Use of home neuromuscular electrical stimulation in the first 6 weeks improves function and reduces pain after primary total knee arthroplasty: a matched comparison

Background: The use of neuromuscular electrical stimulation (NMES) after total knee arthroplasty (TKA) has been demonstrated to facilitate quadriceps muscle recovery and to reduce pain. However, to our knowledge, this therapeutic modality has not been directly tested in patients who receive muscle stimulators for home use immediately after surgery. Therefore, the purpose of this study was to assess the effect of NMES use at home in addition to standard therapy program in patients after primary TKA surgery, and to compare the early functional results to a matching group of post TKA patients who did not receive home NMES units. Methods: A total of 41 patients scheduled for a primary TKA during April 1st, 2017 to January 31st, 2018 were identified as being eligible for the study. There were 15 patients deemed ineligible to be part of the study, resulting in 26 patients who were fitted either 1 week before or within 1 week of surgery a home NMES device. The device was controlled by a smart phone. Patients were asked to use the NMES device daily for 20 minutes, 3 times a day, for 6 weeks after surgery. As their ability to activate their quadriceps muscle improved, patients were encouraged to increase their exercise regimens. The NMES patients were compared to a matched cohort of 26 patients who had a TKA performed between June 1st, 2015 and July 31st, 2016, but did not receive home an NMES device. Comparative outcomes included: timed up and go (TUG) test, single limb stance (SLS) time, time to ascend and descend one flight of stairs, quadriceps lag, active and passive range of motion (ROM), 2-minute walking distance, and pain rating on a visual analog scale (VAS). A P value of 0.05 was set as the threshold for statistical significance for the matched comparison. Results: Patients in the home NMES had significantly better scores for quadriceps lag (P<0.001), TUG (P<0.001), time to ascend and descend one flight of stairs (P=0.001), SLS time (P<0.001). They also experienced significantly lower resting pain (P<0.001) and lower worst reported pain scores (P<0.001) compared to the control cohort. Additionally, there were a higher percentage of patients in the control cohort that could not use stairs reciprocally compared to the home NMES group (53.85% vs. 23.08%). Furthermore, passive range of motion for flexion was statistically better in the home NMES group (P=0.037). Conclusions: This matched comparison of primary TKA patients demonstrated significant pain reductions both at rest and lower worst reported pain scores and improved function with use of the home-based NMES units for the sub-acute phase of recovery. Patients walked longer distances safely as shown by improvements in TUG, quadriceps lag, and single limb support time. Larger proportions of patients in home NMES group were able to negotiate stairs reciprocally and faster than the matched control group. These findings may have important economic and functional implications for the post-operative care of TKA patient.