Differences in Balance Strategies Between Non-specific Chronic Low Back Pain Patients and Healthy Control Subjects During Unstable Sitting.

Study Design. A two group experimental design.
Objective. To investigate differences in postural control strategies of pelvis and trunk movement between non-specific chronic low back pain (CLBP) patients and healthy control subjects using three-dimensional motion analysis.
Summary of Background Data. Increased postural sway assessed by centre of pressure displacements have been documented in low back pain patients. The three-dimensional movement strategies used by low back pain patients to keep their balance are not well documented.
Methods. Nineteen CLBP patients and twenty control subjects were included based on detailed clinical criteria. Every subject was submitted to a postural control test in an unstable sitting position. A three-dimensional motion analysis system, equipped with 7 infra-red M1 camera's, was used to track 9 markers attached to the pelvis and trunk in order to estimate their angular displacement in the 3 cardinal planes.
Results. The total angular deviation in all three directions of pelvis and trunk was higher in the CLBP group compared to the control group. In 4 of the 6 calculated differences, a significant higher deviation was found in the CLBP group (significant p-values between .013 and .047). Subjects of both groups mostly used rotation compared to lateral flexion and flexion-extension displacements of pelvis and trunk to adjust balance disturbance. The CLBP group showed a high correlation (Pearson: .912 - .981) between movement of pelvis and trunk, compared to the control group.
Conclusion. A higher postural sway and high correlation between pelvis and trunk displacements was found in the low back pain group compared to healthy controls.