Performance of selected lightweight wheelchairs on ANSI/RESNA tests. American National Standards Institute-Rehabilitation Engineering and Assistive Technology Society of North America

Design refinement and evaluation of a mobile manual standing wheelchair

PURPOSE

There are no manually propelled wheelchairs on the market that are mobile in both seated and standing positions. In response to this product gap, our group formerly designed a mobile manual standing wheelchair (MMSW) and gathered stakeholder feedback. The purpose of this study was to refine the MMSW based on feedback, including weight and width reduction, and evaluate its performance.

MATERIALS AND METHODS

The MMSW was subjected to ANSI/RESNA stability testing, and three male participants completed a subset of the wheelchair skills test, including a 100-m roll test in the MMSW (seated and standing) and in their ultralight wheelchair.

RESULTS

The MMSW met ANSI/RESNA stability safety standards. During the 100-m roll test, participants reached speeds with the MMSW in both the standing and sitting postures similar or greater than those typical of moving in the home environment (1.11 m/s seated; 0.79 m/s standing). Mobility speeds in the MMSW in the standing position were about three times faster than average walking speeds in exoskeletons (0.26 m/s exoskeletons). With the addition of chain drive bracing to the MMSW, one user was able to reach speeds in the standing position similar to average neurotypical walking speeds indicating the possibility for wheelchair users to be able to move in pace with family and friends.

CONCLUSION

All participants expressed interest in the MMSW to facilitate improved quality of life. Further work is needed to test the utility of the MMSW in home and community settings, and its potential effects on standing time and health outcomes.Implications for rehabilitationManual standing wheelchairs with standing mobility may increase functional utility and length of standing time for manual wheelchair usersIncreased standing time may lead to several health benefits for manual wheelchair users.

Economic evaluation of wheelchairs interventions: a systematic review

OBJECTIVE

The overall aim of this systematic review was to identify and synthesise the best available evidence on effectiveness, resource use and costs involved in wheelchair interventions of adults with mobility limitations.

METHODOLOGY

This systematic review was undertaken in accordance with the Centre for Reviews and Dissemination Guidelines. The protocol for this systematic review was registered with PROSPERO International Prospective Register of Systematic reviews. The following PICOS eligibility criteria were considered: (P) Population was individuals with mobility limitations that live in their community (e.g., non-institutionalized), with aged 18 or older; (I) Intervention was mobility assistive technologies (MAT), such as manual and powered wheelchairs; (C) Comparators (Not Applied); (O) Outcome, the primary outcome of interest, was established as the cost-effectiveness of wheelchair interventions. Direct and indirect costs per unit of effect were expressed in terms of clinical outcome units, quality-adjusted life years gained, utility scores, quality of life measures and incremental cost-effectiveness ratios to inform the economic outcomes. (S) Study design was considered as a health economic evaluation (i.e., including cost-effectiveness analysis, cost-utility analysis and cost benefit analysis as well as partial economic evaluations). The Consolidated Health Economic Evaluation Reporting Standards - CHEERS, checklist was used for summarising and interpreting the results of economic evaluations.

RESULTS

Sixteen studies were included, two were identified as full health economic evaluations and 14 were considered partial health economic evaluations.

CONCLUSION

Only two full health economic analyses of wheelchair interventions have been conducted and both focussed on powered wheelchair provision. There are important gaps in current knowledge regarding wheelchair health economic methods and available outcome measures, which there is a great need for further research.Implication for RehabilitationSystematic reviews of health economic evaluation studies are useful for synthesising economic evidence about health interventions and provide insight in new research development.Organisations involved in the provision of wheelchairs should apply cost-effectiveness outcome measures to help raise the standard of provision, to support evidence-based practice, and to improve resource utilisation.

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.

Factors Influencing Incidence of Wheelchair Repairs and Consequences Among Individuals with Spinal Cord Injury

OBJECTIVE

To investigate the frequency and consequences of wheelchair repairs, looking at the relationship to usage, components, out-of-pocket costs, number of days affecting the user, and factors associated with the need for repairs or consequences.

DESIGN

Survey, cross-sectional.

SETTING

Nine spinal cord injury (SCI) Model Systems centers.

PARTICIPANTS

Wheelchair users with SCI (N=533).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Cost and incidence of wheelchair repairs and consequences and wheelchair usage within the past 6 months.

RESULTS

A total of 310 participants (56%) reported repairs, 127 (42%) of whom experienced at least 1 adverse consequence lasting a median of 5 days (interquartile range [IQR], 2-17.3 days). Repair rates were highest for the seating system, electronics, and tires. Participants were most often stranded at home or forced to use a backup chair. Median out-of-pocket costs were $150 (IQR, $50-$620). Active users, based on type of mobility and terrain, experienced more repairs and consequences than less active users. Repairs were more common among those who were Black (odds ratio [OR], 2.42) or power wheelchair (PWC) users (OR, 1.84), whereas consequences were more common among those who were Black (OR, 2.27), PWC (OR, 2.08) or power assist users (OR, 2.76), and those who had public insurance (OR, 1.70).

CONCLUSIONS

Wheelchair repairs continue to affect more than 50% of wheelchair users with significant financial and personal cost. High repair rates limited participation inside and outside of the home. Consequences lasted longer than 2 weeks for many and may be minimized by a working backup chair. Disparities exist based on participant and wheelchair factors; repairs and adverse consequences appear to hit those most vulnerable with the least financial resources. Costs may be a barrier to repair completion for some individuals. This ongoing problem of high repair rates and their associated effects requires action such as higher standards, access to quicker service, and better training of users on wheelchair maintenance and repair.

