Previous studies showed that natural coral implanted into bone tissue was gradually resorbed and progressively replaced by newly formed bone. The objectives of this study were to compare the fate of two Madreporian corals, Porites and Acropora, after implantation during 1 and 2 months into sheep and pig long bones. These materials are identical in composition (CaCo3) but differ in volume (49 +/- 2%, 12 +/- 4%, respectively) and mean size (250 vs. 500 microns) of porosities. The non-decalcified histological slices were observed under light microscopy. Implant resorption and new bone formation were quantified through an automatic image analysis system. Quantitative results showed that the larger the porosity volume, the greater was the coral resorption as well as the new bone apposition. Large differences were found between the two animal species. Histological findings were identical to those previously reported: implants were resorbed and progressively replaced by newly formed bone. Coral was found to be an osteoconductive biomaterial which acted as a scaffold for a direct osteoblastic apposition and consequently could be an interesting alternative to bone auto-, allo-, or xenografts.

This study has been conducted to evaluate the effect of electromagnetic fields of low frequency and low amplitude on bone growth into porous implants in order to consider a potential clinical application—that is, improvement of the anchorage in articular prostheses intended to be implanted without cement. The experiment has been conducted in vivo on sheep, using porous implants made of Ti-6Al-4V alloy implanted in the cortical bone. The electromagnetic stimulation was provided by external generators connected to Helmholtz coils placed on each side of the stimulated limb. The results of this stimulation have been quantified by measuring the shear properties of the bone/implant interface and the bone regrowth around and into the porous implants in control and stimulated animals. These results were measured in a total of 16 animals sacrificed at three and five weeks after implantation. No improvement was shown in the mechanical properties of the bone/implant interface. On the other hand, the depth of bone tissue ingrowth and the ratio of bony ingrowth within the implant to the total new bone formation increased at five weeks (13 and 20%, respectively) when electromagnetic fields were used. However, this increase is not statistically significant.

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