Ankle Fracture Classifications

Human ankle fractures are classified via two methods---the Danis-Weber system and the Lauge-Hansen classification. Danis-Weber provides simpler explanations based on radiographic evidence, using the position of the fracture in relation to the ankle joint. Lauge-Hansen focuses on the foot's position and its motion in respect to the leg, and involves fracture mechanics as well as pathoanatomy.

Danis-Weber

• This classification system, which is used for primary care treatment, is divided into three subtypes.

  Type A fractures are fibular fractures bellow the syndemosis, in other words, below the ankle joint. These are stable, are characterized by an intact tibiofibular syndesmosis and deltoid ligament, and favorable to treatment via casting.

  Type B fractures occur at the ankle joint, with the tibiofibular syndemosis usually intact. The stability of the ankle, however, can differ depending on whether any ligaments are damaged or if fracture occurs on the medial malleolus.

  Type C fractures occur above the ankle joint. These breaks are always unstable and require some type of internal fixation through surgery. This is the most severe type with the tibiofibular syndesmosis disrupted the medial malleolus fractured and the deltoid ligament injured.

Lauge-Hansen

• Classifying ankle fractures under this system considers whether the foot is supine or pronated, as well as what type of force was applied to the ankle to cause the fracture, either via adduction or external rotation. The five variations are supination-adduction, supination-external rotation, pronation-eversion, pronation-abduction and pronation-dorsiflexion. Additionally, each variation has two to four stages to indicate the severity of the fracture, that initially consider bony or ligament injuries occurring on the side of the ankle due to tension, followed by damage via compression.

  Under Lauge-Hansen, 40-70% of ankle fractures are classified as supination-external rotation. Specific injuries that can occur with this type include rupture of the anterior tibiofibular ligament, oblique or spiral fracture of the lateral malleolus, rupture of the tibiofibular ligament and fracture of the tibial malleolus.

  Pronation-abduction type fractures occur in less than 5% of all cases. These are characterized by rupture of the deltoid ligament, anterior and posterior tibiotalofibular ligaments, fracture of the medial malleolus, and fracture of the fibula at the syndesmosis.

  The percentage of supination-adduction, pronation-eversion, and pronation-dorsiflexion fractures are not specified under the Lauge-Hansen system.

Ankle Anatomy

• Knowledge of ankle anatomy is essential to understanding how fractures are classified. Three bones, the tibia, fibula and talus, make up the ankle. The medial malleolus is the inside part of the tibia, while the posterior malleolus is the tibia's back section. The lateral malleolus is the end of the fibula. Two joints---the ankle joint and the syndesmosis---are involved in ankle fractures. The latter is the joint between the tibia and fibula.