A Deep Dive Into Our New Footrest Design

My name is Evan O’Brien, and I have been volunteering at Kyaro Assistive Tech for the past 12 weeks. I am an undergraduate student of kinesiology with a focus in physical therapy at Oregon State University. My role as a volunteer includes providing another set of medically trained eyes to the Kyaro team when we perform deliveries, fittings, and assessments.

In my time volunteering I have noticed a surprisingly high number of users with significant lower limb asymmetries, meaning their legs are of different lengths or at different angles. This makes it much harder to fit someone for a wheelchair because no standard footrest will fit them. In this post, I hope to provide some interesting insight on why leg asymmetry can be a problem, and how Kyaro has gone about addressing this.

Definitions

Asymmetries can be caused by someone’s bones being different lengths on each side of their body, over or underdeveloped muscles, differences in joint mobility and/or stability, and a host of other potential disparities. Some of the more common reasons for asymmetries I’ve seen in the past few weeks include loss of range of motion (also called a contracture) in a joint due to lack of access to therapy and assistive devices, untreated injuries resulting in a difference in limb length, and birth defects. 

While slight asymmetries are common and relatively harmless, significant asymmetries can negatively impact a person’s health, usually by increasing pressure sore incidence, decreasing postural quality, and contributing to the development of joint contractures.

Pressure Sores

Pressure sores are injuries that develop from prolonged pressure applied to the skin which causes damage to both the skin and underlying tissue. They are one of the greatest dangers, and most common complications, for wheelchair users without feeling in their lower body. Pressure sores can range from mild skin irritation to a bone-deep open wound.                                                                                            

If you’re sitting down, take a moment to feel where your body is bearing your weight. If you’re on a hard surface, you may be able to feel two points of increased pressure near the lowest part of your buttocks. These are colloquially referred to as “sit bones”. You may also notice a sense of increased pressure at the point where your thighs meet the edge of your chair, particularly if the chair is hard and too tall for your calves or too short for your thighs. If your chair is too short, you might feel increased pressure in your feet and high up the back of your thigh and buttocks as your lower thighs are pushed up and are no longer in contact with the chair. If you have feeling in your lower body, you probably adjust your posture automatically and constantly to keep these pressures from hurting you. Now imagine that you are forced to sit in a chair that does not fit you for ten hours a day, every day, before lying down to go to sleep. These points of increased pressure slowly become unbearable as the pressure applied by the weight of your own body kills skin, muscle, and nerve cells which, if untreated, eventually rot away and leave an open wound. 

Pressure sores are particularly prevalent in populations with neurological damage that can result in difficulty walking and lack of sensation such as cerebral palsy, hydrocephalus, and spina bifida. These populations cannot alleviate pressure with the same ease as someone without neurological damage and often can’t notice when pressure reaches a dangerous level. This means pressure sores can develop and worsen without their knowledge. If you cannot move your body and disperse pressure, it is very important that whatever you are sitting on disperses pressure as evenly as possible, hence the effort Kyaro puts into wheelchair cushions and fitting.  

Poorly made or fitted wheelchairs increase pressure sore incidence because they don’t disperse the user’s weight well. This is usually because the wheelchairs are not designed for the user's dimensions and/or the shape of the chair and materials it is made of do not allow the human body to disperse pressure evenly across the bottom of the thighs, buttocks, and back. This is why we measure each individual who orders a wheelchair and make cushions with layers of foam to disperse pressure. 

People with lower limb asymmetry are at even higher risk of pressure sores because the asymmetry can force them to place most of their weight on one side of their body. If a wheelchair's footrest is measured for the longer leg, the shorter leg's foot is left to dangle in space. This increases pressure at the far end of the thigh as it hangs off the edge of the seat. If the footrest is instead measured for the shorter leg, the longer leg is now forced to flex at the hip and knee to compensate for its length. This pushes the underside of the lower thigh up and off the seat, increasing pressure at the foot and underside of the upper thigh and buttock.

Contractures

Joint contractures are when an individual loses mobility at a joint because it is immobilized for a long time, and they are a significant concern to many people with disabilities. Mobility decreases because the body adapts to its new position. The protein that makes up tendons and ligaments becomes unorganized and stiff, muscle fibers that are not being used are consumed, and the production of fluid meant to lubricate the joint decreases. Some of these changes can begin to occur as soon as 24 hours after immobilization and many are functionally permanent if allowed to progress. Moving the joint, either alone or with the help of a caregiver, is critical to preventing the progression of joint contracture.

Lower limb asymmetries, when combined with neurological disorders limiting mobility, can result in asymmetrical contractures when assistive devices provided to the user do not accommodate the asymmetries. Different leg lengths change the resting angles of the hip, knee, and ankle. These changes move the joints away from their most ideal angles and can become permanent if contracture progresses. This permanent reduction in range of motion can radically impact a person’s progress in physical therapy and reduce their quality of life.

Contractures are painful and can change the way that clothes or shoes fit, the user's ability to stand or walk, their ability to transfer into and out of their chair, their ability to use the bathroom, and so many other aspects of daily life. Contractures are far-reaching in their consequences and incredibly difficult to correct, so prevention is key.

Asymmetrical footrests can ensure that whatever biological asymmetries exist in the user are not made worse by contractures. Ensuring an assistive device matches a user’s needs ensures that minimal deterioration of their health occurs and their comfort, quality of life, and health are preserved.

Adapting to Progression/Regression

The human body can change drastically over time. In the context of wheelchair users, the change can generally be defined as positive or negative.

Positive improvement includes the reduction of unwanted symptoms due to surgery and/or physical therapy while negative changes are the worsening of preexisting symptoms or the development of new symptoms due to contracture, muscle atrophy, and/or increased pain. I have visited users with improper devices, taken measurements, and returned a month later with their newly made chair only to find that their condition has deteriorated to the point that adjustments to the chair must be made to accommodate their worsened, or brand new, contractures and posture. Unfortunately, most people with disabilities in Tanzania do not get physical therapy.

When those users make progress, having an assistive device that cannot change with them can impact their health and slow or revert progress. For both of these reasons, having a footrest capable of adjusting to the user's changing body is critical to both preventing deterioration and ensuring positive change is maintained.

You will notice that each of these issues is dependent on the user's wheelchair having one footrest for both of their feet, like our current, standard design.

To be able to get a truly appropriate wheelchair to the people who I was encountering with asymmetries, we needed to design a new footrest.

The new design

With some help from myself and the other clinically trained members of the Kyaro team, the shop staff were able to design a new footrest that addresses each of the problems I’ve discussed above. The new design splits the footrest into two separate parts, which are attached to vertical pipes. Each foot can independently slide up and down on the pipes, and the pipes can be mounted to the wheelchair frame at different angles.

With this footrest, we can properly help users with amazing diversity in their leg shape.

You can see how this new option fits in with all the other customization options for our wheelchairs here, in our configuration tool!

I hope this look into how wheelchairs, bodies, and health interact was interesting. This footrest design is one part of a long journey to design a wheelchair that can truly accommodate the needs of any person, and we look forward to sharing the other steps in this journey as we continue.