Background: The causes of redisplacement following closed treatment of distal metaphyseal radial fractures in children are still controversial. Various risk factors and radiographic indices have been suggested to predict redisplacement. The aims of this study were to prospectively identify the causes of redisplacement and to test the accuracy of previously described radiographic indices and our new method, the "three-point index."
Methods: This prospective study included seventy-five displaced or severely angulated distal radial fractures in seventy-four children under the age of fifteen years. Age, gender, initial complete displacement of the radius, an associated ulnar fracture, the accuracy of the reduction, the maximum degree of obliquity of the fracture line in the sagittal or coronal plane, and the distance to the physis were examined as possible risk factors. Logistic regression analysis was utilized to search for risk factors. We also calculated the cast index, padding index, Canterbury index, gap index, and three-point index on the radiographs of each reduction. The sensitivity, specificity, negative predictive value, and positive predictive value were calculated for each test.
Results: Initial complete displacement and the degree of obliquity of the fracture were the most important risk factors for redisplacement. Fractures that were completely displaced initially were 11.7 times more likely to redisplace than were angulated but incompletely displaced fractures. A 20° oblique fracture was 4.9 times more likely to redisplace and a 30° oblique fracture was 10.9 times more likely to redisplace than was a 0° true transverse fracture. The three-point index was superior to the other radiographic indices for predicting redisplacement, with a sensitivity of 94.7%, a specificity of 95.2%, a negative predictive value of 98.4%, and a positive predictive value of 85.7%. The gap index was the next-best measure, but it had a sensitivity of 63.2%, a specificity of 76.2%, a negative predictive value of 87.3%, and a positive predictive value of 44.4%.
Conclusions: Initial complete displacement and the degree of obliquity of the fracture line are the dominant factors affecting redisplacement. Our new radiographic index, the three-point index, should be used to predict redisplacement and assess the quality of the cast treatment of these fractures.
Level of Evidence: Prognostic Level I. See Instructions to Authors for a complete description of levels of evidence.