Effect of prior mastectomy on outcomes following total shoulder arthroplasty.

BACKGROUND: Mastectomy and its associated treatments may alter shoulder biomechanics and soft-tissue integrity, yet their impact on total shoulder arthroplasty (TSA) outcomes remains unclear. This study evaluated short- and long-term complications following TSA in patients with a history of mastectomy. METHODS: A retrospective cohort analysis was performed using the TriNetX Research Network, including patients who underwent primary TSA. Individuals with a history of mastectomy were identified using procedural and diagnostic coding, and those with contralateral mastectomy and TSA were excluded. Propensity score matching 1:1 was performed to balance demographics and comorbidities. Ninety-day and two-year outcomes were compared between matched cohorts. RESULTS: After matching, 1,865 patients with prior mastectomy were compared with 1,865 controls. Patients with a history of mastectomy had a significantly higher incidence of postoperative lymphedema (3.48% vs. 0.67%; RR 5.15; P < .0001). They also demonstrated increased risk of venous thromboembolism (4.56% vs. 3.11%; RR 1.47; P = .018). Overall postoperative infection rates were higher in the mastectomy cohort (3.96% vs. 2.70%; RR 1.47; P = .0378), including higher rates of cellulitis (2.81% vs. 1.72%; RR 1.63; P = .031). No significant differences were observed for 2-year outcomes. CONCLUSION: Patients with a history of mastectomy undergoing TSA are at increased risk of perioperative postoperative lymphedema, thromboembolic events, and cellulitis. These findings highlight the importance of heightened perioperative surveillance.