Comfort and stability of wheelchair backrests according to the TAWC (tool for assessing wheelchair discomfort)

Abstract

Purpose:

The goal of this study was thus to determine if people with different types of wheelchair backrests on their personal wheelchairs reported different levels of comfort as measured by the Tool for Assessing Wheelchair disComfort (TAWC).

Methods:

Participants were between 18 and 80 years of age and were manual wheelchair users. The TAWC was used to assess the participants’ wheelchair seating discomfort levels with the wheelchair and seating systems.

Results:

We surveyed 131 wheelchair users to assess the comfort of their backrests on their personal wheelchairs and found a trend suggesting that rigid backrests are were less comfortable as compared with sling backrests. This finding was statistically significant in a subgroup of participants with tetraplegia.

Conclusions:

Although many clinicians expect rigid backrests to be more comfortable because they may provide more support, the higher discomfort ratings among rigid backrest users with tetraplegia may be due to sub-optimal shape, fit, adjustment or user preferences.

Background

Almost three million people are wheelchair users in the USA, and approximately five million people are wheelchair users in Europe. Counting only Western countries, nearly 1 in every 100 people are wheelchair users [1]. The number of people who use wheelchairs has increased as the population has aged and medical care has improved [2,3]. Wheelchairs enhance function, increase independence and provide greater accessibility to the home and community for people with disabilities [4,5]. As an individual adapts to his or her disability, the wheelchair often becomes an extension of his or her body. The wheelchair is therefore a critical component that should meet users’ expectations, preferences, physical needs and functional requirements [6]. Different types of wheelchairs have varying comfort and ergonomic ratings due to their varying features. Wheelchairs that have more adjustability typically receive higher ratings on comfort and ergonomics than wheelchairs with minimal adjustability [7]. The ability to extend one’s activity is dependent on one’s equipment. Furthermore, the complexity of the intervention and equipment prescribed to a user is more dependent on a user’s functional needs than a user’s medical diagnosis. Ultra-lightweight wheelchairs not only offer a myriad of options in size and components, but also provide adjustability of seat angle, backrest angle, backrest height and axle position. The adjustability of ultra-lightweight wheelchairs is more likely to promote extended activity times. Combinations of seating systems can lead to extended activities since complex systems are better able to meet functional needs [8]. As the number of individuals using wheelchairs as their primary means of mobility increases, there needs to be more emphasis on making them safer, more effective and readily available.

A wheelchair backrest is essential due to the importance of postural support for wheelchair users. Backrest design and functionality can directly impact the comfort and health of the user, because the backrest provides pressure relief and postural support. In addition to postural support, however, the backrest protects and supports the spine and pelvis. Because the weight of the upper body is sustained through the spine, it is a crucial structural component; therefore, the protection or support of the spine is essential. Boninger et al. conducted a study that radiographically measured kyphosis and scoliosis in a group of individuals with tetraplegia.

According to this study, people with tetraplegia have a higher incidence of kyphosis and scoliosis than people without paralysis [9]. In many cases, wheelchair users have insufficient muscle strength to support and control the spine, so the spine tends to become bent and deformed due to the force of gravity. When the wheelchair backrest does not provide proper postural support for a wheelchair user, combinations of lordosis, kyphosis and/or scoliosis postural deformities may develop or worsen [10].

Backrests have different characteristics, such as height, shape, stiffness, weight and adjustability. These characteristics vary depending on the specific type of backrest. Most commonly, manual wheelchairs use either slings or rigid backrests. Most wheelchair manufacturers and wheelchair users utilize the standard flexible sling upholstery, which is typically made of fabric, for the backrest. Additionally, some sling backrests have adjustable tension, so they can be fitted to the wheelchair user and can be periodically adjusted if necessary or desired. However, because of their flexibility, these backrests provide limited postural support while the user participates in dynamic activities, such as propelling up and down ramps, over various surfaces, and over obstacles. As a result, sling backrests may not provide sufficient support during all activities, including static sitting [11–13], so rigid backrests are often prescribed.

