Many wheelchair casters simply aren’t designed and constructed with enough strength and durability to stand up to daily use, according to research published last year.
This news likely won’t come as a surprise to many readers who have had their own experiences with caster disaster—little wheels causing big problems that range from bumps and bruises to costly repairs and lengthy periods waiting for their rides to be repaired. But what might be a surprise is how widespread the problem is.
It’s true that casters have a difficult job. By necessity, they have to be small, which in itself limits their strength, and their pivoting function also introduces weak points in their design. All of this means they have nowhere near the strength and durability of your ride’s main wheels when it comes to absorbing the impact of the countless bumps, curbs, rocks and other obstacles you encounter in your daily life. But after analyzing this new research, we believe it’s clear that casters can be designed and built better.
The study was conducted at the University of Pittsburgh’s Rehabilitation Engineering Research Center on Improving Health and Function Through Use of Performance Standards in Wheelchair Selection. (Thankfully, there is no acronym for this slightly unwieldy name.) The researchers pored through data from the Wheelchair Repair Registry (WRR), a national US database of mobility device failures and repairs, specifically looking at wheelchair caster failures across several wheelchair types and manufacturers. Their results were published in an article titled Community-based wheelchair caster failures call for improvements in quality and increased frequency of preventative maintenance in the journal Spinal Cord, August 19, 2021.
Wheelchair models were sorted into two main groups: manual wheelchairs and power wheelchairs. These were then subdivided into five model types based on user needs for seat functions and supports, and for maneuverability over different terrain.
Wheelchair Types Included In the Caster Study
Manual Wheelchairs
- Tilt-in-space wheelchairs for less active users that require customized seating and positioning support and who may be dependent on caregivers to push the wheelchair
- Ultralight wheelchairs for users who actively self-propel both indoors and outdoors.
Power Wheelchairs
- Models with minimal power seat function and limited use on uneven surfaces
- Models with some power seat functions and frequent use on uneven surfaces
- Models with maximal power seat function and maneuverability on outdoor terrain.
Failures were categorized as either high-risk or low risk. High-risk failures had the potential for damage to the wheelchair and risk of injury for the user, and included caster wheel fractures and bent parts. Low risk failures included bearing failure and worn-out tires, which have less potential for further equipment damage or personal injury.
The researchers determined the total number of failures, and then broke this down by the failure types and the number of failures for each model type. They found that, between January 2017 and October 2019, the WRR had 6,470 total caster failure entries, which confirmed earlier research demonstrating that these types of breakdowns represent more than a quarter of all wheelchair failures. Of the high-risk caster failures, most occurred in just one to two years of wheelchair use across model types.
“These study findings call for urgent improvements in caster quality,” wrote the authors in the published study, adding that standardization of caster quality would help bring about this change. In fact, the authors, along with other University of Pittsburgh colleagues, are leading development of this standardization. They have built a caster testing machine for the International Society of Wheelchair Professionals (ISWP) and developed the ISO 7176-32 Caster Standard to improve caster quality and prevent high-risk failures and adverse consequences.
“Adoption of the ISO 7176-32 by the FDA and other national bodies will further enforce caster standard testing and quality improvement,” says the study’s lead author, Dr. Anand Mhatre, an assistant professor at the University of Pittsburgh’s Department of Rehabilitation Science & Technology.
Additionally, the study revealed that some manufacturers’ wheelchairs clearly had significantly more failures than those of other manufacturers. Not only that, higher failure rates were seen in specific models. However, all manufacturers were anonymized in the published study, so it’s impossible for consumers to benefit from this finding. It does, however, clearly illustrate that not all casters are built the same, adding to the rationale for clear industry standards.
While it might benefit stakeholders— particular end users—to know which manufacturers are doing a good job and which are not, Mhatre says that it would be counterproductive in terms of the effort to have widespread adoption of standards for caster construction.
“Given how research on failures is positioned— capabilities versus limitations and our ongoing work with manufacturers— we don’t see the benefit in disclosing manufacturers,” he explains. “Our testing facility provides testing services to manufacturers who plan to improve caster quality or test new designs. Other developments in areas of maintenance, selection, and user training can prevent the high-risk failures. More importantly, I would like to join hands with manufacturers and stakeholders to improve user safety and device experience.”
Breaking down the various categories, wheelchair models which were used by people with more complex needs and seating support were more likely to experience high-risk caster failure. For manual wheelchairs, tilt-in-space wheelchairs had nearly double the percentage of high-risk failures compared to ultralight wheelchairs. For power wheelchairs, high-risk failures for the most complex models were 36 percent higher than the most basic models.
“These trends suggest that users who require a higher level of seating support and have complex rehabilitation needs are at a greater risk of experiencing caster failures that can cause user injury and other adverse consequences,” wrote the authors.
On a positive note, the researchers were able to determine that regular preventative maintenance decreased incidence of high-risk failures. They also wrote that they believe that maximizing the wheelchair skills of the users, such as how to best negotiate curbs and road bumps, may prolong the life of casters.
“User education on skills and maintenance can prolong the survival of casters and wheelchair parts and prevent failures,” they wrote.
Besides upgrading your maintenance and wheeling skills, and avoiding terrain or harsh conditions that your wheelchair isn’t designed for, what else can you do to avoid caster disaster?
We suggest playing an active role when you’re seeking a prescription for or buying a new wheelchair. Make sure your occupational therapist or mobility provider is up to speed when it comes to caster problems, and ask them to recommend models offering the most reliable casters. Learn to do preventative maintenance if you’re capable, or ask your mobility provider to inspect and service casters during other repairs. And if you do have a caster disaster, consider asking your mobility provider if there are better, stronger aftermarket products available for your ride instead of replacing the same casters that originally came with it.
This article was originally published in the Spring 2022 issue of The Spin. Read more stories from this issue, including:
- Adaptive Mountain Biking
- Bodybuilding
- Breathing Techniques
- Nerve Regrowth Research
And more!
