Case Author(s): Stephen Schmitter, M.D. and Barry A. Siegel, M.D. , 3/8/01 . Rating: #D2, #Q3

Diagnosis: Osteomyelitis

Brief history:

71 year-old man with a history of right ankle fusion.

Images:

Anterior Radionuclide Angiographic Images of the Feet and Ankles

View main image(bs) in a separate image viewer

View second image(bs). Immediate Static and 3-Hour Delayed Images of the Feet and Ankles

View third image(xr). Radiographs of the Right Foot and Ankle

View fourth image(iw). 24-Hour Bone Scintigraphy/Indium-111 Leukocyte Images of the Right Foot and Ankle

Full history/Diagnosis is available below

Diagnosis: Osteomyelitis

Full history:

71 year-old man with a history of surgical fusion of his right ankle. He now presents with a draining wound from the right ankle and hindfoot. Evaluate for osteomyelitis.

Radiopharmaceutical:

21.1 mCi Tc-99m MDP and 0.4 mCi In-111 labeled autologous leukocytes intravenously

Findings:

Radionuclide angiographic images (main image) obtained during the injection of Tc-99m MDP demonstrate increased flow to the right ankle. Immediate static and delayed images (second image)demonstrate increased uptake in the region of the distal right tibia, ankle joint, and calcaneus. Increased uptake is also seen on blood pool and delayed images in the subtalar and talonavicular joints on the left.

Radiographs (third image) demonstrate post-operative changes from arthrodesis of the right ankle joint. Much of the talus and the distal fibula have been removed. Bone fragmentation is noted along the ankle joint.

Twenty-four hour delayed Tc-99m MDP/In-111 WBC images (fourth image) reveal markedly increased In-111 WBC uptake centered in the region of the right ankle arthrodesis, extending into the distal tibia and calcaneus. The calcaneal and tibial activity appears to be centered along the axis of the second-most proximal cannulated screw. There appears to be a soft tissue component to the In-111 WBC uptake proximally above the ankle anterolaterally and posteriorly. Minimal In-111 WBC uptake is seen in the left ankle.

Discussion:

In-111 labeled white blood cells localize nonspecifically to sites of inflammation that incite a leukocytic response. In acute, pyogenic infection, sensitivity and specificity are both approximately 90%. With suspected osseous infection, variations in marrow distribution can make interpretation difficult, as labeled leukocytes are taken up by bone marrow. Variations in marrow distribution are often seen following trauma or surgery. Because of this, In-111 WBC scintigraphy is often performed in conjunction with Tc-99m sulfur colloid marrow scintigraphy, particularly if infection is suspected in the central skeleton or in patients with orthopedic implants.

When infection is suspected in the hands or feet, marrow imaging is usually not necessary because bone marrow is rarely present at these sites. In this setting, In-111 WBC scintigraphy is often performed in conjunction with bone scintigraphy. Bone scintigraphy provides anatomic detail which is often necessary to distinguish osseous from soft tissue infection.

In this case, there is increased uptake on both bone and leukocyte scintigraphy on the right, consistent with infection. On the left, increased uptake is only seen on bone scintigraphy, consistent with degenerative joint disease.

Reference: Mettler FA and Guiberteau MJ, Essentials of Nuclear Medicine Imaging (ed 4). Philadelphia, W.B. Saunders Co., 1998:392-400.

Followup:

The patient underwent surgical debridement, which demonstrated acute and chronic osteomyelitis and extensive necrosis. Cultures revealed Staphyloccus aureus.

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: iw012

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