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

47 Ankle and Foot 2229 47
Figure 47-30. Tears of the anterior lateral ankle
ligaments in a 47-year-old. Straight axial protondensity
(PD)–weighted (A) and T2-weighted fatsuppressed
(B) images through the syndesmosis show
disruption of the anterior tibiofibular ligament (arrow).
Straight axial PD-weighted (C) and T2-weighted fatsuppressed
(D) images through the top of the ankle
mortise show an interruption (arrowhead) of the
anterior talofibular ligament.
A
B
C
D
Medially, the ankle joint is stabilized by a group of
ligaments that fan out from the distal tip of the medial
malleolus in a triangular configuration and collectively are
called the deltoid ligament. When viewed in the coronal
plane (Fig. 47-31), the deltoid ligament can be seen to
consist of deep fibers that insert on the medial process of
the talus and superficial fibers that insert on the calcaneus
at the sustentaculum tali. Injuries of the deltoid ligament
tend to be sprains* rather than complete ruptures, although
they may be accompanied by bone marrow edema (Fig.
47-32) or even avulsion fractures.
Unlike the ankle tendons, which when visualized by
MRI can be followed over a series of sequential slices in
several planes, the ankle ligaments are usually seen on only
*”Sprains” are defined as stretching or tearing of ligaments and are due to
twisting injuries. “Strains” are defined as stretching or tearing of muscles, often at
the musculotendinous junction, and are caused by sudden and powerful contractions
or from overuse.
one or two slices in a single imaging plane. And when they
are seen in a piecemeal fashion on two images, it can be
difficult to determine whether the two halves of the ligament
are continuous. Certainly, seeing fluid extending
through or around the ankle ligament helps confirm the
diagnosis of a tear, but at the UW our sports medicine clinicians
and orthopedic surgeons do not use MRI to evaluate
the ankle ligaments. They rely on physical examination,
and sometimes stress radiographs, to assess the functional
integrity of the ankle ligaments, ordering MRI primarily for
the bones and tendons.
There are many accessory ossicles that can be present
throughout the skeleton, and these are well documented
in the encyclopedic text by Keats. 27 Many of these normal
variants can be found in the feet. Three of the most commonly
found accessory ossicles in the feet are the os trigonum
posterior to the talus, the accessory navicular medial
to the navicular bone, and the os peroneum plantar to the
calcaneocuboid joint. Although in the vast majority of
people these are nothing more than asymptomatic inci-
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