methods A real-time three-dimensional electromagnetic tracking system was used to measure the movements of the lumbar spine and hips during various anatomical movements. Kinematic analysis was performed in asymptomatic subjects (n=20), and back pain subjects with (n=18) and without (n=24) limitation in straight leg raise. Subjects were requested to perform forward, backward and side bending, and twisting of the trunk. One-way analysis of variance, (ANOVA) was used to compare the maximum magnitude of movements among the three groups. Cross-correlation was employed to reveal the relative time lag between lumbar spine and hips and the strength of correlation of the movements. Results ANOVA revealed that the ranges of various lumbar spine movements were significantly reduced in back pain subjects (p<0.05). During forward bending of trunk, the maximum hip flexion ranges were significantly different among the three groups. However, there were no differences in the hip ranges of movements in the other directions (p<0.05). Back pain subjects required significantly more time to complete all three trunk movements (p<0.05). For forward & backward bending, the contributions of the lumbar spine and hips were approximately equal. During side-bending of the trunk, the magnitude of the lumbar spine movement was more than twice of those of the hips. On the other hand, during trunk twisting, the contribution of the spine was smaller than that of the hips. Back pain and limitation in SLR was found to affect the relative contributions of the lumbar spine and hips during side-bending and twisting of the trunk, but not that for forward and backward bending. The strength of correlation between the movements of the lumbar spine and hip were high in normal subjects for all trunk movements. The mean peak cross-correlation coefficients were generally smaller in back pain subjects (p<0.05). The time lags at peak correlation were not significantly different from zero for all movements (p>0.05) in all groups. Discussion and conclusion The experimental results suggest that back pain is associated with significant changes in the kinematic characteristics of the trunk. Subjects with limited SLR exhibited further reduction in hip flexion when compared with subjects with back pain only. It is suggested that stiffness of posterior hip tissues may contribute to the limitation in SLR and range of movement. It is revealed that back pain patients modify their joint coordination strategies in accomplishing trunk movements and take a longer time to complete the movements. These may seriously affect the functional activities and the quality of life of the patients. Clinically, it is important to evaluate the kinematic characteristics of both the lumbar spine and hip for back pain patients. Assessment of lumbar spine motions alone will not be able to reveal how joint coordination is affected by back pain and the potential implications on functional performance. Exercise program should be aimed to restore not only range of movement but also the movement coordination.