Deformity and degeneration in the hindfoot and midfoot joints of the adult acquired flatfoot.

Adult acquired flatfoot is generally characterized by loss of the longitudinal arch, hindfoot valgus, and forefoot abduction, but the precise deformity has not been adequately described at the level of individual joints. Simulated weightbearing CT scans and plain radiographs of 37 symptomatic flat feet were examined in this study. The degree of arthritic degeneration was assessed in the major hindfoot and midfoot joints, and the location of deformity was studied along the medial column of the arch. Moderate to severe degeneration was seen in about one-third of talonavicular, subtalar, and calcaneocuboid joints. The medial column of the arch collapsed through the talonavicular joint in some feet, through the medial naviculocuneiform joint in others, but rarely through both. First tarsometatarsal joint subluxation was a frequent finding as well. In this small series, neither the degree of degenerative arthritis nor the amount of joint deformity was seen to correlate with patient age. Furthermore, no correlation was observed between foot deformity and joint degeneration.