Reliability of standard foot radiographic measurements

Fifty standing dorsoplantar and lateral foot radiographs were obtained on a consecutive series of patients seen in an orthopaedic foot and ankle clinic. These radiographs were duplicated, and eight common foot measurements were made on each pair by six experienced examiners. Measurements were made in two ways: first by a subjective visual assessment, and second by quantitative evaluation made according to strictly defined criteria. All measurements were made under controlled, ideal conditions with similar high quality goniometers. The results demonstrated overall greater reliability in the quantitative methods than the non-quantitative methods. For each of the quantitative techniques, a cumulated frequency distribution of differences between examiners was calculated. The approximate 95% bounds for these measures were: hallux-metatarsophalangeal angle = 6 degrees, first intermetatarsal angle = 4 degrees, metatarsophalangeal-5 angle = 11 degrees, fourth intermetatarsal angle = 4 degrees, AP talocalcaneal angle = 20 degrees, lateral talocalcaneal angle = 12 degrees, sesamoid station = 2 grades, and forefoot width = 5 mm. Physicians using these parameters to make decisions regarding patient care and clinical outcomes need to keep in mind these potential errors in making foot radiographic measurements.