Trunk Kinematics Using Musculoskeletal Modeling During Range Of Motion Tasks

Abstract

A spine model can be used to predict post-spinal fusion motion needed to perform physical activities in individuals with scoliosis. Full body lumbar spine (FBLS) model (Raabi and Chaudhari, 2016) allows for modeling lumbar spine and pelvis movement and was validated for jogging. However, like other existing adult spine models, FBLS model does not allow for a motion providing thoracic spine. PURPOSE: To adapt the FBLS model for simulating thoracic, lumbar and pelvis motion during trunk rotation in all 3 planes of motion. METHODS: Since T12-L1 in FBLS model is designed as a dependent joint (axial rotation analogous to L5-S1), the constraints between torso and lumbar spine were removed and modified to allow 3 degrees of freedom for T12-L1. Model ROM were adjusted to match for expected ranges of the test tasks. Inverse kinematics (IK) were calculated for the adjusted model. Range of motion (ROM; max-min) at T12-L1 and L5-S1 joints from FBLS were compared to the 3D motion capture data of 3 healthy adults during maximal flexion-extension, lateral bending, and axial rotation tasks. RESULTS: Experimental data calculated for axial rotation for T12-L1 and L5-S1, respectively were 64.4 ± 3.8° and 30.0 ± 7.2° of flexion-extension, 40.8° ± 4° and 10.9° ± 4.7° of lateral bending, and 29.7° ± 3.6° and 13.9° ± 1.1°. While IK from FBLS were 2.4° ± 0.1 and 16.3° ± 2.0 of flexion-extension, 7.9° ± 0.7 and 1.5° ± 0.4° of lateral bending, and 32.7° ± 0.6° and 12.9° ± 4° of axial rotation for T12-L1 and L5-S1, respectively. T12-L1 joint motion from OpenSim and human data movement patterns did not corroborate in sagittal and frontal planes where a disconnection between thoracic and lumbar segments was noted. Subsequently, experimental data was significantly greater than IK for sagittal (mean difference: 96.3% and 45.7%) and frontal planes (80.6% and 86.2%) from FBLS and matched best for transverse plane (10.1% and 7.2%) for T12-L1 and L5-S1, respectively. CONCLUSION: The existing FBLS model shows reasonable promise to be adapted for ROM tasks in transverse plane motion but not for sagittal and frontal planes to model trunk motions greater than those expected in jogging.