Observer variability in the radiographic measurement and classification of metatarsus adductus

The classification system of Berg was evaluated using four observers and the radiographs of 42 feet from patients with metatarsus adductus. Interobserver disagreement in diagnosis was 36%. Intraobserver inconsistency averaged 26%. The error range for the lateral and anteroposterior talocalcaneal angle measurement was 13.6 and 15.1 degrees intraobserver and 19.8 and 25.2 degrees interobserver, respectively. There was no correlation between classification and the length of time required for cast correction. The irregularity of hindfoot ossification centers makes measurements inconsistent and seriously reduces the usefulness of classification based on such measurements.