HISTOMORPHOMETRICAL ANALYSIS OF THE BONE-IMPLANT INTERFACE - COMPARISON OF MICRORADIOGRAPHY AND BRIGHTFIELD MICROSCOPY

Section thickness has been shown to affect the histomorphometrical mea surement of bone-implant contact when analysed under brightfield micro scopy. This study investigated whether microradiography of the bone-im plant interface eliminated the errors associated with thick section an alysis. Seven implant containing sections were utilized. Microradiogra phs of the thick (similar to 100 mu m) sections were taken and the sec tions were subsequently ground to thicknesses of 50 mu m and 25 mu m. Photomicrographs were taken of the microradiographs and of the section s at each thickness (100, 50 and 25 mu m) under brightfield microscopy . The photomicrographs were analysed for direct bone-implant contact i n the cortical passage region and along the total length of the implan t. The effect of section thickness on multiple fluorochrome labelling in 10 rabbit femur specimens was also examined. Centre-to-centre inter label distance was measured for each label pair at a thickness of 100 mu m and then again after the sections were ground to 50 mu m and 25 m u m. The thick (100 mu m) sections showed a significantly greater amou nt of bone-implant contact than either the thin sections or the micror adiographs. There was no difference in direct bone-implant contact mea sured by microradiography or thin sections. However, the microradiogra phic analysis showed a much lower variability of the bone-implant cont act than the sections evaluated under brightfield microscopy. In addit ion, they have the added benefit of providing information on bone mine ral density. Centre-to-centre interlabel distance was not significantl y different for any label pair owing to section thickness. Data from t his study provides evidence that the use of microradiographs for histo morphometrical analysis of the bone-implant interface is superior to b rightfield analysis of thin sections owing to the lower variability of microradiographical data and the ability to obtain bone mineral densi ty measures. Additionally, given that interlabel distance was not sign ificantly affected by section thickness, the use of 100 mu m thick sec tions for analysis of fluorochrome labels in cortical bone is supporte d. (C) 1996 Elsevier Science Limited