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.








A displaced bimalleolar fracture in a 60-year-old female patient is shown. The patient was diabetic, although it was well controlled. There was also a posteromedial fracture of the tibia, which is not well visualized here.








This fracture-dislocation also had a posteromedial distal tibia fracture that can be seen here. In order to minimize the risk of posttraumatic arthrosis, all components of the fracture were fixed.








An intramedullary device was chosen for the fibula in this diabetic patient in an effort to minimize the surgical insult. Syndesmotic instability was noted, and a suture button device was placed.








Lateral view shows anatomic restoration of the ankle. In this setting, an effort must be made to place the medial hardware in a way so as to minimize traffic.






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


Syndesmosis





  • The syndesmosis is the articulation of the tibia and the fibula just proximal to the tibiotalar joint. It is a joint with articular cartilage and is stabilized by the syndesmotic ligaments [anterior-inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous ligament].



  • The incisura fibularis tibiae is the lateral cavity of the tibia with which the fibula articulates. This anatomic feature of the tibia can differ fairly significantly from the almost C shape in the axial plane to a much flatter shape.



Mortise





  • The mortise is composed of the articulation between the tibia and fibula superiorly and the talus inferiorly.



  • Much of the stability of the ankle mortise in stance comes from the bony conformity. A host of ligaments provide static restrictions to various ankle and hindfoot motions, while tendons can provide a dynamic component to this stability.



  • The capsule of the ankle joint is confluent with ligamentous structures laterally, posteriorly, and medially, while extending a few centimeters proximal to the plafond anteriorly. The role of the ankle capsule in ankle function is currently unclear.



  • The articular cartilage of the ankle is fundamentally different from that of the knee in ways that may relatively protect the ankle.



  • The fibula extends distal to the tibia and should form a curve, whereby the distal fibula is confluent with the lateral process of the talus.





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.





General Treatment


Overview





  • The central goal of treatment of an ankle fracture is the restoration of full function. Treatment should be tailored to maximize function and minimize the risk of PTA.



  • Whether surgery is warranted or not will depend on injury and patient factors.



  • If surgery is needed, then the general concepts of anatomic reduction with rigid fixation coupled with delayed weight bearing and early range of motion should generally be followed.



  • More specifically with regards to surgery, length and rotation of the fibula must be restored, while intraarticular fractures must be anatomically reduced.



  • Given the differences involved with different types of fractures, the discussion of treatment will be made for each individual type of fracture.



Supination-Adduction





  • SAD fractures are coronal plane injuries that are essentially the same mechanism as an ankle sprain. With type 1 injuries, there is a Weber A fibula fracture, while type 2 fractures are characterized by impaction of the talus into the medial shoulder of the plafond, creating a characteristic vertical medial malleolus fracture.



  • Marginal impaction can occur in the medial plafond; its presence should be actively sought and assessed with a CT scan if unclear on plain films.



  • SAD 1 fractures are essentially ankle sprain-equivalent injuries and rarely require operative treatment. If operative treatment is necessary, a single longitudinal screw is usually sufficient.



  • SAD 2 fractures will require operative treatment. A longitudinal anteromedial incision will allow access to the joint for disimpaction and anatomic reduction. Bone grafting is occasionally necessary. A medial buttress plate with subchondral lag screws provides optimal fixation.



Supination-External Rotation





  • SER fractures occur through 4 stages.




    • SER 1 fractures: In original description, this injury consisted of tear of AITFL or fracture of Chaput (insertion of AITFL on tibia) or Wagstaffe tubercle (insertion of AITFL on fibula); practically, these injuries, unless they involve large fracture fragment, likely get grouped in with ankle sprains more than fractures; surgical treatment is only rarely necessary



    • SER 2 fractures: Each stage is progressive, and so this would involve an SER 1 and an oblique fracture (Weber B) of the distal fibula; typical fracture orientation runs from anterior inferior to posterior superior



    • SER 3 fractures: SER 2 with either PITFL tear or posterior malleolar fracture



    • SER 4 fractures: SER 3 with either deltoid ligament tear or medial malleolar fracture




  • Generally speaking, SER 4 fractures are treated operatively. It can often be difficult to clearly diagnose SER 2 vs. SER 4 fractures on nonstress radiographs, especially when there is no medial fracture.



  • External rotation stress radiographs can help to differentiate SER 2 from SER 4 fractures. Opening of the medial clear space generally signifies injury to the deltoid ligament, although there has been debate about what degree of opening is truly indicative of injury, and different surgeons have different thoughts. The longitudinal data that would allow for a better understanding of how best to treat these injuries is currently lacking.



