Ankle Injuries Flashcards
Osseous anatomy
The ankle (or mortise) joint consists of the distal tibia (tibial plafond and posterior malleolus), the distal fibula (lateral malleolus), and the talus. The main movement at the ankle joint is plantar and dorsiflexion.
Ligamentous anatomy
Medial side: Deltoid ligament. Divided into superficial and deep portions. It is the primary restraint to valgus tilting of the talus.
Lateral side: Lateral ligament complex consisting from anterior to posterior of the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). Together they resist valgus stress to the ankle, and are a restraint to anterior translation of the talus within the mortise joint.
Syndesmosis: The syndesmosis is a ligament complex between the distal tibia and fibula, holding the two bones together. It is fundamental to the integrity of the ankle joint, and its disruption leads to instability. It consists of (from anterior to posterior) the anterior-inferior tibiofibular ligament (AITFL), the transverse tibiofibular ligament (TTFL), the interosseous membrane, and the posterior-inferior tibiofibular ligament (PITFL).
Presentation and initial management
Patients will present following a traumatic event with a painful, swollen ankle, and reluctance/inability to weight bear.
Ottawa rules can be applied to differentiate between an ankle fracture and sprain, but can be unreliable.
In high energy injuries, management should follow ATLS principles to identify more significant injuries first.
Neurovascular status of the foot should be documented, and open injuries should be excluded.
If an open injury is identified, it should be managed in line with BOAST 4 principles.
If an obvious deformity exists, it should be reduced as soon as possible with appropriate analgesia or conscious sedation.
Radiographs of clearly deformed or dislocated joints are not necessary, and removing the pressure on the surrounding soft tissues from the underlying bony deformity is the priority.
If the fracture pattern is not clinically obvious then plain radiographs are appropriate and will guide the subsequent manipulation during plaster-of-paris below knee backslab application.
Imaging
AP, lateral and mortise views (20 degree internal rotation) are essential to evaluate fracture displacement and syndesmotic injury.
Decreased tibiofibular overlap, medial joint clear space and lateral talar shift all indicate a syndesmotic injury. (In subtle cases of shift, imaging the uninjured ankle can be helpful as a proportion of the population have little or no tibiotalar overlap.)
Where there is suspicion of syndesmosis involvement in the absence of radiographic evidence, stress radiographs can be diagnostic.
Complex fracture patterns (and increasingly posterior malleolar fractures) are best defined using CT.
Lauge-Hansen Classification
Comprises two parts.
First part is the foot position, and the second part is the force applied.
Useful for understanding the forces involved and therefore predict the ligamentous or bony injury.
Results in four injury patterns:
Supination - Adduction (SA) - 10-20%
Supination - External rotation (SER) - 40-75%
Pronation - Abduction (PA) - 5-20%
Pronation - External rotation (PER) - 5-20%
Not often used in clinical practice but good for understanding the principles of ankle fracture.
Danis-Weber Classification
Commonly used.
Based on the level of the fibula fracture in relation to the syndesmosis. The more proximal, the greater the risk of syndesmotic injury and therefore fracture instability.
A - fracture below the level of the syndesmosis - unimalleolar Weber A fractures by definition are stable and therefore can be mobilised fully weight bearing in an ankle boot
B - fracture at the level of the syndesmosis / level of the tibial plafond - can be part of a trimalleolar injury and therefore extremely unstable, requiring fixation. Alternatively, a uni-malleolar Weber B fracture can be a stable injury, and therefore mobilised immediately in an ankle boot. Defining the stability can often involve stress radiographs, or a trial of mobilisation and repeat radiographs. Treating undisplaced ankle fractures in a below knee plaster, non-weight bearing for six weeks is still widely practised and a safe approach.
C - fracture above the level of the syndesmosis. This includes Maisonneuve fractures (proximal fibula fracture), which can be associated with ankle instability. Beware the high fibula fracture - it may be an ankle fracture! - tend to include syndesmotic disruption and are usually bimalleolar (either bony or ligamentous) -> therefore unstable and usually require operative fixation. In addition to the fracture fixation, the syndesmosis usually requires reconstruction/augmentation with screws to restore the joint integrity and function.
The Weber classification is based purely on the the lateral side. All injuries can include a medial or posterior bony or ligamentous injury which also dictates fracture stability (bimalleolar and trimalleolar fractures are more unstable).
Surgical Treatment
When operative fixation is appropriate, it is usually via open reduction and internal fixation using plates and screws. It must be carried out when soft tissue swelling has settled in order to minimise the risk of wound problems. This can often take a week to settle.
The use of fibula nails is expanding, but is not yet mainstream. Ankle fractures can also be treated with external fixation, or with a hind foot nail in patients who need fixation but where soft tissue or bone quality is poor.
