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

INTRODUCTION

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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 multicentre Chilean cohort.

METHODS

This retrospective non-consecutive cohort included 150 unique patients who underwent first revision TKA at five Chilean centres 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 adjusted for age and sex. Sensitivity analyses incorporated revision year and centre and modelled time continuously, including assessment of non-linearity.

RESULTS

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 centre and when time was analysed 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.