Ankle Fractures

KEY FACTS

• The treatment of ankle fractures is chiefly concerned with mitigating and minimizing the risk of posttraumatic arthritis.

• The relative stability of an ankle fracture will ultimately determine whether surgical intervention is warranted.

• Supination-external rotation ankle fractures are the most common rotational injuries.

• Syndesmotic stability must be assessed in all operative ankle fractures; sagittal plane instability is often a more sensitive indicator of the presence of a syndesmotic injury.

• While size has traditionally been the deciding factor as to whether a posterior malleolar fracture should undergo open reduction and internal fixation, the presence of syndesmotic instability and marginal impaction are also deciding factors.

• The presence of medical comorbidities, most notably osteoporosis and diabetes mellitus should influence surgical treatment options.

  • More fixation may be warranted in poor bone or in those whose neuropathy may limit non-weight bearing.

  • A1C > 7.5 has been linked with increased surgical complications.

Overview

• Ankle fractures encompass a broad range of pathology. Generally speaking, as surgeons, we differentiate low-energy rotational injuries (ankle fractures) from higher energy, axial-loading injuries (pilon or plafond fractures). The division between these 2 ranges of pathology can be somewhat gray, as there can obviously be overlap of the mechanisms with some rotation and some axial loading. These injuries more frequently involve the posterior plafond, and so we will talk about these injuries under the posterior pilon and include a discussion of these injuries with rotational ankle fractures. Also included with rotational injuries are coronal plane injuries that often tend to be low energy as well.

• Rotational ankle fractures, or malleolar fractures, are very common injuries with an incidence of almost 170 per 100,000 people in one 10-year incidence study.

• The principle concern with an ankle fracture is ultimately the risk of posttraumatic arthritis (PTA), and, therefore, the goal of treatment is to attempt to minimize the risk of PTA. The mechanisms of PTA are poorly understood. The risk of PTA is likely proportional to some degree to the initial cartilage injury. Any degree of malunion can also increase the risk of PTA in a joint as constrained as the ankle.

• Not all ankle fractures are treated operatively. Operative decision making, in a basic way, comes down to an assessment of stability. If the fracture is deemed to be unstable, then operative treatment is generally recommended. Generally speaking, trimalleolar, bimalleolar, and SER4 equivalent fractures are thought to be unstable and are therefore treated operatively in an effort to minimize the risk of malunion and PTA.

Anatomy

Classification

• There are different ways that ankle fractures can be classified, although Lauge-Hansen still greatly informs the fundamental concepts that dictate thought on ankle fractures.

• The Lauge-Hansen classification describes the position of the foot at the time of injury and then what force is exerted on the ankle to produce the given fracture, ultimately yielding 4 separate types of fracture: Supination-adduction (SAD), supination-external rotation (SER), pronation-abduction (PAB), and pronation-external rotation (PER).

• This system does not encompass all types of ankle fractures, although many fit into these categories. Generally speaking, it does not predict syndesmotic injury, although pronation injuries are thought to be higher risk for syndesmotic injury.

• The simple Danis-Weber classification looks solely at the level of the fibula fracture and its relation to the ankle mortise. Those fractures below the plafond are Weber A, at the plafond Weber B, and above the plafond Weber C. Weber C fractures generally have a higher risk of syndesmotic injury.

• To be sure, neither of these classifications is perfect, as neither system directly guides treatment, nor do they clearly predict outcome.