Reactions and complications after the implantation of Endobon including morphological examination of explants.

In the study described here, the integration of hydroxyapatite (HA) ceramic implants (Endobon) was investigated. These implants have an interconnecting system of pores and are free from foreign protein. The material is not toxic, genotoxic, nor zytotoxic, and it is biocompatible. The progress of integration was investigated by means of clinical and radiological check-ups. From 10 patients, it was possible to obtain samples for histological analysis during a second operation (e.g., metal explantation). Microscopic examination showed bony integration with newly formed bone in direct contact with the HA ceramic; it also showed osteoblasts and osteoid seams. No second operation took place earlier than 4 months after the first operation, yet even after this relatively short period, bony integration was already evident. Clinical observation (based on X-rays, reports of pain, signs of inflammation) showed that in most cases healing was taking place without complications. More general operational complications such as thrombosis or nerve injury were observed in 4 patients. If the implant is not sufficiently protected from mechanical stress, bony integation will not take place, and the implant may fracture. HA ceramic, with a porosity between 30% and 80%, is not comparable to cortical bone but only to spongy bone. This factor must be taken into account when deciding whether a HA ceramic implant is indicated.