The Therapeutic Modality Controversy: Does Neuromuscular Electrical Stimulation (NMES) Have a Role in Treating Post-operative Quadriceps Inhibition and Weakness?

Joseph A. Gallo, DSc, AT, PT and Kevin J. Silva, MSAT

In recent years, therapeutic modalities have become a controversial topic. Some of the criticisms are valid and have caused us to rethink how we use these interventions, while others are examples of generalizations that are not evidence-based. The largest criticism of therapeutic modalities is when they are used as passive stand-alone treatments. Clinical experience and the research have indeed demonstrated limited value when therapeutic modalities are not appropriately integrated into a comprehensive treatment plan. The focus of this article is to demonstrate an evidence-based approach to neuromuscular electrical stimulation (NMES) as an addition to standard care for post-operative quadriceps inhibition and weakness.

Quadriceps strength is the single biggest impairment in the post-operative knee. [1,2,3] During the immediate post-operative period, weakness has been associated with quadriceps activation failure due to surgically induced joint trauma, post-operative joint effusion, and pain.[1,3,4] The decrease in post-operative quadriceps force output during the first four weeks following surgery is most related to deficits in neural recruitment.[1] Post-operative strength deficits upwards of 30% have been observed up to 6-12 months following surgery.[1,3,5] Quadriceps inhibition and weakness has been correlated with decreases in functional performance.[1,2,6]

NMES is used to facilitate weak inhibited muscles that have an intact peripheral nerve. Historically, a traditional NMES muscle re-education approach has been widely used clinically with mixed results. This approach involves having the patient contract the muscle simultaneously with the current. Clinicians tend to prefer the muscle re-education approach because it is perceived to be more functional, however the intensity of contraction is not great enough to induce the same strength gains demonstrated in the high intensity NMES literature.[4,6] The high intensity NMES approach differs in that it focuses on eliciting isometric muscle contractions which produce a minimum of 33-50% of the maximal volitional isometric contraction (MVIC), with more optimal quadriceps strength recovery when ≥50% MVIC is achieved.[6] Furthermore, in high intensity NMES it is not possible for the patient to produce a voluntary contraction while the current is on due to the high intensity. Adding high intensity NMES to standard care in the first 4-6 weeks yields quadriceps strength gains of 13%-26%[4,6] and increases functional performance when compared to standard care alone.[1] Best practices include beginning high intensity NMES as early as 48 hours after surgery and continuing for a minimum of 4-6 weeks in addition to therapeutic exercise and functional activities.[1]

The remainder of this review will focus on best practices for clinical application as outlined in the existing high intensity NMES literature.[4,6,7] The electrodes should be placed with one over the proximal vastus lateralis and the other over the vastus medialis oblique fibers. It is important to use the larger 3”x5” electrodes to ensure adequate muscle fiber recruitment and improved patient tolerance to the electrical stimulation. If smaller 2”x2” electrodes are used, the treatment will not be tolerable for the patient due to the high current density. For further instruction on patient set-up and parameters options refer to the images and table below. It is important to continuously titrate the intensity (mA) upward until the target MVIC is achieved. In the absence of an isokinetic dynamometer, a handheld manual muscle testing dynamotor can be used to quantify force. When instrumentation to quantify force is unavailable, the clinician can use maximal tolerable intensity, evidence of tetanic contraction (no fasciculation), and superior glide of the patella.

This short review demonstrates clinical decision making related to the evidence-base use of electrical stimulation for treating the post-surgical knee.

(Left image) Alternate patient set-up using a strap, instead of a dynamometer. [4] (Middle image) Modified Quadriceps Strength Augmentation Protocol - Knee Extended. [7] (Right image) Quadriceps Strength Augmentation Protocol - Knee Flexed to 60 degrees. [6]

References:

1.Kim K, Croy T, Hertel J, Saliba S. Effects of neuromuscular electrical stimulation after anterior cruciate ligament reconstruction on quadriceps strength, function, and patient-oriented outcomes: a systematic review. Journal of Orthopaedic & Sport Physical Therapy. 2010;40(7):383-391.

2.Bryant AL, Kelley J, Hohmann E. Neuromuscular adaptations and correlates of knee functionality following ACL Reconstruction. Journal of Orthopeadic Research. 2008;January:126-135.

3. Thomas, AC et al. Muscle atrophy contributes to quadriceps weakness after anterior cruciate ligament reconstruction. Journal of Science and Medicine in Sport. 2016; 19(1):7-11.

4.Stevens-Lapsley JE, et al. Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: A randomized controlled trial. Phys Ther. 2012 Feb; 92(2):210-226.

5.Lepley LK. Deficits in quadriceps strength and patient-oriented outcomes at treturn to acticity after ACL reconstruction: a review of the current literature. Sports Health. 2015;7(3):231-238.

6.Synder-Mackler L, Delitto A, Bailey S, Stralka S. Strength of the quadriceps femoris muscle and functional recovery after reconstruction of the anterior cruciate ligament; a prospective randomized clinical trial of electrical stimulation. J Bone Joint Surg.1995;77:1166-1173.

7.Fitzgerald et al. A modified neuromuscular electrical stimulation protocol for quadriceps training following ACL reconstruction. J Ortho Sports Phys Ther. 2003;33:492-501.

Joseph A. Gallo, DSc, AT, PT is a professor and director of the athletic training program at Salem State University, Salem, MA.

Kevin J. Silva, MS, AT is the program assistant and adjunct faculty for the athletic training program at Salem State University, Salem, MA.