Ankle and Foot 47 - Department of Radiology - University of ...

47 Ankle and Foot 2209 47
Figure 47-2. Gross anatomy of the talus as viewed
from the top and medial sides. The green arrows show
an osteochondral lesion of the talus (OLT) in the
medial edge of the dome.
Figure 47-3. Gross anatomy of the ankle joint.
A, The plafond (dotted line) is the transverse cortical
articular surface at the distal end of the tibia. The
mortise is the rectangular opening consisting of the
plafond as well as the inner cortical articular surfaces
(solid lines) of the medial malleolus (MM) and lateral
malleolus (LM). B, The talar dome fits into the ankle
mortise. The joint between the distal tibia and fibula is
the syndesmosis (black bracket).
A
B
the Lisfranc joint is a common site for fracture-dislocations
to occur, particularly in diabetic patients with peripheral
neuropathy. Figure 47-5 illustrates how the base of the
second metatarsal (II) sticks down like a keystone, disrupting
the otherwise relatively smooth tarsometatarsal joint.
For this reason dislocations along the Lisfranc joint are
typically accompanied by fractures across the base of the
second metatarsal.
• Cross-sectional Anatomy of the Tarsal Bones
Figure 47-6 is a series of straight axial images through the
ankle and hindfoot, from proximal (see Fig. 47-6A) to
distal (see Fig. 47-6F). The straight axial plane is well suited
to examine the syndesmosis (see Fig. 47-6B, arrow). The
two joints that make up the Chopart joint, the talonavicular
joint (see Fig. 47-6D) and the calcaneocuboid joint
(see Fig. 47-6F), are also well profiled in the axial plane.
However, the ankle and subtalar joints are not well profiled
in the axial plane, and because examination of these two
joints is usually the primary indication for requesting a CT
of the ankle or hindfoot, other reformatted planes are
required.
Figure 47-7 is a series of straight sagittal images through
the hindfoot, from lateral (see Fig. 47-7A) to medial (see
Fig. 47-7C). Nearly all of the joints are profiled in the sagittal
plane, including the ankle joint, the calcaneocuboid
and talonavicular joints, and the posterior and middle
facets of the subtalar joint. The only joint not well seen in
the sagittal plane is the syndesmosis, but this is easily seen
in the axial plane. The lateral sagittal images are also useful
for visualizing the lateral process of the talus and the anterior
process of the calcaneus (compare Fig. 47-7A with
Fig. 47-4C).
Figure 47-8 is a series of oblique coronal images
through the hindfoot, from posterior (see Fig. 47-8A) to
anterior (see Fig. 47-8D). This plane best profiles the subtalar
joint, and the broad posterior facet can be followed
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9/9/2008 5:33:12 PM