© 2021 Lippincott Williams and Wilkins. All rights reserved.Background:As there is a current increasing tendency to treat displaced tibial shaft fractures in adolescents surgically, it has become more important to predict failure of cast treatment for these patients. In the past, redisplacement of pediatric tibial shaft fractures has been reported at rates of 20% to 40%. Although the efficacy of the three-point index (TPI), gap index, and cast index has been demonstrated for upper extremity fractures in children, to date no index has been shown to accurately predict redisplacement for pediatric tibial shaft fractures. The aim of this study was to determine the predictive factors for redisplacement in pediatric tibial shaft fractures.Methods:In all, 157 displaced pediatric tibial shaft fractures were evaluated retrospectively. Patient age, initial and postreduction fracture angulation, shortening and translation, quality of reduction, obliquity of fracture, associated fibular fractures, and 3 indices (TPI, cast index, and gap index) were analyzed. Receiver operating characteristic analysis was performed to determine the cutoff points and logistic regression was used to show the risk factors of redisplacement.Results:There were 53 female and 104 male patients with a mean age of 9.1 (5 to 15 y) and 45 patients developed redisplacement during the follow-up. Mean TPI and gap index and initial and postreduction fracture translation were higher in patients with redisplacement, while TPI>0.855 and postreduction translation >18% were the only independent risk factors for fracture redisplacement. No differences were observed regarding associated fibular fracture, quality of reduction, initial/postreduction angulation, and shortening.Conclusions:The TPI>0.855 and postreduction translation >18% are independent risk factors for redisplacement of tibial shaft fractures in children. Although the gap index can be useful, the cast index is not an appropriate tool for these fractures.