Humeral component retroversion in the Comprehensive Reverse Shoulder System arthroplasty: rotations, clinical...

The literature highlights various factors influencing rotations in reverse total shoulder arthroplasty (rTSA), including humeral retroversion. Although several studies have noted that increased humeral retroversion leads to reduced internal rotation (IR) and increased external rotation (ER), there have been no randomized trials investigating the relationship between rotations and humeral retroversion. This study aims to determine the optimal degree of retroversion (0°-30°) to achieve the best rotational mobility of the shoulder and to analyze the mobility, clinical functional scores, and quality of life following implantation of a lateralized rTSA (Comprehensive Reverse Shoulder System; Zimmer Biomet).

The study was a single-blinded randomized controlled trial performed at a single institution. It enrolled patients who underwent rTSA surgery at 0° (intervention group) and 30° (control group) of humeral retroversion and were included consecutively at Terrassa Hospital from 2019 to 2022 with a 2-year follow-up. Analyzed variables included demographic, range of motion assessments with ER1 (at 0° of abduction), ER2 (at 90° of abduction), functional ER, functional IR, IR2 (at 90° of abduction), anterior elevation and abduction, and clinical functional assessments using Constant-Murley score, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), Simple Shoulder Test (SST), as well as quality of life measured by 12-Item Short Form Health Survey (SF-12). Statistical significance was set at P < .05.

At the 24-month follow-up, the mean ER1 was 38° ± 11° in the intervention group (0°) and 50° ± 19° in the control group (30°) (P = .012). Functional IR was 6.2 ± 2.8 points in the intervention group (0°) and 5.0 ± 2.7 points in the control group (30°) (P = .050). The range of motion between the 2 groups at the 24-month follow-up did not significantly differ in terms of the mean values of ER2, functional ER, IR2, anterior elevation, and abduction. SST had better results in the intervention group (P = .042), whereas the Constant-Murley score and ASES scores did not differ between the 2 groups. The physical component summary (PCS) of SF-12 in the intervention group showed higher scores that reached a statistically significant difference between groups (P = .039).

Humeral retroversion at 30° improved ER1. Humeral retroversion at 0° achieved higher scores in SST and SF-12 PCS in patients undergoing surgery with a lateralized rTSA using the Comprehensive Reverse Shoulder System.