Functional Outcomes After Reverse Total Shoulder Arthroplasty: Comparing Grammont and Lateralized Prosthesis Designs

Background Reverse total shoulder arthroplasty (RTSA) is an established treatment option for complex proximal humerus fractures, particularly in elderly patients. Different implant designs exist, including traditional medialized (Grammont-type) prostheses and newer lateralized systems. These designs may influence postoperative range of motion, functional outcomes, and complication rates. Purpose This study aimed to compare rotational mobility, functional outcomes, and complication rates between medialized (Grammont-type) and lateralized reverse shoulder prostheses in patients treated for proximal humerus fractures and related conditions. Methods A retrospective comparative study with level III of evidence was conducted including patients treated with RTSA between 2007 and 2023 at a tertiary referral center. Patients were divided into two groups according to prosthesis design: medialized (Grammont-type) prostheses (n = 13; 48.1%) and lateralized prostheses (n = 14; 51.9%). Functional outcomes were assessed using validated clinical scales, including the Single Assessment Numeric Evaluation (SANE), Disabilities of the Arm, Shoulder and Hand (DASH), Constant-Murley score, Simple Shoulder Test (SST), Activities of Daily Living External/Internal Rotation (ADLEIR) score, and EuroQol-5D (EQ-5D). Internal and external rotation were also measured. Statistical analysis was performed using Student's t-test and the Mann-Whitney U test. Results A total of 27 patients were included (22 female (81.5%); mean age 70.3 ± 9.7 years). No statistically significant differences were identified between groups in external rotation (15° vs 20.7°; p > 0.05), internal rotation (p = 0.54), or other range-of-motion parameters (p > 0.05). Functional outcome scores were similar between groups across all evaluated scales (p > 0.05). Complications occurred in three patients (23.1%) in the medialized group and one patient (7.1%) in the lateralized group. The calculated odds ratio was 3.9 (95% CI: 0.3-43.3), although this difference was not statistically significant (p = 0.23). Conclusions No statistically significant differences were identified between medialized and lateralized RTSA designs in terms of rotational mobility, functional outcomes, or complication rates. Given the small sample size, the study is likely underpowered to detect clinically meaningful differences. Further prospective studies with larger sample sizes are required to better evaluate potential differences between prosthetic designs.