Effects of preoperative neuromuscular electrical stimulation on quadriceps strength and functional recovery in total knee arthroplasty. A pilot study. (2010)

BACKGROUND:
Supervised preoperative muscle strengthening programmes (prehabilitation) can improve recovery after total joint arthroplasty but are considered resource intensive. Neuromuscular electrical stimulation (NMES) has been shown to improve quadriceps femoris muscle (QFM)strength and clinical function in subjects with knee osteoarthritis (OA) however it has not been previously investigated as a prehabilitation modality.

METHODS:
This pilot study assessed the compliance of a home-based, NMES prehabilitation programme in patients undergoing total knee arthroplasty (TKA). We evaluated its effect on preoperative and postoperative isometric quadriceps femoris muscle (QFM) strength, QFM cross-sectional area (CSA) and clinical function (subjective and objective). Seventeen subjects were recruited with 14 completing the study (NMES group n = 9; Control group n = 5).

RESULTS:
Overall compliance with the programme was excellent (99%). Preoperative QFM strength increased by 28% (p > 0.05) with associated gains in walk, stair-climb and chair-rise times (p < 0.05). Early postoperative strength loss (approximately 50%) was similar in both groups. Only the NMES group demonstrated significant strength (53.3%, p = 0.011) and functional recovery (p < 0.05) from 6 to 12 weeks post-TKA. QFM CSA decreased by 4% in the NMES group compared to a reduction of 12% in the control group (P > 0.05) at 12 weeks postoperatively compared to baseline. There were only limited associations found between objective and subjective functional outcome instruments.

CONCLUSIONS:
This pilot study has shown that preoperative NMES may improve recovery of quadriceps muscle strength and expedite a return to normal activities in patients undergoing TKA for OA. Recommendations for appropriate outcome instruments in future studies of prehabilitation in TKA have been provided.

My comments:

My conclusions agree with the researchers. Often patients have insurance imposed limitations in the number of therapy visits they are allowed in a year, or large copayments make prolonged therapy unaffordable. However quality EMS units are becoming more and more affordable (~$200), are simple to use with minimal training, and allow arthritic patients to aggressively work muscles surrounding their most irritated joints in a without additional weight bearing, so it’s ideal for home use

Stimulation parameters used had a max intensity of 70 mA, 50 Hz, a changing pulse width between 100-400 uS, 5 seconds on and 10 seconds off, 20 minutes per day for 6 weeks. “Based on the the majority of strength training research with EMS” this isn’t exactly the parameters I would have chosen (I don’t see any use for a changing pulse width I would have used 300-400 uS and I generally use a longer rest period) but the strength and hypertrophy gains were still significant. Another case study I am aware of showed max strength gains after EMS were measured 4 weeks after cessation of use, so prehab is probably an ideal way to get a heads up on preventing atrophy following total knee replacement, and probably any other orthopedic surgery. Having the EMS unit at home already would give patients a heads-up to start immediate post-op EMS, which would further prevent atrophy, restore strength, control pain, and likely decrease the risk of blood clots.

I think an ideal situation to maximize post-op recovery while minimizing costs would be a single visit referral to physical therapy where the patient can learn to use, and obtain that day, a quality, programmable, 4-channel, battery operated, EMS unit, ASAP after the decision is made to go forward with the replacement. They could then use it as little as 12 minutes per day up to the time of their surgery and then immediately thereafter, and start outpatient rehabilitation when ordered by their surgeon at which point they would already have a substantial head start towards recovery.