Lumbar spine orthosis wearing. II. Effect on trunk muscle myoelectric activity.

The effects of wearing commonly prescribed low-back braces and corsets on myoelectric signal levels in the erector spinae and oblique abdominal muscles were investigated. A lumbosacral corset, a chairback brace, and a molded thoracolumbosacral orthosis (TLSO) were studied. Nineteen tasks involving sitting and standing were performed by five healthy adult men. Myoelectric signal levels measured when wearing each orthosis were compared with those measured when performing the same task while wearing no orthosis. The changes in mean myoelectric signal levels ranged from a 9% reduction to a 44% increase when the lumbosacral corset was worn, from a 27% reduction to a 25% increase when the chairback brace was worn, and from a 38% reduction to a 19% increase when the TLSO was worn.

Lumbar spine orthosis wearing. I. Restriction of gross body motions.

The effects of wearing commonly prescribed low-back braces and corsets on restriction of gross body motions were investigated. A lumbosacral corset, a chairback brace, and a molded plastic thoracolumbosacral orthosis (TLSO) were studied. Four trunk movements (flexion, extension, lateral bending, and twisting) were examined in five healthy adult men when standing and sitting. All three orthoses restricted at least some gross body motion to approximately two thirds to one half of no-orthosis values. All three orthoses failed to provide restrictions of at least 10% in at least one motion. Mean motion restriction across all eight movements studied in all five subjects were largest when wearing the TLSO and least when wearing the corset. Gross body motion restrictions relieve lumbar trunk muscle and spine loads.

Response of the intervertebral disk of the rhesus monkey to P-A shear stress.

The relative functions of spinal elements in resisting P-A shear stress are determined from measurements of force and displacement. The response of intact, enucleate and degenerate disks are presented, as well as stress-strain characteristics of the intervertebral disk and the roles of the articular facets and the nucleus pulposus.