Tarsal bone disintegration in leprosy.

Tarsal bone disintegration is characterised by fragmentation and progressive collapse of one or more tarsal bones. It occurs in 10% of leprosy patients, and is responsible for many severe foot deformities associated with this disease. The main cause is micro-traumata, but sensory impairment, sepsis and osteoporosis are predisposing factors. In this series of 400 consecutive patients the talus and navicular were involved most frequently (2% of 119 tarsal lesions). Treatment, including prolonged immobilisation of the foot, results in dense sclerosis of the affected bone, and leaves a functional limb. Initial radiological features include: (i) Bone fragmentation. (ii) Calcified fragments in adjacent soft tissues. (iii) Linear fractures. (iv) Progressive compression and deformity of the affected bone. (v) Loss of density of the affected bone. (vi) Flattening of the longitudinal plantar arch. Illustrative case histories are presented, and the differential diagnosis discussed.