The study was small—just 16 patients—but the results are intriguing. Hans C. Dreyer, P.T., Ph.D., professor of human physiology, University of Oregon, together with the Eugene-based Slocum Research & Education Foundation and the Oregon Research Institute, gave 20 grams of essential amino acids for three weeks to patients before and after knee replacement surgery.
They found that those who took the acids twice daily for a week before and for two weeks after knee replacement surgery recovered faster and had much less muscle atrophy than did a control group taking a placebo. The results are published online in the November issue of the Journal of Clinical Investigation and reported in Medical Press.
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, Dreyer said. In the study, 12 members of a control group who received 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% loss. Eighty percent of atrophy occurred in the first two weeks after surgery. Atrophy in non-operative legs was about 50% 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.
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, must come from food sources, Dreyer noted.
The placebo was alanine, a non-essential amino acid. Both supplements were mixed into pudding, cereal or carbonated beverage based on patient choice. Supplements were consumed an hour after physical therapy to take advantage of optimum protein synthesis after resistance exercises.
“We’ve learned that the essential amino acids were able to mitigate the amount of muscle loss, ” Dreyer said. “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.”
Faster recovery is a big plus for patients, because most of them have been dealing with pain for a long time, said Brian A. Jewett, M.D., a surgeon at the Slocum Center for Orthopedics & Sports Medicine. “Walking and being physically active are difficult for them pre-operatively and post-operatively, but for different reasons, ” he said. “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 six 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 [total knee arthroplasty]. This is clinically very important to me and my patients.”
Six weeks after surgery, patients in the control group took 32% more time to rise from a chair, walk three meters, 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.
“As we’ve measured it, ” Dreyer said, “many who have this surgery experience significant and rapid loss of muscle mass despite the fact that their activity level does not change dramatically relative to pre-surgery, which is low to begin with because of their knee pain.”
