Mixing of Acrylic Bone Cement – Cu

Dunne, NJ, Daly, C, Beverland, D Queens University of Belfast, Belf Musgrave Park Hospital, Belfast Introduction It has been shown that acrylic bone cement is weakened by its porosity, which enhances the formation of microcracks that contribute to major crack propagation . It has also been observed, that mixing procedures play a significant role in determining the quality of bone cement produced . A high degree of porosity is found to exist in cement that is inadequately mixed. Current mixing systems allow for the preparation of the bone cement under the application of a vacuum in a closed, sealed chamber by means of a repeatable mixing action. These systems are perceived to be repeatable, reliable, and operator independent. The objective of this study is to evaluate the quality and consistency of acrylic bone cement prepared by scrub staff in an orthopaedic theatre using a commercially available third generation vacuum mixing syringe, in terms of the level of voids within the cement microstructure. Materials and Methods The mixing devices were stored at 23°C±1°C for a minimum of 24 hours prior to mixing. The acrylic bone cement (Palacos R® with gentamicin, Biomat Merck, UK) was stored at 4°C±1°C for a minimum of 24 hours prior to mixing. Bone cement was mixed using a commercially available third generation mixing device (vacuum = -550mmHg) at Musgrave Park Hospital, Belfast, Northern Ireland. The cement was mixed according to the device manufacturers’ instructions for use. Mixing was carried out during joint replacement surgery by a number of experienced scrub staff (n = 35). The cement remaining at the end of the procedure was allowed to cure within the delivery nozzle, made from linear low-density polyethylene (LLDPE) and having an internal diameter of 10mm. 205 nozzles were collected post-operatively and stored at 23°C±1°C prior to testing. The percentage porosities were determined by measuring the apparent densities based on Archimedes principle and, as a direct result; it was possible to calculate the mean percentage porosities . Results