Conversion Total Knee Arthroplasty After Tibial Plateau Fracture Open Reduction and Internal Fixation: A Propensity-Matched Analysis of 90-Day and One- and Three-Year Outcomes.

INTRODUCTION: Conversion total knee arthroplasty (TKA) following tibial plateau fracture (TPF) open reduction and internal fixation (ORIF) is surgically complex. This study utilized a national-level database to compare 90-day and one- and three-year outcomes between TKA following TPF ORIF and primary TKA. METHODS: A de-identified database was queried (2003 to 2023) for patients ≥ 18 years undergoing conversion TKA within 10 years of TPF ORIF (n = 615). A primary TKA control group (n = 224,331) was identified for one-to-one propensity score-matching, yielding 613 patients per group. The primary outcomes were periprosthetic joint infection (PJI) and revision TKA. The secondary outcomes were manipulation under anesthesia (MUA) and 30-day readmission. A secondary analysis compared TKA after nonoperative TPF (n = 1,989) to primary TKA to characterize the risk associated with fracture alone. A tertiary analysis directly compared TKA after TPF ORIF to nonoperative TPF to characterize the risk attributable to prior hardware. RESULTS: Compared with primary TKA, conversion TKA was associated with an increased risk of PJI (risk ratio [RR] 2.73 to 3.18) and revision TKA (RR, 2.29 to 2.50) across 90-day, and one- and 3-year follow-up periods. The risk of 30-day readmission was also elevated (RR, 2.43). In the secondary and tertiary analyses, respectively, TKA after nonoperatively managed TPF carried greater risk of PJI and revision compared with primary TKA, and TKA after TPF ORIF carried greater risk than TKA after nonoperative TPF. The risk of MUA did not differ between groups. CONCLUSION: Conversion TKA after TPF ORIF carries elevated risks of PJI and revision compared with primary TKA. The risk profile appears to stem from a dual burden: the baseline hazard imposed by the intra-articular fracture and an additive risk associated with prior hardware. These patients require heightened preoperative counseling and tailored surgical strategies.