Abstract 7

IN VITRO ANALYSIS OF ANTIFUNGAL IMPREGNATED POLYMETHYLMETHACRYLATE BONE CEMENT

M. Jabur, B.Goss, C.Lutton, P. Weinrauch, C. Bell, G. Gillet , R.Crawford

Queensland University of Technology, School of Engineering Systems

Fungal infection of total joint arthroplasty is a rare but devastating complication The purpose of this study is to examine the change in mechanical properties with the inclusion of various concentrations of anti-fungal in the cement as well as the release rate from the cement.

Amphotericin powder was mixed in different concentrations with Tobramycin- impregnated Simplex (Stryker). Compressive strength and modulus of standardised specimens was measured. The cumulative dose of amphotericin and tobramycin released measured from various cement/ Amphotericin formulations was measured using UV-V spectrometry.

Incorporation of Amphotericin into the cement showed a statistically increased compressive strength from 107MPa to 123MPa (p<.001) with 4 mixes of antifungal per packet. There was no statistically relevant change in modulus or strain to failure. At 72 hours no significant elution of antifungal (<1%) had occurred and the cumulative release of antibiotic had reached a maximum.

Contrary to expectations the mechanical properties of PMMA cement are improved by the addition of Amphericin B, however the elution of the antifungal is negligible. This is most likely due to the conjugated unsaturation found in amphotericin molecule which will readily react with methyl methacrylate during cement cure. This results in an increase in crosslink density in the bone cement, subsequently improving mechanical strength. The covalent bonds formed between the amphotericin and the cement prevents it from eluting. We suggest that this is not a valid method for treatment of deep fungal infections.

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