Variable Assist Functionality for Indego Exoskeleton

Variable Assist Functionality for Indego Exoskeleton ParkerMany individuals with spinal cord injury (SCI) require full or partial external support of their legs to be able to walk (i.e. using external bracing or neuroprosthetics, or manual facilitation). Exoskeletons may provide an alternative approach to traditional neurorehabilitation techniques. The Indego exoskeleton is able to provide full (100%) robotic assistance throughout the gait cycle for those who need it, and less assistance for those who do not. 

As a physical therapist working with individuals with SCI, Indego’s Variable Assist feature gives me the ability to modulate the level of powered assistance given to my patients. Variable Assist allows me to increase or decrease the level of assistance given by 10% increments at the left and right, hip and knee joints all independently of one another. This customization means that while Indego can replace lost mobility for some, it may also help restore or improve impaired mobility for others. 

Variable Assist for Rehab 

Many patients present with preserved lower extremity function after a spinal cord injury. An estimated 67% of all those with SCI present with some level of incompleteness (sensory or motor function below the level of injury) (National Spinal Cord Injury Statistical Center 2020). For those with motor incomplete injuries (ASIA Impairment Scale C or D) at admission, 71% - 100% can be expected to regain community ambulation, with or without use of lower extremity orthotics, at 1 year post-injury (Scivoletto 2014). Locomotor training, including use of Indego, could potentially help these individuals regain walking function more quickly and efficiently, and with improved gait patterns. 

Additionally, many individuals with complete injuries, like those with low thoracic or high lumbar levels of paraplegia, may also have preserved proximal lower extremity musculature (i.e. hip flexor and/or quadriceps function). Depending on the location of the injury and extent of muscle preservation, locomotor training using Indego may help them to regain some walking function, or could simply help improve their functional mobility (i.e. transfers). 

Using the Variable Assist feature, I can adjust Indego to suit each patient’s unique clinical presentation in order to: 

  1. Challenge the patient, and encourage him or her to use more of their available musculature (trunk or leg) in order to walk. With 100% Indego assistance, patients do not have to contribute their own muscle function in order to walk. While 100% assistance may be beneficial when initially learning how to use Indego, decreasing the amount of assistance at a particular joint can facilitate strength and functional gains outside of Indego.
  2. Provide a cardiovascular workout. Decreasing the level of assistance from the Indego requires the patient to work harder, which increases the cardiovascular and muscular demands to maintain the quality and/or speed of the gait pattern. 
  3. Decrease the “robotic feel.” Many individuals with SCI who have preserved lower extremity function may feel too restricted by the device at 100% Variable Assist. Decreasing the level of robotic assistance may make walking in Indego feel more “normal” and less automated as the patient takes over volitional control and contributes more to the gait pattern. 
  4. Allow the patient to make errors in a safe and controlled manner. Error detection and correction has been shown to facilitate improved motor learning and carryover (Chisholm 2015; Lam 2006; Marchal-Crespo 2013). 

Variable Assist at Home Variable Assist Functionality for Indego Exoskeleton Parker

Individuals with paraplegia who purchase Indego for home use may also benefit from the Variable Assist feature. 

As a non-spinal cord injured individual, it takes very little effort for me to walk in my home or community. Likewise, Indego Users with preserved lower extremity muscle function may keep the Variable Assist level higher to avoid fatigue during casual walking around their home or community.

However, when I go to the gym, I want to challenge myself and get a good cardiovascular workout. Similarly, Indego Users may lower the Variable Assist to achieve a cardiovascular workout when the goal is exercise, rather than casual mobility. Decreasing the level of robotic assistance provides Users with greater challenges, and as such, is usually tolerated for much shorter durations. 

Variable Assist Considerations 

While Indego’s Variable Assist feature can be extremely beneficial for many, it must be used wisely and with discretion. Since decreasing levels of Variable Assist affects both flexion and extension moments surrounding each joint, some individuals may not tolerate changes in assist levels over extended amounts of time due to muscle fatigue. 

For example, a patient who presented to our facility with weak hip flexor preservation (2/5 MMT) and no hip extensor preservation (0/5 MMT) could tolerate walking short bouts at 20% Variable Assist at bilateral hips. However, when he attempted walking for longer durations he noticed an increase in abdominal fatigue and low back pain due to the decreased hip extension stability in stance provided at 20% Variable Assist. If this patient sought purchase of Indego, I would recommend that he maintain a much higher level of variable assistance at his hips for general walking, with the freedom to decrease Variable Assist for short durations of exercise. 

Variable Assist Functionality for Indego Exoskeleton ParkerConclusion 

Indego’s Variable Assist feature provides clinicians, patients, and home Indego users with multiple options for adjusting levels of robotic assist to meet his or her individual goals. Using this feature within the clinical plan of care may help facilitate return to walking function for those with lower extremity preservation after spinal cord injury. Additionally, this feature will likely present unique opportunities in the future when used with other neurological diagnoses affecting the lower extremities, like stroke, traumatic brain injuries, multiple sclerosis, and others. 

 

 

 

Variable Assist Functionality for Indego Exoskeleton ParkerCasey Kandilakis, PT, DPT, NCS is a clinical research scientist at Shepherd Center in Atlanta, Georgia.  Casey received her Bachelor of Science in Exercise Science from the University of Tennessee in 2007, and her Doctorate of Physical Therapy from East Tennessee State University in 2010.  Since that time, Casey has worked in the field of neurological rehabilitation and research, and has lectured at numerous national and international conferences on the use of advanced technologies in rehabilitation and the translation of research into feasible clinical practice.  She became a certified neurologic clinical specialist (NCS) in 2014.  Her current research focuses on the use of advanced technologies and exoskeletons with individuals who have lower extremity deficits due to neurological injury or disease.  Additionally, Casey is a Certified Indego Instructor, and has taught and lectured about Indego to clinicians around the world.

References 

  1. Lam T, Anderschitz M, Dietz V. Contribution of feedback and feedforward strategies to locomotor adaptations. J Neurophysiol. 2006;95:766–773. 
  2. Marchal-Crespo L, Schneider J, Jaeger L, Riener R. Learning a locomotor task: with or without errors? Journal of Neuroengineering and Rehabilitation. 2014;11(25):1-10. 
  3. National Spinal Cord Injury Statistical Center, Facts and Figures at a Glance. Birmingham, AL: University of Alabama at Birmingham, 2020. 
  4. Scivoletto G, Tamburella F, Laurenza L, Torre M, Molinari M. Who is going to walk? A Review of the factors influencing walking recovery after spinal cord injury. Frontiers in Human Neuroscience. March 2014;141(8):1- 11. 

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