Prediction of delayed union of tibial shaft fracture treated with intramedullary nailing: multicenter-study analysis and literature review -the TRON study.

Purpose: We aimed to 1) identify predictors of delayed and nonunion of tibial shaft fractures in patients treated with intramedullary nailing (IMN), including patient demographics and surgical factors, and 2) determine whether the nail/shaft ratio is associated with delayed and nonunion.

Methods: This retrospective, multicenter study included 315 patients with tibial shaft fracture treated with IMN between 2014 and 2019 and excluded patients with insufficient follow-up for 12 months, lost data and inadequate radiographs. Finally, we analyzed 258 patients (184 males; 74 females). Main outcome measurements were delayed union at 6 and nonunion at 12 months after surgery as determined on anteroposterior and lateral radiographs. We extracted the following as risk factors of delayed and nonunion: age, sex, BMI, fracture site, fracture type, injury energy, smoking history, and nail/shaft ratio. We conducted logistic regression analysis to investigate risk factors of delayed and nonunion using these extracted items as explanatory variables.

Results: Type C fracture was independently associated with delayed union (odds ratio 2.9, 95% confidential interval: 1.04-8.09, P = 0.04). Nail/shaft ratio was not an independent factor of delayed union. No independent explanatory factors were related to nonunion.

Conclusions: Type C fractures, which were unstable and fragmented, was associated with delayed union in tibia fractures treated with IMN, whereas nail thickness was not associated with delayed or nonunion fractures.