Tag Archives: paralysis

A Second Chance: Robotic Exoskeletons May Be the Future of Mobility for Patients with Spinal Cord Injuries

No one ever imagines themselves getting seriously injured. Accidents do happen though, like car crashes and unexpected sports injuries. These events can drastically change a person’s life, leaving them unable to perform simple daily tasks without assistance, such as walking. One injury that can radically impact a person’s life is a spinal cord injury. There are approximately a quarter of a million people in the United States with spinal cord injuries, and that number grows by 12,500 each year.

The spine is the center of support in the body. It adds structure and facilitates movement. Its other extremely important job is to protect the spinal cord, which is a column of nerves that runs down the length of the neck and back. The spinal cord is part of the nervous system, and it acts as a messenger, taking orders from the brain and relaying these messages to the rest of the body, telling the muscles what to do. If the spinal cord is injured, the messages can’t be delivered properly. This often results in a loss of mobility.

Diagram of the central and peripheral nervous system showing how the spinal cord connects the brain to nerves that run throughout the body
From OpenStax Anatomy and Physiology on Wikimedia Commons

Most people don’t think about the mechanics involved in the simple act of walking. However, in order to walk, various joints such as the hip, knee, and ankle need to work together, rotating and bearing loads to allow for movement. When your foot hits the ground, the ground imparts a force through the foot which is translated up through the lower extremities to the spine. When a spinal cord injury occurs, the brain is unable to communicate with our muscles which inhibits this load bearing and the resulting movement.

Studies have shown that powered exoskeletons have numerous benefits for patients with spinal cord injuries to help with walking and mobility. These powered exoskeletons are built in various ways to bear loads and encourage movement, and a review of different exoskeletons, along with other rehabilitation devices, discusses differences in design and control of the systems. For example, to allow for control of movement, one exoskeleton was built with motors located at the joints while another was designed with a braking system at the joints.

Photo of the Indego powered exoskeleton
Indego Exoskeleton – From Indego.com

One study researched mobility outcomes for patients with injuries that varied in severity and location on the spine. Some patients were paraplegic, which means their lower extremities were paralyzed, and some patients were tetraplegic/quadriplegic, which means the paralysis affected both their lower and upper extremities. Also, some patients had complete spinal cord injuries, which means all feeling was lost below the injury, while others had incomplete spinal cord injuries, which means they had some feeling and some ability to control movement below the injury. This study showed that powered exoskeletons, specifically the Indego exoskeleton, could help a patient move in both indoor and outdoor settings, and there is potential for patients with paraplegia caused by injuries to the lower spine to use this device to allow greater ease of mobility in public spaces. For patients with more severe injuries, such as those with quadriplegia, the powered exoskeleton allowed for slower movement with supervision and occasional assistance from a therapist. These patients also needed assistance with putting on and removing the device. Therefore, the powered exoskeleton won’t help patients with more severe injuries move on their own in public settings, but it was excellent for exercise and rehabilitation.

These exoskeletons are also proven to be safe and feasible. Patients with complete spinal cord injuries did not report discomfort or injury, and they were able to use a powered exoskeleton more easily than previous rehabilitation technology.

Powered exoskeletons may be the future of movement for those who thought they would never walk again. This further reading contains examples of paraplegics who walked using a powered exoskeleton. Another man even walked marathons using one of these devices:

From Freethink on YouTube

There are limitations on these devices, but the robotics field is swiftly evolving, and the technology is giving patients something they never thought they would have: a second chance.

Put One Foot in Front of the Other? It’s Not that Easy

From Christmas movies to pop songs to motivational posters, we are encouraged to keep putting “one foot in front of the other.” While the sentiment is inspiring, recent studies show that there is a lot more to the seemingly simple task of walking than this phrase would suggest. Understanding this is especially important for balance and mobility after an injury or as people age.

The steps that make up the human walking cycle. Order of steps: heel-strike right, toe-off left, midstance right, heel-strike left, toe-off right, midstance left, hell-strike right. The body spends the time between heel-strike and toe-off with double support and the midstances are single-leg support.

Image from Wikimedia Commons

The human gait has a set structure that switches the weight between each leg, with only 20% of the typical walking motion distributing the weight across both feet. Maintaining balance throughout this process requires coordination in the muscles controlling the hips, knees, ankles, and feet. Mechanically, these adjustments keep the body’s center of mass (also known as center of gravity) over the base formed by feet positioning.

Obstacles and challenges to balance require a body’s quick response to mitigate shifts in the acceleration and momentum at the center of mass. Lack of efficient control over these parameters results in a fall. Many conditions, as well as age, can affect a person’s ability to respond to mobility challenges.