In a cross-sectional study by May et al. [12], participants with recent spinal cord injuries evaluated three different backrest designs while performing four functional tasks. The three different back supports included standard sling upholstery, the Jay J2 back rigid backrest, and the Pindot Pax-Bac. Participants used their own wheelchair or one they were loaning. They evaluated each back-support option over 1–3 days to determine the most suitable back angle setting and to increase their familiarity with the back support. The entire testing period occurred over 10 days for each participant. The four functional tasks included timed forward wheeling, forward vertical reach, ramp ascent and 1-stroke push. Functional performance during the reaching activity was significantly greater when the J2 was used. Participants also reported higher satisfaction scores with the J2 [11–13]. Although these results support the prevailing opinion that rigid backrests are superior to sling, subjects were exposed to each backrest design only briefly, so it is not clear whether these results represent satisfaction after a period of brief use or after longer term use in the community. Therefore, the purpose of this study was to determine if people who have rigid backrests on their wheelchair report different levels of comfort than individuals who use sling backrests. The hypothesis was that long-term wheelchair users with sling backrests would report significantly higher comfort levels than those using rigid backrests as measured by the Tool for Assessing Wheelchair disComfort (TAWC) [14].

Methods

Recruitment

Prior to data collection, the study protocol was approved by the Department of Veterans Affairs Institutional Review Board. Subjects were recruited through the National Disabled Winter Sports Clinic (NDVWSC), the National Veterans Wheelchair Games (NVWG) and the Human Engineering Research Laboratories research registry. Participants were between 18 and 80 years of age and used a manual wheelchair (ultra-light, lightweight and depot) as their primary means of mobility. Subjects with open wounds that would preclude prolonged sitting in order to fill out the forms were excluded from the study.

Protocol

The TAWC was used to assess the participants’ wheelchair seating discomfort levels [14]. Participants were asked to rate the long-term discomfort/comfort related to their backrest that they were using on their own wheelchair. The tool has three parts. The first part is a general information survey on activities completed during the day, and which we did not utilize in this study. The second part is the General Discomfort Assessment (GDA), which was used in this study as an overall measure of discomfort. It comprises Discomfort Rating Subscale (DRS) and Comfort Rating Subscale (CRS) (Table 1). The DRS has eight statements about discomfort, and the CRS has five statements about comfort. The summation of the DRS score and CRS score results in the GDA score. This section has a total of 13 statements, each scored on a 7-point Likert Scale. Total possible score ranges from 13 to 91, with lower total scores indicating more comfort and higher scores indicating less comfort. The third part is The Discomfort Intensity Rating (DIR), which we used to identify locations in the body where discomfort was felt. This portion of the TAWC requires participants to assign a number on a scale from 0 to 10 to explain a discomfort level for each of 8 regions of the body, where a rating of 0 is no discomfort and a rating of 10 is severe discomfort. The regions of the body were the back, neck, buttocks, legs, arms, feet and hands. Then, participants are allowed to list one additional body part and the discomfort in that region and score it from 0 to 10. According to the scoring instructions of the DIR, a score of “1” is added to the participant’s score of each of the first 8 items. Thus, the possible adjusted score for each of the first 8 items becomes 1–11. A score of “1” is added to the last question if a body part is listed, but 0 is added if left blank. Thus, the last question can have a total of 0–11 possible points.

Table 1.

The GDA portion of TAWC.

Subscales of discomfort	Subscales of comfort
1 (strongly disagree) to 7 (strongly agree)	7 (strongly disagree) to 1 (strongly agree)
I feel poorly positioned	I feel no pain
I feel like I have been in one position for too long	I feel stable (not sliding or falling)
I feel like I need to move or shift my position	I feel comfortable
I feel aches, stiffness or soreness	I feel good
I feel pressure in some part or parts of my body	I feel able to concentrate on my work or activities
I feel too hot or cold or damp
I seek distraction to relieve discomfort
I feel uncomfortable

Statistical analysis was completed using SPSS 20.00 (Chicago, IL). Significance levels were set a priori at p=0.05.

Primary statistical analysis (all participants)

Chi-square and individual t-tests were used to compare baseline demographic factors (gender, age and years of wheelchair use) between those with sling backrests and those with rigid backrests. Three individual Analysis of Covariance (ANCOVA) analyses were then performed to compare backrest groups with respect to total GDA score and both subscale scores while controlling for significant covariates.

Secondary statistical analysis (subgroup of subjects with paraplegia and tetraplegia)

Because spinal cord injury (SCI) was a large subgroup, a secondary analysis was conducted using only those with SCI. Participants were first divided into paraplegia and tetraplegia groups.

In the paraplegia group, Fishers exact and individual t-tests were used to compare groups with respect to gender, age and years of wheelchair use. Because no covariates were found, three individual t-tests were used to compare backrests groups with respect to total GDA score and both subscale scores.

In the tetraplegia group, chi-square and individual t-tests were used to compare baseline demographic factors (gender, age and years of wheelchair use) between those with sling backrests and those with rigid backrests. Three individual ANCOVA analyses were then performed to compare backrest groups with respect to total GDA score and both subscale scores while controlling for significant covariates.