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

Wheelchair castors fail frequently causing physical, social and economic consequences for wheelchair users. These failures occur in spite of established wheelchair test methods and regulations, suggesting that the existing tests may not be sufficient to screen poorly designed castors. An expert stakeholder group, convened by the International Society of Wheelchair Professionals (ISWP), noted castor failures as a high priority and recommended that a new castor testing system should be developed. In a previous study, the effect of shock exposure on castor durability was studied. The current paper extends the previous work and focuses on the development of a castor testing protocol based on shock, corrosion and abrasion exposure data collected in the community. The testing protocol was applied to 8 different castor models tested under four conditions: shock, corrosion + shock, abrasion + shock and abrasion + corrosion + shock. For each model, a total of n = 8 samples were evaluated across the four conditions. Results demonstrate that corrosion and abrasion reduced castor durability between 13% to 100% depending on the model. Importantly, the inclusion of corrosion and abrasion resulted in changes in the failure modes for 75% of the tested models and two-thirds of the altered failure modes are associated with increased risk of injury for wheelchair users. These results suggest that corrosion and abrasion present in the community reduce castor durability, thus supporting their inclusion in the castor testing protocol and potentially other wheelchair standards.

Development, reliability, and piloting of a wheelchair caster failure inspection tool (C-FIT)

Introduction: Wheelchair casters fail frequently in the field causing multiple user consequences and wheelchair breakdowns. To inform caster design improvement, there exists no validated tools that can collect caster failures. This need motivated the development of a user-reported, caster failure inspection tool (C-FIT).Methods: To develop C-FIT, a multistep design and testing approach was used which included face validity testing, test-retest reliability testing and expert review. Reliability testing was conducted with two independent cohorts of wheelchair professionals who inspected caster failures physically and online through pictures. The tool was revised based on testing outcomes and expert feedback. For preliminary data collection and evaluating usability, C-FIT was piloted at wheelchair service centers in Scotland, Indonesia and Mexico.Results: Caster failure items reported in the literature were screened to develop the initial list of C-FIT items. Face validity testing conducted through surveys with wheelchair experts (n = 6) provided 14 items for C-FIT inclusion. The test-retest reliability was found to be high for 10 items with physical failure inspections (n = 12). For each of these items, 75% or more participants had substantial to almost perfect agreement scores (κ = 0.6-1.0). Lower reliability scores were found with online failure inspections (n = 11). C-FIT received positive usability feedback from study participants and data collectors in the field. Pilot field data (n = 31) included comprehensive details about failures useful for manufacturers, designers and researchers to improve caster designs.Conclusions: The C-FIT tool developed in this study has substantial reliability and can be used for documenting caster failures at wheelchair service centers.Implications for rehabilitationCollecting data on caster failures is an important first step to inform design improvements and caster quality testing methods.The caster failure inspection tool is a reliable tool that can be used during wheelchair repair and servicing to collect caster failures in a standardized way.The failure data can be used by wheelchair manufacturers, designers, technicians and researchers to develop reliable caster designs. Wheelchair providers can select caster designs based on context of use.

Comparison of High-Strength Aluminum Ultralight Wheelchairs Using ANSI/RESNA Testing Standards

Background: The use of ultralight manual wheelchairs has been shown to benefit wheelchair users when compared to other types. New aluminum alloy frame materials coming to the market have not been independently evaluated for durability and cost benefit. Methods: Three 70XX aluminum ultralight wheelchair models were tested and compared based on dimensions, stability, and durability using the ANSI/RESNA standards. The results were also compared to previous manual wheelchair studies. Results: This study found that there were no significant cost benefit or durability differences between the wheelchairs tested and previous aluminum or titanium ultralight rigid models. Additionally, 5 of the 9 wheelchairs tested failed to meet the minimum ANSI/RESNA requirements for durability. Conclusion: These results are similar to results from previous rigid ultralight wheelchair studies and indicate that the quality of wheelchairs of this type has not improved and better requirements are necessary for wheelchairs marketed in the United States.

Development of wheelchair caster testing equipment and preliminary testing of caster models

BACKGROUND

Because of the adverse environmental conditions present in less-resourced environments (LREs), the World Health Organization (WHO) has recommended that specialised wheelchair test methods may need to be developed to support product quality standards in these environments. A group of experts identified caster test methods as a high priority because of their common failure in LREs, and the insufficiency of existing test methods described in the International Organization for Standardization (ISO) Wheelchair Testing Standards (ISO 7176).

OBJECTIVES

To develop and demonstrate the feasibility of a caster system test method.

METHOD

Background literature and expert opinions were collected to identify existing caster test methods, caster failures common in LREs and environmental conditions present in LREs. Several conceptual designs for the caster testing method were developed, and through an iterative process using expert feedback, a final concept and a design were developed and a prototype was fabricated. Feasibility tests were conducted by testing a series of caster systems from wheelchairs used in LREs, and failure modes were recorded and compared to anecdotal reports about field failures.

RESULTS

The new caster testing system was developed and it provides the flexibility to expose caster systems to typical conditions in LREs. Caster failures such as stem bolt fractures, fork fractures, bearing failures and tire cracking occurred during testing trials and are consistent with field failures.

CONCLUSION

The new caster test system has the capability to incorporate necessary test factors that degrade caster quality in LREs. Future work includes developing and validating a testing protocol that results in failure modes common during wheelchair use in LRE.

Developing product quality standards for wheelchairs used in less-resourced environments

BACKGROUND

Premature failures of wheelchairs in less-resourced environments (LREs) may be because of shortcomings in product regulation and quality standards. The standards published by the International Organization for Standardization (ISO) specify wheelchair tests for durability, safety and performance, but their applicability to products used in the rugged conditions of LREs is unclear. Because of this, wheelchair-related guidelines published by the World Health Organization recommended developing more rigorous durability tests for wheelchairs.

