Biomechanical comparison of fusionless growth modulation corrective techniques in pediatric scoliosis

Fusionless growth-sparing implants for the treatment of adolescent idiopathic scoliosis (AIS) attempt to manipulate vertebral growth to restore spinal alignment. This study critically explores different implants utilizing a human spine scoliotic finite element model (FEM). Stainless steel (SS) and shape memory alloy (SMA) staples and flexible tethers were modeled and alternatively integrated around the apex of the convexity of the scoliotic model. Stress profiles over vertebral growth plates were obtained. Two years of growth was simulated with non-instrumented and instrumented models, as curvature changes were quantified. Apical asymmetrical stresses in non-instrumented and instrumented scoliotic models with SS staple, flexible tether, and SMA staple were 0.48, 0.48, 0.23, and 0.33 MPa, respectively. Patient data and non-instrumented model progressed from 28° to 62° of thoracic Cobb angle over 2 years. Simulated projected long-term thoracic Cobb angles of instrumented models are 31° with SS staple, 31° with flexible tether, and 34° with SMA staple. Initial implant compression achieved during instrumentation provided a significant influence on initial and long-term spinal profiles. The developed FEM provides an effective platform with which to explore, critique, and enhance fusionless growth-sparing techniques.