A temporary spanning external fixator was applied under general anesthesia and the patient returned a week later for definitive fixation. On this occasion, the external fixator was removed except for 2 tibial half-pins which had been placed proximal to the fracture site. A circular frame (2 rings) was constructed using these half-pins attached to a full ring proximally and a non-olive wire through the talus connected to a full ring distally. This frame was used to distract and reduce the talus under the mortise. A second non-olive wire (posterior wire) was passed manually from medial to lateral behind the displaced posterior malleolar fragment (between the tibia and posterior tendons exiting anterior to the fibula) and connected to the distal ring of the frame. The posterior wire was then gradually tensioned until the posterior fragments were anatomically reduced. Three anteroposterior cancellous screws were inserted percutaneously to hold the reduction. A fully threaded cortical screw was inserted distally to close a small residual step in the articular surface, whereas a fully threaded cancellous screw was used to hold the medial malleolus reduced (Fig. 3).
Fibular alignment and length were maintained with a 2 mm K-wire inserted retrograde along the intramedullary canal with the end curved and buried subcutaneously. The circular frame was then removed.
The patient was discharged the following day with his ankle immobilized in plaster for 4 weeks and non-weightbearing for 6 weeks. At 13 weeks postoperatively, the patient reported no pain, had full range of movement, and no prominent metalwork. Plain ankle radiographs showed continued successful maintenance of reduction with evidence of fracture union (Fig. 4). Follow-up at 12 months revealed the patient was completely satisfied with his ankle outcome and had returned to all normal activities. He experienced no pain and only occasional stiffness when climbing many flights of stairs.
Although ankle fractures involving the posterior malleolus are associated with worse functional outcomes,4,5 it is unclear whether this simply reflects the effect of higher energy injuries. Biomechanical studies have suggested that the posterior malleolus is necessary for preventing excessive internal rotation and stability of the talus.6,15–17 However, posterior instability of the talus does not feature in isolated posterior malleolus fractures.16,18
Most authors recommend anatomic reduction when the posterior malleolar fragment exceeds >25% of the tibiotalar articular surface.8,19,20 In such cases, careful reduction is important as fixation in a nonanatomic position has a less satisfactory outcome than conservative management.21
However, closed reduction is rarely achievable given the vertical fracture line and relative instability when held in plaster.22 A number of techniques have been used to reduce and maintain the posterior malleolus in these injuries. The earliest reported percutaneous technique involved skeletal traction through the calcaneus for 3 weeks before immobilizing the limb non-weightbearing for 8 weeks.23
Posterior malleolus fractures are most commonly reduced indirectly. The medial and/or lateral malleoli are fixed by established methods which may be sufficient to reduce the posterior malleolus, for example, by virtue of an intact posterior tibiofibular ligament on reduction of the fibula. Once anatomic congruence has been achieved, the posterior malleolar fragment can be evaluated intraoperatively and fixed if necessary.
Use of a monolateral external fixator (delta frame configuration) for temporary ankle distraction and indirect reduction almost always leads to posterior displacement of posterior fragments. However, distraction applied to the ankle joint through a circular external fixator can be directed in any plane depending on the position in which distraction bars are attached to the proximal and distal rings, for example, more anterior attachment will displace fragments more posteriorly and vice versa.
Alternatively open reduction can be achieved by direct, posteromedial, or posterolateral approaches. Choice of reduction and fixation technique depends on fragment characteristics (eg, size, displacement), associated injuries (eg, concomitant fibula fracture), and operator preference. The fracture can be approached directly with the patient lying prone, particularly in the presence of a large posterior malleolar fragment or substantial comminution. By contrast, posteromedial injuries are approached medially by retraction of the neurovascular bundle and flexor tendons. The posterolateral approach has been frequently described as providing good exposure to both the fibula and posterior malleolus. For example, Miller22 approached the ankle through a posterolateral incision and used a bespoke clamp with one limb inserted through a hole drilled perpendicular to the tibial shaft and proximal to the fracture line. The clamp was then tightened to reduce the fragment and maintained using a buttress plate medial to the clamp. He achieved satisfactory reduction in 5 of the 6 reported cases. The posterolateral approach is frequently used in these injuries and has been described in detail elsewhere.14 Briefly, a longitudinal incision is created between the posterior fibular border and the lateral boundary of the tendo Achilles. Structures at risk during this approach include the sural and superficial peroneal nerves. The fracture site is cleaned of callus and interposing soft tissue before dorsiflexing the ankle to increase space for reduction. The fragment is then levered into position with the aid of a ball spike, bone tamp, and periarticular clamp as necessary. Once reduction has been confirmed fluoroscopically, it should be held, for example, using a 1/3 tubular plate. Advantages of the posterolateral approach include direct visualization of reduction, application of a buttress plate, and concomitant fibular fixation.11 However, it has been associated with increased risk of poor wound healing, prominent metalwork, and complex regional pain syndrome relative to medial and lateral approaches in some published series.12,14
Our case illustrates a new percutaneous technique for achieving a satisfactory reduction of posterior malleolar fragments in complex ankle fractures. Possible benefits include improved posterior malleolar fragment reduction (with consequent increased ankle stability), reduced soft-tissue disruption, and minimal scarring, which would potentially accelerate recovery and return to normal activity including work.
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Keywords:© 2014 by Lippincott Williams & Wilkins
pilon fracture; trimalleolar ankle fracture; posterior malleolus