Fractures with complex fracture patterns are associated with increased rate of subsequent conversion to total knee arthroplasty after a tibial plateau fracture: an observational cohort study of 12,012 patients from the Swedish Fracture Register.

Background: Tibial plateau fractures (TPFs) can be associated with development of significant joint degeneration, which can lead to functional impairment and pain severe enough to necessitate conversion to total knee arthroplasty (TKA). The factors influencing the progression to TKA after TPF, including preoperative fracture and patient characteristics, remain unclear. This study aimed to assess the national conversion rate to TKA following TPF depending on fracture type.

Patients and methods: The cohort consisted of all patients aged 18 years and older at time of injury with a TPF registered in the Swedish Fracture Register (SFR) between 2012 and 2023. The SFR holds information on baseline patient characteristics including fracture classification according to the AO/OTA system. Conversion to TKA was identified through linkage with the Swedish Arthroplasty Register (SAR). Kaplan-Meier survival analyses investigated conversion rate. Cox regression was performed to assess association between fracture type and TKA conversion adjusted for age, sex, and injury energy level. The follow-up period ranged from 0 to 12 years, with a mean of 4.2 years.

Results: A total of 12,012 patients with a mean age of 57 years were included; 63% were women. The observed conversion rate after 5 years was 2.8% in all patients and 4.1% in surgically treated patients. The conversion rate at 5 years was highest in the 65-74 years age group with 5.2%. Fractures with comminuted fracture patterns, particularly AO/OTA 41B3, 41C2, and 41C3, were associated with significantly increased risks of conversion, with adjusted hazard ratios (aHRs) of 2.1 (95% CI 1.3-3.3), 2.3 (1.2-4.5), and 3.2 (95% CI 2.0-4.5), respectively. High-energy trauma did not increase the risk of conversion, nor did sex. Increasing age was associated with an increased risk of conversion up to the age of 84, while age over 85 was not.

Conclusions: Fractures with complex fracture patterns, particularly AO/OTA 41B3, 41C2, and 41C3, were associated with an increased TKA conversion rate following TPF. The conversion rate increased with increasing age, but sex and high-energy injury mechanisms did not affect conversion rate. On a national level, 3% of patients were converted to TKA within 5 years of sustaining a TPF, and 4% of patients treated surgically. This may help surgeons when counseling patients with TPFs.