99Tc(m)-polyclonal IgG scintigraphy in the detection of infected hip and knee prostheses.

We investigated the usefulness of 99Tc(m)-polyclonal human IgG (99Tc[m]-HIG) scintigraphy in the diagnosis of infected hip and knee prostheses. Twenty-nine scintigraphic studies were performed in 27 patients (17 females, 10 males) with a suspected prosthetic infection. As some patients had bilateral prostheses, a total of 35 prostheses were evaluated. There were 25 hip replacements and 10 knee prostheses. The images were analysed both visually and quantitatively. The scintigraphic results were compared with the culture results of surgical specimens and also with clinical follow-up after 3 months. Increased uptake was observed in 22 prostheses, of which 12 were true-positive and 10 were false-positive results. Staphylococci were the agents most commonly isolated. In all false-positive patients, aseptic inflammation was diagnosed. Based on quantitative analysis, no statistically significant difference was found between the true-positive and false-positive cases. For the prostheses as a whole, the sensitivity, specificity, positive predictive value and negative predictive value were 100%, 41%, 54% and 100% respectively. For the hip prostheses alone, these values were 100%, 53%, 57% and 100% respectively. Taking its high sensitivity and predictive value into consideration, 99Tc(m)-HIG scintigraphy can be used as a screening test to help eliminate prosthetic infection.