Case Author(s): Tate Allen, M.D. and Jerold Wallis, M.D. , 10/23/98 . Rating: #D3, #Q4

Diagnosis: Infected Prosthesis

Brief history:

Drainage though a cutaneous fistula in the left knee

Images:

Anterior and Posterior Whole Body In-111 Labeled WBC's

View main image(iw) in a separate image viewer

View second image(iw). Anterior Tc-99m Sulfur Colloid (left) and In-111 Labeled WBC's (right) images of the knees.

View third image(xr). X-rays of the Left Knee

Full history/Diagnosis is available below

Diagnosis: Infected Prosthesis

Full history:

This is a 52-year-old female who is status post wide local excision of a leiomyosarcoma of the distal left femur. A distal left femoral and knee prosthesis was placed. This became infected and subsequently removed, sterilized, and later replaced. Subsequently, a cutaneous fistula formed with intermittent drainage. A In-111 labeled WBC's exam was requested to evaluate for an infected prosthesis.

Radiopharmaceutical:

474 uCi In-111 labeled autologous leukocytes i.v., Tc-99m filtered sulfur colloid i.v.

Findings:

The whole body In-111 labeled WBC images demonstrate increased activity in the left knee. Bone marrow imaging is performed for comparison at the same time of the WBC's study to assess the distribution of normal marrow (although in this case it is known there is no marrow in the region of the resected bone). There is discordant uptake (increased indium-111 activity with no increase in sulfur colloid activity) in the distal portion of remaining left femur. This is consistent with osteomyelitis adjacent to the femoral prosthesis. In addition, increased In-111 WBC activity is present in the distal left thigh and left knee consistent with soft tissue infection around the prosthesis. There is concordant uptake of In-111 labeled WBC's and sulfur colloid in the left patella and proximal tibia consistent with normal bone marrow activity.

Discussion:

Combined leukocyte and sulfur colloid marrow imaging offers the advantage of excluding apparently increased WBC uptake secondary to asymmetry of normal bone marrow activity. In the region of bone, incongruent leukocyte and bone marrow findings with increased WBC uptake relative to colloid activity is diagnostic for osteomyelitis.

Followup:

The patient is scheduled for removal of the infected prosthesis.

ACR Codes and Keywords:

References and General Discussion of Indium -111 WBC Scintigraphy (Anatomic field:Skeletal System, Category:Effect of Trauma)

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Case number: iw009

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