Impact of hypothyroidism on short-term and long-term outcomes in total hip arthroplasty: A national database propensity matched cohort study

Background: Hypothyroidism is a common endocrine disorder that presents challenges for total hip arthroplasty (THA) due to its effects on cardiovascular, metabolic, and immune systems. Prior studies associate hypothyroidism with increased perioperative risks, such as infections and delayed wound healing, but its impact on long-term mechanical outcomes remains underexplored. This study evaluates 90-day medical and 2-year mechanical complications in hypothyroid patients undergoing THA to inform risk management. Methods: A retrospective cohort study was conducted using the TriNetX database to identify patients who underwent THA between January 1, 2010, and December 31, 2022. Patients were divided into hypothyroid and non-hypothyroid cohorts, including both treated and untreated cases. 90-day perioperative outcomes included infections, sepsis, thromboembolic events, wound complications, anemia, renal failure, and mortality. 2-year mechanical outcomes included periprosthetic fractures, implant failure, periprosthetic joint infection (PJI), and aseptic loosening. Propensity score matching controlled for age, sex, BMI, and comorbidities. Data analysis included risk and odds ratios, Kaplan-Meier survival analysis, and a significance threshold of p < 0.05. Results: After propensity score matching, hypothyroid and non-hypothyroid cohorts were balanced across key demographic and clinical variables. Within 90 days, hypothyroid patients demonstrated significantly higher rates of anemia (9.7 % vs. 7.7 %; RD 0.020, p < 0.001; RR 1.25), infections, sepsis, renal failure, hematoma, seroma, hospital readmissions, and mortality. At 2 years, they experienced increased risks of implant failure (3.6 % vs. 2.9 %; RD 0.007, p < 0.001; RR 1.22), PJI, periprosthetic fractures, aseptic loosening, and reoperation. Kaplan-Meier analysis confirmed reduced implant survival (95.8 % vs. 96.5 %; p < 0.001; HR 1.19). Conclusion: Hypothyroidism increases the risk of both short- and long-term complications following THA. These findings support preoperative thyroid control and tailored perioperative strategies to improve outcomes in this high-risk population.