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Polyactive a 55/45 poly(ethylene oxide)/poly(butylene terephthalate) copolyether ester, was investigated as regards its general in vitro and in vivo biocompatibility. Special attention was directed to the interactions of the polymer with bone.

An in vitro bone forming system is described in which interface reactions were studied with calcium phospates. A layer of hydroxyapatite or fluorapatite was applied on tissue culture plastic using the plasma-spray technique. Interactions between the bone forming cells and the extracellular matrix on one hand and the plasma-sprayed calcium phosphates on the other hand, were studied using light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray microanalysis (XRMA).

In order to test the suitability of hydroxyapatite implants for use in tympanoplasty, a study was performed in which the behaviour of these biomaterials was observed in the infected middle ear of the rat. Infection was induced by means of intratympanical injection of a Staphylococcus aureus suspension. The reactions observed show great resemblance with the events witnessed in the middle ear infected without implant. Another similarity can be demonstrated between the implant inserted in the infected tympanon and the implant remaining in the non infected middle ear cavity. All implants are characterized by a mucosal and bony lining. Macropores, when present, become filled with fibrous tissue, gradually replaced by bone. The bonding between the tissue and the implant appears to be tight.

Rontgen microanalysis revealed the accumulation of trace elements such as silicon, titanium, aluminum, iron, and chromium in electron-dense inclusion bodies in the cytoplasm of phagocytes associated with the implantation of a tricalcium phosphate ceramic, EstaneR polyether urethane, HPOE/PBT copolymer or polypropylene oxide into the rat middle ear. The constituent element magnesium was found as well. In only one case did hydroxyapatite implanted in the human middle ear give rise to the presence of these elements in phagocyte cytoplasm, and trace element accumulation at the implantation site was not found for SilasticR implants.