Essential amino acid supplementation in patients following total knee arthroplasty

Abstract

Background: By the year 2030, 3.48 million older U.S. adults are projected to undergo total knee arthroplasty (TKA). Following this surgery, considerable muscle atrophy occurs, resulting in decreased strength and impaired functional mobility. Essential amino acids (EAAs) have been shown to attenuate muscle loss during periods of reduced activity and may be beneficial for TKA patients.

Methods: We used a double-blind, placebo-controlled, randomized clinical trial with 28 older adults undergoing TKA. Patients were randomized to ingest either 20 g of EAAs (n = 16) or placebo (n = 12) twice daily between meals for 1 week before and 2 weeks after TKA. At baseline, 2 weeks, and 6 weeks after TKA, an MRI was performed to determine mid-thigh muscle and adipose tissue volume. Muscle strength and functional mobility were also measured at these times.

Results: TKA patients receiving placebo exhibited greater quadriceps muscle atrophy, with a -14.3 ± 3.6% change from baseline to 2 weeks after surgery compared with -3.4 ± 3.1% for the EAA group (F = 5.16, P = 0.036) and a -18.4 ± 2.3% change from baseline to 6 weeks after surgery for placebo versus -6.2 ± 2.2% for the EAA group (F = 14.14, P = 0.001). EAAs also attenuated atrophy in the nonoperated quadriceps and in the hamstring and adductor muscles of both extremities. The EAA group performed better at 2 and 6 weeks after surgery on functional mobility tests (all P < 0.05). Change in quadriceps muscle atrophy was significantly associated with change in functional mobility (F = 5.78, P = 0.021).

Conclusion: EAA treatment attenuated muscle atrophy and accelerated the return of functional mobility in older adults following TKA.

Trial registration: Clinicaltrials.gov NCT00760383.

Figures

Figure 1. Study flow.

Random assignments to treatment group, reasons for exclusion and withdrawal, and study completion.

Figure 2. Muscle atrophy.

Raw values from baseline for quadriceps and hamstrings and adductor muscle loss between groups. EAA treatment attenuated operated (TKA) quadriceps atrophy by 4.6-fold versus placebo 2 weeks postoperation. EAAs also mitigated operated quadriceps and hamstrings and adductor muscle atrophy by 3-fold (quadriceps) and 2.2-fold (hamstrings and adductors) at 6 weeks postoperation and by 3- and 4-fold in the quadriceps and hamstrings and adductors, respectively, in the nonoperated thigh. Mid-thigh muscle volume was measured with Analyze version 11.0 software. Values are the mean ± SEM. Placebo group, n = 12; EAA group, n = 16.

Figure 3. Representative mid-thigh MR images of the operated thigh at baseline (pre-TKA), 2 weeks after TKA, and 6 weeks after TKA for the placebo and EAA groups.

Placebo images are from a 71-year-old female, and EAA images are from a 74-year-old female.

Figure 4. Functional mobility.

EAA supplementation accelerated the return of functional mobility versus placebo 6 weeks after TKA. For the TUG test, the subjects began the test in a seated position (all were tested using the same chair), then stood up, walked forward 3 meters across a line that was clearly marked on the floor, then turned around, walked back 3 meters, and sat down in the same chair. Subjects were given verbal instructions to complete the task “as fast and as safely as you can,” and the total time was recorded. Total time to go up the stairs and the time to go down were measured. Timing started as soon as the subjects made their initial movements forward or upward. The starting point for the descent portion was when subjects completely faced the stairs. The end point was when both of the subject’s feet were at the starting spot on the ground in front of the staircase. All subjects were provided with verbal instructions to complete the test “as fast and as safely as you can.” Subjects were timed (seconds) as they ascended 8 steps (stair-climb up) and descended 8 steps (stair-climb down) at baseline and 6 weeks after TKA. The same set of stairs was used for each testing session. Values represent the mean percentage change from baseline ± SEM. Placebo group, n = 12; EAA group, n = 16.