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

47 Ankle and Foot 2277 47
Figure 47-85. Example of a Lisfranc amputation
in a 53-year-old who has had chronic peripheral
neuropathy of unknown cause since 16 years of age.
Lateral (A), anteroposterior (B), and (C) oblique
radiographs. Cu, cuboid; 1, 2, and 3 indicate the first,
second, and third cuneiforms.
A
B
C
bears his name, he did describe an amputation along the
tarsometatarsal joint, an example of which is shown in
Figure 47-85.
In a Lisfranc dislocation, the second to fifth metatarsals
are dislocated laterally, or dorsolaterally, relative to the
tarsal bones. The Lisfranc dislocations are subdivided into
two categories based on what happens to the first metatarsal
relative to the other four. If the first metatarsal dislocates
laterally along with the second to fifth metatarsals, it
is called homolateral (Fig. 47-86). If the first metatarsal
diverges from the other four metatarsals, remaining aligned
with the medial cuneiform (Fig. 47-87), or if the first
metatarsal dislocates medially (Fig. 47-88), it is called
divergent.
When a Lisfranc fracture is grossly displaced, a CT scan
is not needed to confirm the diagnosis. However, because
the exact location of dislocated metatarsals may be difficult
to discern based solely on radiographs, a threedimensionally
reformatted CT scan may prove useful in
presurgical planning (see Figs. 47-86H and 47-87F and G).
The three-dimensional nature of these dislocations can
best be appreciated by creating a series of three-dimensional
images rotated along longitudinal and transverse
axes and played as a movie loop on the PACS. We find that
a series of 36 images, each 10 degrees apart, works well.
When only minimally displaced, Lisfranc dislocations
can be difficult to discern radiographically, and close attention
should be paid to the Lisfranc joint on all views of the
foot. Normally there is perfect alignment between the first
metatarsal base and first (or medial) cuneiform, between
the second metatarsal and the second (or middle) cuneiform,
and between the third metatarsal and the third (or
lateral) cuneiform. Also, the bases of the fourth and fifth
metatarsals should be perfectly aligned with their individual
facets on the cuboid (see Fig. 47-86A and B). One clue
that a nondisplaced Lisfranc dislocation may be present is
fracture fragments off the base of the second metatarsal. As
shown on the three-dimensional CT in Figure 47-5, the
base of the second metatarsal extends more proximally
across the Lisfranc joint than do the other metatarsals.
Thus, when dislocations occur along the Lisfranc joint, it
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