BIOTRIBOLOGY: The Tribology of Living Tissues

BIOTRIBOLOGY

The study of friction, lubrication and wear in biological systems, specifically articular joints.

As in man-made machines, excessive wear and tear of moving parts can cause grave breakdowns in the human body. When artificial materials such as polyethylene or titanium perform poorly in the real world of bone, muscle and blood, a special subset of tribologists are summoned. These specialists in biological friction and lubrication-called biotribologists-are helping medical researchers understand wear-related breakdowns and create treatments that get the body up and running again.

With 206 bones in the adult human body, powered by about 600 muscles, there is much to understand and much that can go wrong, tribologically speaking. In addition to bones and muscle, the body relies on many other moving parts: the beating heart, chewing teeth and blinking eyes. The body also produces its own unique lubricants-tears, saliva and synovial joint fluid-which biotribologists must understand as completely as their counterparts in machine labs grasp the properties of oil and synthetic lubricants.

"From a scientific viewpoint, there are many interesting questions about the tribology of moving tissues," says Myron Spector, professor of orthopedic surgery at Harvard Medical School. "In the human body many tissues move in relation to one another, and the body has to allow for that movement or the tissue will split and break down."

MAKING HIP REPLACEMENTS LAST

Artificial hips are widely considered the most successful advance in orthopedic surgery in the last 100 years. With its high success rate, hip replacement surgery offers people with diseased joints not only freedom from pain but also the chance to walk, run or even dance again. An estimated 300,000 people in the United States undergo hip-replacement procedure each year.

Still, the success is incomplete. Based on the wear characteristics of their component materials, artificial hips should last a patient's lifetime. But in reality these devices last only 12 to 15 years in the human body. Replacing them means another major surgery for the patient.