Outcomes of modular diaphyseal vs. nonmodular metaphyseal reverse total shoulder arthroplasty stem for 3- and 4-part proximal humerus fractures.

BACKGROUND

Proximal humerus fractures (PHFs) are increasingly prevalent in the aging population, with reverse shoulder arthroplasty (rTSA) emerging as a preferred surgical treatment for complex fracture patterns. Recent advancements have introduced shorter, metaphyseal-fixation humeral stems as alternatives to traditional modular diaphyseal stems. However, limited data exist comparing the clinical outcomes of these designs following rTSA for PHF.

METHODS

A retrospective analysis of 99 patients undergoing rTSA for acute three- or four-part PHFs between 2014 and 2024 was conducted. Patients received either a modular diaphyseal stem (n = 66) or a nonmodular metaphyseal stem (n = 33). Demographics, perioperative variables, American Shoulder and Elbow Surgeons scores, visual analog scale scores, range of motion, complications, and revision rates were compared. Statistical analyses included t-tests for continuous variables and chi-squared tests for categorical data.

RESULTS

No significant differences were observed between groups in terms of demographics, comorbidities, hospital stay, or overall postoperative complications. The modular diaphyseal cohort had a significantly longer operative time and follow-up duration. Postoperative American Shoulder and Elbow Surgeons scores were higher in the diaphyseal group (76.35 vs. 65.58, P = .015), while the metaphyseal group demonstrated superior abduction (74.55° vs. 57.93°, P = .0267) and external rotation (32.12° vs. 14.79°, P < .0001). No significant differences were found in postoperative visual analog scale scores (P = .117) or revision rates (P = 1.00).

CONCLUSION

Both modular diaphyseal and nonmodular metaphyseal stem designs offer safe and effective options for rTSA following PHF, with distinct advantages. Modular stems may provide improved functional scores over longer follow-up, whereas metaphyseal stems may enhance range of motion. These findings support individualized surgical planning based on patient anatomy, functional goals, and revision risk. Further long-term studies are warranted to optimize implant selection.