Interobserver Reliability of Radiographic Measurements of Contralateral Feet of Pediatric Patients with Unilateral Clubfoot

Abstract

Radiographs have traditionally been used to describe and quantify foot deformities in infants and children. We hypothesized that the interobserver reliability of measurements obtained from radiographs of pediatric feet would be low, especially with regard to the infant foot, and that normal ranges and standard deviations would decrease in association with increasing patient age. We retrospectively reviewed 494 radiographs of 121 patients treated for unilateral clubfoot at our institution and studied the contralateral normal foot. All anteroposterior radiographs, lateral radiographs, and lateral radiographs made with the foot in maximum dorsiflexion were analyzed by three observers, and the values were recorded. The databases created by the three observers were statistically analyzed according to five predefined age groups (birth to less than three months, three months to less than twelve months, twelve months to less than three years, three years to less than seven years, and seven years to less than fourteen years). The anteroposterior talocalcaneal angle was rated as having good interobserver reliability (i.e., an intraclass correlation coefficient of 0.61 to 0.80) for all patients in each age group. Other angles that were associated with good interobserver reliability were the anteroposterior calcaneus-fifth metatarsal angle in the twelve months to less than three-year age group, the three-year to less than seven-year age group, and the seven-year to less than fourteen-year age group; the lateral talocalcaneal angle in the three-year to less than seven-year age group; the lateral tibiotalar angle in the three-year to less than seven-year age group; and the lateral talus-first metatarsal angle in the seven-year to less than fourteen-year age group. All other angles were rated as having very good interobserver reliability (i.e., an intraclass correlation coefficient of 0.81 to 1). The mean difference and the maximum difference among the observers decreased for all angles in nearly all age groups. Interobserver reliability with regard to the radiographic measurement of pediatric feet was higher than expected, although measurement discrepancies can be as great as 30° with the infant foot. Interobserver reliability tended to improve with increasing patient age. The standard deviation showed a trend toward a decrease as patient age increased, although the trend was less notable than expected.