Increased glenoid baseplate retroversion improves internal rotation following reverse shoulder arthroplasty

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Internal rotation following reverse total shoulder arthroplasty (RTSA) often shows minimal improvement.
• Glenoid baseplate version is a critical factor influencing shoulder joint biomechanics.
• Understanding the impact of baseplate version is key to optimizing RTSA outcomes.

Purpose of the Study:

• To evaluate the effect of glenoid baseplate version on postoperative internal rotation after RTSA.
• To assess the influence of baseplate retroversion on external rotation (ER) and patient-reported outcomes (PROs).

Main Methods:

• Retrospective review of a multicenter database of patients undergoing primary RTSA with a 135° humeral prosthesis and lateralized glenoid.
• Analysis of preoperative and postoperative radiographs to determine glenoid baseplate version and change in version (ΔRV).
• Stratification of patients based on postoperative retroversion (<10°, 10°-19°, >20°) and comparison of outcomes using regression and ANOVA.

Main Results:

• Postoperative baseplate retroversion >10° correlated with a 20° gain in internal rotation at 90° (IR90) without affecting external rotation at 90° (ER90).
• Increased retroversion (>10°) was linked to significantly better Constant-Murley and Single Assessment Numeric Evaluation scores.
• An increase in ΔRV >10° improved IR90 without compromising ER0 or forward flexion (FF).

Conclusions:

• A postoperative baseplate retroversion exceeding 10° significantly enhances IR90, ER90, and patient-reported outcomes at 2-year follow-up.
• Intentional or accepted baseplate retroversion may improve overall shoulder function, warranting consideration during RTSA.
• While not improving IRspine, baseplate retroversion positively impacts functional outcomes, suggesting its potential benefit when fixation permits.