An Exciting Find on NMES and Shoulder Sublaxation

Whilst sitting back on a Friday afternoon and reflecting upon our last blog post (now with a significantly greater understanding of hemiplegia and how it has the potential to affect a stroke victims everyday life so drastically), we began reviewing the literature surrounding NMES parameters and clinical studies. Chae et al (1998), explains that the nerve fibre recruitment properties elicited by normal physiological mechanisms and NMES have contrasting preferences. Normal physiological mechanisms initially recruit the neurons with the smallest diameter prior to the recruitment of larger diameter fibres. This differs from Neuromuscular Electrical Stimulation (NMES) which mediates a nerve recruitment pattern following the principle of ‘reverse recruitment order’, thus preferentially recruiting the large-diameter nerve fibres which are responsible for innervating the larger motor units (Sheffler et al, 2007).

As we continued to read articles in relation to NMES and upper limb recovery post stroke, we came across an interesting article and substantial supportive evidence in regards to NMES and its ability to reduce sublaxation of the shoulder joint. This is achieved through NMES inducing contractions of the shoulder muscles, thus pulling the head of the humerus into the glenoid fossa (Chae et al, 1998). Re-education of the glenohumeral joint is an essential requirement of a post stroke rehabilitation program as it ensures the anatomically correct positioning of the humeral head in the glenoid fossa. As a result of NMES ensuring this correct joint alignment, a stable base is maintained for optimal functional use of the upper extremity (NMES Guidelines for Treatment, 2010). Whilst reflecting upon this article we began to appreciate NMES’ ability to ensure that the correct alignment of the shoulder joint is achieved post stroke.

Figure 2.1. Shoulder subluxation and the use of electrical stimulation. The top image displays chronic shoulder sublaxation. The bottom image shows the alignment of the shoulder during application of electrical stimulation.

Excited by our new found understanding of the role NMES plays in post stroke recovery of the upper limb, we continued to review the literature. Baker & Parker (1986) ensured our knowledge of the topic continued to develop. They stated that the primary advantage of NMES is its ability to maintain joint integrity throughout the flaccid period of post stroke recovery, thus preventing the early implementation of stretching the shoulder capsule (Baker et al, 1986). Due to the complexities of this multi-articular joint, NMES is most useful in the initial phase of ROM. As we continued to reflect upon what we were reading, our understanding grew. We were now fully aware that because of the multi-articular nature of the shoulder joint, NMES provides the initial foundation and enhances the development of muscle strength and function of the upper limb post stroke. AMAZING!

       

Figure 2.2. Comparison of a stable shoulder capsule and a shoulder capsule post sublaxation

According to Chae et al (1998), early protection of the shoulder capsule has the capability to result in a faster recovery of the upper extremity function post stroke. Just as we began to think nothing could hamper the positive outcomes of NMES and its' ability to facilitate recovery post stroke, Sheffler et al (2007) proved us wrong. Sheffler et al (2007) explains that the clinical application of NMES is currently limited to neurological injuries involving the Upper Motor Neuron (UMN), including conditions such as spinal cord injury, stroke and cerebral palsy, being dependant on intact alpha Lower Motor Neurons (LMN). We can therefore conclude that NMES treatment and UMN conditions are inextricably linked.

Figure 2.3. NMES and its limitation to neurological injuries involving the Upper Motor Neuron

With our understanding of NMES and the positive impact it has on reducing sublaxation of the shoulder capsule post stroke now completely fuelled, we look forward to going into greater detail of the NMES parameters specific to post stroke upper limb recovery next time!

Until then,
Meg and Hayley.

REFERENCES

Baker. L.L. & Parker. K. (1986) Neuromuscular Electrical Stimulation of the Muscles Surrounding the Shoulder. Annual Biomedical Eng 66 (12).

Chae, J., Bethoux, F., Bohinc, T., Dobos, L., Davis, T. & Friedl, A. (1998) Neuromuscular Stimulation for Upper Extremity Motor and Functional Recovery in Acute Hemiplegia. Stroke. (29) 975-979.

Sheffer, L.,R. & Chae, J. (2007) Neuromuscular electrical stimulation in neurorehabilitation 35(5); 562- 590.

NMES Guidelines for Treatment. (2010) Retrieved February 25, 2011.
http://www.empi.com/uploadedFiles/Empi_Products/Pain_Management_-_TENS/gait

Images;
http://stroke.ahajournals.org/cgi/content/full/30/5/963/F1
http://www.ottobock.com/cps/rde/xchg/ob_us_en/hs.xsl/15708.html
http://mywellcare.ca/physiotherapy/tens_units
http://injuryexplained.com/frozenshoulder.html
http://www.inmotionjax.com/exercise/Instability.html