Fractures in the Region of the Ankle
Pott's Fracture.—It must be understood that various lesions occurring in the region of the ankle-joint are included under the clinical term “Pott's fracture.” Although of a similar nature, and produced by the same forms of violence, these vary considerably in their anatomy and clinical features. They are all the result of combined eversion and abduction of the foot—produced, for example, by slipping off the kerbstone, or by jumping from a height and landing on the medial side of the foot.
When forcible eversion is the chief movement, the tightening of the deltoid (internal lateral) ligament usually tears off the medial malleolus across its base. The talus is then brought to bear on the lateral malleolus, and the force continuing to act, the lower end of the fibula is pressed laterally, and breaks close above the malleolus. The tibio-fibular interosseous ligament may rupture, or the outer portion of the tibia, to which it is attached, may be avulsed. This form is sometimes called Dupuytren's fracture. When the bones are widely separated in Dupuytren's fracture the talus may be forced up between them.
When the movement of abduction predominates, the deltoid ligament is usually ruptured, or the anterior edge or tip of the medial malleolus torn off. The tibio-fibular interosseous ligament usually resists, and an oblique fracture of the fibula 2 or 4 inches above its lower end results.
Clinical Features.—In a considerable proportion of cases—in our experience in the majority—this fracture is not accompanied by any marked deformity of the foot, and the patient is often able to walk after the injury with only a slight limp.
In others, however, the deformity is marked and characteristic ([Fig. 94]). The foot is everted, its inner side resting on the ground. The medial malleolus is unduly prominent, stretching the skin, which may give way if the patient attempts to walk. The foot, having lost the support of the malleoli, is often displaced backward, and the toes are pointed by the contraction of the calf muscles. There is abnormal mobility—both from side to side and antero-posteriorly—and crepitus may be elicited. The points of tenderness are over the deltoid ligament or medial malleolus, the inferior tibio-fibular joint, and at the seat of fracture of the fibula. Distal pressure over the shaft of the fibula, or on the extreme tip of the malleolus, may elicit pain and crepitus at the seat of fracture. There is usually considerable ecchymosis and swelling in the hollows below and behind the malleoli; and the malleoli appear to be nearer the level of the sole. In Dupuytren's fracture, when the talus passes up between the tibia and fibula, there is great broadening of the ankle.
Fig. 94.—Radiogram of Pott's Fracture with lateral displacement of foot.
There is often considerable difficulty in distinguishing a sprain of the ankle from a fracture without displacement, as both forms of injury result from the same kinds of violence, and are rapidly followed by swelling and discoloration of the overlying soft parts. In a sprain, the point of maximum tenderness is over the ligaments and tendon sheaths that have been damaged, while in fracture the site of the break is the most tender spot. The X-rays are useful in the diagnosis of doubtful cases.