OBJECTIVES

This study was performed to identify the additional tests needed for LREs.

METHODS

First, a literature review of the development of ISO test standards, wheelchair standards testing studies and wheelchair evaluations in LREs was performed. Second, expert advice from members of the Standards Working Group of the International Society of Wheelchair Professionals (ISWP) was compiled and reviewed.

RESULTS

A total of 35 articles were included in the literature review. Participation from LREs was not observed in the ISO standards development. As per wheelchair testing study evidence, wheelchair models delivered in LREs did not meet the minimum standards requirement. Multiple part failures and repairs were observed with reviewed field evaluation studies. ISWP experts noted that several testing factors responsible for premature failures with wheelchair parts are not included in the standards and accordingly provided advice for additional test development.

CONCLUSION

The study findings indicate the need to develop a wide range of tests, with specific tests for measuring corrosion resistance of the entire wheelchair, rolling resistance of castors and rear wheels, and durability of whole wheelchair and castor assemblies.

Development of a wheelchair maintenance training programme and questionnaire for clinicians and wheelchair users

Purpose of state: The aims of this study were to develop a Wheelchair Maintenance Training Programme (WMTP) as a tool for clinicians to teach wheelchair users (and caregivers when applicable) in a group setting to perform basic maintenance at home in the USA and to develop a Wheelchair Maintenance Training Questionnaire (WMT-Q) to evaluate wheelchair maintenance knowledge in clinicians, manual and power wheelchair users.

METHODS

The WMTP and WMT-Q were developed through an iterative process.

RESULTS

A convenience sample of clinicians (n = 17), manual wheelchair (n ∞ 5), power wheelchair users (n = 4) and caregivers (n = 4) provided feedback on the training programme. A convenience sample of clinicians (n = 38), manual wheelchair (n = 25), and power wheelchair users (n = 30) answered the WMT-Q throughout different phases of development. The subscores of the WMT-Q achieved a reliability that ranged between ICC(3,1) = 0.48 to ICC(3,1) = 0.89. The WMTP and WMT-Q were implemented with 15 clinicians who received in-person training in the USA using the materials developed and showed a significant increase in all except one of the WMT-Q subscores after the WMTP (p < 0.007).

CONCLUSION

The WMTP will continue to be revised as it is further implemented. The WMT-Q is an acceptable instrument to measure pre- and post-training maintenance knowledge. Implications for Rehabilitation The Wheelchair Maintenance Training Program can be used to educate rehabilitation clinicians and technicians to improve wheelchair service and delivery to end users. This training complements the World Health Organization basic wheelchair service curriculum, which only includes training of the clinicians, but does not include detailed information to train wheelchair users and caregivers. This training program offers a time efficient method for providing education to end users in a group setting that may mitigate adverse consequences resulting from wheelchair breakdown. This training program has significant potential for impact among wheelchair users in areas where access to repair services is limited.

Evidence-Based Strategies for Preserving Mobility for Elderly and Aging Manual Wheelchair Users

Elderly and aging manual wheelchair (MWC) users have increased risk for accelerated loss of function and mobility that greatly limits independence and affects quality of life. This review paper addresses important issues for preserving function and mobility for elderly and aging individuals who use a MWC by presenting the current available evidence and recommendations. These include recommendations for maximizing function, by decreasing pain, improving the ability to self-propel, and prolonging mobility and endurance through ergonomics, individualized wheelchair selection and configuration, and adaptations for increasing the capacity to handle the daily mobility demands through training, strengthening, and exercise. Each recommendation is supported by current research in each relevant area.

Evaluation of lightweight wheelchairs using ANSI/RESNA testing standards

Lightweight wheelchairs are characterized by their low cost and limited range of adjustment. Our study evaluated three different folding lightweight wheelchair models using the American National Standards Institute/Rehabilitation Engineering Society of North America (ANSI/RESNA) standards to see whether quality had improved since the previous data were reported. On the basis of reports of increasing breakdown rates in the community, we hypothesized that the quality of these wheelchairs had declined. Seven of the nine wheelchairs tested failed to pass the multidrum test durability requirements. An average of 194,502 +/- 172,668 equivalent cycles was completed, which is similar to the previous test results and far below the 400,000 minimum required to pass the ANSI/RESNA requirements. This was also significantly worse than the test results for aluminum ultralight folding wheelchairs. Overall, our results uncovered some disturbing issues with these wheelchairs and suggest that manufacturers should put more effort into this category to improve quality. To improve the durability of lightweight wheelchairs, we suggested that stronger regulations be developed that require wheelchairs to be tested by independent and certified test laboratories. We also proposed a wheelchair rating system based on the National Highway Transportation Safety Administration vehicle crash ratings to assist clinicians and end users when comparing the durability of different wheelchairs.

Evaluation of scooters using ANSI/RESNA standards

To date, only one research study has evaluated how scooters respond to static and dynamic stability. However, no other studies have evaluated how scooters respond to adverse conditions and how they perform in all standard tests. A selection of 12 three-wheeled scooters was tested according to American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/ RESNA) wheelchair standards. Scooter models included the Victory, Gogo, Golden Companion (GC) I, and GC II. Victory and GC II were the most stable scooters. The Gogo scooters were the least dynamically stable. Five scooters (3 Gogo, 1 GC I, 1 GC II) failed the environmental condition tests. All GC I and II scooters failed parts of the power and control system tests. All scooters passed static and impact tests; however, all Gogo scooters and one GC II scooter had structural or motor failure during durability tests. The scooter models' survival life ranged from 62,512 to 1,178,230 cycles out of the 400,000 needed to pass the test. Tiller failures (typically tiller tube snapping) occurred with an average of 1,483 N force applied to the tiller structure. Our results indicate that these commercially available devices may not meet ANSI/RESNA standards. In addition, the tiller test should be conducted with scooters to further ensure their safety and durability and should use a test dummy with weight capacity according to the mobility device capacity.

