BIOMECHANICAL PROPERTIES OF CORTICAL ALLOGRAFT BONE USING A NEW METHOD OF BONE STRENGTH MEASUREMENT - A COMPARISON OF FRESH, FRESH-FROZEN AND IRRADIATED BONE

There have been conflicting reports on the effects of gamma irradiatio n on the material properties of cortical allograft bone, To investigat e changes which result from the method of preparation, test samples mu st be produced with similar mechanical properties to minimise variatio ns other than those resulting from treatment, We describe a new method for the comparative measurement of bone strength using standard bone samples. We used 233 samples from six cadavers to study the effects of irradiation at a standard dose (28 kGy) alone and combined with deep freezing. We also investigated the effects of varying the dose from 6. 8 to 60 kGy (n = 132), None of the treatments had any effect on the el astic behaviour of the samples, but there was a reduction in strength to 64% of control values (p<0.01) after irradiation with 28 kGy. There was also a dose-dependent reduction in strength and in the ability of the samples to absorb work before failure. We suggest that irradiatio n may cause an alteration in the bone matrix of allograft bone, but pr ovided it is used in situations in which loading is within its elastic region, then failure should not occur.