Optimization of implant selection and positioning for reverse total shoulder arthroplasty using three-dimensional computed tomography-guided simulation software with scapulothoracic motion.

BACKGROUND

Although three-dimensional (3D) simulation has improved accuracy of implant placement, its role in optimizing postoperative range of motion (ROM) remains incompletely defined. The purpose of this study was to use a 3D simulation model incorporating scapulothoracic motion to evaluate how implant variables for reverse total shoulder arthroplasty (rTSA) impact standard ROM and functional activities of daily living.

METHODS

Patients undergoing rTSA from August 2025 to October 2025 were included. Demographics were recorded. Implant parameters recorded included glenosphere size, eccentricity, glenosphere lateralization, polyethylene insert thickness, humeral neck-shaft angle (NSA), humeral stem version, and baseplate version. Outcomes were total ROM, with secondary analyses assessing the effect of individual implant variables on ROM. A 3D simulation model (CORIOGRAPH MODELER, Smith+Nephew) with scapulothoracic and glenohumeral-simulated motion evaluated impingement-free ROM across all implant parameters and 12 motions.

RESULTS

Forty-nine patients were included at a median 70.1 years old. Most common surgical indications were glenohumeral osteoarthritis (34.6%) followed by rotator cuff arthropathy (26.5%). Across simulated configurations, larger glenospheres, eccentric glenosphere positioning, and increased glenosphere lateralization were associated with greater impingement-free ROM (P < .05). Higher NSA was associated with lower ROM (P < .05). Multivariable regression found NSA and glenosphere size to be the strongest independent contributors to maximal ROM across multiple motions.

CONCLUSION

Using a 3D simulation model incorporating scapulothoracic motion, rTSA implant positioning was shown to influence impingement-free ROM. Larger and eccentric glenospheres with increased lateralization consistently improved ROM, while higher NSAs limited motion across multiple planes. NSA and glenosphere size were the strongest independent predictors of maximal ROM.