Comparative ergonomic assessment of manual wheelchairs by paraplegic users

PURPOSE

The aim of the present study was to describe and test the reliability of a comprehensive product-centered approach to assessing functional performance and wheelchair user perceptions on device ergonomics and satisfaction of performance. A pilot study was implemented using this approach to evaluate differences among four manual wheelchairs.

METHOD

Six wheelchair users with complete spinal cord injury (SCI) at the thoracic level and with no previous upper limbs impairment were recruited for this study. After finishing circuit tasks, subjects were asked to complete a questionnaire about ergonomic wheelchair characteristics (manoeuvrability, stability, comfort and ease of propulsion) and satisfaction about task performance. On the other hand, objective data were recorded during user performance as the time required to complete each test, kinetic wheelchair propulsion data obtained with two SMARTWheels® and physiological parameters (heart rate and physiological index).

RESULTS

Kuschall Champion® and Otto Bock Voyage® wheelchairs were ranked best for most ergonomic aspects specially in manoeuvrability (p < 0.05). Less time was required to execute most of the circuit tasks in both wheelchair models (p < 0.05).

CONCLUSIONS

This approach proposed highlight the importance of looking both kinds of information, user perception and user functional performance when evaluating a wheelchair or comparing across devices.

Increases in wheelchair breakdowns, repairs, and adverse consequences for people with traumatic spinal cord injury

OBJECTIVE

The aims of this study were to report the current incidence of wheelchair breakdowns, repairs, and consequences and to compare current data with historical data.

DESIGN

A convenience sample survey of 723 participants with spinal cord injury who use a wheelchair for more than 40 hrs/wk treated at a Spinal Cord Injury Model Systems center was conducted.

RESULTS

Significant increases were found in the number of participants reporting repairs (7.8%) and adverse consequences (23.5%) in a 6-mo period (2006-2011) compared with historical data (2004-2006) (P < 0.001). When examining current data, minorities experienced a greater frequency and higher number of reported consequences (P = 0.03). Power wheelchair users reported a higher number of repairs and consequences than did manual wheelchair users (P < 0.001). Wheelchairs equipped with seat functions were associated with a greater frequency of adverse consequences (P = 0.01). Repairs did not vary across funding source, but individuals with wheelchairs provided by Medicare and Medicaid reported a higher frequency of consequences than did the combined group of the Department of Vocational Rehabilitation, Worker's Compensation, and the Veterans Administration (P = 0.034 and P = 0.013, respectively).

CONCLUSIONS

The incidence and consequences of repairs are increasing from what was already a very high statistic in this United States population. Further investigation into causality is required, and intervention is needed to reverse this potential trend.

Effects of wheelchair mass on the physiologic responses, perception of exertion, and performance during various simulated daily tasks

OBJECTIVE

To verify whether additional manual wheelchair mass above a critical level would produce, during many daily tasks, an increase in physiologic parameters, an increase in the perceived exertion, and a decrease in performance.

DESIGN

A repeated-measurement design.

SETTING

Six standardized tests thought to mimic daily activities.

PARTICIPANTS

Volunteers (N=21), 8 men with spinal cord injuries (SCIs; mean age, 34+/-12y; range, 19-56y) and 13 able-bodied persons (11 men and 2 women; mean, 24+/-5y; range, 18-37y).

INTERVENTIONS

Random additional masses ("0", 1, 2, 5kg) were placed under the seat of a multisport manual wheelchair (mass approximately 10kg) out of the subject's field of vision.

MAIN OUTCOME MEASURES

Energy expenditure (EE; total o(2) consumed), heart rate (total number of beats), perceived exertion (visual analog scale), and performance (seconds to execute a sprint test) were measured.

RESULTS

For all tests, there was no significant effect of mass found for either group for the EE, heart rate, and performance. In addition, for all tests, no significant effect of mass was found for the SCI group for the visual analog perceived exertion. However, for the able-bodied group, the added mass had a significant effect for the visual analog perceived exertion (F=6.11; P=.02) in the Stop-and-Go test. A post hoc Tukey test showed a significant difference between the 0kg and 5kg mass conditions (P<.01; d=.8), between 1kg and 5kg (P=.02; d=.6), and between 2kg and 5kg (P=.01; d=.6).

CONCLUSIONS

Based on these findings, it can be concluded that, under the conditions of this study, additional mass (up to 5kg) loaded on a multisport manual wheelchair does not seem have any effect on EE, heart rate, or performance and has a minor effect on the visual analog perceived exertion evaluated in many activities of daily living.

Wheelchair repairs, breakdown, and adverse consequences for people with traumatic spinal cord injury

McClure LA, Boninger ML, Oyster ML, Williams S, Houlihan B, Lieberman JA, Cooper RA. Wheelchair repairs, breakdown, and adverse consequences for people with traumatic spinal cord injury.

OBJECTIVES

To investigate the frequency of repairs that occurred in a 6-month period and the consequences of breakdowns on wheelchair users living with spinal cord injuries (SCIs), and to determine whether certain wheelchair and subject characteristics are associated with an increased number of repairs and adverse consequences.

DESIGN

Convenience sample survey.

SETTING

Sixteen Model Spinal Cord Injury Systems Centers that are part of the national database funded through the Department of Education, National Institute on Disability and Rehabilitation Research.

PARTICIPANTS

People with SCI who use a wheelchair for more than 40h/wk (N=2213).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

The frequency of wheelchair repairs and occurrence of adverse consequences caused by a wheelchair breakdown in a 6-month period.

