Fractures of the Tarsal Bones. Fractures of these bones have been found far more frequently than was thought before the use of the X-ray. Many cases of tarsal fracture have been treated for sprains of the ankle. It is only when the recovery is slow or the injury is followed by a traumatic flat foot that the surgeon begins to suspect that a more serious condition was present at the time of the original injury.
The astragalus and os calcis are the tarsal bones that are usually affected. Fractures of the os calcis, in the majority of cases, are due to compression. The patient falls from a height to the ground, on a hard substance. The os calcis is crushed between the astragalus and the ground.
There are three general types of fracture of the os calcis:
1. That in which the fracture has been confined largely to that portion lying behind a vertical plane through the middle of the body of the astragalus. There are three varieties of this heel fragment type: (a) cases with one large heel fragment; (b) cases of small heel fragments (in this variety, also called avulsion fracture, the sudden contraction of the calf muscles pulls the fragment off; at times the tendo Achillis itself is torn off from the attachment to the os calcis at the same time); (c) cases showing only fissures in the bone.
2. Comminution of the anterior half of the os calcis.
3. All the cases of extensive comminution of the bones; the bone is literally shattered.
Fractures of the Astragalus. These can be divided into: (a) those of the neck; (b) those of the body. The former are the most common fractures of the astragalus. They may follow sudden dorsal flexion, or forced supination, or pronation of the foot. They may be due to a fall from a height or from direct violence. Fractures of the body of the astragalus are usually the result of a crushing force which ordinarily have a like effect on the body of the os calcis, and are often associated with fractures of the latter bone. The variety of fractures is considerable, varying from two large fragments, to complete comminution of the bone.
A fact of considerable importance in the interpretation of skiagraphs of fractures of the astragalus, is a knowledge of the presence in many normal individuals of a little bone known as the os trigonum. It may occur detached from the astragalus or may be attached to it as a process, on its posterior aspect, and on account of the swelling and pain around the ankle, a diagnosis can seldom be made without the routine use of the X-ray in every injury in this region.
The swelling, with obliteration of the depressions normally present around the ankle, does not differ from that characteristic of a sprain of the ankle or of a Pott’s fracture. If there is extensive comminution of the os calcis or astragalus, the malleoli may be a little lower than normal.
The X-ray must always remain our most reliable means of diagnosis at the time of the injury. At a later period the chief symptoms are a painful flat foot, ankylosis of the ankle joint, pain and difficulty in pronating and supinating the foot.