Results

Participants

A total of 131 individuals (average age 52.7±10.7) participated in this study and completed the questionnaire. Table 2 presents demographic data for all participants.

Table 2.

Demographic information of all participants.

Demographic measure	Number of participants (percentage)
Disability
Spinal cord injury	99 (76)
Amputation	5 (3.8)
Multiple sclerosis	7 (5.3)
Traumatic brain injury	2 (1.5)
Other	4 (3.1)
Combination of disabilities with SCI	10 (7.6)
Combination of disabilities without SCI	4 (3.1)
Gender
Male	107 (81.7)
Female	24 (18.3)

On average, participants had been using a wheelchair as their primary means of mobility for 20.6±12.1 years; 71.8% of wheelchair users (n=94) were using a sling backrest, and 28.2% (n=37) were using a rigid backrest.

One of the largest disability categories was spinal cord injury. Among 99 subjects with spinal cord injuries, 33 participants had tetraplegia, 64 participants had paraplegia and 2 subjects did not report the injury level (Figure 1).

Figure 1.

Subgroup of participants with spinal cord injury.

Results from primary analysis (all participants)

There were no significant differences between backrest groups based on gender (p=0.130). Significant differences were found between backrest groups based on age (p=0.003) and years of using a wheelchair (p=0.0120). Sling backrest users were older (54.1±10.6 versus 48.3±10.1 yrs) and had spent more years in a wheelchair (22.3±12.4 versus 16.4±10.5 yrs) compared with rigid backrest users (Table 3).

Table 3.

GDA (all participants).

Ratings	Mean (SD) sling (N=94)	Mean (SD) rigid (N=37)	p Value (two-tailed)
Discomfort subscale	27.5 (12.0)	29.4 (10.6)	0.261
Comfort subscale	15.9 (7.0)	17.2 (6.1)	0.301
Total	43.3 (17.0)	46.6 (15.9)	0.210

Higher values indicate more discomfort.

Total GDA scores (p=0.21) and both subscale scores (DRS: p=0.261, CRS: p=0.301) did not differ significantly across backrest groups, when controlling for the covariates of age and years using a wheelchair.

Results from secondary analysis (spinal cord injury only)

In those with paraplegia, no differences were seen in backrest groups with respect to gender, age or years in a wheelchair. Likewise, backrest groups also had statistically similar total GDA scores (p=0.781) and subscale scores (p=0.510, p=0.662).

In those with tetraplegia, sling backrest users were older (53.5±9.9 versus 46.1±9.0) and had spent more time in a wheelchair (25.4±9.1 versus 15.5±9.3 yrs), but backrest groups did not differ by gender. Total GDA score and DRS score (p=0.239) were statistically similar across backrest groups (p=0.105) but differed significantly with respect to CRS score (p=0.045), when controlling for covariates of age and years in a wheelchair (Table 4).

Table 4.

GDA (tetraplegia and paraplegia).

Ratings	Tetraplegia			Paraplegia
	Mean (SD) sling (N=18)	Mean (SD) rigid (N=15)	p Value (two-tailed)	Mean (SD) sling (N=46)	Mean (SD) rigid (N=18)	p Value (two-tailed)
Discomfort subscale	27.8 (10.0)	30.5 (9.8)	0.239	26.8 (12.3)	27.7 (10.8)	0.510
Comfort subscale	13.9 (5.0)	17.3 (5.5)	0.045*	16.6 (7.6)	17.0 (6.7)	0.662
Total	41.7 (13.3)	47.9 (14.6)	0.781	43.3 (17.2)	44.7 (–16.4)	0.239

Higher values indicate more discomfort.

^*Significant effect (p ≤ 0.005).

Median DIR scores are reported in Table 5 and Figure 2. Overall, the back was the body part that received the highest discomfort scores.

Table 5.

Median of discomfort intensity rating by area of body and participant groups.

Body areas	Entire group		Tetraplegia		Paraplegia
	Rating median sling	Rating median rigid	Rating median sling	Rating median rigid	Rating median sling	Rating median rigid
Back	4 (1–11)	5 (1–11)	5 (1–9)	5 (1–9)	3 (1–11)	6 (1–11)
Neck	1.5 (1–11)	3 (1–11)	3 (1–11)	3 (1–11)	1 (1–10)	2 (1–10)
Buttocks	2 (1–11)	5 (1–10)	3 (1–11)	6 (1–10)	2 (1–11)	3 (1–9)
Legs	2.5 (1–11)	1 (1–10)	1 (1–8)	3 (1–10)	2.5 (1–11)	1 (1–10)
Arms	1 (1–11)	1 (1–9)	1 (1–7)	1 (1–9)	1 (1–7)	1 (1–7)
Feet	1 (1–11)	1 (1–10)	1 (1–8)	3 (1–9)	1 (1–11)	1 (1–10)
Hands	1 (1–9)	1 (1–10)	1 (1–9)	1 (1–8)	1 (1–7)	1 (1–10)
Overall discomfort	4 (1–11)	5 (1–9)	3 (1–8)	5 (1–8)	4 (1–9)	4 (1–9)

Figure 2.

