Structural characteristics associated with radiographic severity of first metatarsophalangeal joint osteoarthritis.

OBJECTIVE: To determine whether foot structure varies according to the presence and radiographic severity of first metatarsophalangeal joint osteoarthritis (first MTPJ OA). METHODS: Weight-bearing dorso-plantar and lateral radiographs were obtained for the symptomatic foot of 185 participants (105 females, aged 22 to 85 years) with clinically diagnosed first MTPJ OA. A validated atlas was used to classify participants as having radiographic first MTPJ OA and to stratified into three categories of severity (none/mild, moderate, severe). Bone length, 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. RESULTS: One hundred and fifty participants were categorised as having radiographic first MTPJ 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 MTPJ OA displayed a greater hallux abductus interphalangeal angle. Increasing radiographic severity of first MTPJ OA was associated with a larger hallux abductus interphalangeal angle, wider first metatarsal and proximal phalanx and smaller intermetatarsal angle. No differences in medial arch measurements were observed between the categories. CONCLUSION: First ray alignment and morphology differ according to the presence and severity of first MTPJ OA. Prospective studies are required to determine whether the observed differences are a cause or consequence of OA.