One specific study looked at how people who had had a stroke and subsequent partial paralysis on one side (paresis) faced mobility challenges compared with healthy folks. This condition effects approximately 400,000-500,000 people in the United States annually. It presents a unique opportunity to compare an individual’s non-damaged stride with their deficient stride at the point in the gait at which only one leg is on the ground (SLS, or single-leg-stride). The timing of the gait, the body’s momentum in all three planes of the body, and the location of the center of mass were recorded in this study.

Anatomical planes of the body. The sagittal plane splits the body left and right. The coronal plane splits the body forward and back. The transverse plane splits the body top and bottom.
Image from Wikimedia Commons

Versus healthy people, stroke survivors had significant trouble regulating momentum in the coronal plane, making falls more likely. Although it makes sense that momentum regulation suffers when muscles are paretic, it is yet unclear why the coronal plane was most affected. Additionally, post-stroke individuals’ centers of gravity were higher, which is also linked to instability. For stroke survivors, the partially paralyzed SLS took longer and extended farther from the center of mass than the regular SLS. While this is not as immediately dangerous as increasing falling risk, it slows mobility, unevenly works muscles (which can lead to injury), and is less efficient.

Going forward, these findings can be used to improve mobility success in people with balance issues or after injuries. This could manifest in better technologies, such as walkers that better help settle a person’s center of mass and partial exoskeletons that would help a person mitigate acceleration and momentum changes, or more targeted and individualistic physical therapies to strengthen weakened muscles and practice patient-specific challenges, such as overcoming obstacles that threaten coronal-plane balance. Understanding more about balance adjustment when walking may make some common phrases trite, but its potential benefits have life-changing impacts for many.

Further Reading and Sources:

Stroke/Paresis Information

Stability of Stepping

Medical Marvel: Robotic exoskeletons enable those with spinal cord injury to walk again

Claire Lomas surrounded by supporters as she walks the 2012 London Marathon
Lulu Kyriacou [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
A fall off of her horse in 2007 caused Claire Lomas to lose all function in her legs. In 2012, she completed the London Marathon, all 26.2 miles. Robotic exoskeletons can literally get people back on their feet shortly after a spinal cord injury occurs, but how exactly do these medical devices not only supplement but restore human performance? What does the future look like for robotic exoskeletons and those with paralysis?

There are approximately 300,000 people living with SCI in the United States, with 17,700 affected annually. So what exactly is a spinal cord injury? A spinal cord injury occurs when trauma, disease, or compression due to tumors causes damage to your spinal cord, which is responsible for your body’s motor functions (voluntary muscle movements), sensory functions (what you feel, such as temperature, pressure and pain), and autonomous functions (your heart beat, body temperature regulation, or digestion). Injuries are classified as complete or incomplete, with complete corresponding to a total loss of function or sensory feedback in areas of the body which are lower than the injury level.

Image showing the area of injury corresponding to the resulting level of paralysis
http://www.living-with-attendant-care.info/Content/Spinal_Cord_Injury_c_Understanding_spinal_cord_injury.html

Studies have shown that people with spinal cord injury, specifically individuals with paraplegia-paralysis who retain function of their upper limbs, prioritize walking as the main function they wish to regain. Robotic exoskeletons, which operate in collaboration with the user to reinforce and retrain certain functions, may be the answer to this pressing need. An exoskeleton  facilitates untethered step repetitions and evenly redistributes the user’s weight to his or her core, minimizing stress on the user’s back, neck, and shoulder muscles. One study testing the exoskeleton from Ekso Bionics also showed an improvement in unassisted balance, since the device only initiates the next step if the user properly shifts his or her weight. Though primarily used for gait or mobility training in rehabilitation facilities, these devices are on their way to becoming everyday mobility aids for people with paralysis.

Rehabilitation for spinal cord injuries is long and tedious. Robotic exoskeletons enable patients to begin rehabilitation early after injury, which helps to prevent joint contracture (which is a limit in a joint’s range of motion, preserve muscle memory and strength, retain bone density, and ensure proper functioning of the digestive and respiratory systems). Humans are meant to be vertical and active, so just the act of standing reduces spasticity (perpetual muscle contraction) and pain, decreases the risk of pressure ulcers or osteoporosis from sitting or laying down for extended periods, and improves bowel and bladder functioning. Moreover, the ability to stand at eye-level and walk again reduces instances of depression.

Despite all of these benefits, current models aren’t perfect yet. The energy demand to operate the devices and consequential fatigue of the user limits long-term use, which restricts use outside of therapy. When people hear exoskeleton, images of Marvel’s Iron Man or soldiers carrying heavy packs come to mind. The advance of robotic exoskeletons may expand their use beyond rehabilitation facilities, allowing them to become integrated into everyday life.