Ankle & hindfoot

Published on 01/04/2015 by admin

Filed under Radiology

Last modified 01/04/2015

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Ankle & hindfoot

Regularly overlooked injuries1

Talus: talar dome osteochondral lesion; neck of talus fracture; medial or lateral process fractures. Calcaneum: acute fracture; stress fracture.

Syndesmotic widening (tear of tibiofibular membrane).

Base of 5th metatarsal fracture.

The standard radiographs

Ankle: AP mortice (20° internal rotation) and Lateral. Sometimes a Straight AP2.

Calcaneal injury: an additional Axial.

Abbreviations

AP, anterior-posterior; AVN, avascular necrosis; CT, computed tomography; MT, metatarsal; RTA, road traffic accident.

Normal anatomy

Lateral view—bones and joints

The lateral and medial malleoli can be identified. Helpful hints to aid identification:

The posterior lip (or tubercle) of the tibia, conventionally and inaccurately referred to as the posterior malleolus, is well shown.

The calcaneum and its sustentaculum tali are demonstrated. Bohler’s angle can be assessed for normality.

The base of the 5th metatarsal is often included.

image

AP mortice

The mortice projection is obtained with slight (20°) internal rotation so that the fibula does not overlap the talus.

The joint space should be of uniform width all the way around. This space is well seen medially, it continues over the superior aspect of the dome of the talus, on to the lateral side of the joint.

The width of the joint space measures approximately 4 mm2.

The surface of the talar dome should be smooth, smooth, smooth. No irregularity, no notching, no defect.

The lateral process (also known as the lateral tubercle) of the talus is an important structure. The talocalcaneal ligament attaches to this part of the bone.

A useful rule: the bones of the tibia and fibula should always overlap on the mortice view. Any clear separation between these two bones should lead you to question whether the interosseous membrane is torn.

image

Analysis: the checklists1,3,4

AP mortice

Check the:

Normal AP mortice view.

All of the checkpoints are normal.

Note that part of the fibula overlaps part of the tibia. This is a characteristically normal appearance on a mortice view.

image

Normal AP mortice view. A child.

The growth plates and all of the other checkpoints are normal.

image

Axial view

Check the:

The normal standing foot seen from behind. This drawing may help you to understand the anatomy on the axial view of the calcaneum. The sustentaculum tali is the shelf-like part of the calcaneum which extends medially to support part of the head of the talus.

image