Reliability and relationship of radiographic measurements in hallux valgus.

BACKGROUND: Although various radiographic measurements have been developed and used for evaluating hallux valgus, not all are universally believed to be necessary and their relationships have not been clearly established. Determining which are related could provide some insight into which might be useful and which would not.

QUESTIONS/PURPOSES: We investigated the reliability of eight radiographic measurements used to evaluate hallux valgus, and determined which were correlated and which predicted the hallux valgus angle.

METHODS: We determined eight radiographic indices for 732 patients (mean age, 51 years; SD, 17 years; 107 males and 625 females) with hallux valgus: hallux valgus angle, intermetatarsal angle, hallux interphalangeal angle, distal metatarsal articular angle, proximal phalangeal articular angle, simplified metatarsus adductus angle, first metatarsal protrusion distance, and sesamoid rotation angle. Intraobserver and interobserver reliabilities of each radiographic measurement were analyzed on 36 feet from 36 randomly selected patients. Correlations among the radiographic measurements were analyzed. Radiographic measurements predicting hallux valgus angle were evaluated using multiple regression analysis.

RESULTS: Hallux valgus angle had the highest reliability, whereas the distal metatarsal articular angle and simplified metatarsus adductus angle had the lowest. Distal metatarsal articular angle, intermetatarsal angle, and sesamoid rotation angle had the highest correlations with hallux valgus angle. Distal metatarsal articular angle correlated with sesamoid rotation angle. The intermetatarsal angle, interphalangeal angle, distal metatarsal articular angle, first metatarsal protrusion distance, sesamoid rotation angle, and metatarsus adductus angle predicted the hallux valgus angle.

CONCLUSIONS: We suggest using hallux valgus angle, intermetatarsal angle, interphalangeal angle, sesamoid rotation angle, and first metatarsal protrusion distance considering their reliability and prediction of the deformity.