Antibiotic Distribution in a Bone Cement Spacer Sample

Shiramizu K; Lovric V; Leung AMD; +Walsh WR Surgical & Orthopaedic Research Laboratories, University of New South Wales, Sydney, Australia [email protected] INTRODUCTION Deep infection after total joint replacement is a severe complication, and the use of antibiotic-loaded bone cement as a joint spacer is an established and efficient treatment method to treat infected arthroplasties. When preparing the cement spacer for infected hip arthroplasty, the outline of the spacer is generally cylindrical to fill the medullary space in the femur. The cylindrical part of the spacer is almost identical whether it is fabricated with an articulating mold, a cement gun nozzle, or simply handmade. Hand mixing of high-dose antibiotics (> 2g of antibiotic per 40g of bone cement) with bone cement is still inevitable in order to fabricate the antibiotic loaded cement spacer for infected arthroplasty. Considering no commercially availably high-dose antibiotic loaded bone cement products are available. Hanssen et al. recommended that the polymethylmethacrylate monomer and powder should be mixed first to form the liquid cement before adding the antibiotic powder [1]. The rationale behind this recommendation was that combining high-dose antibiotic powder to bone cement before the liquid monomer was introduced made mixing difficult. Furthermore, although in their paper there were many descriptions about the cement and antibiotics dosage, there was no discussion of the effect different cement viscosity would have on the mixing difficulty of the antibiotic powder. This study was undertaken to investigate the effect of cement mixing technical tip recommended by Hanssen et al. on antibiotic distribution in a cylindrical cement spacer model. Tetracycline was used as the antibiotic and its distribution was quantitatively calculated by obtaining images under the fluorescent light microscope. Furthermore, we also investigated whether the difference of cement viscosity had any significant effect on antibiotic distribution in the cement spacer model when using the traditional cement mixing technique i.e. the addition of antibiotic powder to bone cement powder before adding the liquid monomer.