September 22, 2010

Tendons: What Causes Sprains, Strains & Tears

(Ivanhoe Newswire) -- Tendons are the body's marionette strings. They connect bones and bones to muscles, allowing you wiggle your ears, scratch your back, and even burst into a sprint. This is all possible until you feel and unusual tug on the strings leaving you with a sprain, strain, or a tear. Surgeons try to repair more than 300,000 of these injuries every year, and doctor's visits for soreness fly into the millions. Scientists can now look all the way down to the atoms our tendons are made up of and discover the reason for these strains, sprains, and tears.

Using a combination of nanoscience and biomedical and civil engineering scientists uncovered single threads, which are fibrils of collagen that make up the tendons. Knowing this information can be vital to catching weak tendons before they fail.

"The fibrils are about five times stronger and can strain about five times farther than a tendon," Steven Eppell, a professor of biomedical engineering and senior author of the study was quoted as saying. "About 80 to 90 percent of a tendon is collagen but mechanical properties like strength are probably controlled by the other stuff."

Molecules called proteoglycans are the cement that holds the fibrils together, and scientists believe that this is the weak part of the tendon. It would be very hard to test the cement in between the fibrils, so scientists tested the collagen fibrils to see how strong they were and realized that it had to be the cement causing all the problems.

"It's the equivalent of what civil engineers use to test a steel beam under 100,000 pounds of pressure, shrunk to the micro level," Roberto Ballarini, a professor of civil engineering formerly at Case Western Reserve and now chairman of civil engineering at the University of Minnesota and co-author of the study was quoted as saying. Ballarini is one of the inventors of the device to test the fibrils' strength.

In this landmark study, the scientists glued one end of the fibrils, taken from sea cucumbers, to a stationary base and the other end to a moveable pad. When pulled apart, the fibrils stretched up to 100 percent of their resting length before breaking, and a tendon stretches only 10 to 20 percent before breaking.

The investigators think water actually toughens fibrils and tendons as a whole. Since the proteoglycans in the cement control the degree of hydration around the fibrils, the team believes they may be the best targets when designing drugs to control tendon strength.

SOURCE: Biophysical Journal, published online September 21, 2010