Objectives <p>Osteoporosis is a prevalent comorbidity in patients undergoing total or reverse shoulder arthroplasty and is associated with higher rates of periprosthetic fracture, implant loosening, and revision surgery. While bisphosphonates are commonly used to treat osteoporosis, prior research has primarily examined preoperative use. This study aimed to evaluate the association between postoperative bisphosphonate initiation and implant-related complications, particularly revision surgery, in osteoporotic patients undergoing shoulder arthroplasty.</p> Design <p>We used the TriNetX U.S. Collaborative Network to identify adults (≥ 18 years) with osteoporosis who underwent total shoulder arthroplasty (TSA) or reverse shoulder arthroplasty (RSA) between 2016 and 2021. Patients were categorized by postoperative bisphosphonate use, defined as initiation within one month after surgery. Propensity score matching (1:1) based on demographics and comorbidities yielded 1,489 patients per group. The primary outcome was a composite of revision surgery, periprosthetic fracture, implant loosening, and periprosthetic joint infection at 6 months. Secondary outcomes were the individual components at 6 months and 2 years. Landmark analyses evaluated the composite outcome at 30-day and 1 year postoperatively.</p> Results <p>At 6 months, the bisphosphonate group had a lower composite complication rate compared with controls (11.0% vs. 13.4%; HR, 0.79; 95% CI, 0.63–0.98; <i>P</i> = 0.038), primarily driven by a lower revision rate (3.0% vs. 4.2%; HR, 0.67; 95% CI, 0.46–0.99; <i>P</i> = 0.041). No significant differences were observed for periprosthetic fracture, implant loosening, or infection. At 2 years, revision rates remained lower in the bisphosphonate group (7.1% vs. 8.9%; HR, 0.71; 95% CI, 0.55–0.92; <i>P</i> = 0.009), while other complication rates were comparable. In the landmark analysis, postoperative bisphosphonate use was associated with a lower hazard of composite implant-related complications at 1 year.</p> Conclusions <p>In this large real-world cohort, postoperative bisphosphonate initiation was associated with lower rates of composite implant-related complications and revision surgery following shoulder arthroplasty. Although causal inference cannot be established due to the observational design, these findings suggest postoperative bisphosphonate use as a potentially modifiable factor that warrants further investigation in prospective studies.</p> Level of evidence <p>Level III, retrospective comparative study, treatment study.</p>