RESULTS

Within a 6-month period, 44.8% of full-time wheelchair users completed a repair, and 8.7% had an adverse consequence occur. People who use power wheelchairs required significantly more repairs (P<.001), and adverse consequences occurred more frequently (P<.001) compared with manual wheelchair users. The presence of power seat functions, and a person's occupational status or sex did not influence the number of repairs or adverse consequences.

CONCLUSIONS

Frequent repairs and breakdown can negatively impact a person's life by decreasing community participation and threatening health and safety. Mandatory compliance with the American National Standards Institute and the Rehabilitation Engineering and Assistive Technology Society of North America standards, changes in insurance reimbursement policy, and patient and clinician education are necessary to reduce the number of repairs and adverse consequences that occur.

Trends and issues in wheelchair technologies

There is an overwhelming need for wheelchairs and the research and development required to make them safer, more effective, and widely available. The following areas are of particular importance: practitioner credentials, accreditation, device evaluation, device user training, patient education, clinical prescribing criteria, national contracts, and access to new technology. There are over 170 U.S. wheelchair manufacturers with a total reported income of $1.33 billion. However, of these companies, only five had sales in excess of $100 million. Wheelchairs account for about 1% of Medicare spending. Use of assistive technology is an increasingly common way of adapting to a disability. The emergence of advanced mobility devices shows promise for the contribution of engineering to the amelioration of mobility impairments for millions of people who have disabilities or who are elderly. Some of the trends in wheelchairs are going to require new service delivery mechanisms, changes to public policy, and certainly greater coordination between consumers, policy makers, manufacturers, researchers, and service providers.

Engineering better wheelchairs to enhance community participation

With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.

Fatigue testing of selected suspension manual wheelchairs using ANSI/RESNA standards

OBJECTIVES

To evaluate the durability and value of 3 common suspension manual wheelchairs and to compare the results with those of previously tested lightweight and ultra-lightweight folding-frame wheelchairs.

DESIGN

Standardized fatigue testing and cost analysis of 3 suspension manual wheelchairs from 3 different manufacturers.

SETTING

A rehabilitation engineering center.

SPECIMENS

Nine suspension manual wheelchairs.

INTERVENTIONS

Wheelchairs were fitted with a standardized wheelchair test dummy and tested on a series of fatigue tests, consistent with those developed by the International Organization for Standardization. Main outcome measures Fatigue life (measured as the number of equivalent cycles completed) and value (equivalent cycles divided by cost) were compared among all wheelchairs.

RESULTS

Analysis of variance revealed significant differences (P< or =.05) in the number of equivalent cycles among the suspension wheelchairs tested. When compared with previously tested ultra-lightweight and lightweight wheelchairs, the suspension wheelchairs failed to show significant improvements; however, significant improvements were found between individual suspension and lightweight wheelchairs.

CONCLUSIONS

We found little evidence to suggest that suspension manual wheelchairs provide advantages in terms of durability or value over standard lightweight and ultra-lightweight folding-frame wheelchairs.

Durability, value, and reliability of selected electric powered wheelchairs11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To compare the durability, value, and reliability of selected electric powered wheelchairs (EPWs), purchased in 1998.

DESIGN

Engineering standards tests of quality and performance.

SETTING

A rehabilitation engineering center.

SPECIMENS

Fifteen EPWs: 3 each of the Jazzy, Quickie, Lancer, Arrow, and Chairman models.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Wheelchairs were evaluated for durability (lifespan), value (durability, cost), and reliability (rate of repairs) using 2-drum and curb-drop machines in accordance with the standards of the American National Standards Institute and Rehabilitation Engineering and Assistive Technology Society of North America.

RESULTS

The 5 brands differed significantly (P<or=.05) in durability, value, and reliability, except in terms of reliability of supplier repairs. The Arrow had the highest durability, value, and reliability in terms of the number of consumer failures, supplier failures, repairs, failures, consumer repairs and failures, and supplier repairs and failures. The Lancer had the poorest durability and reliability, and the Chairman had the lowest value. K0014 wheelchairs (Arrow, Permobil) were significantly more durable than K0011 wheelchairs (Jazzy, Quickie, Lancer). No significant differences in durability with respect to rear-wheel-drive (Arrow, Lancer, Quickie), mid-wheel-drive (Jazzy), or front-wheel-drive (Chairman) wheelchairs were found.

CONCLUSIONS

The Arrow consistently outperformed the other wheelchairs in nearly every area studied, and K0014 wheelchairs were more durable than K0011 wheelchairs. These results can be used as an objective comparison guide for clinicians and consumers, as long as they are used in conjunction with other important selection criteria. Manufacturers can use these results as a guide for continued efforts to produce higher quality wheelchairs. Care should be taken when making comparisons, however, because the 5 brands had different features. Purchased in 1998, these models may be used for several more years. In addition, problem areas in these models may still be present in newer models.

Evaluation of selected electric-powered wheelchairs using the ANSI/RESNA standards

OBJECTIVES

To compare the performance characteristics of different electric-powered wheelchairs (EPWs) and to evaluate the effectiveness of the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/RESNA) wheelchair standards.

DESIGN

Five types of EPWs were selected. Three wheelchairs of each type were tested according to the ANSI/RESNA wheelchair standards.

SETTING

Rehabilitation engineering center.

SPECIMENS

Fifteen wheelchairs.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Static tipping angle; dynamic tipping score; braking distance; energy consumption; static, impact, and fatigue strength; and climatic conditioning.

