Acute vs Delayed Primary Reverse Shoulder Arthroplasty for Treatment of Proximal Humerus Fractures: Protocol for a Systematic Review and Meta-Analysis (Preprint)

BACKGROUND Proximal humerus fractures are common in older adults, and reverse shoulder arthroplasty (RSA) has become an established option for complex displaced fractures, but the optimal timing of surgery after injury remains uncertain. Previous systematic reviews combined patients undergoing delayed arthroplasty after failed nonoperative management with those undergoing salvage arthroplasty after failed surgical treatment, leaving the isolated effect of surgical timing unclear. OBJECTIVE This study aims to compare the outcomes of RSA performed early after injury with those of RSA performed after an initial period of nonoperative management, in adults with proximal humerus fractures. METHODS This protocol follows the PRISMA-P (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols) guidelines. Systematic literature searches will be conducted across 3 electronic databases, namely PubMed/MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials, together with ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, and Google Scholar. No language or publication date restrictions will be applied. Eligible studies are randomized and nonrandomized comparative studies of adults in which the threshold separating early from late RSA declared by the primary study lies between 4 and 6 weeks from injury. Studies whose late arm comprises arthroplasty performed as a revision of previous surgical treatment will be excluded, unless data for patients initially managed nonoperatively are reported separately. The primary outcomes are reoperation, defined as any subsequent operation on the index shoulder, and functional status measured with the ASES, Constant-Murley, DASH, and SPADI scores.Two independent reviewers will screen the studies and extract data, and any disputes will be resolved by a third reviewer. When data is sufficiently available in the pooled studies, a meta-analysis for each outcome will be conducted using a random-effects model, using Cochrane RevMan Web (version 11.0.0). For the risk-of-bias assessment, the Risk of Bias in Nonrandomized Studies of Interventions tool and version 2 of the Cochrane risk-of-bias tool for randomized trials will be used, and the certainty of evidence will be rated with GRADE. RESULTS This protocol was registered in PROSPERO on July 10, 2026. Literature searching started in July 2026 and will be updated before the final analysis. Screening, data extraction, and quantitative meta-analysis are scheduled to start in November 2026, with the full review manuscript planned for submission by January 2027. CONCLUSIONS This meta-analysis will quantify the effect of surgical timing on reoperation and shoulder function after RSA for proximal humerus fractures, separating delayed arthroplasty after failed nonoperative treatment from salvage arthroplasty after failed surgical treatment. The synthesized evidence can inform the decision of whether to attempt a period of nonoperative management before arthroplasty in older adults. CLINICALTRIAL PROSPERO CRD420261403142; https://www.crd.york.ac.uk/PROSPERO/view/CRD420261403142