In the emergency department, isolated fibular ankle fractures are frequently characterized using the Danis-Weber classification system. This fracture classification system, based on the level of the fibular fracture in relation to the ankle joint, can help determine which injuries are likely to require surgical intervention. The Weber classification is simple, reliable, and reproducible, and thus it has been utilized routinely by emergency physicians.1,2
Explore This IssueACEP Now: Vol 39 – No 04 – April 2020
Injuries to the distal fibula, below the talar dome, are classified as type A and are stable fractures. Weber C fractures are above the ankle joint and are associated with a syndesmotic injury. Weber C fractures are almost always unstable and require surgical intervention. Weber B fractures occur at the level of the tibiofibular ligaments, just above the talar dome, and happen primarily through a mechanism of ankle supination and external rotation (SER).3 These type B fractures are sometimes stable, and patients can ambulate on them as tolerated; in other cases, they are unstable and require open reduction and internal fixation (ORIF). The focus of this article is to help emergency physicians choose the proper method for determining that stability.
Do They Need an Operation?
The primary consideration regarding need for operative management of a closed ankle fracture is stability. In general, most stable ankle fractures can undergo nonoperative management by a primary care physician. Unstable ankle fractures are one of the primary indications for orthopedic referral. Any bi- or trimalleolar fracture should be considered unstable because of the disruption of the bony architecture on both the medial and lateral side of the joint.
With Weber B fractures, the stability of the ankle joint depends on injury to the tibiofibular ligaments and the deltoid ligament. The deltoid ligament, which runs from the medial malleolus to the calcaneus, talus, and navicular bones, plays a vital role in maintaining correct talus positioning. A talar shift of 1 mm results in a 42 percent decrease in tibiotalar contact area, which can lead to significant increases in contact stress.4 In what appears as an otherwise isolated Weber B fibular injury, a tear of the deltoid ligament can be considered “equivalent to a medial malleolar fracture,” qualifying the fracture mechanically as unstable, thus requiring operative management.5
Clinical signs such as medial ankle pain, swelling, and ecchymosis are not reliable in identifying a deltoid ligament injury.3 For this reason, assessing deltoid ligament integrity is of critical importance in determining the stability of an ankle fracture. To do this, emergency physicians need to employ stress radiographs to assess the stability of the ankle joint.