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

BACKGROUND: 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.

MATERIALS AND METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.