The aim of this study was to histologically evaluate the cellular reaction to 33 degradable bone substitute materials implanted in a drill hole model in sheep. The different materials were based on calciumphosphate cement, calciumsulfate, hydrogel and silk and had already been classified as biocompatible in earlier studies. The histological evaluation took place 6 – 8 weeks post operationem and lymphocytes, plasma cells, macrophages and multinucleated foreign body cells (MFBC) were quantified in four different zones of the drill hole.
The degradation from peripheral to central led to a specific pattern of cells. Calciumphosphate cements were mainly degraded by macrophages, while many MFBC were found in silk-based and some of the hydrogel-based materials. Shape and size of the phagocytes were determined by the degraded material. In the disintegration process of large-molecular materials based on silk or hydrogel, MFBC were expected, but did not interfere with the biocompatibility. The formation of new bone was detected right next to MFBC. The rest of some silk-based materials were encircled by fibrous tissue, which may be connected to a lower biocompatibility.
According to the available results, this research confirms that the MFBC which were regularly encountered in the degradation of various materials are part of a normal disintegration process and not a sign of a reduced biocompatibility.