A preliminary study of the release of quaternary ammonium antimicrobial compounds from acrylic bone cement

The quaternary ammonium compounds benzalkonium chloride and cetyl pyridinium chloride have been studied as potential anti-microbial additives for incorporation into acrylic bone cement. Using the commercial bone cement Palacos K-40, each compound was added at 1% and 5% by mass. Setting time of the cement was 9.75 min. This did not change when benzalkonium chloride (5%) was present, but was shortened to 9.00 min by 5% cetyl pyridinium chloride. Release of additive was estimated by determining chloride release from set cement specimens using a chloride-ion selective electrode. This showed that release occurred but was a complicated process and did not follow simple diffusion-based kinetics. Release thus appeared to occur by a similar overall mechanism to that of gentamicin sulphate from bone cements. The results show that these anti-microbial compounds can be incorporated into acrylic bone cement and then released in a satisfactory manner and suggest that these compounds have the potential to replace gentamicin sulphate as active ingredients in orthopaedic cements.