Pre-operative quadriceps femoris neuromuscular electrical stimulation in total knee arthroplasty : a clinical and molecular analysis.
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Patients with knee osteoarthritis (OA) have asymmetrical muscle weakness due to neuromuscular activation deficits and muscle atrophy. Quadriceps muscle (QFM) strength declines after total knee arthroplasty (TKA) with associated functional impairment. The ultimate purpose of this investigation was to determine the effects of preoperative neuromuscular electrical stimulation (NMES) on quadriceps muscle strength and functional recovery after TKA. Patients undergoing TKA for advanced knee OA were randomised into control or intervention (NMES) groups. NMES was applied to the affected QFM for 20 min, 5 days/week, for 8 weeks pre-TKA. QFM and hamstring (HS) strength were determined isokinetically and QFM cross-sectional area (CSA) calculated using MRI planimetry. Outcomes were assessed both objectively (walk, stair-climb and chair-rise tests) and subjectively (WOMAC, SF-36 and oxford knee scores). All evaluations were performed at baseline and preoperatively with strength and function also tested at 6 and 12 weeks post-TKA. Muscle samples were obtained from the vastus lateralis muscle at baseline and immediately preoperatively. Expression of myosin heavy chain (MHC) mRNA and genes associated with muscle hypertrophy (IGF-1) and atrophy (MAFbx and MURF-1) were determined using RT-PCR. The NMES group increased isokinetic QFM strength (36%; p=0.008) and CSA (7.4%; p=0.036) preoperatively. Functional capacity also improved in the NMES group (walk, 9% [p=0.008]; stair-climb, 20% [p=0.008]; chair-rise, 34% [p=0.008]). MHC-llx mRNA decreased by 42% indicating a fast to slow fibre shift. IGF-1 was upregulated in response to NMES, although MURF-1 and MAFbx did not change. Only the NMES group increased QFM strength from 6 to 12 weeks post-TKA (53%; p=0.011) with associated improvements in objective function. At 12 weeks post-TKA, the NMES groups were better than the control group at stair-climb (62%, p=0.029) and chair-rise (34%, p=0.019) tests. The control group had greater muscle atrophy than the NMES group at 12 weeks post-TKA (12.1% vs. 3.7%). Substantial increases in preoperative muscle strength can be achieved following an unsupervised NMES program in subjects with advanced knee OA. Associated with this is an increase in muscle mass, IGF-1 expression and improvements in functional capacity. These effects translated into improved strength and functional recovery after TKA. We have also shown that changes in MHC isoform expression in response to NMES are similar to those seen with volitional exercise.