The Effect of Component Lateralization in Reverse Total Shoulder Arthroplasty on Muscle Function and Scapular Strains During Simulated Active Motion: An Ex-Vivo Biomechanical Study

Description

This presentation from the ISTA 2024 conference held in Nashville offers an in-depth examination of the biomechanical study focused on component lateralization and reverse total shoulder arthroplasty (TSA), highlighting its effects on muscle function and scapular strains during simulated active motion. The speaker, David T Axford begins by acknowledging the funding source for the research and notes the absence of substantial biomechanical evidence to support various lateralization strategies during shoulder surgery.



The objective is to assess how isolated lateralization on the glenoid and humeral sides, as well as different lateralization ratios, impact muscle forces and scapular strains. Utilizing seven cadaveric specimens, the study simulates various conditions, including natural shoulder mechanics and several configurations of TSA. This approach allows the investigation of scapular plane abduction and internal/external rotation, although the latter is set aside for brevity in presentation.



The methods include a shoulder motion simulator and 3D printed mounts tailored to each specimen, enabling precise measurement of muscle forces and scapular strains under various conditions of lateralization. The study reports notable shifts in muscle forces, particularly observing increased anterior deltoid forces during low elevation while noting decreased supraspinatus and infraspinatus forces across configurations.



The results unveil that humeral lateralization leads to significant decreases in deltoid forces, while glenoid lateralization showcases slight increases, albeit not statistically significant. Furthermore, the impact on scapular strains reveals contrasting profiles between TSA conditions and native shoulder, indicating that lateralization primarily on the humerus results in less strain compared to a combined approach.



The conclusion emphasizes that humeral lateralization may result in lower deltoid forces and scapula strains versus combined lateralization strategies, urging further exploration into optimal configurations for better outcomes in shoulder surgeries.

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