(i) Bone – the tissue we work with

There are two basic processes of bone formation – intramembranous and endochondral, which give rise to the flat bones and long bones respectively. Embryological development and subsequent modelling gives rise to an immensely strong composite tissue with organic and inorganic elements organized superbly for form and function. Far from being a static ‘skeleton’ built to last a lifetime, all bones are active metabolically, being constantly turned over and playing a crucial role in calcium metabolism. Furthermore it is a tissue that reacts to external applied forces, growing structurally stronger in response to increased loading over time but thinning or dismantling when not needed so that each bone is sufficient for the environment in which it operates – not too big and strong and not too thin and weak.