Spontaneous fracture of the navicular bone in the horse.

After a short review of previous literature about fractures of the navicular bone in horses, the symptoms and the pathological-anatomical changes of the condition are described. The most important clinical symptom is acute severe lameness without significant swellings, but with pronounced pain reaction to rotation of the coffin joint. After rest the lameness is reduced considerably, but without treatment it can persist for several years. Adherences between the deep flexor tendon and the site of the fracture and eventual damage to the coffin joint are considered to be the cause of the persisting lameness. Three case reports are given where the horses were shoed with full bar shoes with clips and high calks, and were given two months rest in a box. After that the rehabilitation was started with increasing load on the leg in question in spite of some initial lameness. The three horses all regained their full working capacity after ca. 6 months' treatment. There is no formation of callus at the site of the fracture, but only a firm formation of fibrous tissue which does not bother the horse unless the fragments are too much dislocated giving rise to a greater destruction of the coffin joint. Radiographically the fracture line persists for the rest of the horse's life.