Classification
In 1922, Ashhurst and Bromer[14] provided the first comprehensive classification of ankle fractures by mechanism of injury. They looked retrospectively at the radiographs of 300 cases, determining that roughly 60% were produced by external rotation, 20% by abduction, 15% by adduction, 3% by vertical loading or compression, and 2% by direct violence. They further suggested that 3° of severity existed within each category: first degree injuries involved only one malleolus, second degree injuries were bimalleolar, and third degree injuries were supramalleolar fractures -- but supramalleolar fractures do not represent a progression in severity of external rotation, abduction, or adduction. The classification also fails to emphasize sufficiently ligamentous damage or to make clear that most ankle injuries are produced by a combination of forces rather than a unidirectional force.
The most meticulous and comprehensive classification of ankle injuries was provided by Lauge-Hansen[15,16,17,18,19] in a series of articles beginning in 1948. He combined cadaver experiments and observations at surgery to distinguish five basic mechanisms of injury. Both the pattern and sequence of injury were, he believed, influenced by the position of the foot at the time the injuring force was delivered. Within each of the five fracture mechanisms ( Table 1 ), he distinguished two to four stages of injury progression, beginning with bony and/or ligamentous injuries that occur on the side of the ankle subjected to tension forces, followed by damage to the bony structures on the side of the ankle subjected to compression forces -- the single exception being supination-external rotation injuries, in which the supinated position of the foot protects the medial structures until after compression injuries have occurred laterally (Fig 4).
Lauge-Hansen produced combined injuries experimentally by placing the foot in different positions before delivering the force of injury, but his belief that external rotation produced significant syndesmotic damage only when the foot was pronated was disproved by Pankovich,[20] who found that syndesmotic injury might follow external rotation of the supinated foot as well.
Another shortcoming of the Lauge-Hansen classification lies in its failure to distinguish clearly between nonarticular posterior lip fractures and fractures that involve the articular surface, which entail the addition of axial loading for their production.
Lauge-Hansen believed that closed reduction of ankle injuries should be based on a reversal of the injuring forces in exact inverse order to that in which they occurred. However, his elaborate descriptions of "pathogenetic reduction" are cumbersome and probably unnecessary, since it has not been substantiated that reversing the injuring forces in this manner produces a more anatomic or stable reduction than their reversal in random order. Thus, while the therapeutic practicality of Lauge-Hansen's approach may be called into question, he did advance the understanding of ankle injuries significantly by defining clearly the relationship between ligamentous injury and fracture pattern, and by describing the sequences and degrees of injury produced by forces acting in different directions.
The Danis-Weber classification is based on the premise that the higher the fibular fracture, the greater the syndesmotic injury, likelihood of displacement, and need for open reduction and internal fixation (ORIF).[21,22] Type A is a transverse fibular fracture caused by adduction and internal rotation. Type B, resulting from external rotation, is depicted as a short oblique fibular fracture directed mediolaterally upward from the tib ial plafond. There are two type C fractures: type C 1 is an oblique medial-to-lateral fibular fracture produced by abduction; type C 2 fractures result from a combination of abduction and external rotation, producing more extensive syndesmotic injury and a higher fibular fracture (Fig 5). This classification incorrectly depicts the plane of obliquity for type B fractures, which is anterior-to-posterior rather than medial-to-lateral, ie, in the sagittal rather than in the coronal plane. The advantages of this classification system lie in its simplicity and in the recognition (in C 2 injuries) of the connections between ligamentous injuries and fractures, though the assumption that the level of the fibular fracture is the major determinant of the need for open reduction has not been validated.
Figure 5.
Danis-Weber classification[21] of ankle injuries.
J South Orthop Assoc. 2000;9(2) © 2000 Southern Medical Association
Cite this: Fractures of the Ankle: Pathogenesis and Treatment - Medscape - Jun 01, 2000.
