Cold Bone Defect on Granulocytes Labelled with Technetium-99m-HMPAO Scintigraphy: Significance and Usefulness for Diagnosis and Follow-up of Osteoarticular Infections

99mTc-HMPAO labelled white blood cell scintigraphy in patients with osteoarticular infection: the value of late images for diagnostic accuracy and interobserver reproducibility

The objectives of this study were to evaluate the diagnostic value of 99mTc-HMPAO labelled white blood cell scintigraphy (WBCS) in patients with suspected osteomyelitis using late images and to study interobserver reproducibility. This study prospectively included 120 patients, and after a follow-up of one year, only 70 patients (n = 49 with implants, n = 21 without implants) were selected. The final diagnosis of infection was based either on microbiological data (n = 54) or follow-up (n = 16). We performed WBCS with 4 h and 24 h scans. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 77%, 72%, 83%, 64%, and 75% at 4 h, and 74%, 87%, 91%, 59%, and 79% at 24 h, respectively. The interobserver reproducibility shows a 63% prevalence of agreement between results (kappa = 0.5) at 4 h and 80% (kappa = 0.74) at 24 h, respectively. WBCS with 24-h images improves specificity and interobserver reproducibility in patients with suspected osteoarticular sepsis.

White blood cell scintigraphy for differentiation of infection and aseptic loosening: a retrospective study of 76 painful hip prostheses

BACKGROUND

Diagnosis of an infected arthroplasty is often difficult. Fever, abnormal physical findings, radiographic changes, findings at bone scintigraphy, an elevated erythrocyte sedimentation rate, CRP, and leucocytosis are not specific enough. We evaluated the diagnostic value of white blood cell scintigraphy.

METHODS

We retrospectively reviewed 76 cases (66 patients) admitted for white blood cell scintigraphy with a clinical suspicion of infection in a hip prosthesis during the period 1995-2003. The leukocytes were labeled with (99m)Tc-HMPAO or with (111)In-oxin. Anterior and posterior views were taken of both hip joints at 3 different time points after injection: 1 h, 3 h, and 22 h. Infection was verified by means of bacteriological cultures, histopathological findings, intraoperative frozen sections, and follow-up (up to 3.5 years).

RESULTS

Of 76 scintigraphies, 51 were negative and 25 were positive. There were 81% true positive, 94% true negative, 6% false positive, and 19% false negative outcomes.

INTERPRETATION

White blood cell scintigraphy with additional late imaging is an effective tool for differentiation between loosening and infection in painful hip arthroplasty.

Imaging of osteomyelitis: current concepts

Osteomyelitis frequently requires more than one imaging technique for an accurate diagnosis. Conventional radiography still remains the first imaging modality. MRI and nuclear medicine are the most sensitive and specific methods for the detection of osteomyelitis. MRI provides more accurate information regarding the extent of the infectious process. Ultrasound represents a noninvasive method to evaluate the involved soft tissues and cortical bone and may provide guidance for diagnostic or therapeutic aspiration, drainage, or tissue biopsy. CT scan can be a useful method to detect early osseous erosion and to document the presence of sequestra. PET and SPECT are highly accurate techniques for the evaluation of chronic osteomyelitis, allowing differentiation from soft tissue infection.

Apport de l'imagerie au diagnostic de l'infection ostéoarticulaire

Radiographic diagnosis plays an important role in bone and joint infection management but the techniques used do not all present the same interest. Conventional radiography may not be informative during the first weeks and ultrasonography is especially useful to show accumulation of intra articular fluid or edematous soft-tissue. Computed tomography, magnetic resonance imaging, bone scintigraphy are the best exams for this diagnosis. According to the type of infection (septic arthritis, osteomyelitis, spondylodiskitis, diabetic foot, prosthetic joint infection), and to anatomical localization, the examination is chosen depending on its sensitivity and its specificity for bone and joint infection management.