The First Metatarsophalangeal Arc Circumference: Correlation with Angular Measurements

Abstract

The contribution of the different anatomical aspects represented by individual angles to the overall hallux valgus deformity has not been previously examined, and data on the interrelationship of angular measurements are lacking. The objectives of this study were to determine the center of the circle formed by the first metatarsophalangeal arc circumference and to correlate the location of the center with the hallux valgus angle (HVA), the intermetatarsal angle (IMA), the distal metatarsal articular angle (DMAA), and the proximal phalangeal articular angle (PPAA) measurements. A total of 1933 dorsoplantar weightbearing radiographs of the foot from 1182 patients were analyzed. Measurements evaluated were the IMA, HVA, DMAA, and PPAA. All measurements were performed using a computer program. The arc was defined by the midpoint of the curvature of the medial metaphyseal flare of the hallux proximal phalanx and the proximal and distal metadiaphyseal junctions of the medial border of the hallux. By means of the computer program, the circle's center location was calculated and then outlined according to its position inside or outside of the foot. The smaller the HVA, the larger the circle and the distance between the foot and the center, and vice versa. Similar findings were observed for the DMAA and IMA. Severe hallux valgus deformities (HVA of more than 40 degrees) were associated with location of the center inside the foot. The long radius of the circle was significantly correlated with the HVA values (p < 0.001). This new approach offers the possibility of summarizing in a single point the correlation of different angular measurements.