Radiographic Verification of the Feasibility of Intramedullary Nailing in Tibial Shaft Fractures Distal to Total Knee Arthroplasty

<b>Background</b>: Tibial shaft fractures distal to total knee arthroplasty (TKA) are commonly treated with plate fixation, which requires prolonged weight-bearing restriction. Although intramedullary nailing (IMN) has been attempted in selected cases, its feasibility remains controversial. This study aimed to assess the radiographic feasibility of IMN using anatomical parameters on lateral knee radiographs. <b>Methods</b>: A total of 271 lateral knee radiographs after TKA (January 2022 to October 2023) were retrospectively reviewed. Nail corridor and superior and inferior tibial tuberosity angles were measured on true lateral views. Tibial component size, keel length, BMI, age, and sex were analyzed for their association with nail corridor dimensions. Calibration was performed using known implant sizes. <b>Results</b>: Of the 271 lateral knee radiographs reviewed, 248 patients were included in the final analysis. The mean nail corridor was 9.27 ± 2.41 mm. The average superior and inferior tibial tuberosity angles were 105.88° and 155.79°, respectively. The tibial component size and keel length were not correlated with the nail corridor. In contrast, both superior (β = 0.252, <i>p</i> < 0.001) and inferior (β = 0.148, <i>p</i> = 0.003) tibial tuberosity angles were significantly associated with the nail corridor. No differences were observed in sex or BMI. <b>Conclusions</b>: IMN may be radiographically feasible in selected patients with tibial shaft fractures distal to TKA. The superior and inferior tibial tuberosity angles are anatomical parameters associated with the nail corridor and may serve as reference measures during preoperative radiographic assessment.