Shape of the lateral edge of the first metatarsal head changes depending on the rotation and inclination of the first metatarsal: a study using digitally reconstructed radiographs

Positive round sign of the first metatarsal head on the dorsoplantar radiograph of the foot was significantly associated with increased pronation as well as decreased inclination of the first metatarsal. Negative round sign may be used as an indicator of effective correction of first metatarsal pronation during hallux valgus surgery.