Temporal distribution of recorded indications for first revision total knee arthroplasty: a multicenter Chilean cohort of 150 patients

INTRODUCTION/OBJECTIVES: Recorded indications for first revision total knee arthroplasty (TKA) may vary with time after the primary procedure. This study compared their distribution among early and late first revisions in a multicenter Chilean cohort. METHODS: This retrospective nonconsecutive cohort included 150 unique patients who underwent first revision TKA at five Chilean centers between 2018 and 2026. Revisions were classified as early (<24 months) or late (≥24 months). Indication distributions were compared using categorical tests, including a fixed-margin Monte Carlo procedure for sparse cells. Logistic regression was adjusted for age and sex. Sensitivity analyses incorporated revision year and center and modeled time continuously, including assessment of nonlinearity. RESULTS: The mean age was 70.1 ± 9.5 years, and 97 patients (64.7%) were women. Fifty-three revisions (35.3%) were early, and 97 (64.7%) were late. The indication distribution differed by timing (Monte Carlo p = 0.0003; Cramér's V = 0.41). Infection was the most frequent early indication (18/53, 34.0%), whereas aseptic loosening accounted for more than half of late revisions (52/97, 53.6%). After adjustment for age and sex, late revision was associated with higher odds that aseptic loosening was the recorded indication (adjusted odds ratio [OR], 6.70; 95% confidence interval [CI], 2.80-16.00; p < 0.001). Early revision was associated with higher odds that infection was the recorded indication (adjusted OR, 3.21; 95% CI, 1.40-7.34; p = 0.006). Estimates were similar after accounting for revision year and center and when time was analyzed continuously. CONCLUSION: Among the included first revisions, infection was the most frequent recorded indication before 24 months, whereas aseptic loosening was the most frequent indication thereafter. These within-cohort associations remain subject to selection bias, diagnostic misclassification, and residual confounding and do not estimate cause-specific revision risk after primary TKA. LEVEL OF EVIDENCE: III.