Osteointegration of an alumina matrix composite ceramic with a porous surface: mechanical and histological results of an animal experiment

The aim of this study was to analyse mechanically and histologically the osteointegration of porous-surfaced ceramic implants made of an alumina matrix composite (AMC) by assessing maximum shear strength and histomorphometric bone ongrowth. The surfaces of the cylindrically shaped AMC test implants were characterised by a porosity of 40% and a pore size of 150 to 300 microm. A total of 24 test cylinders was implanted bilaterally into the femurs of 6 female adult Goettinger minipigs. 12 weeks after surgery the animals were sacrificed. 12 test implants were used for a push-out test and 12 test implants were evaluated histologically. The mean maximum shear strength of the bone-implant interface was 7.6 +/- 2.0 MPa. Direct bone attachment was found in 7.4 +/- 3.4% of the histologically analysed surfaces. In summary, porous-surfaced AMC test implants demonstrated good mechanical stability in spite of a low percentage of bone ongrowth. This discrepancy could potentially be explained by bone ingrowth into the pores and subsequent interlocking mechanisms.