Comparison of bone-implant contact and bone-implant volume between 2D-histological sections and 3D-SRµCT slices

Histological imaging is still considered the gold standard for analysing bone formation around metallic implants. Generally, a limited number of histological sections per sample are used for the approximation of mean values of peri-implant bone formation. In this study we compared statistically the results of bone-implant contact (BIC) and bone-implant volume (BIV) obtained by histological sections, with those obtained by X-ray absorption images from synchrotron radiation micro-computed tomography (SRµCT) using osseointegrated screw-shaped implants from a mini-pig study. Comparing the BIC results of 3-4 histological sections per implant sample with the appropriate 3-4 SRµCT slices showed a non-significant difference of 1.9 % (p = 0.703). The contact area assessed by the whole 3D information from the SRµCT measurement in comparison to the histomorphometric results showed a non-significant difference in BIC of 4.9 % (p = 0.171). The amount of the bone-implant volume in the histological sections and the appropriate SRµCT slices showed a non-significant difference by only 1.4 % (p = 0.736) and also remains non-significant with 2.6 % (p = 0.323) using the volumetric SRµCT information. We conclude that for a clinical evaluation of implant osseointegration with histological imaging at least 3-4 sections per sample are sufficient to represent the BIC or BIV for a sample. Due to the fact that in this study we have found a significant intra-sample variation in BIC of up to ± 35 % the selection of only one or two histological sections per sample may strongly influence the determined BIC.