Differences in Balance Strategies Between Nonspecific Chronic Low Back Pain Patients and Healthy Control Subjects During Unstable Sitting

Study Design. A 2-group experimental design. Objective. To investigate differences in postural control strategies of pelvis and trunk movement between nonspecific chronic low back pain (CLBP) patients and healthy control subjects using 3-dimensional motion analysis. Summary of Background Data. Increased postural sway assessed by center of pressure displacements have been documented in patients with low back pain (LBP). The 3-dimensional movement strategies used by patients with LBP to keep their balance are not well documented. Methods. Nineteen CLBP patients and 20 control subjects were included based on detailed clinical criteria. Every subject was submitted to a postural control test in an unstable sitting position. A 3-dimensional motion analysis system, equipped with 7 infrared M1 cameras, was used to track 9 markers attached to the pelvis and trunk to estimate their angular displacement in the 3 cardinal planes. Results. The total angular deviation in all 3 directions of pelvis and trunk was higher in the CLBP group compared with the control group. In 4 of the 6 calculated differences, a significant higher deviation was found in the CLBP group (significant P-values between 0.013 and 0.047). Subjects of both groups mostly used rotation compared with lateral flexion and flexion/extension displacements of pelvis and trunk to adjust balance disturbance. The CLBP group showed a high correlation (Pearson: 0.912-0.981) between movement of pelvis and trunk, compared with the control group. Conclusion. A higher postural sway and high correlation between pelvis and trunk displacements was found in the LBP group compared with healthy controls.