Abstract
A common method to derive both qualitative and quantitative data to evaluate osseointegration of implants is histomorphometry. The present study describes a new image reconstruction algorithm comparing the results of bone-to-implant contact (BIC) evaluated by means of µCT with histomorphometry data. Custom-made conical titanium alloyed (Ti6Al4V) implants were inserted in the distal tibial bone of female Sprague-Dawley rats. Different surface configurations were examined: Ti6Al4V implants with plasma-polymerized allylamine (PPAAm) coating and plasma-polymerized ethylenediamine (PPEDA) coating as well as implants without surface coating. After six weeks postoperatively, tibiae were explanted and BIC was determined by µCT (3D) and afterwards by histomorphometry (2D). In comparison to uncoated Ti6Al4V implants demonstrating low BIC of 32.4% (histomorphometry) and 51.3% (µCT), PPAAm and PPEDA coated implants showed a nonsignificant increase in BIC (histomorphometry: 45.7% and 53.5% and µCT: 51.8% and 62.0%, resp.). Mean BIC calculated by µCT was higher for all surface configurations compared to BIC detected by histomorphometry. Overall, a high correlation coefficient of 0.70 (p < 0.002) was found between 3D and 2D quantification of BIC. The μCT analysis seems to be suitable as a nondestructive and accurate 3D imaging method for the evaluation of the bone-implant interface.
Highlights
The surface characteristics of uncemented orthopaedic implants play an important role in the success or failure of implant anchoring after total joint replacement
Implants with the plasma-polymerized ethylenediamine (PPEDA) coating revealed a clear but not significant increase in bone-to-implant contact (BIC) evaluated by μCT (p = 0.329) and histomorphometry (p = 0.126)
The results demonstrate a nearly 11% higher mean BIC with decreased standard deviation calculated by μCT as compared to BIC detected by histomorphometry
Summary
The surface characteristics of uncemented orthopaedic implants play an important role in the success or failure of implant anchoring after total joint replacement. For the long-term survival of uncemented implants, an appropriate ongrowth of bone cells is required [1]. Osteoblast functions can be promoted by influencing the surface topography on the one hand [2, 3] and, on the other hand, cellular adhesion can be influenced by changing the surface chemistry [2, 4, 5]. By means of plasma-polymerization, positively charged, nanometre-thin coatings can be deposited to the implant surfaces [6]. Nitrogen-rich plasma-polymer coatings using the monomers allylamine and ethylenediamine with nitrogen functional groups seem to be suitable for the enhancement of adhesion and ongrowth of human osteoblasts [7, 8]
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