Hind-mid-forefoot Deformity in Hallux Valgus Deformity in Rheumatoid Arthritis: Radiographic Evaluation Grouped by Existence of Dorsal Dislocation of Second Metatarsophalangeal Joint

Abstract

Hallux valgus deformity combined with dorsal dislocation of the second metatarsophalangeal joint is frequently observed in rheumatoid arthritis cases. However, hallux valgus deformity without lesser toe dislocation is also seen in rheumatoid cases. Dislocated second toe cause the loss of the lateral support on the hallux, suggesting the importance to confirm the state of lesser toe MTP joint when assessing the risk of HV recurrence after surgery, and there may be some differences in the mechanical transmission between hind-mid and forefoot based on whether dorsal dislocation of the MTP joint in the lesser toe is present, although findings are unclear. This study examined the relationship between radiographic findings from the hind, mid, and forefoot and hallux valgus angle in rheumatoid arthritis cases grouped based on the presence or absence of dorsal dislocation of the second metatarsophalangeal joint. X-rays of 160 feet and ankles with rheumatoid arthritis were evaluated for the first metatarsophalangeal Larsen grade, existence of second metatarsophalangeal dorsal dislocation, hallux valgus angle, intermetatarsal angle between the first and second intermetatarsals, shape of the first metatarsal head, position of the sesamoid, the metatarsus primus varus angle, diastasis between the base of the first and second metatarsals, angle between long axis of the talus and short axis of the navicular, internal arch angle, tibio-calcaneal angle, and calcaneal lateral offset. Based on Pearson product-moment correlation coefficient test, involvement of hindfoot deformity should always be considered when assessing hallux valgus deformity in rheumatoid arthritis patients. Although mechanism of mechanical transmission through hindfoot to Lisfranc joint seems to be different by the presence or absence of dorsal dislocation of the second metatarsophalangeal joint, Lisfranc looseness also must be considered when assessing hallux valgus including the surgery to avoid the progression or recurrence in rheumatoid arthritis cases. Dorsal dislocation of the second metatarsophalangeal joint strongly influences the exacerbation of hallux valgus in rheumatoid arthritis cases. Thus, it is may be important to achieve adequate reduction of the second metatarsophalangeal joint dislocation and make a stable metatarsophalangeal joint to avoid recurrence of hallux valgus after forefoot surgery in rheumatoid arthritis.