Clinical impact of scapular stress fracture after reverse total shoulder arthroplasty: a single-center propensity score-matched analysis.

BACKGROUND: Scapular stress fracture (SSF) is a recognized complication after reverse total shoulder arthroplasty (rTSA), yet its clinical impact remains controversial. This study aimed to determine the incidence of SSF after rTSA, compare outcomes with a 1:3 propensity score-matched control group, and evaluate the influence of fracture location, treatment modality, and radiographic union on clinical outcomes. METHODS: A total of 551 consecutive primary rTSAs performed between January 2010 and December 2024 at a single tertiary referral center were retrospectively reviewed. Thirty patients developed postoperative SSF; 28 with a minimum follow-up of 12 months after SSF diagnosis were included for outcome analysis. Eighty-four control patients without SSF were selected using 1:3 propensity score matching based on age, sex, bone mineral density, implant type, and history of prior shoulder surgery. Clinical outcomes included visual analog scale (VAS) pain score, University of California, Los Angeles (UCLA) score, American Shoulder and Elbow Surgeons (ASES) score, subjective shoulder value (SSV), and active range of motion (ROM). Subgroup analyses were conducted according to fracture location, treatment modality, and radiographic union. The mean follow-up duration after rTSA was 52.5 ± 36.2 months and 47.1 ± 27.1 months in the SSF and control groups, respectively. RESULTS: The incidence of SSF was 5.4% (30 of 551 cases). Final VAS pain score, UCLA score, ASES score, and SSV did not differ significantly between groups. However, the SSF group demonstrated significantly reduced forward flexion (126.1° vs. 136.2°, P = .011) and abduction (103.2° vs. 117.3°, P = .003). According to the Levy classification, there were 4 type I, 16 type II, and 8 type III fractures. Fracture location significantly affected final forward flexion (P = .046) and abduction (P = .037), with type III fractures demonstrating the poorest ROM. Treatment modality (operative vs. nonoperative) and radiographic union did not significantly influence final clinical outcomes. CONCLUSION: SSF occurred in 5.4% of primary rTSAs. Although patient-reported outcomes were comparable to matched controls, SSF was associated with significantly decreased shoulder elevation. Fracture location influenced ROM recovery, whereas treatment modality and radiographic union did not significantly affect final clinical outcomes. LEVEL OF EVIDENCE: Level III, Retrospective Cohort Comparison, Prognosis Study.