Forefoot deformity in rheumatoid arthritis - a comparison of shod and non-shod populations

L.W. Mason, M. Dave, K. Hariharan

Introduction: All reported RA forefoot deformities in the literature so far have arisen from shoe wearing populations. Our aim in this study was to compare hallucal deformities seen in a shod to a non-shod population.

Methods: A case-control study was undertaken in two specialist foot and ankle units, one in India and one in the UK. All patients suffering from RA and attending for consideration of forefoot surgery from January 2007 to October 2013 were included in this study. Standardized anteroposterior weight bearing radiographs were obtained to measure the hallux valgus, inter-metatarsal and metatarsus primus varus angles.

Results: In the shod population, there was 1 hallux varus deformity, 10 without hallucal deformity and 90 feet with varying degrees of hallux valgus deformity. 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 5^th toe in a varus position. This was seen in 95% (n=96) of the shod population. In the unshod population, the most common lesser toe deformity seen was varus deviation or dislocation. This was present in 80% (n=20) of the unshod population.

Conclusion: Instability of the metatarsophalangeal joint in the rheumatoid foot predisposes it to significant deformity. External forces of shoe wear dictate the deformity, with hallux valgus being the most likely scenario in a shoe-wearing patient. In the non-shoe wearing population, intrinsic forces and weight bearing forces determine the deformity, with hallux varus being the most common presenting problem.