Reliability and relationship of radiographic measurements in hallux valgus

Abstract

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.

Figures

Fig. 1

On the weightbearing dorsoplantar foot radiograph, angles between lines were measured. Various lines were drawn; line a is the longitudinal axis of the distal phalanx of the big toe, line b is the longitudinal axis of the proximal phalanx, line c is orientation of the proximal phalangeal base articular surface, line d is the longitudinal axis of the first metatarsal, line e is the longitudinal axis of the second metatarsal, line f is the longitudinal axis of the middle cuneiform, and line g is the longitudinal axis of the talus. Hallux valgus angle is the angle between b and d, intermetatarsal angle is the angle between d and e, interphalangeal angle is the angle between a and b, proximal phalangeal articular angle is the angle between b and c, and simplified metatarsus adductus angle is the angle between e and f.

Fig. 2

The distal metatarsal articular angle (asterisk) is the angle between a perpendicular line to the longitudinal axis of the first metatarsal and a line delineating the orientation of the metatarsal head articular surface.

Fig. 3

The first metatarsal protrusion distance is the difference between the arcs of the bisecting lines of the first (a) and second metatarsals (b) from the common intersection of the two lines.

Fig. 4

The sesamoid rotation angle is the angular relationship between the weightbearing surface and a line connecting the most inferior aspect of the medial and lateral sesamoid (angle between a and b).