The necessity for prolonged immobilization of the wrist in fractures of the carpal navicular in order to prevent non-union is due to the anatomical variations in the blood supply to the bone. In 13 per cent. of 297 carpal naviculars studied grossly there were no arterial foramina proximal to the mid-portion of the bone, the commonest site of fracture. In 20 per cent. there was one arterial foramen proximal to the waist, while in 67 per cent. two or more foramina were found. Fracture through the mid-portion of the bone could, therefore, interrupt the blood supply in about one-third of the cases and lead to necrosis. Unless immobilization is absolute and prolonged, non-union is liable to develop in these cases.
Conservative surgery (Beck's drilling), followed by adequate immobilization, is the treatment of choice for non-united fractures of the carpal navicular. It is less mutilating than either partial or complete excision of the navicular and results in bony union without alteration of the normal architecture of the wrist.