MRI can identify high intensity bands around implants that correspond to radiolucent lines on X-Ray: an ex vivo study of sheep acetabulae

Abstract

We have investigated the use of magnetic resonance imaging in categorizing the tissue interface between bone and bone cement after total hip replacement surgery. In an ex vivo sheep model we compared correlations between the thicknesses of radiolucent lines measured from plain radiographs and corresponding high signal intensity bands in MRI scans. Correlations obtained for the three main Gruen Zones were in the range between r2 = 0.58 (superior zone), and r2 = 0.86 (inferior zone). In two specimens MRI was able to detect high signal intensity bands that were not visible in the radiographs. The average thickness of the high signal intensity bands measured on the MRI scans ranged from 14.6% (Zone 2) to 39.9% (Zone 3) larger than the corresponding radiolucent lines measured on the plain radiographs. Magnetic resonance imaging has the advantage over current techniques in that it is noninvasive and does not use ionizing radiation. If problems associated with metal artifacts can be reduced, these potential advantages may make MRI the method of choice in longitudinal studies for assessment of osteointegration and analysis of fibrous membranes.