Design and evaluation of a laboratory-based wheelchair castor testing protocol using community data

Power wheelchair usage and repair are associated: a retrospective analysis

Purpose: This study evaluates the effect of power wheelchair telemonitoring and battery charging training on user charging behavior and repair measures and assesses the relationship between wheelchair usage and repair measures to support technician-led servicing.Methods: This is a retrospective analysis of two matched cohorts with a total of n=237 users from the NHS service dataset. In the training cohort, a wheelchair usage telemonitoring device monitored the battery usage of n=119 power wheelchair users for 12 months. Users whose battery charging behavior was not optimal were instructed on appropriate charging practices. Wheelchair usage parameters of wheelchair drive and power time every month were used to predict repairs and associated costs.Results: Fifty-four out of 119 users in the training cohort did not charge batteries regularly and were instructed on appropriate charging. Twenty-six of them changed their behavior and charged their batteries every night. This cohort experienced reduced battery repairs by 18%, wheelchair repairs by 11%, and repair costs by £3,092 compared to a matched standard care cohort (n=118). User age and drive time were associated with repair measures. Drive time predicted time-to-failure for wheelchair parts and classified failure risk with the area under the receiver operating characteristic curve as 0.71 (95% CI 0.61 to 0.82; p<.001). Conclusions: By leveraging the significant relationships between wheelchair usage and repairs, wheelchair users at risk of part failures can be identified, and technician-led servicing tools for proactive interventions can be developed. Wheelchair battery health telemonitoring and instructing users on appropriate battery charging reduced repairs and associated costs.

Community-based wheelchair caster failures call for improvements in quality and increased frequency of preventative maintenance

STUDY DESIGN

Secondary data analysis of wheelchair failures and service repair logs from a network of wheelchair suppliers.

OBJECTIVE

To determine the frequency of wheelchair caster failures and service repairs across wheelchair manufacturers and models and investigate the relationships between them.

SETTING

Wheelchair caster failures and service repairs occurred in the community.

METHODS

Reported caster failure types were classified based on the risk they pose for user injuries and wheelchair damage. Caster failures experienced by users of tilt-in-space and ultralightweight manual wheelchair models and Group 2, 3 and 4 power wheelchair models between January 2017 and October 2019 were analyzed using Chi-Square tests for independence. Correlational analysis of failures and service repairs was performed.

RESULTS

A total of 6470 failures and 151 service repairs reported across four manufacturers and five models were analyzed. Failure types were significantly associated with manufacturers and models, respectively. Users of tilt-in-space wheelchairs, who require greater seating support, experienced twice the proportion of high-risk caster failures than the ultralightweight manual wheelchair users. Similarly, Group 3 and 4 power wheelchair users, who have complex rehabilitation needs, experienced 15-36% more high-risk failures than Group 2 users. Service repairs negatively correlated with high-risk manual wheelchair caster failures.

CONCLUSIONS

Wheelchair users who have greater seating and complex rehabilitation needs are at a higher risk for sustaining injuries and secondary health complications due to frequent caster failures. The study findings call for significant reforms in product quality and preventative maintenance practices that can reduce wheelchair failures and user consequences.

Accelerated wear testing shows that thermoplastic bushings could be a cost-effective and durable alternative to traditional bearings for wheelchair caster use

Introduction

Wheelchair caster bearings often suffer high-risk failures that lead to adverse consequences such as user injuries, suggesting that design improvements are necessary. This study aimed to compare thermoplastic bushings to standard roller bearings for potential improvements in durability and cost-effectiveness.

Methods

The durability and cost-effectiveness of two thermoplastic bushing models and two metallic ball-bearing models were tested using a standard lab-based accelerated wear testing protocol. Bushings and bearings were installed on a standard 8″ caster, and four samples per model underwent testing (16 total samples).

Results

All failures were experienced by the stem rolling element. The thermoplastic bushings experienced higher mean durability than the standard ball-bearings. There were significant differences in durability across the tested models, F(3,12) = 3.88, p = 0.04. The durability of thermoplastic bushing #2 was higher than the standard type ZZ shielded deep groove ball bearings, p < 0.05. There were significant differences in cost-effectiveness across the tested models, F(3,12) = 7.64, p = 0.004. The cost-effectiveness of both thermoplastic bushings were significantly higher compared to type 2RS sealed deep groove bearings, p < 0.05.

Conclusions

The use of thermoplastic bushings can lower product cost and potentially reduce caster failures in the community that are associated with adverse consequences including user injuries.

Rolling resistance of casters increases significantly after two years of simulated use

Introduction

Manual wheelchair propulsion is associated with upper limb pain and injury, and clinical guidelines recommend minimizing propulsive force to lower health risks. One of the strategies to reduce propulsive force is by minimizing rolling resistance (RR). Product testing studies suggest that RR of casters is affected by wear and tear which could have implications on the health risk of wheelchair users. The study will investigate the relationship between caster RR and environmental exposure using standard testing protocols.

Methods

RR of ten casters representing a range of diameters for different models of wheelchairs were measured before and after environmental exposure that includes corrosion, shock and abrasion simulating two years of community use.

Results

Four casters exhibited failures during durability testing, one catastrophically. Increases to RR after corrosion, shock and abrasion exposure were statistically significant using mixed-effects modeling, and four casters had increased RR greater than 20%.

Conclusions

Many of the casters evaluated exhibited increased RR forces and failure after environmental exposure. Improved caster design and use of corrosion resistant materials may reduce these failures. In addition, modification of the provision process could include replacement casters to reduce failures and avoid breakdowns that leave manual wheelchair users stranded or injured.