- Can you describe the radiograph?
This is an AP and lateral radiograph of the left ankle. It shows a bimalleolar ankle fracture.
- How would you classify this injury, and how is it best managed definitively?
I would use the Lauge–Hansen classification to identify the injury and guide my management. This is a supination–adduction (SAD) type injury. In this case, the joint does appear generally congruent but where there is joint subluxation I would undertake emergent relocation in the emergency department under sedation with a thorough pre- and post-reduction neurovascular assessment. Assuming there is no contraindication to surgery, I would advise surgical management.
The important point regarding this is recognition of the articular impaction of the tibial plafond. This is best addressed from the medial side first, using the split in the medial malleolus to access the marginal impaction. This is disimpacted and reduced first before the vertical shear type fracture of the medial malleolus is but- tressed with a plate. I would then turn my attention to the distal fibula, where I would reduce the fracture through a direct lateral approach and apply a lag screw and neutralisation plate. I would allow the patient to mobilise as able in a below knee cast for a period of 6 weeks before removing the plaster cast.
I would restrict the weight bearing status of the patient in a below knee cast for a period of 6 weeks before commencing weight bearing due to the intra-articular nature of the injury.
- What other types of ankle fracture are identified by the Lauge–Hansen classifica- tion system?
The Lauge–Hansen classification was based on a cadaveric study where the ankle was held in either supination or pronation, and further subdivided by the deforming forces which were applied (adduction, abduction and external rotation). This dem- onstrated a reliable sequence of injuries which occurred sequentially with increas- ing force. There are two supination type injuries and two pronation type injuries.
The injury pictured above is a SAD type ankle fracture. This only has two stages. First, there is a transverse avulsion type fracture of the distal fibula or ATFL rup- ture, followed by a vertical sheer type fracture of the medial malleolus with varying degrees of articular impaction.
The second supination type injury is the most common ankle fracture: The supination–external rotation (SER) type ankle fracture. This has four stages: SER 1 consists of rupture of the AITFL; SER 2 is characterised by the classical oblique fracture of the fibula at the level of the syndesmosis; SER 3 involves the posterior structures with either a rupture of the PITFL or a fracture of the posterior malleolus; SER 4 is the final stage, which involves the medial side with an oblique medial mal- leolus fracture or rupture of the deep deltoid ligament.
The first of the pronation injuries is the pronation–external rotation (PER) type ankle fracture. This has four stages: PER 1 consists of an oblique medial malleolus fracture or deep deltoid ligament rupture; PER 2 progresses to an AITFL rupture or avulsion fracture of Chaput’s tubercle; PER 3 is characterised by a high fibular fracture (generally a simple fracture unlike in the PAB 3 fractures); PER 4 consists of rupture of the PITFL or a posterior malleolus fracture.
The final classification is the pronation–abduction (PAB) type ankle fracture (see separate station in Chapter 7). This has three stages, starting with the medial side (transverse avulsion type fracture of the medial malleolus or deep deltoid rup- ture), followed by an injury to the AITFL (or avulsion of Chaput’s tubercle), with the final stage being characterised by a comminuted Weber C fracture of the fibula.
- In the context of a posterior malleolus fracture, when would you consider fixation?
I would advocate fixation of a posterior malleolus fracture when it comprises >25% of the joint surface, or the talus is subluxed posteriorly. I would utilise two anterior to posterior screws inserted with a mini-open approach to avoid the multitude of tendons and neurovascular structures crossing the anterior ankle. If the fragment does not reduce closed, a posterolateral approach to the ankle would be employed to allow for open reduction, followed by application of a buttress plate.
