Centrifugation of antibiotic impregnated bone cement

Centrifugation is used to increase the strength of bone cement in total joint arthroplasty. Antibiotics have been incorporated into cement for the treatment and prophylaxis of infection. To determine the effect of centrifugation on antibiotic containing cement, tobramycin and cefamandole impregnated Surgical Simplex P polymethylmethacrylate was centrifuged using manufacturers' techniques. The concentration of antibiotics was measured throughout the cement column by a zone of inhibition bioassay. No difference in the distribution of the antibiotics could be demonstrated as compared to hand mixed controls. Centrifugation decreased the number of large air inclusions overall, however, a significant number were noted to remain at the top of the centrifugation gradient. It was concluded that centrifugation of an antibiotic impregnated bone cement, utilizing this technique, may be used without disturbing the antibiotic distribution. Discarding the top 1 cm of liquid centrifuged column to remove residual air inclusions is recommended.