Osteoarticular biomechanics system: from organ to tissue and cell

Bones perform a variety of mechanical and metabolic functions in the human body: they give the body its external shape, and hold and protect soft tissue. Dynamically, they enable the transmission of muscular forces. Together with the joints, they thus play a major role in human movement.

Although bone is the biological tissue that has been most studied by biomechanists, knowledge in certain areas has yet to progress. Such is the case of growing bone. A better understanding of the mechanical properties of children's bones, their evolution with growth, their fracture characteristics and their regeneration process is necessary, for example, to improve vehicle safety devices, and to understand certain pathologies and their treatments.

Today, life expectancy is increasing considerably, but the mechanical quality of tissues, and bone in particular, is not being maintained. As a result, more and more patients each year are undergoing bone reconstruction treatments. At the same time, these treatments must meet the ever-increasing demands of patients who wish to maintain their quality of life and their physical and sporting activities. Bone ageing and pathologies, degradation of joint tissues, fractures and their repair are major public health issues. Total arthroplasty, of the hip or knee for example, involves replacing the affected joint with a prosthesis. They are performed after fractures linked or not to the degeneration of calcified tissues or the deterioration of joint surfaces, when the pain a patient feels becomes unbearable and limits his or her movements.

Surgeons are also turning to alternative treatments for extensive bone loss. Current work is focused on developing new therapies that promote and induce functional bone regeneration. More generally, these approaches aim to reconstitute different tissues (bone, cartilage, skin, etc.) structurally and functionally, by combining biomaterials and stem cells in vitro to develop devices that can then be implanted in patients.

Thus, the biomechanical study of an osteoarticular system, whether healthy, pathological or repaired, requires an integrated multi-disciplinary, multi-scale and multi-physics approach developed through strong links between biomechanists, biologists, materials specialists (in the sense of materials science) and clinicians. Analyses must address the responses of these systems at their various significant scales (cell, tissue and organ) in their mechanical, biological environment in physiological and pathological cases.

The aim of this article is to present the work of biomechanists in these fields. The first section deals with bone growth and aging, the second with prosthetics, and the third with cellular biomechanics....