Anterior Vertebral Body Growth Modulation: Assessment of the 2-year Predictive Capability of a Patient-specific Finite-element Planning Tool and of the Growth Modulation Biomechanics.

ABSTRACT

STUDY DESIGN: Numerical planning and simulation of immediate and after 2 years growth modulation effects of anterior vertebral body growth modulation (AVBGM). OBJECTIVE: The objective was to evaluate the planning tool predictive capability for immediate, 1-year, and 2-year postoperative correction and biomechanical effect on growth modulation over time. SUMMARY OF BACKGROUND DATA AVBGM is used to treat pediatric scoliotic patients with remaining growth potential. A planning tool based on a finite element model (FEM) of pediatric scoliosis integrating growth was previously developed to simulate AVBGM installation and growth modulation effect. METHODS: Forty-five patients to be instrumented with AVBGM were recruited. A patient-specific FEM was preoperatively generated using a 3D reconstruction obtained from biplanar radiographs. The FEM was used to assess different instrumentation configurations. The strategy offering the optimal 2-year postoperative correction was selected for surgery. Simulated 3D correction indices, as well as stresses applied on vertebral epiphyseal growth plates, intervertebral discs, and instrumentation, were computed. RESULTS: On average, six configurations per case were tested. Immediate, 1-year, and 2-year postoperative 3D correction indices were predicted within 4° of that of actual results in coronal plane, whereas it was <0.8 cm (±2%) for spinal height. Immediate postoperative correction was of 40%, whereas an additional correction of respectively 13% and 3% occurred at 1- and 2 year postoperative. The convex/concave side computed forces difference at the apical level following AVBGM installation was decreased by 39% on growth plates and 46% on intervertebral discs. CONCLUSION: This study demonstrates the FEM clinical usefulness to rationalize surgical planning by providing clinically relevant correction predictions. The AVBGM biomechanical effect on growth modulation over time seemed to be maximized during the first year following the installation. LEVEL OF EVIDENCE 3.