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Walking after an incomplete spinal cord injury using an implanted functional electrical stimulation system

Posted on 6th March 2014 by Mandi McCoy

Evidence Reviews
assisted walking

Introduction:

The number of incomplete spinal cord injuries (in regards to complete) have increased secondary to improved early care and safety features in motor vehicles.  Although an incomplete spinal cord injuries (SCI) are usually less severe, the impact on the individual’s function and participation are still limited. The use of functional electrical stimulation (FES) (use of electrical stimulation through electrodes to elicit a muscle contraction) has been used to improve health and independence in persons with paraplegia by improving the cardiovascular fitness, decreasing the risk of diabetes and even the risk of osteoporosis. However, the use of surface and percutaneous electrodes become impractical and inconvenient for long-term use in functional ambulation secondary to the amount of leads and channels needed. Unlike surface electrodes, fully implanted electrodes are more practical in the long-term functional use as well as offer cosmetic benefits and reliability. This article addresses the functional and therapeutic effects of an implanted FES system on walking after an incomplete SCI.

Hardin E, Kobetic R, Murray L, Corado-Ahmed M, et al. Walking after incomplete spinal cord injury using an implanted FES system: A case report. JRRD. 2007; 44(3): 333-346.

What did the article look at?

The purpose of this case report was to quantify the therapeutic and functional effects of an implanted FES system on walking after incomplete cervical SCI. The authors used maximal walking distance as the main outcome, and hypothesised that exercises and gait training with FES would improve voluntary motor control and baseline volitional walking ability and increase the strength, endurance and repeatability of muscle contraction.  The subject was a 22 year old male who acquired an incomplete cervical SCI 18 months ago and was able to stand with an assistive device but unable to initiate a step with either leg. The subject participate in a 26 week therapy program in which was broken up into the following treatments:

  1. Pre-Implantation: 8 weeks (36 sessions)
  • During these 8 weeks the main goal was to maximize the patient’s voluntary function and response to activity. Patient performed robotic body-weight support treadmill training (BWSTT) with 60% of his body weight and using surface electrode stimulation to initiate and facilitate gait
  • Patient demonstrated increased muscle girth in lower leg (4cm), decrease in number and severity of spasms but did not show improvement in over ground walking and still remained non-ambulator

2.  Implantation: 6 weeks (12 sessions)

  • Prior to implantation, the authors performed a gait analysis to depict the placement of the electrodes based on the use of surface electrical stimulation. The depicted that the intramuscular implanted electrodes to be placed in the following muscles bilaterally: (1) hip musculature to elicit bending at the hip and knee and to increase standing stability  (2) the quadricep muscles to initiate straightening of the leg (3) and on the anterior portion of the lower leg to assist with keeping the toes up during ambulation. An 8-channel receiver was placed subcutaneously in the lower-left quadrant of the abdomen.
  • After 2 week recovery period, the patient then participated in a 4 week progressive exercise program to rebuild strength and tolerance for electrical stimulation and ambulation

3.  Post-Implantation: 12 weeks (36 sessions)

  • Patient participated in 2-3 supervised gait training sessions per week. Initially the gait training consisted of both BWSTT (using the minimum amount of support required for the patient to achieve the highest quality gait with a target of less than 30%) and over ground walking with patterns of electrical stimulation individualised to the patient’s abilities. After completing 2 sessions of combined gait training, the patient was then progressed to only over ground gait training. Electrical stimulation was activated by the patient via finger and hand triggers, in which there were over 5 switches for each step and part of the gait cycle that the patient was trained to use properly and efficiently
  • Along with supervised gait training, the patient also performed a daily exercise routine at home consisting of patterns of stimulation for strengthening and building endurance.

How did they measure outcomes?

Data was collected at pre- and post-implantation as well as some data was collected at 6 weeks after post-implantation to assess progress. The authors used multiple outcome measures to help quantify the therapeutic and functional effects of implanted FES system, including the following:

  • Isokinetic Dynamometer: for quadriceps muscle contractions to measure strength (volitional, FES alone and combined volitional efforts with FES). Measured pre- and post-implant
  • Seven-Camera Vicon Motion Capturing system: For mechanical gait analysis; performed at week 6 and week 12 after implantation. Gait speed and step length were also measured using this system.
  • Heart Rate, VO2 and Metabolic Equivalents: Measured during the 6 minute walk test before and after exercise and gait training
  • Functional Ambulation Category(FAC) and SCI-Functional Ambulation Inventory (SCI-FAI): used to assess pre- and post-implant walking ability.

What were the results?

After 12 weeks of using an implanted FES system, the participant had shown significant improvements in walking speed (increased from 0.02m/s to 0.20 m/s) moving him from non-ambulatory category to limited independent community ambulator, walking distance (increased from 14m in 11 minutes to 309m in 30minutes) and an increase in FAC score from 0 (no walking ability) to 4 (independent ambulation) as well as an increase in his SCI-FAI score- from 0/20 to 18/20 in gait parameters. Patient demonstrated a decrease in physiological costs secondary to: improved walking VO2, small increase in respiration frequency and tidal volume and decreased resting energy expenditure. However, the patient only showed mild strength improvements, with a majority consisting in distal lower limb muscles.

Were there any limitations?

I have been unable to find the parent article of the ongoing study that this article was based from. I found this to be a very interesting article and am curious as to why I have not heard of implanted FES systems being used more frequently since there was such great results as found by this study. However, I did find that study would be very difficult to reproduce as there is much ambiguity in which protocols and therapeutic procedures were used specifically. There is no specific measures as to how long BWSTT was used (duration) or the duration of over-ground walking. I also would be interested in if there were any accommodation effects to the stimulation that the patient may or may not have had.

What is my preference for treatment?

Much more research needs to be performed and reviewed before I would openly discuss this option with a patient of mine. I would like to see the long-term benefits, any adverse effects with implanted electrodes, reliability over a prolonged period and so forth. However, this article presents great results that would definitely make me more open to the idea for the right candidate in order to assist them in becoming more independent and functional.

Reference:

Hardin E, Kobetic R, Murray L, Corado-Ahmed M, et al. Walking after incomplete spinal cord injury using an implanted FES system: A case report. JRRD. 2007; 44(3): 333-346.

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Mandi McCoy

I am a third year student in the Doctor of Physical Therapy program at Elon University in Elon, North Carolina. My personal physical therapy interests include neurological impairments such as stroke and spinal cord injury rehab. View more posts from Mandi

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