JSES - 2026-05-01 - Journal Article; Comparative Study
Outcomes of modular diaphyseal vs. nonmodular metaphyseal reverse total shoulder arthroplasty stem for 3- and 4-part proximal humerus fractures.
Pamula A, Lachance AD, Whittemore C, Choi JY
Topics
Key Takeaway
Metaphyseal stems yielded superior abduction (74.6° vs. 57.9°) and external rotation (32.1° vs. 14.8°) after RSA for 3- and 4-part PHF, while diaphyseal stems produced higher ASES scores (76.4 vs. 65.6), with no difference in revision rates.
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Summary
This retrospective study compared modular diaphyseal vs. nonmodular metaphyseal humeral stem designs in 99 patients undergoing RSA for acute 3- or 4-part PHFs from 2014–2024. Metaphyseal stems produced greater abduction (74.6° vs. 57.9°, P=0.027) and external rotation (32.1° vs. 14.8°, P<0.0001), while diaphyseal stems yielded higher ASES scores (76.4 vs. 65.6, P=0.015). Complication rates, VAS pain scores, and revision rates were equivalent between groups.
Key Limitation
The unequal and uncontrolled follow-up duration between groups (diaphyseal longer) systematically biases the ASES score comparison and undermines the primary functional outcome analysis.
Original Abstract
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.