The ankle joint, like many others in the human body, is a rugged yet complex joint. When broken, the ankle can be extremely painful and mobility can be restricted to great extents. There are several bones that comprise the ankle joint, and fractures are often named and classified according to the bones involved.
Avulsion Fracture
An avulsion fracture can be a bit ambiguous in that while many interpret this injury as a fracture, many in the orthopedic and other medical specialties consider this as much an ankle ligament injury as a fracture. The knobs of the ankle are called malleoli--one on the outside and one on the inside of the ankle. The outer, lateral malleolus, is a major attachment point for the outer stabilizing ligaments. In acute, inversion, or rollover, injuries, an extreme amount of tension pressure is exerted on the ligaments, especially at these attachments.
When forces reach a failure level, one of two things may happen--either the bone will fracture or the ligament will traumatically rupture. In some cases, however, the ligament will literally tear away from the lateral malleolus but take a small fragment of bone with it. This is what is described as an avulsion fracture.
Fibula Fracture
The lateral malleolus is actually the tip of the larger fibula bone that composes the outer knob of the ankle. Many types of twisting injuries can cause the fibula to fracture farther up its shaft and a bit farther away from the actual ankle joint. This is still considered and ankle fracture though its treatment is a bit different.
When the fibula breaks at this location, it can create a destabilizing situation within the ankle joint, thus requiring surgical repair by way of screws and plates.
Bimalleolar Fracture
When both knobs, or malleoli, of the ankle are broken, a seriously unstable situation exists called a bimalleolar fracture. Without proper surgical fixation and stabilization of this fracture type, healing may well be delayed, and the ankle could be left grossly deformed, unstable and ripe for traumatic arthritis to develop.
Pilon Fractures
Pilon fractures of the ankle can occur with fractures of both malleoli, incorporating fracture components of the distal end going towards the ankle portion of the tibia, where it articulates with the talus bone on the foot side of the joint. This creates yet another potentially serious issue with joint surface integrity and must be dealt with surgically to restore any irregularities and step-offs of the joint surfaces. This injury inherently carries with it a much higher risk of post-traumatic arthritis development.
