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

47 Ankle and Foot 2251 47
A
B
C
Figure 47-58. Morton’s neuroma in a 44-year-old: short-axis images
through the second metatarsal head. The marker (m) indicates the site
of maximum tenderness. A, T1-weighted image demonstrates a small
lobule of decreased signal (black arrow) between and below the heads
of the second and third metatarsals. Morton’s neuromas are seldom
more conspicuous than this on T1-weighted images. B, T2-weighted
fat-suppressed images of Morton’s neuromas usually show little (open
arrowhead), if any, edema. C, The administration of intravenous
gadolinium makes the vascularized Morton’s neuroma (arrow) much
more conspicuous on this T1-weighted fat-suppressed image.
both ankles are useful when the integrity of the syndesmosis
is questioned. To understand the mechanism of syndesmotic
injury, we find it is helpful to review the Weber*
staging system for ankle fractures.
Figure 47-59 shows two models of the ankle mortise.
On the left is a skeleton model showing the relationship
of the talus to the malleoli and syndesmosis. On the right
is a schematic. The tibia is connected to the fibula by the
intraosseous membrane (IOM), a sheet of connective tissue
that runs along the length of the diaphyses. Where the
distal fibula fits into a groove in the distal tibia is the syndesmosis.
The syndesmotic ligaments, the anterior and
posterior tibiofibular ligaments, maintain the integrity of
this syndesmotic joint. The integrity of the ankle joint is
maintained laterally by the anterior and posterior talofibular
ligaments, and medially by the deltoid ligament.
Figure 47-60 illustrates how either inversion or eversion
rotational injuries to the talus cause both avulsive
and compressive forces on the malleoli. Figure 47-60A
illustrates a Weber type A injury, radiographically on the
left and schematically on the right. As the talus undergoes
an inversion rotational injury, it applies avulsive pulling
forces on the lateral side of the mortise and compressive
pushing forces on the medial side. The lateral avulsive
forces may cause strain or tearing of the talofibular ligaments,
or they may cause an avulsion fracture through the
lateral malleolus, pulling it off the fibular shaft. Conversely,
the compressive forces on the medial side can fracture
through the medial malleolus, pushing it away from the
*Bernhard Georg Weber (1927-2002), a Swiss orthopedist, nearly gave up
medicine and surgery to pursue his dream of becoming an architect. During his
surgical training in Zurich, though, he recognized that orthopedics would satisfy
his interest in medicine and technology and his need for artistic expression.
Besides fracture treatment, he designed a new hip prosthesis and developed a
tibial realignment osteotomy procedure to treat prematurely degenerated knees.
In fact, he underwent this realignment procedure himself bilaterally to enable him
to continue with two of his passions, skiing and tennis. His skill at skiing was such
that he was certified as a championship instructor.
Figure 47-59. Models of the ankle mortise. Left,
Skeletal model. Right, Schematic. The intraosseous
membrane (IOM) is shown in yellow. The syndesmotic
ligaments, the anterior and posterior tibiofibular
ligaments (Tib-Fig Lig), are modeled in green. The
anterior and posterior talofibular ligaments (Talo-Fib
Lig) are modeled in purple. The deltoid ligament (Delt
Lig) is shown in blue. LM, lateral malleolus; MM,
medial malleolus.
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