Structural Characteristics Associated With Radiographic Severity of First Metatarsophalangeal Joint Osteoarthritis

To determine whether foot structure varies according to the presence and radiographic severity of first metatarsophalangeal (MTP) joint osteoarthritis (OA).

Weight-bearing dorsiplantar and lateral radiographs were obtained for the symptomatic foot of 185 participants (105 women, ages 22-85 years) with clinically diagnosed first MTP joint OA. A validated atlas was used to classify participants as having radiographic first MTP joint OA and to stratify into 3 categories of severity (none/mild, moderate, severe). Bone length and width and angular measures of the forefoot and medial arch were performed on radiographs, and differences between categories were compared using univariate general linear models, adjusting for confounders.

A total of 150 participants were categorized as having radiographic first MTP joint OA, and participants were further stratified into none/mild (n = 35), moderate (n = 69), or severe (n = 81) OA categories. Participants with radiographically defined first MTP joint OA displayed a greater hallux abductus interphalangeal angle. Greater radiographic severity of first MTP joint OA was associated with a larger hallux abductus interphalangeal angle, a wider first metatarsal and proximal phalanx, and a smaller intermetatarsal angle. No differences in medial arch measurements were observed between the categories.

First ray alignment and morphology differed according to the presence and severity of first MTP joint OA. Prospective studies are required to determine whether the observed differences are a cause or consequence of OA.