Volumetric computerized tomography as a measurement of periprosthetic acetabular osteolysis and its correlation with wear

Osteolysis, which is considered to be a major source of morbidity following total hip joint replacement, has been notoriously difficult to measure accurately, particularly in the acetabular area. In order to study periacetabular osteolysis, specialized software for computerized tomography (CT) scan image analysis has been developed. This software (3D-CT) eliminates metal artifacts, allows three-dimensional segmentation of the CT image, and reconstructs the segmented image to provide an accurate representation and measurement of volume for osteolytic lesions. In the present study, 20 patients underwent periacetabular osteolytic volume determination using 3D-CT, functional assessment (using the Harris Hip Scale, the Western Ontario and McMaster University Osteoarthritis Index, and the short form 36 questionnaire), and two-dimensional analysis of volumetic polyethylene wear using digitalized plain films. Periacetabular osteolysis correlated directly with the polyethylene wear rate (relative risk [RR]=0.494, P=0.027). If one patient with an acetabular revision, one patient with recurrent dislocation, and one patient with a Biomet prosthesis are excluded, then the correlation between wear and osteolysis is improved (RR = 0.685, P=0.002). In summary, the current study demonstrates both the feasibility of CT imaging of periacetabular osteolysis and the correlation between polyethylene wear and osteolytic volume, providing a potential outcome measure for clinical trials that are designed to examine interventions in this complex disease process.