Pilon Fracture

Excerpt

“Pilon,” the French word for pestle, was first used by Etienne Destot in 1911 as an analogy for the mechanical function of the distal tibia on the talus. Fractures of the distal tibial plafond are also termed pilon fractures to describe the high energy axial compression force of the tibia as it acts as a pestle, driving vertically into the talus. These fractures account for approximately 1% to 10% of the lower leg or tibial fractures and are often associated with severe bone comminution and soft tissue compromise. Pilon fractures may also involve metaphyseal extension and can have associated fibular fractures.

The distal tibia has a quadrilateral cross-sectional shape and together with the fibula, ligaments, and capsule, forms the ankle mortise. This topography is designed to maximize the articular surface area with the dome of the talus and minimize the stress on the ankle joint. The tibia and fibula are held together by the interosseous membrane, anterior inferior and posterior inferior tibiofibular ligaments. The vascular supply of the tibial plafond derives from branches of the anterior tibial, posterior tibial, and peroneal arteries.

The two most common classification systems used to describe pilon fractures are the Ruedi-Allgower classification and the AO/OTA classification. Type I Ruedi-Allgower fractures are defined as nondisplaced “cleavage fractures” of the tibial plafond. Displacement is defined as greater than 2 mm of incongruity at the articular surface or mal-alignment greater than 10 degrees in any plane. In Ruedi and Allgower’s initial publication, type-I fractures were associated with the highest rate of satisfactory reduction using closed methods. Type-II fractures are defined as simple displacement without comminution of the articular surface, while type-III fractures are defined by substantial articular comminution often associated with metaphyseal impaction. Type-III fractures are the most frequent presentation, comprising approximately 25% to 71% of all pilon fractures. In the AO/OTA classification for long bone fractures, pilon fractures are classified as extra-articular (43A), partial articular (43B), and intra-articular (43C), and further subclassified based on the degree of comminution. In addition to classifying the fracture type, consideration must be given to the extent of soft tissue damage using the Gustilo-Anderson classification for open fractures or the Tscherne classification for closed fractures.