Adult acquired flatfoot fusions

Description: Johnson and Strom (1989) recommended subtalar fusion for correction of the acquired flatfoot when the deformity of the foot was fixed (stage 3). This was based on the concept that the midfoot and forefoot would follow the calcaneum – the "two-piece concept".
As the commonest deformity of adult acquired flatfoot is maximal at the talonavicular joint (Kitaoka et al 1998) it seems logical to consider stabilising this joint to restore the anatomy. Talonavicular fusion produces marked limitation of hindfoot motion in a cadaver model: 70% of pronation/supination and 25% of dorsiflexion/plantarflexion (Gellman et al 1987). Fogel et al (1982) performed gait analysis on patients 9 years after talonavicular fusion and found up to 30% loss of inversion/eversion, particularly on slopes, and reduction in late-stance plantarflexion.