Reliability and Validity of Radiographic Measurements in Hindfoot Varus and Valgus

Background: Clinical decision-making in the treatment of foot deformities is based primarily on the results of the physical examination and the radiographic findings. The purpose of this study was to determine the validity and reliability of commonly used radiographic measurements of hindfoot valgus and varus deformities. Methods: Seventy-two patients with hindfoot deformity (thirty-six hindfoot valgus, mean age 15.5 years; thirty-six hindfoot varus, mean age 30.2 years) were evaluated. Nine representative indices on weight-bearing radiographs were assessed. Three examiners measured the radiographic indices at two sessions, and intraobserver and interobserver reliability was determined. Discriminant validity of the radiographic measurements between hindfoot valgus and varus was evaluated. The correlation with pedobarographic findings in evaluating the distribution of foot pressure during gait was assessed for convergent validity. Results: Naviculocuboid overlap, anteroposterior talonavicular coverage angle, anteroposterior talus-first metatarsal angle, calcaneal pitch angle, and lateral talus-first metatarsal angle showed excellent reliability. Naviculocuboid overlap, anteroposterior talonavicular coverage angle, and anteroposterior talus-first metatarsal angle showed excellent discriminant validity (in terms of effect-size r) and convergent validity (in terms of correlation coefficients with pedobarography). Conclusions: Naviculocuboid overlap, anteroposterior talonavicular coverage angle, and anteroposterior talus-first metatarsal angle are reliable and valid measures for the evaluation of hindfoot valgus and varus deformities. Level of Evidence: Diagnostic Level Ill. See Instructions to Authors for a complete description of levels of evidence.