In 54 patients fractures of the long bones were stabilized with limited-contact dynamic compression plates (LC-DCP) made of titanium. The implant surfaces were anodized to an interference colour of gold. The surface morphology effects the tissue response to the implant and was therefore examined. At implant retrieval, about 18 months post operatively (range 11 to 27), samples of the soft tissue layer covering the plate were excised and analysed by histomorphometrical means. The aim was to study the soft tissue reactions at the implant site and further to correlate itto the clinical symptoms of the patients. At retrieval the plates were covered by a connective tissue layer of 2 mm thickness on average. In patients with local pain a comparatively significant higher number of round cells (p=0.001) and macrophages (p=0.01) was found. This is consistent with a chronic granulomatous inflammatory reaction. The localized tissue discoloration observed in about half of the patients was confirmed as being due to titanium, but it was not the focus of a cellular reaction and was not correlated with pain. In general the implant showed good biocompatibility with excellent or good clinical results in 96% of patients.

Adhesion of tissues to biomaterials is desirable to prevent bacterial proliferation and for epithelial/transmucosal sealing of transcutaneous appliances, but can be counter-productive elsewhere, e.g. implants contacting tendons or maxillofacial subcutaneous tissue. It is therefore important to gauge adhesion strength of tissues to biomaterials before clinical use. Peel-testing is widely used for industrial product adhesion monitoring, but has rarely been applied biomedically. Here we describe peel-testing instrumentation designed for testing adherence of soft tissues to biomaterials. It offers the advantage that a 90 degrees angle between peel and substrate is maintained, simplifying determination of applied normal forces separating tissue layers from material surfaces. The device is portable and can be brought directly to the specimen removal site. This minimizes time delays between explantation and testing, maintaining the tissue/biomaterial interface in the freshest possible state closely approximating in vivo conditions, and so avoids measurement artifacts. So far, the instrument has been used to test adhesion of tape to a biomaterial surface (for determining the device's technical performance), assess strength of tissue adhesives, and measure adhesion of subcutaneous tissue to orthopaedic biomaterials. However, its versatility suggests additional applications for the peel-tester where adhesion of soft tissue to biomaterials is of interest.

Generally, implants give rise to toxic reactions and favour the formation and propagation of local infections. Adherance of the soft tissue to the implant prevents the development of fluid filled cavities, thus being of particular interest as a prophylactic measure in arresting spread of infections. Teflon cylinders with an etched surface have been investigated by optical and electron microskopic means following subcutane implantation in mice. We were able to demonstrate closed tissue contact. Signs of toxic tissue reactions were completely absent.