Effects of a lumbar support on spine posture and motion assessed by electrogoniometer and continuous recording.

OBJECTIVE: To determine whether belt wearing causes changes in lumbar posture and motion during standing and work-related activities. DESIGN: The lumbar spine sagittal kinematics of healthy subjects were assessed with an electrogoniometer during a dynamic test and continuous recording with and without a lumbar support. Correlation between data from electrogoniometer and X-ray was established in preliminary experiments. BACKGROUND: The effects of a lumbar support were previously investigated in few patients using radiological or invasive techniques under laboratory conditions, with special regard to the restriction of global motion in flexion and extension. Whether lumbar posture may also be involved during belt wearing remains unclear. There is also no evidence that these changes affecting lumbar motion and posture persist during prolonged activities. METHODS: The correlation between electrogoniometer and radiographic data was assessed in 12 subjects. Lumbar curve angles were evaluated in 15 healthy subjects, with and without one type of lumbar support, during standing in orthostatic, fully-flexed and fully-extended positions and during work-related activities with a portable computer. Lumbar motion parameters were flexion, extension and total range of motion. Lumbar posture parameters were lumbar curve angle in orthostatic position and mean lumbar curve angle during continuous recording. RESULTS: Electrogoniometric and radiographic data from lumbar curve angles and motion changes during flexion/extension of the spine were slightly different but reasonably well correlated (r = 0.58-0.77). The lumbar support decreased the mean total range of motion of the lumbar spine during a single flexion/extension movement by 17% and during continuous recording by 22%. The lumbar curve angle in the orthostatic position was reduced by 3 degrees and the mean lumbar curve (assessed by continuous recording) was reduced by 4 degrees (mean for 15 subjects). There were major individual changes in these two parameters and the reduction in lumbar curvature was correlated with the initial (r = 0.66-0.72). CONCLUSION: Electrogoniometer data on lumbar motion are reasonably well correlated with X-ray data. The comparative values registered during flexion/extension tests and continuous recording confirm that a support belt limits slightly global lumbar motion. As changes affecting postural parameters (orthostatic or mean values during continuous recording) depend on subject morphometry, individual parameters should be taken in account when evaluating and using a lumbar support.