Patient-specific finite element modeling of scoliotic curve progression using region-specific stress-modulated vertebral growth

Abstract

Purpose This study describes the creation of patient-specific (PS) osteo-ligamentous finite element (FE) models of the spine, ribcage, and pelvis, simulation of up to three years of region-specific, stress-modulated growth, and validation of simulated curve progression with patient clinical angle measurements. Research Question: Does the inclusion of region-specific, stress-modulated vertebral growth, in addition to scaling based on age, weight, skeletal maturity, and spine flexibility allow for clinically accurate scoliotic curve progression prediction in patient-specific FE models of the spine, ribcage, and pelvis? Methods Frontal, lateral, and lateral bending X-Rays of five AIS patients were obtained for approximately three-year timespans. PS-FE models were generated by morphing a normative template FE model with landmark points obtained from patient X-rays at the initial X-ray timepoint. Vertebral growth behavior and response to stress, as well as model material properties were made patient-specific based on several prognostic factors. Spine curvature angles from the PS–FE models were compared to the corresponding X-ray measurements. Results Average FE model errors were 6.3 ± 4.6°, 12.2 ± 6.6°, 8.9 ± 7.7°, and 5.3 ± 3.4° for thoracic Cobb, lumbar Cobb, kyphosis, and lordosis angles, respectively. Average error in prediction of vertebral wedging at the apex and adjacent levels was 3.2 ± 2.2°. Vertebral column stress ranged from 0.11 MPa in tension to 0.79 MPa in compression. Conclusion Integration of region-specific stress-modulated growth, as well as adjustment of growth and material properties based on patient-specific data yielded clinically useful prediction accuracy while maintaining physiological stress magnitudes. This framework can be further developed for PS surgical simulation.

In vitro coupled motions of the whole human thoracic and lumbar spine with rib cage

“…[11][12][13] To the authors' knowledge, no quantitative data exist on in vitro region-specific coupled motions of the whole human TS and LS (T1-L5) with rib cage. Such kinematics data may be used to validate computational models of the spine [18][19][20] that predict the performance of implants and surgical interventions, and to better understand spinal biomechanics in deformity, [21][22][23] degeneration, and trauma [24][25][26][27][28] as well as the biofidelity of surrogate animal spine models. 29 Therefore, the objective of this in vitro biomechanical study is to quantify the coupled motions of the whole human TS and LS with rib cage.…”