Inter- and intraobserver reliability in the radiographic evaluation of adult flatfoot deformity

Adult acquired flatfoot is a complex deformity with numerous radiographic measurements described to define it. The purpose of this study was to evaluate the inter- and intraobserver reliability of six radiographic measurements using digital and conventional radiographs.

Three digital weightbearing radiographs consisting of anteroposterior, lateral, and hindfoot alignment views were obtained at presentation for 20 consecutive patients. Six radiographic measurements were made for each patient: talus/second metatarsal angle, calcaneal pitch angle, talus/first metatarsal angle, medial cuneiform/fifth metatarsal distance, tibial/calcaneal displacement, and calcaneal angulation. Each radiograph was evaluated on multiple occasions by a senior orthopaedic surgery resident, a junior orthopaedic surgery resident, and a third-year medical student. Inter- and intraobserver reliability was determined using measurements made on digital radiographs.

Interobserver reliabilities were 0.830 for talus/second metatarsal angle, 0.948 for calcaneal pitch angle, 0.781 for talus/first metatarsal angle, 0.991 for medial cuneiform/fifth metatarsal distance, 0.870 for tibial/calcaneal displacement, and 0.834 for calcaneal angulation. Interobserver reliability was similar for digital and conventional radiographs, and intraobserver reliability increased with observer experience.

Adult acquired flatfoot deformity is a complex condition that is difficult to quantify radiographically. The medial cuneiform/fifth metatarsal distance and the calcaneal pitch angle were found to have the highest interobserver reliability. Intraobserver reliability increased with observer experience.