Lumbar corsets: their effect on three-dimensional kinematics of the pelvis.

Lumbar corsets have been recommended for low back pain patients as a way of stabilizing the lumbar region, facilitating flexion movements, and reducing pain. However, little is known about how these devices affect lumbar motion. To determine the degree of changes in the lumbar region, our approach was to quantify three-dimensional kinematic data of the pelvis in harness-supported treadmill walking. Twelve healthy subjects (age=32+/-11.8 years) walked on a motorized treadmill at 4.5 km/h with and without wearing a lumbar corset. Three external markers overlying the sacrum were tracked by three ultrasound microphones, determining a local coordinate system, to obtain pelvic motions in the frontal, sagittal, and transverse planes. Raw kinematic data were low-pass filtered and normalized relative to the right heel strike. Mean values for net angular displacements of the pelvis were calculated for each plane within the 5th and 95th percentile. The Student's t-test demonstrated significant differences (P<0.001) between the corset/no-corset conditions in the frontal plane. An average 40% decrease in the relative pelvis up- and downward movement occurred in the frontal plane (4.1 degrees+/-2.9 degrees vs. 7.1 degrees+/-3.3 degrees). The analysis revealed no significant differences of net angular displacements in the sagittal (2.9 degrees+/-1.4 vs. 3.4 degrees+/-1.7 degrees) and the transverse planes (4.4 degrees+/-2.6 degrees vs. 4.3 degrees+/-2.1 degrees).