A Detailed Kinematic Multibody Model of the Shoulder Complex After Total Shoulder Replacement

Multibody modeling allows reproducible and comparative analyses of shoulder dynamics after total shoulder replacement (TSR). For inverse dynamics an accurate representation of the musculoskeletal kinematics from motion capture is fundamental. Although current optimization-based approaches effectively identify the underlying skeletal motion in terms of position, velocities and accelerations are not consistently provided. The purpose was therefore to introduce a multibody model of the shoulder complex after TSR implantation with detailed representation of the muscle apparatus that directly generates the musculoskeletal kinematics from motion capture data. The inherent inverse kinematics problem is resolved by implementation of a potential field method. Sensitivity analysis was performed to determine the model’s tracking capability. Scapular motion showed overall good agreement with measurements from the literature. The approach yields equivalent results to current approaches with the benefit of directly computing accelerations without formulation of an optimization problem. The multibody model presented will be used for further inverse dynamics analyses regarding various loading conditions of different TSR designs.