INTRODUCTION AND EPIDEMIOLOGY
Given the mobility of the ankle joint and our bipedal existence, ankle injuries are a common complaint. They represent about 4% of all visits to the ED.1 Previous ankle sprain and participation in contact sports are risk factors for ankle injuries.2,3
The proximal part of the ankle mortise is composed of the distal fibula and tibia that fits on top of the talus. These bones are wider anteriorly than posteriorly. Joint stability is provided by medial and lateral malleoli extending on either side of the talus. The medial deltoid ligament, lateral ligament complex, and syndesmosis are the three distinct groups of ligaments that stabilize the ankle4 (Figure 276-1). The deltoid ligament is the strongest of these ligaments and is a thick, triangular band of tissue originating from the medial malleolus. The lateral ligament complex consists of the lateral malleolus that attaches to the anterior and posterior aspects of the talus and calcaneus by the anterior talofibular, posterior talofibular, and calcaneofibular ligaments, respectively. This ligament complex, weaker than the deltoid and prone to inversion injuries, is commonly injured and represents 85% of all ankle sprains.5 The syndesmosis, which holds the tibia and fibula together, yet allows the fibula to rotate, is a group of four distinct ligaments attaching the distal tibia to the fibula just above the talus (Figure 276-1). While the fibula has no direct contact to the weight-bearing portion of the talus, the syndesmosis transmits about 16% of the axial load to the fibula.6
Ligaments of the ankle joint. A. The three lateral ligaments: the anterior and posterior talofibular ligaments and the calcaneofibular ligament. B. The four bands of the deltoid ligament: the anterior and posterior tibiotalar, the tibiocalcaneal, and the tibionavicular. C. Anterior and posterior view of the ankle syndesmosis. The ligaments of the syndesmosis are the anterior inferior tibiofibular ligament, the posterior inferior tibiofibular ligament, the transverse ligament, and the interosseous ligament, which connects the entire length of the tibia and fibula.
The ankle is considered a hinged joint, but ligamentous attachments allow for some rotation and translation within the mortise of the talar dome.6 Branches of the sciatic nerve, the superficial peroneal, deep peroneal, peroneal, and tibial, innervate the four muscle groups of the ankle joint with branches of the popliteal artery serving as the blood supply (Figure 276-2). The tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles run over the anterior aspect of the joint and are responsible for dorsiflexion. Inversion is accomplished by the tibialis posterior, flexor digitorum longus, and flexor hallucis longus. The peroneus longus and brevis muscles, sharing a common synovial sheath held in place by a groove on the posterior aspect of the lateral malleolus ...