Impact of Frailty on Total Knee Arthroplasty Outcomes: A Propensity-Matched Study of 133,264 Patients Using the Modified Frailty Index.

Abstract

Frailty is a known critical determinant of surgical outcomes. However, it lacks routine integration into total knee arthroplasty (TKA) risk assessment. This study evaluated the association between preoperative frailty, measured by the 5-factor modified frailty index (mFI-5), and adverse medical and surgical outcomes following TKA. This retrospective cohort analysis utilized a large national database (2003 to 2020), including patients ≥ 50 years undergoing primary TKA. Patients were stratified by mFI-5 score: non-frail (0 to 1), moderately frail (2), and severely frail (≥ 3). Propensity score matching (1:1) balanced cohorts for age, sex, race, and body mass index. Outcomes included 90-day medical and surgical complications, 2- and 5-year surgical outcomes (revision, periprosthetic fracture, mechanical complications, and infection), mortality, and healthcare utilization (readmissions and emergency department [ED] visits). Relative risks (RR) with 95% confidence intervals (CI) were calculated, applying Bonferroni corrections (significance P < 0.0167). Frailty severity demonstrated a clear graded increase in complications. Severely frail patients had significantly higher 90-day risks of mortality, myocardial infarction, acute kidney failure, pneumonia, sepsis, anemia, falls, readmissions, and ED visits compared with non-frail patients (all P < 0.0167). Surgical risks similarly increased over time, with severely frail patients showing higher 5-year rates of revision, periprosthetic joint infection, mechanical complications, and periprosthetic fracture. Moderately frail patients demonstrated complication patterns that fell between those of non-frail and severely frail groups. Frailty was also associated with increased 2- and 5-year mortality. The mFI-5 effectively stratifies TKA patients by frailty severity and reveals a dose-dependent relationship with adverse outcomes. Moderate and severe frailty independently predict increased 90-day, 2-year, and 5-year morbidity, mortality, and healthcare use. Integrating mFI-5 into preoperative assessment may benefit orthopaedic surgeons in targeted optimization and counseling to mitigate risks in high-risk TKA patients.