Ankle and Foot 47 - Department of Radiology - University of ...
Ankle and Foot 47 - Department of Radiology - University of ... Ankle and Foot 47 - Department of Radiology - University of ...
2250 VII Imaging of the Musculoskeletal System A B Figure 47-56. Schwannoma in a 67-year-old. A, Lateral radiograph shows a round soft tissue mass posterior to the talus. B, Sagittal T1-weighted image shows the mass to be homogeneously relatively dark, with no invasion into the overlying subcutaneus fat or the underlying talus. C, Sagittal inversion recovery image shows the mass to be heterogeneously bright. This is the classic appearance of a schwannoma. D, Sagittal T1-weighted fat-suppressed image after intravenous gadolinium administration shows heterogeneous enhancement, confirming that this is a vascularized mass and not a cyst. C D A C B D Figure 47-57. Synovial cyst in a 51-year-old. A, Lateral radiograph shows a round soft tissue mass dorsal to the metatarsals. B, Sagittal T1-weighted image shows the mass to be homogeneously relatively dark. C, Sagittal T2-weighted fat-suppressed image shows the mass to be homogeneously bright. This is the classic appearance of a simple cyst. There is a small lobule distal to the main cyst. D, Sagittal T1- weighted fat-suppressed image after intravenous gadolinium (IVGd) shows enhancement of only the thin synovial lining but not the cyst fluid. Short-axis T1-weighted (E), T2-weighted fat-suppressed (F), and T1-weighted fat-suppressed post-IVGd (G) images through the cyst demonstrate the same signal characteristics as in the sagittal plane. The gray arrows in F and G indicate areas of inadequate fat suppression near the fifth toe. E F G Ch047-A05375.indd 2250 9/9/2008 5:34:38 PM
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. Ch047-A05375.indd 2251 9/9/2008 5:34:40 PM
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2250 VII Imaging <strong>of</strong> the Musculoskeletal System<br />
A<br />
B<br />
Figure <strong>47</strong>-56. Schwannoma in a 67-year-old.<br />
A, Lateral radiograph shows a round s<strong>of</strong>t tissue mass<br />
posterior to the talus. B, Sagittal T1-weighted image<br />
shows the mass to be homogeneously relatively dark,<br />
with no invasion into the overlying subcutaneus fat or<br />
the underlying talus. C, Sagittal inversion recovery<br />
image shows the mass to be heterogeneously bright.<br />
This is the classic appearance <strong>of</strong> a schwannoma.<br />
D, Sagittal T1-weighted fat-suppressed image after<br />
intravenous gadolinium administration shows<br />
heterogeneous enhancement, confirming that this is a<br />
vascularized mass <strong>and</strong> not a cyst.<br />
C<br />
D<br />
A<br />
C<br />
B<br />
D<br />
Figure <strong>47</strong>-57. Synovial cyst in a 51-year-old.<br />
A, Lateral radiograph shows a round s<strong>of</strong>t tissue mass<br />
dorsal to the metatarsals. B, Sagittal T1-weighted<br />
image shows the mass to be homogeneously relatively<br />
dark. C, Sagittal T2-weighted fat-suppressed image<br />
shows the mass to be homogeneously bright. This is<br />
the classic appearance <strong>of</strong> a simple cyst. There is a<br />
small lobule distal to the main cyst. D, Sagittal T1-<br />
weighted fat-suppressed image after intravenous<br />
gadolinium (IVGd) shows enhancement <strong>of</strong> only the<br />
thin synovial lining but not the cyst fluid. Short-axis<br />
T1-weighted (E), T2-weighted fat-suppressed (F), <strong>and</strong><br />
T1-weighted fat-suppressed post-IVGd (G) images<br />
through the cyst demonstrate the same signal<br />
characteristics as in the sagittal plane. The gray arrows<br />
in F <strong>and</strong> G indicate areas <strong>of</strong> inadequate fat<br />
suppression near the fifth toe.<br />
E<br />
F<br />
G<br />
Ch0<strong>47</strong>-A05375.indd 2250<br />
9/9/2008 5:34:38 PM
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