Diagnostic of infection after total knee replacement

Aim: In this study, the accuracy of antigranulocyte scintigraphy as a diagnostic means prior to revision in infected total knee replacement was compared to that of preoperative joint aspiration and laboratory parameters. The most efficient combination of all diagnostic methods was calculated and thus a diagnostic algorithm recommended. The value of PCR was compared to commonly used techniques of microbiological culturing. Methods: Preoperative diagnostic means for infection of 50 total knee replacements in 45 patients requiring revision surgery, were retrospectively analyzed. Inclusion criteria were the intraoperative microbiological and histological verification of infection. Sensitivity, specificity, negative and positive prediction value of C-reactive protein (CRP) and leukocytes, antigranulocyte scintigraphy with Tc-99m-labeled antibodies, and preoperative joint aspiration were calculated. Furthermore, the accuracy of the different techniques of culturing was compared to that of the polymerase chain reaction (PCR) based on the intraoperative histological findings. Two blinded examiners evaluated specimens taken intraoperatively according to the criteria of Mirra. Results: We observed a sensitivity of 1.0, a specificity of 0.82, a positive prediction value of 0.83 and a negative prediction value of 1.0 for the antigranulocyte scintigraphy. The sensitivity of preoperative joint aspiration was 0.5, the specificity 1.0, and the positive and negative prediction values were 1.0 and 0.5. Correlated to the intraoperative histological findings the accuracy of PCR and culturing was comparable. The highest accuracy was obtained for blood culture samples. Conclusion: Compared to preoperative joint aspiration the antigranulocyte scintigraphy proved to be more sensitive in the diagnosis an infected knee replacement while having a high specificity. An advantage of PCR compared to the common microbiological culturing techniques was not observed.