EFFECTS OF IRRADIATION ON THE BIOMECHANICS OF OSSEOINTEGRATION - AN EXPERIMENTAL IN-VIVO STUDY IN RATS

The present study reports on the late effects of increasing doses of r adiation on the biomechanics of commercially pure titanium implants (f ixtures) installed in the proximal tibia in 26 rats. Twelve weeks afte r various doses (10, 20, 30, and 35 Gy) of irradiation, the fixtures w ere inserted into rat tibiae, and after another eight weeks these were tested mechanically in vivo. Acute dose dependent skin reactions deve loped after all doses except 10 Gy, but most subsided within two to th ree weeks. There was a statistically significant reduction in torsion but the pull-out load was not significantly reduced for single doses u p to 30 Gy. Histological analysis showed that bone remodelling was imp aired. Shear stresses and shear moduli were estimated for the bone-imp lant inter-face and in the surrounding bone tissue. These estimated st resses and moduli were not found to be correlated to the dose of radia tion.