B6. Pilon fracture. Fractures and ligament injuries of the ankle
Ankle injuries are one of the most common causes of presentation to primary care and emergency departments. They are common injuries and include ankle sprain (only ligaments involved) and ankle fractures (broken bones). Rolling or twisting the ankle is the most common cause. Symptoms include pain, tenderness, swelling, and discoloration. The Ottawa ankle rules are used to determine which patients require X-ray to rule out fracture. Most ankle fractures affect one or both malleoli.
Ankle fractures are classified according to Weber, according to the location of the fracture line relative to the syndesmosis. Fractures usually cause inability to bear weight. Stable ankle fractures are treated conservatively with cast. Unstable fractures are treated with ORIF.
Ankle sprains are more common and less serious than ankle fractures. A syndesmotic sprain is one in which syndesmotic structures (which are critical to ankle stability) are injured. Ankle sprains are mostly treated conservatively.
A pilon fracture is a special form of ankle fracture of the distal tibia which is intra-articular. It is caused by axial forces on the ankle. These fractures are severe and may also cause ankle deformity. These fractures are often treated surgically. Pilon fractures often occur together with fibular fractures.
A Maisonneuve fracture is the combination of a medial malleolar fracture, a proximal fibular fracture, a tear of the distal tibiofibular syndesmosis, and the interosseus membrane.
Etiology
Ankle injuries are commonly caused by rolling, twisting, or turning the ankle which stretches and possibly tears the supporting ligaments of the ankle. The most common mechanism is inversion of the ankle, which damages the lateral ligaments.
Pilon fractures are caused by axial forces on the ankle. Maisonneuve fractures are caused by pronation and external rotation of the ankle.
Classification
Ankle fractures are classified according to the Weber classification, which considers the level of the fracture.
| Weber type | Description | Mechanism of injury |
| Weber A | Fracture below the syndesmosis | Pronation |
| Weber B | Fracture at the level of the syndesmosis | Supination |
| Weber C | Fracture above the level of the syndesmosis | Supination |
Fractures are also classified according to how many malleoli are affected, which is related to the remaining ankle stability:
| Fracture | Stability |
| Unimalleolar fracture | Usually stable |
| Volkmann triangle (posterior edge of the tibia) fracture | Usually unstable (usually associated with other malleolar fractures) |
| Bimalleolar fracture (lateral and medial) | Mostly unstable |
| Trimalleolar fracture (lateral, medial, and Volkmann triangle) | Always unstable |
The Volkmann triangle is also known as the posterior malleolus.
Pilon fractures are classified according to the Rüedi and Allgöwer classification. Ankle sprains are not classified in any particular way.
Clinical features
Pain, tenderness, swelling and discoloration are possible symptoms in all types of ankle injuries. Inability to bear weight on the leg is suspicious for fracture.
Pilon fracture are severe fracture which cause severe pain, ankle deformity, and inability to bear weight.
Diagnosis and evaluation
X-ray can’t diagnose an ankle sprain, but it can diagnose fractures. As such, not all ankle injuries require x-ray. The Ottawa ankle rules were developed to determine which patients who present with ankle injury needs x-ray and who don’t, to avoid unnecessary examinations. In those who don’t fulfil the Ottawa ankle rules and the injury was not part of high energy trauma, x-ray is not necessary (as fracture is very unlikely).
The squeeze test is used to look for a syndesmotic sprain. Squeezing the fibula against the tibia at the mid-calf level elicits pain at the syndesmotic structures (just above the ankle joint).
The anterior drawer test of the ankle is used to demonstrate excessive anterior displacement of the talus. The talar tilt test is used to demonstrate excessive ankle inversion.
Ankle sprains which don’t improve after some weeks should be evaluated with MRI. CT may be required for preoperative planning for fractures.
Treatment
Treatment of ankle sprains are conservative in most cases and include RICE (rest, ice, compression, elevation) and possibly fixation with cast or braces (orthoses). Surgery may be used for severe sprains, professional athletes, failure of conservative therapy, and chronic instability. Possibilities include suturing and the Evans method.
Stable ankle fractures are managed with RICE and cast fixation for 6 – 8 weeks. Unstable fractures are managed with surgery, either plate or screw fixation.
Type I and II pilon fractures are managed conservatively or with ORIF. Type III pilon fractures are managed in two phases: first external fixation and later ORIF.
Proprioception and strength training is useful to prevent future ankle injuries.