Case Author(s): Matt Jaksha, M.D. and Keith Fischer,M.D.
, 1/9/98 . Rating: #D2, #Q3
Diagnosis: Osteomyelitis of great toe
Brief history:
60 year old male with infection of left great toe.
Images:
Tc-99m MDP Angiographic and Immediate blood pool images are shown
View main image(bs) in a separate image viewer
View second image(bs).
2 hour delayed Tc-99m MDP plantar image
View third image(iw).
Delayed Tc-99m MDP and In-111 WBC images obtained simultaneously
View fourth image(xr).
Radiographs of the left foot 10 weeks and 2 weeks prior
Full history/Diagnosis is available below
Diagnosis: Osteomyelitis of great toe
Full history:
This is a 60 year old man with a history of diabetes and multiple
amputations of toes on the left. The patient has had an infection of
the left great toe for 2 months. There is now a draining ulcer at
the base of the left great toe, lateral aspect. This study is
requested to evaluate for osteomyelitis.
Radiopharmaceutical:
Tc-99m MDP and In-111 leukocytes
Findings:
The first two phases of the bone scan demonstrate increased blood flow
and blood pool activity to the left foot. The 2 hour delayed Tc-99m MDP
images show increased activity at the tarso-metatarsal region as well
as in the forefoot, in the area of interest. The 24 hour delayed In-111
labelled WBC images show a single focal area of increased acitivity in
the distal left foot. Radiographs 10 weeks prior to the current study
showed, among other things, a fracture at the base of the first proximal
phalanx, lateral aspect. Subsequent radiographs, 2 weeks prior to the
current exam, demonstrate dissolution of that fracture fragment with a
poorly defined margin of the adjacent phalanx.
Discussion:
An infection is clearly demonstrated by the focal accumulation of leukocytes.
However, localizing the infection in this foot which demonstrates
extensive Charcot changes is difficult. Not only is there increased
osteoblastic activity in the midfoot(typical of a Charcot foot), but
there is extensive increased activity in the region of the first and
second toes. As this does not conform to the increased WBC acccumulation,
it presumably does not all represent infection. In fact, all of the
abnormal osteoblastic activity could be related to trauma or a healed
infection, with the active site only in the adjacent soft tissues.
Recognizing the fracture fragment on the initial radiographs and its
dissolution on the subsequent radiograph is key.
Followup:
Obtaining the bone scitigraphy and labelled leukocyte images simultaneously allows us to superimpose those images and more precisely localize the
infection. The focus in fact lies between the first and second toes,
corresponding to the site of the fracture fragment. There is no bony
activity at the site because the infection has almost completely
destroyed the fracture fragment.
View followup image(iw).
Location of the In-111 focus (circle) in the delayed Tc-99m MDP image when cine
mode is used to "superimpose" the two studies.
Major teaching point(s):
Perfoming bone scintigraphy and In-111 labelled WBC imaging simultaneously
can be useful when there are other abnormalities causing increased uptake
of the bone agent(e.g. Charcot foot, healing fracture) and when it may
be difficult to localize any abnormal WBC accumulation.
As in this case, it can be difficult to digitally superimpose two studies
if one has significantly fewer counts relative to the other. Here, the
In-111 leukocyte study has few counts relative to the Tc-99m MDP, and relative to background. The use of
the cine mode allows us to display them separately, but localize the
activity of the leukocytes relative to the bone.
ACR Codes and Keywords:
References and General Discussion of Indium -111 WBC Scintigraphy (Anatomic field:Skeletal System, Category:Inflammation,Infection)
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Case number: iw007
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