Relationships between strap tension, interface pressures and spine correction in brace treatment of scoliosis.

The Boston brace has been shown to efficiently prevent scoliosis curve progression. However, it rarely achieves complete 3-D correction; its adjustment being often empirical and its biomechanical modes of action still remaining poorly understood. This study investigates the in-brace spinal shape (correction) in relationship with the patient's out-of-brace deformation, and the adjustment parameters of the brace, namely the strap tensions and the equivalent forces calculated at the patient-brace interface. Many of the observed relationships illustrate the fact that the in-brace spinal shape is strongly related to the characteristics of the patient's out-of-brace deformation. The pattern of pressure distribution as described by the equivalent forces computed in the thoracic, lumbar, pelvic and sternal regions has important effect on the in-brace Cobb angles, lumbar lordosis, frontal and sagittal imbalances and the apical axial rotations. The complex role of the strap tension on the correction has not been explained and needs further investigation. This project has the potential to give insight into the biomechanical effects of brace treatment by providing a statistical model leading to more rational and personalized brace adjustments.