Bone bonding strength of calcium phosphate ceramic coated strain gauges

Although strain transfer from bone to gauge has been used as an indication of the extent of bone bonding to calcium phosphate ceramic (CPC) coated strain gauges, interface strength measurements have not been reported. In order to develop bone-bonded gauges that remain attached to bone surfaces for long periods, the strength of the CPC-bone interface must be optimized. A shear test to assess the interface strength of the CPC-bone interface was developed using the femora of 120-day-old male rats. The mean interface strength of a blended CPC coating bonded to the femora of the rats for 6 weeks in vivo was 4.8+/-2.4 MPa, and one specimen achieved a strength of nearly 10 MPa. This mean strength value is higher then the CPC-gauge interface strength reported in early studies, but it is lower than recently developed heat treated CPC-gauge interfaces that have average strengths of approximately 7.0+/-2.0 MPa.