Background: Effective methods of treating an unstable distal radial fracture are described in the literature, but there is no reliable method of identifying an unstable fracture in time to initiate appropriate treatment. The purposes of this study were to identify the predictors of fracture instability and to construct a method of prospectively predicting the radiographic outcome.

Methods: Data on approximately 4000 distal radial fractures were prospectively recorded over a 5.5-year period. The database was validated by reexamining a sample of it. Demographic data on the patients and mode of injury, as well as the fracture classification and measurements, were recorded at the time of presentation. Outcome measures consisted of radiographic measurements made at one week and six weeks and assessment of carpal alignment at six weeks. Univariate and multiple logistic regression analyses were performed to identify the significance of the data obtained at presentation in the prediction of early and late instability as well as the risk of malunion and carpal malalignment.

Results: The predictors of early and late instability and malunion differed according to the displacement of the fracture at presentation. Patient age, metaphyseal comminution of the fracture, and ulnar variance were the most consistent predictors of radiographic outcome. Dorsal angulation was not found to be significant in the prediction of radiographic outcome for displaced fractures. The degree to which the patient was independent was predictive of malunion in minimally displaced and displaced fractures. Formulas that are predictive of each of the seven radiographic outcome measurements were constructed.

Conclusions: The study succeeded in identifying the factors that are prognostic of the radiographic outcome for distal radial fractures. Formulas to predict the radiographic outcome were constructed as the independent prognostic significance of these factors was quantified. These formulas can be used to inform the surgeon's decision about the nature of primary treatment of fractures of the distal aspect of the radius. However, they must be validated by further studies before they are used to impact the management of distal radial fractures.

Level of Evidence: Prognostic Level I. See Instructions to Authors for a complete description of levels of evidence.