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Education And Debate

ABC of Emergency Radiology: THE ANKLE

BMJ 1994; 308 doi: (Published 29 January 1994) Cite this as: BMJ 1994;308:331
  1. D O'Keeffe,
  2. D A Nicholson,
  3. P A Driscoll,
  4. D Marsh

    A large proportion of the radiographs performed in accident and emergency departments are for injuries to the ankle. This article describes an effective system by which non-specialists can request appropriate radiographs and interpret them. It is essential to be familiar with the anatomy of the ankle and understand how it can be damaged.

    FIG 1

    Normal anteroposterior ankle radiograph and line diagram.

    FIG 2

    Normal lateral ankle radiograph and line diagram.

    Two views of the ankle are required for proper assessment

    Important anatomical considerations


    The talus is the key to understanding the ankle. This bone is surrounded by a circle made of bones and ligaments. Superiorly the distal tibia is joined to the distal fibula by three ligaments (fig 3). These are the posterior and anterior tibiofibular ligaments and the interosseous membrane.

    FIG 3

    Line diagram of important ligaments in ankle.

    Ankle movements

    • Dorsiflexion and plantar flexion occur at the ankle joint

    • Inversion and eversion occur at the subtalar joint

    There are two important collateral ligament complexes. The collateral ligamental complexes and malleoli combine with the distal tibial articular surface to lock the talus in a mortice. Plantar flexion and dorsiflexion of the ankle occur at this joint. The talus is divided into a body (including the dome), neck, and head. The dome has a wide anterior aspect giving it a trapezoid shape. In extreme dorsiflexion the talus is wedged between the malleoli and all the associated ligaments are taut. Therefore in this position there is little movement of the ankle mortice. This is an important factor in various types of injuries.

    The talus has a vulnerable blood supply similar to the scaphoid in the wrist. As the talus has no muscular or tendinous attachments it relies on the integrity of the capsule for nutrition. The proximal part (body) is supplied into the distal aspect (head), and a fracture of the …

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