Bone as a material

Bone is an exceptional material that is lightweight for efficient movement but also exhibits excellent strength and stiffness to provide structural support, facilitate movement, and protect internal organs. These material properties are imparted by a composite material of organic proteins and mineral crystals that are intricately organized on many scales. Healthy bone can renew itself, adapt its architecture, and repair fractures. This is facilitated by specialized biological cells from bone surfaces and marrow that can digest aged or damaged bone and reform new bone tissue. This unique behavior allows bone to maintain strength and continue to serve its functions throughout life. However, certain traumatic injuries and pathological diseases, most notably osteoporosis, can lead to bone fractures that do not repair or cause immobility, severe pain, and deformity. As a result, much study has been dedicated to understanding the normal biomechanical behavior of bone and delineating how fractures arise. Therapeutic strategies have been developed that can reduce fracture susceptibility during osteoporosis to a certain extent. However, existing treatments only reduce fracture susceptibility by 50%. Tissue engineering and regenerative medicine approaches strive to develop alternative strategies to regenerate deficient bone, but as yet, such approaches have not successfully reproduced the exceptional properties of bone as a material.