LONG-TERM BONE RESPONSE TO PARTICULATE INJECTABLE CERAMIC

Biphasic calcium phosphate particles (BCP), alone or combined with a c ellulosic ether vehicle in an injectable composite material (COMP), we re implanted in femurs of rabbits. The long-term follow-up (up to 78 w eeks) indicated: (1) BCr and COMP induced a foreign-body inflammatory reaction but without fibrous encapsulation Phagocytosis was mediated b y mononucleated macrophages (MC) and giant multinucleated cells (GMNC) . Phagocytosis was stronger with COMP and required the recruitment of GMNC while it primarily involved MC in the case of BCP. (2) There appe ared to be no significant difference between the bone ingrowth in the defects packed with BCP (dBCP) and in those filled with COMP (dCOMP). Bone reconstruction mostly was achieved after 4 weeks in dBCP but took more time to reach the center of dCOMP. High bone remodeling was obse rved at the last, evaluation times, especially in the case of COMP. (3 ) Degradation of the materials occurred mainly during the first 4 week s and was more severe for COMP, which probably was related to the smal ler granulometry of its mineral phase. Cell-mediated degradation went on for the 78 weeks and followed two processes: phagocytosis and/or ex tracellular dissolution of the calcium phosphate particles. (C) 1998 J ohn Wiley & Sons, Inc.