Post-yield relaxation behavior of bovine cancellous bone.

Relaxation studies were conducted on specimens of bovine cancellous bone at post-yield strains. Stress and strain were measured for 1000s and the relaxation modulus was determined. Fifteen cylindrical, cancellous bone specimens were removed from one bovine femur in the anterior-posterior direction. The relaxation modulus was found to be a function of strain. Therefore cancellous bone is non-linearly viscoelastic/viscoplastic in the plastic region. A power law regression was fit to the relaxation modulus data. The multiplicative constant was found to be statistically related through a power law relationship to both strain (p<0.0005) and apparent density (p<0.0005) while the power coefficient was found to be related through a power law relationship, E(t, epsilon)=A(epsilon)t(-n(epsilon)), to strain (p<0.0005), but not apparent density.