Patient and Surgical Factors Associated With Long-Term Mortality Outcomes Up to Fifteen Years After Total Hip and Knee Arthroplasty: An Australian Orthopaedic Association National Joint Replacement Registry Study

BACKGROUND: Mortality rates following total hip arthroplasty (THA) and total knee arthroplasty (TKA) arthroplasty display distinct temporal patterns often attributed to patient selection bias, perioperative optimization, and comorbidities. Understanding these mortality patterns is essential for epidemiological and health economic longitudinal modeling. METHODS: We conducted a national registry-based cohort study in Australia using data from 1999 to 2022, examining primary and revision THA and TKA procedures for osteoarthritis. We assessed patient factors (age, sex, body mass index, and American Society of Anaesthesiologists score), and surgical factors (procedure, fixation, bearing surface, and implant volume) in relation to long-term mortality. Standardized mortality ratios were calculated by comparing observed and expected deaths based on national mortality rates. RESULTS: Our study included 540,181 THA and 880,036 TKA procedures. Temporal trends in mortality rates were observed, with a reduction in mortality rate observed up to seven years for both primary THA and primary TKA after the index procedure and an increased mortality rate observed thereafter. All patient factors were associated with differences in mortality rates, with younger (age range, 45 to 49 years) patients for primary TKA demonstrating the strongest association with mortality excess (15 years; standardized mortality ratios 2.02; 95% confidence interval 1.66 to 2.46). Revision procedures were associated with higher mortality rates compared to their respective primary procedures at all time points. CONCLUSIONS: Our study finds noncausal associations between patient and surgical factors and mortality up to fifteen years following THA and TKA for osteoarthritis in Australia. These findings are crucial for calibrating epidemiological and economic models and enhancing the precision of longitudinal outcome predictions for arthroplasty patients. While limitations exist, our study informs clinical practice, healthcare policies, and future research in arthroplasty surgery on a national scale, with potential relevance to similar populations worldwide. LEVEL OF EVIDENCE: Level III, therapeutic study.