From bowing to fracture : radiolucent lines as a predictor of progression in congenital pseudarthrosis of the tibia.

AIMS: Congenital anterolateral bowing of the tibia represents the prefracture stage of congenital pseudarthrosis of the tibia. However, specific radiological factors which are predictive of fracture remain poorly defined. The aim of this study, therefore, was to investigate whether the presence of radiolucent lines could serve as a predictive factor for the development of a fracture in patients with Crawford types I to III congenital pseudarthrosis of the tibia.

METHODS: We retrospectively reviewed 251 children with congenital pseudarthrosis of the tibia who were treated between 2015 and 2020. Demographic, clinical, and radiological data were collected, and the presence and extent of radiolucent lines were systematically assessed. Inter- and intraobserver agreement were evaluated using κ coefficients. Group comparisons used the independent-samples t-test, chi-squared test, or Fisher's exact test, as appropriate. Independent predictive factors of fracture were identified with multivariable logistic regression. Fracture-free survival was evaluated using Kaplan-Meier analysis.

RESULTS: A total of 142 children with Crawford types I to III congenital pseudarthrosis of the tibia met the inclusion criteria. The assessment of radiolucent lines showed high inter- and intraobserver agreement. Radiolucent lines were strongly associated with the occurrence of a fracture. The risk of fracture differed significantly across Crawford sub-types (p = 0.002) and the extent of radiolucent lines (quantified by the r-value) (p = 0.037). Crawford types II and III were associated with a significantly higher risk of fracture than type I (both adjusted p < 0.05). Similarly, patients with r ≥ 2/3 had a higher risk of fracture than those with r < 1/3 (adjusted p < 0.05). Multivariable logistic regression identified radiolucent lines and Crawford type as independent risk factors for fracture. A significantly reduced fracture-free survival in patients with radiolucent lines, both in the overall cohort and within the individual Crawford types I to III (p < 0.0001 for types I to III, type I, and type II; p = 0.0002 for type III), was shown in the Kaplan-Meier analysis.

CONCLUSION: Radiolucent lines may represent a new radiological predictive factor of fracture in patients with Crawford types I to III congenital pseudarthrosis of the tibia. Their prognostic value for predicting the time to fracture appears to vary across Crawford types. Combining the assessment of radiolucent lines with the Crawford classification could improve the stratification of the risk of fracture, providing a more precise framework for surveillance and timely intervention in these patients.