Abstract

The differentiation of septic and aseptic total knee arthroplasty (TKA) loosening often generates major difficulties. Nuclear medicine imaging of infection has proven to have a high potential. Therefore, we evaluated the diagnostic accuracy of ^99mTc-DPD triple-phase bone scintigraphy (TPBS) in combination with ^99mTc-labelled antigranulocyte antibody (BW 250/183) for the differentiation of septic and aseptic TKA loosening. Eighty seven patients with 94 TKA were investigated between 2003 and 2007. TPBS was classified as abnormal when an increased blood supply and increased bone uptake around the TKA was visible. BW 250/183 was considered positive for infection, when the activity around the TKA increased from 4 hr to 24 hr by more than 10% as compared with normal bone marrow images after injection of the radioabelled monoclonal antigranulocyte antibody. TPBS was true positive for septic and aseptic loosening in all patients, whereas false positive results for septic loosening were found in 9/20 cases (n=45%). False positive results with TPBS were correctly diagnosed by a negative BW 250/183 scan. These results suggest that TPBS is highly sensitive for the diagnosis of TKA loosening, whereas BW 250/183 allows for a specific diagnosis of periprosthetic infection. The combination of both is complementary and increases in diagnostic accuracy significantly (p<0.001).