A Literature Based Study on the Effectiveness of Neuromuscular Electrical Stimulation (NMES) on Quadriceps Strength And Knee Function or Movement following ACL Reconstruction of the Knee

INTRODUCTION

Anterior cruciate ligament (ACL) rupture is one of the most debilitating and incapacitating injuries to the knee (Cowling and Steele 2001). 80,000 to 250,000 ACL injuries occur annually (Fu et al. 2008).Various treatment options such as ACL reconstruction or surgery are available to reduce the morbidity of this condition (Bach et al. 2002). It has been suggested that ACL reconstruction is associated with muscle strength deficits and might essential to address muscle strength, function, and knee stability in the rehabilitation process after surgery. Neuromuscular electrical stimulation (NMES), a treatment intervention utilising electricity to stimulate muscles and nerves, has been recommended by clinicians and physiotherapists to restore and maintain muscle strength, function, and knee stability post-ACL reconstruction (Fu et al. 2008). Lake (1992) proposed two mechanisms of how neuromuscular electrical stimulation works to enhance muscle strength and augment muscle mass. The first mechanism suggests that NMES enhances muscle strength the same way as that of the voluntary exercise.The other mechanism proposes that muscle strength produced by NMES is caused by the reversal of voluntary recruitment order with a selective augmentation of type II muscle fibres. These proposed mechanisms have been the basis of various studies dwelling on the application of neuromuscular electrical stimulation on various medical conditions and its importance to rehabilitation programmes. This study aims to investigate the effectiveness in improving quadriceps strength following reconstruction of ACL rupture. This study also aims to investigate the effectiveness of NMES in improving knee movement following reconstruction of ACL rupture.

Studies published in English and conducted in the last 10 years that that used NMES as a form of intervention together with standard care in a population who have undergone ACL were included in the literature reviews.Studies included improvement of quadriceps strength and knee movement or knee function as key patient outcomes.Systematic reviews were also included. Exclusion criteria include non-English studies; studies which were performed on the elderly and the very young such as those age 18 years old and younger; studies which were published more than 10 years ago; studies which used NMES after surgical procedures other than ACL.

Key words like ‗neuromuscular electrical stimulation‘, ‗anterior cruciate ligament reconstruction‘, ‗quadriceps strength‘, and ‗knee function‘ were used in retrieving studies from Medline, Pubmed, CINAHL, EBSCO and COCHRANE databases.Manual search was also done in print journals from the University

The Critical Appraisal Skills Programme (CASP) critiquing tool for RCTs and systematic reviews were used to analyse the 10 studies (CASP 2006). The Physiotherapy Evidence Database (PEDro) scale was also used to provide the level of physical therapy evidence that the extracted studies have.

RESULT:

All 10 studies utilising the randomised controlled trial study design utilised NMES as a supplement to a standard rehabilitation protocol. The control groups of these studies used the standard rehabilitation protocol as the intervention while the experimental groups utilised a combination of NMES and the standard rehabilitation protocol. The degree of NMES stimulation, however, differed in each of these studies. There were also differences in treatment outcomes and in the number of experimental groups.

randomised them to three groups. The first group or control received the standard rehabilitation programme while the second and third groups received NMES. The second group received the traditional NMES while the last group received a garment-integrated NMES. Outcome measures for the study included isokinetic strength of the injured and uninjured knees when extended at 90 and 180 degrees. Functional tests of proprioception were also assessed. Assessment was conducted at baseline and measurements were done 6 weeks, 12 weeks and 6 months after the intervention. Findings of the study suggested that the group receiving the standard rehabilitation programme supported with garment-integrated NMES significantly (p<0.001) improved extensor strength of the knee and knee movement following ACL reconstruction at 6 months follow-up. A critique of the study using CASP revealed that the investigators asked a clearly focused question. The interventions were well explained as shown in table 1. The population studied were composed of patients who underwent ACL reconstruction. However, the study failed to explain its eligibility criteria and only detailed the number of patients included in the study and the age range of the group. The results were presented using a comparison of the findings of the experimental groups against the control group. The patient outcomes were used to determine if significant differences existed between traditional NMES, garment-integrated NMES and the control group. Finally, the results could be applied to current practice since the sample population were composed of healthy individuals who suffered from ACL rupture. The same treatment could be provided in local care settings. The study could also provide important information to policy makers and other physiotherapists since the study suggested that garment-integrated NMES was more effective than standard NMES. This intervention was suggested to improve knee function by improving knee strength and allowed extension of the knee. In the PEDro Scale of evidence, Feil et al. (2011) did not explain their eligibility criteria. However, there was random allocation but no concealed allocation. In an earlier study conducted by Fitzgerald et al. (2003), a modified NMES protocol was used to determine whether it would improve quadriceps strength after ACL reconstruction. suggested that NMES, when coupled with exercise, is more effective in improving the quadriceps strength of patients when compared to standard rehabilitation only. However, only a few of the studies suggested that NMES could also improve knee movement or knee function. An evaluation of the RCTs and the systematic reviews suggested that the outcome of improvement on knee movement or knee function was not included as one of the patient outcomes measured by the investigators. Further, the studies also suggested that different NMES parameters were used. For instance, the RCTs (Feil et al 2011; Fitzgerald et al. 2003; Ross 2000; Paternostro-Sluga et al. 1999; Snyder-Mackler et al. 1995, 1991; Liber et al. 1996; Draper and Ballard 1991) had inconsistencies on the duration, intensity and frequency of NMES application. Interestingly, the thematic analysis showed that a number of the patients in the RCTs and systematic reviews used patient self-treatment. This would show that in actual practice, NMES would not be difficult to administer since patients could operate the NMES stimulators by themselves. On the other hand, Kim et al. (2010) noted that the low levels of electrical stimulation might not yield sufficient effect on quadriceps strength. The lack of generalisability, as seen by the relatively small sample size of the RCTs and the systematic reviews, is another issue that should be considered when applying NMES in actual practice. Greenhalgh (2010) explained that RCTs with very few sample sizes could limit the applicability of the findings to a larger and more heterogeneous population. As stressed earlier, sustainability of the intervention in improving quadriceps strength or knee movement or function is another issue. Most of the patients were followed-up at varying number of weeks with some patients followed up at 16 weeks to determine the benefits of NMES. However, a common observation in the findings of the study was that the effects of NMES declined over time. It is unclear whether NMES should be administered for prolonged periods and at regular intervals to elicit long-term effects on both quadriceps strength and knee function or movement. It should also be noted that in the study by Fitzgerald et al. (2003), prolonged NMES intervention, such as 16 weeks duration, would help hasten the healing and return to normal activities of athletes with ACL rupture injuries. Further, studies on the impact of NMES on knee movement or function are few. Hence, it would be difficult to make generalisations on the efficacy of NMES in improving knee movement or function.

