The goal of this study was to examine the relationship between gentamicin concentration in Palacos R bone cement (in the mass fraction range of 0-9.4%) and various properties of the cement. The results from the thermal, density, and static compression tests show that gentamicin favors the cement polymerization in its final steps, and forms a diphasic structure with the cement [poly(methylmethacrylate)] matrix. The static compression properties in the dry state are only slightly modified by the presence of the antibiotic. Concerning aging in water at 37 degrees C, two types of behavior can be distinguished: below a critical concentration, approximately 3-4%, the extraction of gentamicin by water is slow and there is only a slight change of static compression properties. In contrast, above this critical concentration, the gentamicin extraction is fast and almost complete after 48 weeks, and there is a considerable loss of static compression properties.

SynopsisThe flexural fatigue properties were studied for PP injection-molded samples of different molecular weight and well-defined skin-core morphology (see Part I). It can be clearly seen that the crack initiation always OCCUR in the subskin layer of higher macromolecular orientation, and propagates towards the core. The mechanisos of cracking are discusoed on the basis of fatigue kinetic data and analytical meesurements on the stressed sections. The important influence of p d g conditions, essentially holding pressure on the fatigue behavior is illustrated.

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