Forefoot Deformity in Rheumatoid Arthritis: A Comparison of Shod and Unshod Populations.

UNLABELLED: All reported rheumatoid arthritis (RA) forefoot deformities in the literature thus far have arisen from shoe wearing populations. Our aim in this study was to compare hallucal deformities seen in a shod population with an unshod population. A population comparison was undertaken in 2 specialized foot and ankle units, one in India and one in the United Kingdom. In the shod population, there was 1 hallux varus deformity, 10 without hallucal deformity, and 90 hallux valgus deformities. In contrast, in the unshod population, there were 19 hallux varus deformities and 6 hallux valgus deformities. There was great variability in the lesser toe deformity seen. In the shod population, it was most common to see dorsal subluxation or dislocation, with the fifth toe in a varus position. In the unshod population, the most common lesser toe deformity seen was varus deviation or dislocation. Instability of the metatarsophalangeal joint in the rheumatoid foot predisposes it to significant deformity. In the non-shoe wearing population, intrinsic muscle forces and weight bearing forces are the most likely determinants of the deformity, with hallux varus being a more common presenting problem. In the shod population, the external forces of shoe wear dictate the direction of deformity. LEVELS OF EVIDENCE: Prognostic, Level III: Case control study.