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

2286 VII Imaging of the Musculoskeletal System
Figure 47-92. A 34-year-old man came to the
emergency department complaining of acute
onset of nontraumatic pain of his left great toe.
A, Anteroposterior radiograph of the left foot, with the
area in the dashed box magnified to the right. A thin,
white, curved line was observed just outside the
lateral diaphyseal cortex of the first metatarsal
(ellipse). Initially, this was mistakenly thought to
present a periosteal reaction from the first metatarsal,
rather than what it truly was: an eroded lateral
sesamoid. There is also a marginal erosion of the
medial first metatarsal head (white arrow). B, Axial CT
scan through the sesamoids of the great toes
bilaterally shows two normal sesamoids on the right,
whereas on the left only a thin shell of the eroded
lateral sesamoid remains (ellipse).
A
B
joint fluid reveals strongly negative birefringent crystals
under a polarizing microscope. CT is seldom used in the
workup of gout. However, CT scans of the feet obtained
for other reasons may unexpectedly reveal the finding of
gout (Fig. 47-92).
• Arthrodesis
When the chronic pain from severe arthritis cannot be
controlled medically, a surgical arthrodesis may be
desirable. Once solid bony fusion across the joint has been
achieved, that fused joint should be pain free. And even
though the patient no longer has any motion at that joint
after arthrodesis, before arthrodesis the joint may have
been so limited by pain and lack of articular hyaline cartilage
that the patient may have had very little functional
range of motion to begin with.
When patients remain symptomatic after an attempted
arthrodesis, CT can be used to assess the degree of solid
bony bridging, if any. Although there may be several metal
plates and screws within the scanning FOV, these tend to
cause relatively little CT streak artifact, especially when
Ch047-A05375.indd 2286
9/9/2008 5:35:38 PM