Computational reverse shoulder prosthesis model: Experimental data and verification.

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Musculoskeletal Modeling

Background:

• Reverse shoulder prosthesis aims to restore shoulder function but its biomechanical effects require further understanding.
• Geometrical changes from implants significantly impact shoulder joint mechanics.
• Evaluating the influence of the Delta reverse shoulder prosthesis on shoulder biomechanics is crucial.

Purpose of the Study:

• To evaluate how the Delta reverse shoulder prosthesis influences the biomechanical behavior of the shoulder joint using a large-scale musculoskeletal model.
• To assess kinematic and muscle activity changes in patients with reverse shoulder prostheses.
• To validate a musculoskeletal model by comparing predicted muscle forces with experimental EMG data.

Main Methods:

• Acquisition of kinematic data (unloaded abduction and forward flexion) via video-imaging for healthy and reverse shoulder groups.
• Collection of synchronous EMG data from 7 superficial shoulder muscles.
• Solving the muscle force sharing problem through minimization of metabolic energy consumption.

Main Results:

• Increased lateral rotation of the scapula and greater scapulothoracic joint contribution observed in the reverse shoulder group.
• Musculoskeletal model predicted increased activity in deltoid, teres minor, pectoralis major (clavicular fibers), and coracobrachialis muscles.
• Good correlation found between predicted muscle forces and acquired EMG data, validating the model.
• Lower shoulder joint reaction forces were found in the reverse shoulder group compared to the control group.

Conclusions:

• The study provides biomechanical insights into the effects of reverse shoulder prosthesis.
• The validated musculoskeletal model can be used for further research on shoulder joint mechanics.
• Reverse shoulder prosthesis leads to altered shoulder kinematics and muscle activation patterns, with reduced joint forces.