RESULTS

There were significant differences (P<.05) among the 5 types of EPWs for static stability when facing both uphill and downhill in the most-stable and least-stable configurations. There were significant differences (P<.05) among the EPWs on most of the dynamic stability tests. There were also significant differences (P<.05) among EPWs for all the effectiveness of brakes conditions, as well as between 2 wheelchairs for the energy consumption testing. There were several failures among the wheelchairs during the static, impact, and fatigue strength testing and during the climatic testing.

CONCLUSIONS

The results show that EPWs can vary greatly with respect to static and dynamic stability, braking distance, range, strength testing, and climatic conditioning. All these factors have a substantial effect on safety and performance.

Influence of Wheelchair Front Caster Wheel on Reverse Directional Stability

The purpose of this research was to study directional stability during reversing of rear-wheel drive, electric powered wheelchairs (EPW) under different initial front caster orientations. Specifically, the weight distribution differences caused by certain initial caster orientations were examined as a possible mechanism for causing directional instability that could lead to accidents. Directional stability was quantified by measuring the drive direction error of the EPW by a motion analysis system. The ground reaction forces were collected to determine the load on the front casters, as well as back-emf data to attain the speed of the motors. The drive direction error was found to be different for various initial caster orientations. Drive direction error was greatest when both casters were oriented 90 degrees to the left or right, and least when both casters were oriented forward. The results show that drive direction error corresponds to the loading difference on the casters. The data indicates that loading differences may cause asymmetric drag on the casters, which in turn causes unbalanced torque load on the motors. This leads to a difference in motor speed and drive direction error.

Wheelchair Caster Loading During Frontal Impact

Many wheelchair users are required or choose to use their wheelchairs as a motor vehicle seat during transport. It is therefore key that the wheelchair components be designed to tolerate crash-level loading conditions. Casters are particularly prone to failure under crash loading conditions. Our study evaluated wheelchair caster loading during 20g/48 kph frontal sled impact testing using an 85-kg surrogate wheelchair base (SWCB) with casters positioned on a load-measuring platform. A Hybrid III 50th percentile male test dummy was seated in the SWCB, which simulated a power wheelchair and was secured using four-point tiedowns. Various rear securement point heights and wheelchair seating systems were used to study their effect on caster loading. Caster normal loading was found to vary from 769 to 7,209 N depending on rear securement location and integrity of the seating system. Dynamic sled impact test results showed that normal loading of the front wheelchair casters was influenced by wheelchair seating system integrity and rear wheelchair securement height. Shear loading varied from 781 to 1,589 N and did not appear to be dependent on seat integrity or rear securement height. The load/time histories measured during dynamic impact testing can be used to guide the development of transit-safe caster design.

A Pilot Study on Community Usage of a Pushrim-Activated, Power-Assisted Wheelchair

Manual wheelchair propulsion combined with other stresses to the upper extremities may result in secondary injury. Possible solutions would be to devise alternative methods of propulsion, such as a pushrim-activated, power-assist wheelchair (PAPAW). The goals of this study were to examine the usage of the PAPAW in a real world setting and to characterize the driving habits of manual wheelchair users. Feedback was also obtained regarding subjects' opinions with respect to the PAPAW: their likes and dislikes. A PAPAW was provided to subjects for 2 weeks. Usage (average and total distance traveled and velocity) was tracked for both the PAPAW and the subjects' own wheelchairs. Significant differences in usage were not seen between the personal wheelchairs or the PAPAW. As a result, weeks were combined to provide an overall examination of driving characteristics. The average distance traveled over an average day was 1,671.4 +/- 314.8 m with an average velocity of 0.44 +/- 0.09 m/second. This pilot study provides an idea of manual wheelchair usage in a population of individuals with spinal cord injury. The lack of significant findings between the PAPAW and the subjects' own wheelchairs may be a function of study methodology such as sample size and length of follow-up in the new wheelchair. Future studies should expand upon the pilot work completed here, strengthening the design.

A comparison of functional mobility in standard vs. ultralight wheelchairs as measured by performance on a community obstacle course

PURPOSE

Appropriate wheelchair prescription requires maximizing user function while justifying cost. The purpose of this study was to investigate differences in a user's performance of mobility skills (on a community obstacle course) between an ultralight (UWC) and standard wheelchair (SWC).

SUBJECTS

Sixty healthy adults (mean = 28.3 years) without wheelchair experience performed one course trial.

METHODS

Participants were randomly assigned to an UWC or a SWC. Researchers recorded time for completion, Rating of Perceived Exertion (RPE), and number, location, and types of errors committed. Errors included contact of WC and any obstacle, front casters leaving the ground, or loss of directional control (veering).

RESULTS

A MANOVA of the data (p < 0.05) showed a significant difference in numbers of contact errors (higher in the SWC) and castor errors (higher in the UWC) between the two wheelchairs. Number of veering errors, time to complete, and RPE were not significantly different.

CONCLUSIONS

Differences in wheelchair design can lead to differences in a user's performance of functional mobility skills. Choice of wheelchair may affect a user's ability to be independent in a community setting.

Comparison of fatigue life for 3 types of manual wheelchairs

OBJECTIVES

To examine 3 types of manual wheelchairs-ultralight wheelchairs (UWs), lightweight wheelchairs (LWs), and depot wheelchairs (DWs)-and to compare the fatigue life between the wheelchair types.

DESIGN

A database of different manual wheelchairs tested according to the International Organization for Standardization (ISO). Fatigue life was determined by using standards that define methods accepted internationally using double-drum and curb-drop testing equipment.

SETTING

A rehabilitation engineering center.

SPECIMENS

Sixty-one manual wheelchairs: 25 DWs, 22 UWs, and 14 LWs.

MAIN OUTCOME MEASURES

Wheelchairs were examined for differences in fatigue life based on equivalent cycles. Unique survival curves were fit and compared for each wheelchair type.

