Optimum fixation at bone/bone cement interface by interposing HA granules (IBBC)

It would be a revolutionary idea to interpose unresorbable osteoconductive HA at bone and bone cement interface by expecting chemical bonding of HA with bone and osteoconduction forever to prevent radiolucent line and loosening. As a surgical procedure, less than two layers of HA granules of 300 to 500 micron in diameter were smeared on the bone surface just before the cement insertion (Interface Bioactive Bone Cement:IBBC). In animal experiments, at one week, bone ingrowth began into one to two layers of HA granules. At two to three weeks, bone ingrowth completed. The bonding strength in the case of IBBC without anchor holes at six weeks attained to 50% of non-IBBC and IBBC with anchor holes and showed the same tendency as HA coating on the smooth surface. In clinical cases, the majority of HA granules were incorporated into dense cortical bone and cancellous bone connected to adjacent dense cortical bone and cancellous bone, respectively. The shape and sizes of HA granules were not changed at 17 years. In conventional bone cement (Non-IBBC) and cementless fixation, the spaces will appear at the bone interface due to aging of bone. As unresorbable crystalline HA is used in IBBC and HA is osteoconductive, at present enduring osteoconduction could be expected in only IBBC.