Surgical Planning and Follow-up of Anterior Vertebral Body Growth Modulation in Pediatric Idiopathic Scoliosis Using a Patient-Specific Finite Element Model Integrating Growth Modulation

Abstract

Study design: Numerical planning and simulation of immediate and post-two-year growth modulation effects of Anterior Vertebral Body Growth Modulation (AVBGM).

Objectives: To develop a planning tool based on a patient-specific finite element model (FEM) of pediatric scoliosis integrating growth to computationally assess the 3D biomechanical effects of AVBGM.

Summary of background data: AVBGM is a recently introduced fusionless compression-based approach for pediatric scoliotic patients presenting progressive curves. Surgical planning is mostly empirical, with reported issues including overcorrection (inversion of the side) of the curve and a lack of control on 3D correction.

Methods: Twenty pediatric scoliotic patients instrumented with AVBGM were assessed. An osseoligamentous FEM of the spine, rib cage, and pelvis was generated before surgery using the patient's 3D reconstruction obtained from calibrated biplanar radiographs. For each case, different scenarios of AVBGM and two years of vertebral growth and growth modulation due to gravitational loads and forces from AVBGM were simulated. Simulated correction indices in the coronal, sagittal, and transverse planes for the retained scenario were computed and a posteriori compared to actual patient's postoperative and two years' follow-up data.

Results: The simulated immediate postoperative Cobb angles were on average within 3° of that of the actual correction, while it was ±5° for kyphosis/lordosis angles, and ±5° for apical axial rotation. For the simulated 2-year postoperative follow-up, correction results were predicted at ±3° for Cobb angles and ±5° for kyphosis/lordosis angles, ±2% for T1-L5 height, and ±4° for apical axial rotation.

Conclusion: A numeric model simulating immediate and post-two-year effects of AVBGM enabled to assess different implant configurations to support surgical planning.

Level of evidence: Level III.

Keywords: Anterior vertebral body growth modulation; Finite element modeling; Fusionless; Idiopathic scoliosis; Numerical surgical planning.