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

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.

Development of a Finite Element Model of the Pediatric Thoracic and Lumbar Spine, Ribcage, and Pelvis With Orthotropic Region-Specific Vertebral Growth.

Finite element (FE) modeling of the spine has increasingly been applied in orthopedic precision-medicine approaches. Previously published FE models of the pediatric spine growth have made simplifications in the geometry of anatomical structures, material properties, and representation of vertebral growth. To address those limitations, a comprehensive FE model of a pediatric (10-year-old) osteo-ligamentous thoracic and lumbar spine (T1-L5 with intervertebral discs (IVDs) and ligaments), ribcage, and pelvis with age- and level-specific ligament properties and orthotropic region-specific vertebral growth was developed and validated.

Part 2. Review and meta-analysis of studies on modulation of longitudinal bone growth and growth plate activity: A micro-scale perspective.

Macro-scale changes in longitudinal bone growth resulting from mechanical loading were shown in Part 1 of this review to depend on load magnitude, anatomical location, and species. While no significant effect on longitudinal growth was observed by varying frequency and amplitude of cyclic loading, such variations, in addition to loading duration and species, were shown to affect the morphology, viability, and gene and protein expression within the growth plate. Intermittent compression regimens were shown to preserve or increase growth plate height while stimulating increased chondrocyte presence in the hypertrophic zone relative to persistent and static loading regimens.

Part 1. Review and meta-analysis of studies on modulation of longitudinal bone growth and growth plate activity: A macro-scale perspective.

Growth modulation is an emerging method for treatment of angular skeletal deformities such as adolescent idiopathic scoliosis (AIS). The Hueter-Volkmann law, by which growth is stimulated in tension and inhibited in compression, is widely understood, and applied in current growth-modulating interventions such as anterior vertebral body tethering (AVBT) for AIS. However, without quantification of the growth rate effects of tension or compression, the possibility of under- or over- correction exists.