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"We've learned that the essential amino acids were able to mitigate the amount of muscle loss," Hans C. Dreyer says. "The functional measures that we looked at—getting up out of a chair, going up a flight of stairs, and going back down the stairs—were all back to baseline in the treatment group, whereas in the placebo group those times on all of the functional measures were much longer." (Credit: Steve Depolo/Flickr)

amino acids

Amino acids may let new knees work faster

Amino acid supplements before and after knee replacement surgery help patients recover faster and suffer less muscle atrophy, according to new research.

The approach could spell relief and speed recovery for a growing population of aging adults who face total knee-replacements because of loss of mobility and pain problems. An estimated 3.48 million Americans are projected to need the surgery, known as total knee arthroplasty (TKA), by 2030.

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The study is online ahead of print in the Journal of Clinical Investigation.

Losing less muscle

Atrophy in the quadriceps, a group of four muscles on the front of the thigh, has been a long-running problem following knee-replacement surgeries, says Hans C. Dreyer, professor of human physiology at the University of Oregon.

In the study, 12 members of a control group receiving 40 grams a day of a non-essential amino acid supplement, a placebo, averaged an 18.4 loss in quadriceps muscle mass in their operated leg six weeks after surgery; those getting the supplement of eight essential amino acids (EEA) averaged a 6.2 percent loss.

Eighty percent of atrophy occurred in the first two weeks after surgery. Atrophy in non-operative legs was about 50 percent of that in the operative leg in both groups. Muscle mass changes were seen with magnetic resonance imaging done at two and six weeks after surgery.

“We’ve learned that the essential amino acids were able to mitigate the amount of muscle loss,” Dreyer says. “The functional measures that we looked at—getting up out of a chair, going up a flight of stairs, and going back down the stairs—were all back to baseline in the treatment group, whereas in the placebo group those times on all of the functional measures were much longer. That suggests that this is a means at which we can accelerate functional recovery.”

Using the knee

Faster recovery is a big plus for patients, because most of them have been dealing with pain for a long time, says Brian A. Jewett, a surgeon at the Slocum Center for Orthopedics and Sports Medicine.

“Walking and being physically active are difficult for them pre-operatively and post-operatively, but for different reasons,” he says. “Surgery removes the pre-operative pain and disability, and physical therapy helps restore range of motion and strength post-operatively. EAA appear to facilitate this process, presumably by reducing muscle loss.

“In the end, if I can get my patients able to go up and down stairs and get up from a chair sooner then this is much better for their overall health, and we saw this occur 6 weeks after surgery in the EAA group. This also suggests a durability-of-treatment effect because EAA treatment was stopped two weeks after surgery and functional mobility measures were recorded four weeks later, or six weeks after TKA. This is clinically very important to me and my patients.”

Six weeks after surgery, patients in the control group took 32 percent more time to rise from a chair, walk three meters (about 10 feet), turn around, and sit back down, compared to before surgery.

Patients receiving essential amino acids took about the same amount of time as before surgery. Control patients took even longer to maneuver stairs after surgery. Again, times remained the same for the EEA group pre- and post-operatively.

In the supplement

The essential amino acid supplement contained rapidly absorbed raw amino acids—a mix of histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, and valine. Essential amino acids, which are not naturally produced by the body and must come from food sources, help the body in many ways, including tissue repair.

The placebo was alanine, a non-essential amino acid. Both supplements were mixed into pudding, cereal, or a carbonated beverage, based on patient choice. Supplements were consumed an hour after physical therapy to take advantage of optimum protein synthesis after resistance exercises.

Researchers hope to expand their work to see how a longer duration of supplementation affects patients at six months and a year after surgery. Another potential benefit, Jewett says, is that combined with technological improvements in the components used in knee-joint replacement surgeries, such supplementation with essential amino acids may allow for the possibility of patients who elect to undergo surgery earlier in life to return to work and daily activities faster, which are important outcomes for patients.

The findings are part of an ongoing collaboration, led by Dreyer, with the Slocum Research & Education Foundation and the Oregon Research Institute.

The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, and the Medical Research Foundation based at Oregon Health and Sciences University in Portland, supported the research.

Source: University of Oregon

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