Dynamics of bone marrow pressure with tapping of titanium and hydroxyapatite implants in rabbits

The purpose of the present study was to evaluate the difference in stress transfer between titanium (Ti) and hydroxyapatite (HA) by the measurement of bone marrow pressure using a catheter pressure transducer. Ti and HA implants were inserted in the tibiae of rabbits. A hole of 1 mm in diameter was drilled in the bone and a fine catheter pressure transducer was placed in the bone marrow through a tube. The top of the abutment was vertically tapped with an impulse hammer, and the acceleration signal from the hammer and pressure signal from the catheter pressure transducer were examined. The time of contact (impulse duration) recorded in the impulse with Ti and HA was 166+/-17 micro sec and 164 +/- 17 micro sec, respectively. Maximum bone marrow pressure (BMP) with Ti and HA was 54.2 +/- 32.6 and 47.5 +/- 10.0 mmHg, respectively. Variation of the BMP with Ti was significantly larger than that with HA (P < 0.05). A negative correlation coefficient between impulse duration and BMP was found. The results of the present study suggest that the stress transfer is different between Ti and HA implants using dynamics of the bone marrow pressure.