gms | German Medical Science

The impairment of skeletal muscle microcirculation by a biomaterial may have profound consequences. Due to excellent physical and corrosion characteristics CoCrMo-, Ti-6Al-4V- and Ti-6Al-7Nb-alloys are commonly used in orthopedic surgery. Yet concern has been raised concerning the implications of inevitable corrosion product of these metals on the surrounding biologic environment, particulary in the case of CoCrMo. We therefore studied in vivo nutritive perfusion and leukocyte response of striated muscle to these alloys, thereby drawing conclusions on their inflammatory potential.

For in vivo fluorescence microscopy a dorsal skinfold chamber was implanted in 28 hamsters. This model permits quantitative assement of microhemodynamic parameters and cellular mechanisms within the microcirculation of the striated muscle tissue in the awake animal over a prolonged period of time. Furthermore, microvascular permeability can be analysed by quantifying the extravasation of macromolecules. The animals were randomly assigned to the following groups: cpTi (n=7), Ti-6Al-4V (n=7), Ti-6Al-7Nb (n=7) and controls (n=7). For each tested biomaterial 4 mm² large implant samples with a thickness of 0,5 mm were implanted into the dorsal skinfold chamber.

We could demonstrate that the implant material CoCrMo has a marked impact on local microvascular parameters. While the Ti-alloys Ti-6Al-4V and Ti-6Al-7Nb induced an only transient and moderate inflammatory response, the implantation of a CoCrMo sample led to a distinct and persistent activation of leukocytes combined with disruption of the microvascular endothelial integrity and marked leukocyte extravasation. Animals with Ti-alloys showed a clear tendency of recuperation, while in all but one CoCrMo-treated animals a breakdown of microcirculation prior to the scheduled end of the experiment was observed. Overall the alloy Ti-6Al-7Nb was tolerated slightly better than Ti-6Al-4V under the chosen test conditions, though this discrepancy was not statistically significant.

Conclusively, the commonly used biomaterials Ti-6Al-7Nb and Ti-6Al-4V induce a considerably lower inflammatory answer of the skeletal muscle microvascular system, compared to a CoCrMo-alloy. With a minimum of adverse host reaction, our results indicate that on a biological level Ti-alloys are the superior metallic implant materials.