Abstract
Antibiotic-loaded poly (methyl methacrylate) bone cement (ALBC) is widely used for anchoring joint replacements as a means of reducing the potential for peri-prosthetic joint infection (primary cases) and treating a patient who has an infected joint replacement (revision cases). One shortcoming of the cement is the high maximum exothermic temperature experienced upon polymerization (Tmax), a phenomenon that, it has been postulated, may cause or be implicated in thermal necrosis of peri-prosthetic tissues. There are many reports in the literature on methods of reducing Tmax, with one such study involving the addition of a phase change material (microencapsulated paraffin) (MEPAR) to the cement powder or adding a chain-stopping chemical (1-dodecyl mercaptan) (DDM) to the liquid. In that report, the results of gentamicin elution tests were presented. In the present work, those results were used to calculate various indices of gentamicin elution kinetics, namely 1) diffusion coefficient (Dgent); and 2) values of the coefficients in four equations that are widely used to model antibiotic elution from ALBCs. We found 1) the difference in Dgent of either a MEPAR- or DDM-containing formulation, on the one hand, and that of the control cement, on the other, was not significant; and 2) a consistent trend in the value of only one coefficient in one of the four model equations, with this change suggesting insignificant difference in gentamicin elution mechanism between an experimental cement formulation and the control cement. The implications of these findings for guiding selection of additives that simultaneously produce significant reduction of Tmax but minimal effect on gentamicin elution kinetics are discussed. This guide is a novel contribution to the literature.
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