Review Question - QID 1195

The clinical photographs demonstrate a varus hindfoot and cavus midfoot. The clinical exam is highlighted by a relatively strong peroneus longus and posterior tibialis muscles which overpower the relatively weak peroneus brevis and anterior tibialis muscle. This imbalance results in hindfoot varus and forefoot pronation. Treatment is directed by determining the flexibility of the deformity.

A cavus foot is commonly associated with plantar flexion of the first metatarsal. With peroneus longus dominance, the forefoot pronates secondarily leading to hindfoot varus. Coleman’s (lateral) block test, shown in Illustration A, is used to assess the hindfoot flexibility of the cavovarus foot. A supple hindfoot will correct to neutral or slight valgus when the block is placed under the lateral hindfoot. Correction of the hindfoot varus position implies the hindfoot deformity is not fixed and the the forefoot is the primary deformity. Thus, the calcaneus is spared from an osteotomy (e.g. Dwyer lateral closing wedge osteotomy) during surgical correction. A dorsiflexion osteotomy of the first metatarsal and plantar fascia release will help correct the cavus deformity as well as allow restoration of the “tripod” foot alignment. Finally, the supple hindfoot will passively correct from the varus position into a neutral position.

Fortin et al reviewed 13 feet in 10 patients with subtle cavovarus deformity. They found an association between pes cavus and chronic lateral ankle instability with subsequent development of medial ankle arthritis. They stated that these findings may represent the natural history of longstanding, untreated cavovarus foot deformity.