Determination of three-dimensional corrective force in adolescent idiopathic scoliosis and biomechanical finite element analysis

Abstract Background: Adolescent idiopathic scoliosis is a complex three-dimensional deformity of spine and soft tissues. It is usually treated with spinal brace if Cobb angle is less than 40°. To date, displacement and rotation of human vertebrae and ribs in three-dimensional space have not been fully considered in treatment of scoliosis. Three dimensional corrective forces in treatment of scoliosis are still unclear and very less attention has paid on it. Methods: An objective function of corrective force in three-dimensional space is defined. Computed tomography images were used to reconstruct three dimensional model of scoliotic trunk. Computer aided engineering software Abaqus was used to establish finite element model of deformed spine and its biomechanical characteristics were analyzed. By adjusting magnitude and position of corrective forces, objective function is minimized to achieve best orthopedic effect. The proposed corrective conditions were divided into three groups: 1. thoracic deformity; 2. lumbar deformity; 3. both thoracic and lumbar deformities were considered. Results: In all three cases, the objective function was reduced by 58%, 52%, and 63%, respectively. The best correction force point is located on convex side of maximum displacement of vertebral body. Conclusions: Using minimum objective function method, spinal deformity in three-dimensional space can be sufficiently reduced. This study provides scientific basis for design of a new corrective brace for treatment of scoliosis.