Use of 18F-FDG-PET in the diagnosis of endoprosthetic loosening of knee and hip implants

Abstract

To diagnose septic and aseptic loosening 18-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) has been described with good results for hip arthroplasties. The purpose of the present study was to examine whether there is a difference of feasibility in detecting loosening of hip versus knee prostheses by use of (18)F-FDG-PET. Thirty-two patients with lower limb arthroplasty complaints (74 components) were studied preoperatively with (18)F-FDG-PET. The interpretation of (18)F-FDG-PET was done according to evaluated criteria. The final diagnosis based on intraoperative findings in all cases including microbiological examinations. For hip arthroplasty sensitivity/specificity of (18)F-FDG-PET towards implant loosening was 80%/87%. For infectious loosening of hip endoprostheses sensitivity/specificity was 67%/83%. In knee endoprostheses sensitivity/specificity for loosening was 56%/82% and 14%/89% for infection. The sensitivity of the results for knee and hip joints in regard to infectious versus aseptic loosening was significantly different. We confirm that (18)F-FDG-PET is an appropriate tool to diagnose hip arthroplasty loosening. Differing from that (18)F-FDG-PET showed a significant lower sensitivity/specificity in detecting septic loosening of knee endoprostheses. It may therefore be necessary to use different methods to diagnose loosening of endoprostheses depending on the type of implant which is examined.