Sacrum becomes a single bone at ___ years of age.:-

Sacrum The five sacral veebrae are separated by cailage until pubey. Later, fusion of epiphyses takes place and ossification of interveebral discs extend from below upwards. Sacrum becomes single bone at 21-25 years of age. Sometimes, it leaves a gap between S1 and S2, until 32 years called as 'lapsed union'.