Advances in metal artifact reduction may expand the potential role of CT. FDG-PET/CT Whole Body FDG-PET/CT scans may be useful for detecting infection after joint replacement. FDG-PET images reflect relative levels of glucose uptake and thus reflect the localized level of increased metabolic activity. Zhuang et al [68] reported that elevated glycolytic activity causes inflammatory cells such as neutrophils and activated macrophages to be FDG avid at sites of inflammation and infection. Some periprosthetic uptake may occur because of marrow activity, and adding marrow scanning can increase specificity [69]. In these instances, the marrow study would be performed the next day using a different camera type because the marrow scan relies on lower energy photons (PET, 511keV; Tc-99m, 140 keV). Zhuang et al [68] studied 36 painful knee prostheses using FDG-PET and identified 10 of 11 infected cases but had false-positive results in 7 cases (sensitivity of 90.9%, specificity of 72%, and accuracy of 77.8% for detecting infection). This was a lower accuracy than found in assessment of hip prostheses. The cause for the large number of false-positives was not known. Aksoy et al [70] found a positive predictive value (PPV) of 28% (15 of 54) for infection in 54 patients with painful joint prosthesis (24 knee, 48 hip) using FDG-PET. Manthey et al [71] reported that, by analyzing intensity and periprosthetic uptake patterns on FDG-PET, accurate differentiation among aseptic loosening, synovitis, and infection is possible. Kwee and Kwee [72] reports FDG Imaging After Total Knee Arthroplasty uptake at the bone-prosthesis interface has been consistently reported as diagnostic criterion for knee prosthetic joint infection. Kwee et al [73] in a meta-analysis reported that the specificity of FDG-PET for diagnosing infection was significantly lower for knee prostheses (74.8%) than for hip prostheses (89.8%).
Imaging After Total Knee Arthroplasty. Advances in metal artifact reduction may expand the potential role of CT. FDG-PET/CT Whole Body FDG-PET/CT scans may be useful for detecting infection after joint replacement. FDG-PET images reflect relative levels of glucose uptake and thus reflect the localized level of increased metabolic activity. Zhuang et al [68] reported that elevated glycolytic activity causes inflammatory cells such as neutrophils and activated macrophages to be FDG avid at sites of inflammation and infection. Some periprosthetic uptake may occur because of marrow activity, and adding marrow scanning can increase specificity [69]. In these instances, the marrow study would be performed the next day using a different camera type because the marrow scan relies on lower energy photons (PET, 511keV; Tc-99m, 140 keV). Zhuang et al [68] studied 36 painful knee prostheses using FDG-PET and identified 10 of 11 infected cases but had false-positive results in 7 cases (sensitivity of 90.9%, specificity of 72%, and accuracy of 77.8% for detecting infection). This was a lower accuracy than found in assessment of hip prostheses. The cause for the large number of false-positives was not known. Aksoy et al [70] found a positive predictive value (PPV) of 28% (15 of 54) for infection in 54 patients with painful joint prosthesis (24 knee, 48 hip) using FDG-PET. Manthey et al [71] reported that, by analyzing intensity and periprosthetic uptake patterns on FDG-PET, accurate differentiation among aseptic loosening, synovitis, and infection is possible. Kwee and Kwee [72] reports FDG Imaging After Total Knee Arthroplasty uptake at the bone-prosthesis interface has been consistently reported as diagnostic criterion for knee prosthetic joint infection. Kwee et al [73] in a meta-analysis reported that the specificity of FDG-PET for diagnosing infection was significantly lower for knee prostheses (74.8%) than for hip prostheses (89.8%).