RESULTS

The UWs lasted the longest, with a mean of 309,362 equivalent cycles. The DWs faired the worst, with a mean of 117,210 equivalent cycles. The Kaplan-Meier survival curves were significantly different (p < .001), with the UWs having the longest fatigue life.

CONCLUSION

Fatigue life for UWs is significantly greater (p < .05) than LWs and DWs, indicating wheelchairs differ in durability.

Wheelchair armrest strength testing

There are about 1.4 million manual wheelchair users, 100,000 electric-powered wheelchair users, and 60,000 electric-powered scooter users. The current study was undertaken to determine if the fasteners of a clamp-type armrest receiver were prone to failure. The first test was used to examine the potential misalignment of the armrest receiver components that attach it to the frame. The second test was to evaluate the entire armrest using the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America armrest static strength standard. Finally, we conducted three fatigue tests. The first fatigue test was performed by repeating the static stability tests multiple times. The last two tests were a modified version of the double-drum wheelchair fatigue test used to apply repeated loading and vibration simultaneously. A paired t-test showed that there is no statistically significant difference (p = 0.08), with a confidence of 95%, between critical alignment measurements. The armrest including the receiver passed the standard requirement of a force of 760 N being applied outward at 15 degrees. During fatigue testing, we found that armrests did not exhibit any visible or functional damage. Upon completion of the tests, the armrests and receivers functioned properly. At about 100,289 cycles on a double-drum test machine, three bolts failed on each armrest receiver when the screws were loosened to have only five threads engaged prior to commencing the test. The design of the armrest tested was in compliance with existing national and international standards. Currently, both International Standards Organization and American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society committees are developing standards for seating systems that will include static, impact, and fatigue strength testing of devices like lateral torso supports, lateral hip support, etc. Methods similar to those explored in this study should be considered. This study may help manufacturers when designing products and purchasers or regulatory agencies when attempting to evaluate the safety and quality of armrest assemblies.

Evaluation of a pushrim-activated, power-assisted wheelchair

OBJECTIVE

To evaluate a novel pushrim-activated, power-assisted wheelchair (PAPAW) for compliance with wheelchair standards, metabolic energy cost during propulsion, and ergonomics during selected activities of daily living (ADLs).

DESIGN

A 3-phase study, the second and third of which were repeated-measures designs.

SETTING

A rehabilitation engineering center within a Veterans Affairs medical center.

PATIENTS

Eleven full-time, community-dwelling, manual wheelchair users (4 women, 6 men) with spinal cord injuries or multiple sclerosis.

INTERVENTIONS

Phase 1: Compliance testing, with a test dummy, in accordance with the wheelchair standards of the American National Standards Institute and the Rehabilitation Engineering and Assistive Technology Society of North America. Phase 2: Metabolic energy consumption testing-at 2 speeds and 3 resistance levels-in subjects' manual wheelchair and the PAPAW. Phase 3: Evaluation of ability to perform ADLs and ergonomics of the PAPAW compared with the subjects personal wheelchair.

MAIN OUTCOME MEASURES

Phase 1: The PAPAW's static stability, static strength, impact strength, fatigue strength, environmental response, obstacle climbing ability, range, maximum speed, and braking distance. Phase 2: Subjects' oxygen consumption per minute, minute ventilation, and heart rate during different speeds and workloads with a PAPAW and their own wheelchairs. Phase 3: Subject ratings of perceived comfort and basic ergonomics while performing selected ADLs. Completion time, stroke frequency, and heart rate during each ADL.

RESULTS

Phase 1: The PAPAW was found to be in compliance with wheelchair standards. Phase 2: With the PAPAW, the user had a significantly lower oxygen consumption (&Vdot;O(2)mL/min: p <.0001; &Vdot;O(2)mL/kg x min: p <.0001) and heart rate (p <.0001) when compared with a manual wheelchair at different speeds. Phase 3: The PAPAW had a significantly higher mean ergonomic evaluation (p <.01) than the subjects' personal wheelchairs. The results of comparing the ratings of the car transfer between the PAPAW and the subjects' personal wheelchair showed a significant difference in the task of taking the wheels off (p <.001) and putting the wheels back on (p =.001), with the PAPAW receiving lower ratings.

CONCLUSION

This study indicated that the PAPAW is compliant with wheelchair standards, reduces the energy demand placed on the user during propulsion, and that subjects rated its ergonomics favorably when compared with their personal wheelchair. PAPAWs may provide manual wheelchairs with a less physiologically stressful means of mobility with few adaptations to the vehicle or home environment.

Road loads acting on manual wheelchairs

A barrier to performing more in-depth analyzes during the wheelchair design process is a lack of dynamic reaction force and moment data, and the instrumentation to collect this data. Instrumentation was developed to collect the dynamic force and moment data. New data collections methodologies and analysis techniques were implemented to facilitate computer-aided-engineering for wheelchair designs. Data were collected during standardized wheelchair fatigue tests, while driving over a simulated road course within a laboratory, and while driving in the community. Seventeen subjects participated in this study. Based upon the three test conditions, a pseudo-statistical distribution of the force and moment data at both a caster and rear wheel was developed. The key parameters describing the distribution and the extremums of the data (minima and maxima) were compared using analysis of variance. The results showed that the force and moment distributions and extreme values were similar for the both sets of human trials (i.e., simulated road course and field trials). However, the standardized testing (i.e., wheelchair fatigue testing) differed from both human trials. The force/moment data gathered during this study are suitable for inputs in finite element analysis and dynamic modeling. Our results suggest that the fatigue tests should be modified to change the magnitude and increase the frequency of the forces and moments imparted on the wheelchair. The data reported from this study can be used to improve wheelchair standards and to facilitate computer-aided-engineer in wheelchair design.

