Introduction. Osteolysis is a periprosthetic bone loss associated with both cemented and noncemented arthroplasties. It is believed to be caused by cellular reaction to wear particles, especially from polyethylene, and is considered to be a major source of morbidity following total hip replacement. Roentgenographycally it appears as a diffuse cortical thinning or focal cystic lesion, but major bone loss may precede this finding. In advanced osteolysis, implant stability is impaired, and component revision is mandatory. Thus early detection of osteolysis is crucial to allow minor procedure of curettage and insert revision.

Three dimensional imaging tool for early detection and follow up of the osteolytic cysts is needed. The conventional CT incorporates streak artifacts around metallic implants that make the interpretation of the images extremely unreliable. We report our preliminary experience with new 16-slice CT techniques that improve the diagnosis of osteolysis.

Materials and methods. Twenty one patients with suspected osteolysis underwent CT examination of the involved region with a new 16-slice GE Lightspeed scanner. 16 patients had a hip arthroplasty and 5 patients a knee arthroplasty. Different slice thickness was examined. Standard, soft and boneplus filters were tested for the axial images and reconstructions. MPR with 0.625mm, 1.25 and 2.5mm slice thickness, 3D-MIP and VR reconstruction methods were performed for each patient and the best technique for minimizing streak artifacts and evaluation of periprosthetic bone was determined by two radiologists and an orthopedic surgeon.

Results. The axial images in various slice thickness showed massive streak artifacts but the thinner slices of 0.625mm showed better demonstration of fine bony details around the prosthesis. Standard filter was superior compared to the soft and boneplus filters for bony changes. MPR and MIP reconstructions reduced markedly the impact of the metal artifacts but MPR using 1.25mm slice thickness was superior to MIP for appreciation of the texture of the periprosthetic bone.

Conclusions. In our study, a proper technique of 16-slice computerized tomography allows early detection and follow up of osteolytic lesions, that may significantly help in the decision making process, and may enable avoiding major surgery.