This review suggests that NMES could help patients recover quadriceps strength and knee function studies supporting the effectiveness of NMES on improving knee movement. The different RCTs and systematic reviews used NMES with standard exercise rehabilitation and compared this to standard exercise only or EMG biofeedback. The results showed better or moderate improvements when NMES was used as an adjunct to exercise.

Findings from this study revealed that quadriceps strength could improve with the introduction of NMES with standard rehabilitation or exercise therapy. However, the improvements were only moderate.

REFERENCES

Bach F, Carlier R, Elis J, Mompoint D, Feydy A, Judet O, Beaufils P and Vallee C (2002) Anterior Cruciate Ligament Reconstruction with Bioabsorbable Polyglycolic Acid Interference Screws: MR Imaging Follow up. Radiology. 225(2), pp. 541-550. CASP (2006) 10 questions to help you make sense of randomized controlled trials, England: Public Health Resource Unit. Cowling E and Steele J (2001) Is Lower Limb Muscle Synchrony during Landing Affected by Gender? Implications for Variations in ACL Injury Rates. Journal of Electromyography and Kinesiology. 11 (4), pp. 263-268. Draper V and Ballard L. (1991) Electrical stimulation versus electromyographic biofeedback in the recovery of quadriceps femoris muscle function following anterior cruciate ligament surgery. Physical Therapy, 71, pp. 455-461. Feil S, Newell J, Minogue C and Paessler H (2011) The effectiveness of supplementing a standard rehabilitation with superimposed neuromuscular electrical stimulation after anterior cruciate ligament reconstruction: a prospective, randomized, single-blind study. American Journal of Sports Medicine. 39(6), pp. 1238-1247. Fitzgerald G, Piya S and Irrgang J (2003) A modified neuromuscular electrical stimulation protocol for quadriceps strength following anterior cruciate ligament reconstruction. Journal of Orthopaedic & Sports Physical Therapy. 33(9), pp. 492-501.

Greenhalgh T (2010) How to read a paper: the basics of evidence-based medicine, West Sussex, UK: John Wiley and Sons. Kim K, Croy T, Hertel J and Saliba S (2010) Effects of neuromuscular electrical stimulation after anterior cruciate ligament reconstruction on quadriceps strength, function, and patient-oriented outcomes: a systematic review. Journal of Orthopaedic & Sports Physical Therapy. 40(7), pp. 383-391. Lake D (1992) Neuromuscular Electrical Stimulation: An Overview and its Application in the Treatment of Sports Injuries. Sports Medicine. 13 (5), pp. 320-336. Paternostro-Sluga T, Fialka C, Alacamliogliu Y, Saradeth T and Fialka-Moser V (1999) Neuromuscular electrical stimulation after anterior cruciate ligament surgery. Clinical Orthopaedics and Related Research. 368, pp. 166-175. Richardson M, Cramer J, Bemben D, Shehab R, Glover J and Bemben M (2006) Effects of Age and ACL Reconstruction on Quadriceps Gamma Loop Function. Journal of Geriatric Physical Therapy. 29 (1), pp. 26-32. Ross M (2000) The effect of neuromuscular electrical stimulation during closed kinetic chain exercise on lower extremity performance following anterior cruciate ligament reconstruction. Sports Medicine, Training and Rehabilitation. 9(4), pp. 239-251. Snyder-Mackler L, Ladin S, Schepsis A and Young J (1991) Electrical stimulation of the thigh muscles after reconstruction of the anterior cruciate ligament. Journal of Bone and Joint Surgery. 73(7), pp. 1025-1036. Snyder-Mackler L, Delitto A, Bailey S and Stralka S (1995) Strength of the quadriceps femoris muscle and functional recovery after reconstruction of the anterior cruciate ligament. A prospective, randomized clinical trial of electrical stimulation. Journal of Bone and Joint Surgery. 77(8), pp. 1166-1173.

Senior Physiotherapist at Prince Sultan Military Medical City, Riyadh, KSA