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Less than a decade ago, clinical epidemiologist Ian Stiell, working with emergency department physicians, formulated the Ottawa Ankle Rules.1 The local climate was highly conducive to slips and falls. The rules are intended to guide clinical decisions about the efficient use of radiography in the diagnosis of malleolar zone fractures and midfoot zone fractures, minimising expenditure, unnecessary exposure to ionising radiation and emergency department waiting times for patients. In summary, they state that radiographic examination is not required unless, in the first instance, there is tenderness at the posterior edge or tip of the medial or lateral malleolus, or in the latter instance over the navicular bone or base of the fifth metatarsal. The rules leave fractures of the talus as an intrinsic “blind spot”, and seem to assume that fractures of the cuboid bone are innocuous, in the two distinct “zones” respectively. A later article2 encapsulated Ian Stiell's motivation in drawing up the Ottawa Ankle Rules (OAR). The OAR project had demonstrated that more than 95% of patients with ankle injuries had radiographic examinations, but that 85% of the radiographs showed no fractures. A group of Ottawa emergency physicians developed the two rules described above, and their application reduced radiographic examinations by 28% for the ankle, and 14% for the foot, (that is, by 2/7 and 1/7). Inability to bear weight either initially, or on examination, requires radiography.
A 31 year old man was parachuting when his main parachute failed to open. Using a reserve parachute, he landed awkwardly on an aircraft's wing on his left foot. He was immediately aware of pain in his left ankle, but was able to pack his parachute and travel home. He took analgesia overnight, and presented to our accident and emergency department the next day.
The patient had sustained an “acute ankle injury” as defined by OAR. On examination he had an antalgic gait, so by definition he was weight bearing, and the ankle was not radiographed. He was given a compression bandage, and advised to rest and elevate the limb. On the fifth day after the injury he returned, still complaining of pain in the ankle. Once again, the malleoli were non-tender, and he was discharged. After two weeks, a third consultation at a different hospital resulted in an ankle radiograph that showed a fracture of the dome of the talus.
Continued evaluation of the OAR in North America by emergency department physicians has led to confirmation of the original thesis, with sensitivities calculated at 100%.3,4 A comparatively small study of 71 children5 has suggested that the rules can be extended to paediatric patients.
The only major dissenting paper comes from outside that continent.6 In New Zealand a prospective, multicentre trial of 350 adult patients presenting with acute ankle injuries correlating with the OAR gave the following results. There were 75 fractures in 350 patients, five of which would have been missed by the clinical decision rule. These included one fracture of the talus, and one of the cuboid. The study concluded that the sensitivity of the rule was 93%, and the false negative rate 14%, which was “unacceptable for application in emergency departments in New Zealand.”
Talar fractures are potentially very serious, requiring a prolonged period of negative weight bearing, and carrying a significant risk of avascular necrosis. While they are commoner in high velocity injuries, such as falls from a height or motor vehicle accidents, they can also occur during forced hyperextension injuries in simple stumbles and falls. The authors recommend that such risk is best managed by excluding all high velocity incidents (however trivial they may seem at first) and all forced hyperextension injuries from inclusion, or triage, into the Ottawa Ankle Rules.
Conflicts of interest: none.