Simulating the effect of glenohumeral capsulorrhaphy on kinematics and muscle function

This study aimed to use a predictive simulation framework to examine shoulder kinematics, muscular effort, and task performance during functional upper limb movements under simulated selective glenohumeral capsulorrhaphy. A musculoskeletal model of the torso and upper limb was adapted to include passive restraints that simulated the changes in shoulder range of motion stemming from selective glenohumeral capsulorrhaphy procedures (anteroinferior, anterosuperior, posteroinferior, posterosuperior, and total anterior, inferior, posterior, and superior). Predictive muscle-driven simulations of three functional movements (upward reach, forward reach, and head touch) were generated with each model. Shoulder kinematics (elevation, elevation plane, and axial rotation), muscle cost (i.e., muscular effort), and task performance time were compared to a baseline model to assess the impact of the capsulorrhaphy procedures. Minimal differences in shoulder kinematics and task performance times were observed, suggesting that task performance could be maintained across the capsulorrhaphy conditions. Increased muscle cost was observed under the selective capsulorrhaphy conditions, however this was dependent on the task and capsulorrhaphy condition. Larger increases in muscle cost were observed under the capsulorrhaphy conditions that incurred the greatest reductions in shoulder range of motion (i.e., total inferior, total anterior, anteroinferior, and total posterior conditions) and during tasks that required shoulder kinematics closer to end range of motion (i.e., upward reach and head touch). The elevated muscle loading observed could present a risk to joint capsule repair. Appropriate rehabilitation following glenohumeral capsulorrhaphy is required to account for the elevated demands placed on muscles, particularly when a significant range of motion loss presents.