The evaluation of reverse shoulder lateralization on deltoid forces and scapular fracture risk: A computational study

Abstract

Reverse shoulder arthroplasty (RSA) can treat severe rotator cuff deficiency, but its medialized design of the shoulder's center of rotation (CoR) has been associated with scapular notching. Although lateralization of CoR provides a larger impingement-free range of motion, the changes in component positioning alter the biomechanics and may cause unforeseen complications. This work quantified the muscle forces and predicted the scapula fracture risk by coupling dynamic simulation analysis with finite element modeling. To identify bone failure patterns, the results were analyzed using three common failure measures. A parametric study showed greater lateralization produced higher strain/stress concentrations in the scapular spine (Levy Region Type II), with approximately a 10% increase for the 12 ​mm lateralized scenario, compared to a neutral configuration. Significant differences in fracture risk patterns were found between the maximum principal stress/strain results and the von Mises stress results. The lateralized configurations could increase the muscle and joint reaction forces during abduction and induce scapular fracture. Studying the effects of RSA lateralization on scapular fracture risk can help guide the continued optimization of RSA performance and surgical techniques. The findings of relationships between the loading style and bone failure measures can provide valuable insight into the investigation of bone failure criteria.

Keywords

• Reverse shoulder arthroplasty
• Shoulder biomechanics
• Computational modeling
• Lateralization
• Scapular fracture