Personalized biomechanical simulations of orthotic treatment in idiopathic scoliosis.

OBJECTIVES: To analyse patient-specific bracing biomechanics in the treatment of scoliosis.
DESIGN: Two complementary computer tools have been developed to quantify the brace action on scoliotic spine from pressure measurements, and to simulate its effect on patient-adapted finite element model.
BACKGROUND: Brace pad forces and brace effect on spine deformities have been reported. However, the brace mechanisms still need to be better understood to obtain more effective treatments.
METHODS: The 3D geometry of the spine and rib cage of three scoliotic adolescents treated by the Boston brace was obtained using a multiview radiographic reconstruction technique. A personalized biomechanical model was constructed for each patient. Pressures generated by the brace on the thorax were measured using pressure sensors. For each zone with a threshold pressure higher than 30 mmHg, a total equivalent force was calculated and applied to the corresponding model nodes.
RESULTS: The pressure were generally scattered on the overall torso, with the highest pressures measured on five distinct regions: right thoracic, left lumbar, abdominal, right and left sides of the pelvis. The equivalent forces were of 18-73 N. Differences between simulated deformed shapes and real in-brace geometry of the patients were less than 6 and 9.8 mm for the vertebral positions in the coronal and sagittal planes, and 7.7 degrees for the Cobb angles.
CONCLUSION: The results supported the feasibility of such approach to analyse patient-specific bracing biomechanics, which may be useful in the design of more effective braces.