  • Some authors view opening of the medial clear space in a binary fashion, whereby a differentiation is made between those that nearly dislocate vs. those that widen a couple millimeters. Widening of a few millimeters is ultimately of unclear significance, especially given the inherent error in measurement, the lack of a consistently superior mode of measurement, and the inherent difficulty of standardizing how hard one should pull. Further, early results suggest that many of these equivocal injuries will stabilize under the mortise and attain stability over time, although, once again, more relevant long term data is lacking.



Pronation-Abduction





  • Like SAD fractures, PAB fractures are strictly coronal plane injuries, although the injury starts on the medial side.




    • PAB 1 fractures: Transverse medial malleolar fracture



    • PAB 2 fractures: PAB 1 + disruption of the syndesmotic ligaments with possible posterior malleolar fracture



    • PAB 3 fractures: PAB 2 + Weber C comminuted fibula fracture




  • These fractures will often need surgery, as they will be displaced; syndesmotic disruption is common with these injuries.



  • Attaining appropriate length and rotation of the fibula can be challenging in these fibula fractures, especially with significant comminution.



  • Talar dome fractures can occur from shear stresses associated with the fracture.



Pronation-External Rotation





  • Like SER fractures, PER fractures occur through 4 stages.




    • PER 1 fractures: Transverse medial malleolar fracture



    • PER 2 fractures: PER 1 + AITFL tear



    • PER 3 fractures: PER 2 + spiral fibular fracture (Weber C), anterior superior to posterior inferior



    • PER 4 fractures: PER 3 + PITFL tear or posterior malleolar fracture




  • As before, PER injuries are often associated with syndesmotic disruption.



  • Operative treatment is the norm for these injuries.



Posterior Pilon Fractures





  • Posterior pilon fractures can encompass any of the above if the injury has an axial component.



  • You will often see some marginal impaction of the fracture with an impacted fragment anterior to the posterior malleolar fracture.



  • They may necessitate a posterolateral approach to the ankle, utilizing the interval between the peroneal tendons laterally and the flexor hallucis longus medially. Care must be taken to protect the sural nerve given its proximity to the approach.



  • While traditional thinking on posterior malleolar fractures focused on the size of the fractured fragment as the main feature influencing surgical decision making, surgeons now also take into account the presence of any marginal impaction and the effect of PITFL restoration on syndesmotic stability.



  • Good results have been achieved with these injuries, although these injuries must be recognized and treated appropriately.



Syndesmosis Disruption





  • Disruption of the syndesmosis often represents a diagnostic challenge. In the setting of an ankle fracture, the fibula is typically stabilized prior to assessing syndesmotic instability.



  • The Cotton test is the most widely known test of syndesmotic instability, whereby the fibula is clamped, and any widening is sought in the coronal plane. A more sensitive measure of syndesmotic instability, however, may be seen in the sagittal plane where excess sagittal motion of the fibula relative to the tibia may indicate syndesmotic instability.



  • Other authors have suggested using arthroscopic evaluation to assess for syndesmotic instability.



  • An anatomic reduction of the syndesmosis is likely best achieved with an open reduction in order to directly place the fibula into the incisura. Further, some authors have noted that the quality of syndesmosis reduction correlates directly with outcome.



  • Syndesmotic reduction can be maintained with either syndesmotic screws or suture button devices. Some evidence suggests that suture button devices may be more forgiving in terms of reduction and may allow for better results in terms of functional outcome, quality of life, and pain.



Perioperative and Postoperative Care





  • Outpatient management of ankle fractures may be cheaper and associated with less medical morbidity postoperatively. A delay in timing between injury and surgery does not appear to adversely affect outcome.



  • Pain management focuses on minimizing the use of opioid medications by providing multimodal analgesia.



  • Deep vein thrombosis (DVT) prophylaxis appears unnecessary after ankle fracture given the low incidence of DVT and pulmonary embolism after ankle fracture. DVT prophylaxis should be considered in patients that are high risk.



  • Weight-bearing recommendations after ankle open reduction and internal fixation (ORIF) surgery have historically been a source of significant variability, often based more on tradition than any objective criteria.



  • Recent evidence has shown no difference in wound complications, infection, loss of reduction, or hardware failure with 2 weeks of non-weight bearing (NWB) as opposed to 6 weeks of NWB after ORIF of multiple types of ankle fractures.


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Oct 29, 2019 | Posted by in ORTHOPEDIC | Comments Off on Ankle Fractures
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