Manual wheelchair pushrim biomechanics and axle position

OBJECTIVE

The biomechanics of wheelchair propulsion have been linked to upper extremity injury. Specifically, prior studies have correlated increased median nerve dysfunction with increasing propulsion frequency and a higher rate of rise of the resultant, or total, pushrim force. Despite this link, there is little research on the effect of wheelchair setup on propulsion biomechanics. The objective of this study was to determine the effect of rear axle position relative to the shoulder on pushrim biomechanics.

DESIGN

Case series.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Forty individuals with paraplegia who use manual wheelchairs for mobility.

INTERVENTION

Subjects propelled their own wheelchairs on a dynamometer at two different steady-state speeds and going from a dead stop to maximum speed. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system.

MAIN OUTCOME MEASURES

Position of the axle relative to the shoulder at rest both horizontal (XPOS) and vertical (YPOS), and pushrim biomechanical variables including frequency of propulsion, peak and rate of rise of the resultant force, planar moment, and push angle. Partial correlation coefficients between relative axle position and propulsion biomechanics variables were calculated.

RESULTS

After controlling for subject characteristics, XPOS was significantly correlated with the frequency of propulsion (p < .01) and the rate of rise of the resultant force (p < .05). In addition, both XPOS and YPOS were significantly correlated with the push angle at multiple speeds (p < .05).

CONCLUSION

Specific biomechanical parameters known to correlate with median nerve injuries were found to be related to axle position relative to the shoulder. Providing wheelchair users with adjustable axle position and then fitting the user to the wheelchair can improve propulsion biomechanics and likely reduce the risk of injury.

User assessment of manual wheelchair ride comfort and ergonomics

OBJECTIVE

To examine wheelchair-user perceived ride comfort during propulsion and to compare the ride comfort of ultralight and lightweight manual wheelchairs. An ultralight wheelchair is defined as having a high degree of adjustability, whereas a lightweight wheelchair has minimal adjustability.

DESIGN AND PARTICIPANTS

Repeated measures design of a sample of 30 community-dwelling manual wheelchair users evaluating 7 different manual wheelchairs over an activities of daily living course.

SETTING

A rehabilitation engineering center.

MAIN OUTCOME MEASURES

Subject ratings of perceived ride comfort and basic ergonomics while propelling over the activities of daily living course. Ratings were recorded for each wheelchair on individual tasks and for the course overall.

RESULTS

The Invacare Action XT wheelchair was ranked best for both ride comfort and basic ergonomics. The ride-comfort scores (p < .05) and wheelchair ergonomics ratings (p < .05) for the ultralight wheelchair group were significantly different from those for lightweight wheelchair group.

CONCLUSION

There are differences in perceived ride comfort and basic ergonomics between the designs of the wheelchairs (lightweight vs ultralight). Subjects perceived that ultralight wheelchairs were more comfortable and had better basic ergonomics than lightweight wheelchairs.

Fatigue-life of two manual wheelchair cross-brace designs

OBJECTIVE

To compare the durability of two designs of cross-braces for folding manual wheelchairs and to determine the nature of wheelchair cross-brace failures.

DESIGN

Fatigue testing of two folding wheelchair cross-brace designs (one with a rectangular cross-section and the other with a circular cross-section). A total of 20 cross-brace pairs were tested.

RESULTS

The cross-braces with a circular cross-section endured a mean +/- SD of 100,159 +/- 45,814 cycles before experiencing a fatigue failure, whereas the cross-braces with a rectangular cross-section endured an average of 261,254 +/- 160,741 cycles. A t test showed significant differences (p = .01) in fatigue-life between cross-braces with a circular cross-section versus cross-braces with a rectangular cross-section. All 20 cross-braces experienced similar fatigue failures that would develop at the bolt hole where the two cross-braces connect to form a hinge.

CONCLUSION

The results suggest that the rectangular cross-brace design has a longer fatigue-life than the circular cross-brace design. People should regularly inspect the cross-brace for cracks. The area around the bolt forming the hinge should be inspected carefully. If a crack is observed, the cross-brace should be replaced immediately.

Evaluation of selected ultralight manual wheelchairs using ANSI/RESNA standards

OBJECTIVES

To provide data for clinicians and wheelchair users to compare the durability, strength, stability, and cost effectiveness of four different ultralight wheelchair models, and to compare the results of this study with those published for lightweight wheelchairs.

DESIGN

Standards testing and cost-effectiveness analysis of four wheelchair models from different manufacturers (12 wheelchairs total).

RESULTS

There were significant differences (p< or =.05) in the fatigue life and value (equivalent cycles per dollar) among the ultralight wheelchairs tested. There was also a significant difference (p< or =.05) in rearward stability tilt angle for the least and most stable configurations. There were no differences in forward and lateral stability. The ultralight wheelchairs (1,009,108 cycles) had significantly (p< or =.05) higher fatigue lives than previously reported for lightweight wheelchairs (187,370 cycles). The lightweight wheelchairs had a mean value of 210 cycles per dollar compared to 673 cycles per dollar for the ultralight wheelchairs. The difference in value for the lightweight and ultralight wheelchairs was statistically significant (p< or =.05).

CONCLUSION

There were differences in the fatigue life and value among the four models of ultralight manual wheelchairs tested. This indicates that ultralight manual wheelchairs are not all of equal quality. The fatigue life and value of the ultralight manual wheelchairs were significantly higher than those previously reported for lightweight manual wheelchairs. This indicates that ultralight wheelchairs may be of higher quality than lightweight manual wheelchairs. Clinicians and consumers should seriously consider selecting an ultralight manual wheelchair to meet their wheelchair mobility needs.