A case series.
The purpose of this case series was to assess the effect of high-intensity neuromuscular electrical stimulation (NMES) on quadriceps strength and voluntary activation following total knee arthroplasty (TKA).
Following TKA, patients exhibit long-term weakness of the quadriceps and diminished functional capacity compared to age-matched healthy controls. The pain and swelling that results from surgery may contribute to quadriceps weakness. The use of high-intensity NMES has previously been shown to be effective in quickly restoring quadriceps strength in patients with weakness after surgery.
METHODS AND MEASURES:
All patients were treated for 6 weeks, 2 to 3 visits per week, in outpatient rehabilitation. Five patients (NMES group) participated in a voluntary exercise program for both knees and NMES for the weaker knee. Three patients (exercise group) participated in a voluntary exercise program for both knees without NMES. For each treatment session, 10 isometric electrically elicited muscle contractions were administered at maximally tolerated doses to the initially weaker leg of the NMES group. Quadriceps strength and muscle activation were repeatedly assessed up to 6 months after surgery using burst superimposition techniques.
At 6 months, the weak NMES-treated legs of 4 of 5 patients in the NMES group had surpassed the strength of the contralateral leg. In contrast, none of the weak legs in the exercise group were stronger than the contralateral leg at 6 months. Changes in quadriceps muscle activation mirrored the changes exhibited in strength.
When NMES was added to a voluntary exercise program, deficits in quadriceps muscle strength and activation resolved quickly after TKA.
This study showed some serious results and was a very interesting read, particularly for a study that was done 10 years ago. Parameters used were:
- Machine type: Versastim 380
- Wave form: 2500 Hz alternating sinusoidal, 50 bursts per second
- Duty Cycle: 10s on 80s off
- Duration: 10 contractions
- Intensity: maximum tolerated
- Electrodes: 2 20 cm square placed on quadriceps
Having the weak leg with EMS surpass the strength of the strong leg is very meaningful with percent increases of the weak EMS leg increasing 221-451% compared to weak leg of the controls (that did exercise only) increasing 41-148%. Research also noted a greater increase in strength with those who tolerated greater intensity of electric stimulation. The exercise program in this study was pretty close to what would be considered “typical” and inferior to more intensive exercise programs. Such that optimal recovery from a total knee replacement should include the best of EMS and exercise programs. Patients, therapists and physicians should understand that the patient is not just trying to recover strength loss from the surgery but typically from years of disuse due to the the arthritis in the first place.
As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.
Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.