Efficacy of a Novel Thoracopelvic Orthosis in Reducing Lumbar Spine Loading and Muscle Fatigue in Flexion: A Study with Weighted Garments

The purpose of this thesis was to design and test a novel electromechanical thoracopelvic orthosis called the Exoskeletal Spinal Support, or ESS. We tested the overall hypothesis that the activity of the postural muscles of the lower back in erect and flexed postures, while wearing and not wearing a weighted garment, can be reduced by the ESS. Two experiments informed the design of the ESS. The first experiment was a repeated-measures study of the effect of a weighted garment (a lead vest) on shoulder and lower back muscle activity of 19 young healthy adults. The results showed that use of the lead vest did not significantly increase muscle activity in any of the three muscle groups studied. The second experiment was a repeated-measures study of factors contributing to the normal contact stress developed at the interface between a partial thoracic orthosis and the skin of 20 healthy young men. The ESS was designed and programmed so that its microcontroller monitored the interface contact stress and commanded its four linear actuators to adjust the orthosis configuration so as to maintain a near-constant trunk extensor moment over a range of trunk flexion. The final experiment was a preliminary validation study of the ESS on a single subject in a variety of loading conditions and flexed postures, with lumbar muscle activity as the primary outcome. The results suggest that at 5° forward flexion, the ESS reduced normalized erector spinae muscle activity by up to 11%. However, when the lead vest was worn over the ESS, muscle activity increased, perhaps due to a change in spine posture or an artifact. Nonetheless we conclude that the ESS has promise as the first "active" orthosis. Its mechanical interactions with the trunk can be programmed via software alone. These interactions include the use of the constant corrective moment used here, but also include the ability to change the damping behavior and program any linear or curvilinear relationship between applied moment and thorax inclination in the sagittal or coronal planes. This technology allows for the possibility of telemanaging orthotic treatment in the future.