Personalized biomechanical simulations of orthotic treatment in idiopathic scoliosis

Abstract

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 mm Hg, 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° 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. Relevance The analysis of bracing biomechanics in the treatment of scoliosis requires the development of biomedical engineering techniques allowing both a personalized evaluation and a design improvement of the treatment. The in-demand benefits of “computer assisted medicine” for the scoliotic patients are an improved brace treatment, prevention from invasive surgery, and an increased quality of life.