Isolated fractures of the lateral malleolus are the most common type of ankle fractures. The Weber classification system is commonly used to describe these fractures and is based on the level of the fracture in relation to the ankle syndesmosis.
Type A Weber fractures occur below the level of the syndesmosis of the ankle. The syndesmosis remains intact, which permits patient to bear weight as tolerated in a walking boot or cast. Displaced fractures with a gap are prone to nonunion and should be fixed with open reduction and internal fixation.
Type B Weber fractures are the most common. These fractures occur at the level of the syndesmosis and may disrupt the anterior syndesmosis ligament. If an associated fracture of the posterior malleolus is present, an injury of the posterior syndesmosis ligament is likely, which causes further instability of the ankle. For nondisplaced fractures, protected weight-bearing with routine serial radiographs are recommended to monitor for widening of the syndesmosis or fracture displacement. Displaced and shortened fractures as well as those with widening of the syndesmosis should undergo surgical fixation.
Type C Weber fractures occur above the syndesmosis and are usually unstable. These fractures often result in widening of the ankle syndesmosis and frequently are found in ankle fracture dislocations. Nondisplaced fractures without an injury of the syndesmosis do not require surgical fixation. As with Weber type B fractures, displaced fractures and those with injuries of the syndesmosis require surgery.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- Aiyer AA, Zachwieja EC, Lawrie CM. Management of isolated lateral malleolus fractures. J Am Acad Orthop Surg. 2019;27(2):50-59.
- Wheeless CR. Weber A fractures: lateral malleolus. Wheeless Textbook of Orthopaedics. http://www.wheelessonline.com/ortho/weber_a_fractures_lateral_malleolus. Updated November 27, 2012. Accessed April 25, 2019.