Median discomfort intensity ratings by area of body for all participants (1=no discomfort, 11=severe discomfort).

Discussion

Contrary to our hypothesis, there were no significant differences on the Total GDA score based on backrest type, when all participants were analyzed, or when participants were analyzed as paraplegia and tetraplegia groups. In fact, the overall trend was for rigid backrest users to have more discomfort than sling users. One explanation is that wheelchair design has been changing rapidly over the past two decades [1,15]. Therefore, long-term wheelchair users may be less comfortable when switching to a rigid backrest, since they were accustomed to a sling-style seat, which was the only choice available when they first received their chair.

The most significant finding from this study was that, when GDA subscale scores were analyzed, rigid backrest users in the tetraplegia group had significantly more discomfort than sling backrest users with tetraplegia. This difference was not seen in the paraplegia group or when participants of all disabilities were analyzed. No differences were found for the discomfort subscale score across any groups. However, all trends were consistent and supported more discomfort with rigid backrests. The first explanation for this finding is that many users with tetraplegia may have had rigid backrests that were sub-optimally fitted or adjusted for the functions that they carry out in daily life. The second explanation is sling upholstery tends to allow the users to reposition themselves more in their wheelchair. The third is that rigid back support does not allow for adjustment and variation of the user’s position, even though it may provide more support. Fourth, despite cushioning on the backrest, the backrest shell is still firm and fixed in position, which users may find uncomfortable without dynamic adjustment. Finally, the tetraplegia group likely has more compromised trunk and pelvic stability in general [16]. Rigid backrests are sometimes added to provide this stability, but they do not allow dynamic movement. Lack of dynamic movement may be perceived as discomfort. This group may be more reliant on the sling backrest, whose fabric may provide more comfort due to allowance of dynamic movement, but less postural support. Individuals with paraplegia have greater trunk control, thereby able to change positions more frequently; as such, the backrest may not play as large a role in comfort as it does in tetraplegia. They do not rely on backrests as much, because they move on their own. However, to reduce the risk of lordosis, kyphosis and/or scoliosis postural deformities, proper postural support is essential, which might lead one to assume that a rigid backrest is superior [10].

On the DIR, the back was one of two body parts that ranked highest for discomfort. This high discomfort level emphasizes the need to focus on improving backrest design, specifically to increase comfort while providing adequate postural support.

The trends seen in this study are contrary to previous studies on the short-term use of backrests, which favor rigid backrests as having more desirable features [12,13]. This emphasizes the need to evaluate the long-term performance of backrests with experienced users.

Study limitations and future directions

This study is limited by sample size. According to our power analysis, 315 subjects in each group are necessary to demonstrate significance at 80% power. This may suggest that the TAWC is not sensitive enough to detect differences in discomfort in this population. The TAWC asks broad questions about overall discomfort, which may be caused by issues and components other than the backrest. Also, the TAWC questionnaire asks questions only about discomfort and comfort, not other symptoms or the impact discomfort may have on functional tasks. Wheelchair backrests are also important for supporting functional abilities, so future work should examine the long-term functional outcomes from using backrests. It is important to note that the TAWC has been used in previous studies to evaluate discomfort after sitting for approximately 4 h. Participants in this study were asked to rate their long-term discomfort using the TAWC since no other measure for long-term seating discomfort exists. Development of such a measure is needed. It would also be helpful to design a questionnaire to ask participants about their reactions to comfort, appearance and texture/material of seating systems, as these also play a role in backrest selection. Unfortunately, we did not ask how long the wheelchair users had been using the backrest supports in their current wheelchair. Additionally, controlling for type and setup of the wheelchair may help elucidate differences based on backrest type. Clinicians play a critical role when ordering and fitting rigid backrests [17,18]. As we do not know the experience of the clinicians who prescribed the wheelchairs to the users in this study, it is possible that our participants obtained their wheelchair through untrained clinicians, which may have influenced the findings of this study.

Conclusion

Although rigid backrests should theoretically provide a more stable base of support for the spine, this study shows that long-term (420 years) wheelchair users with sling backrests trend toward having more comfort than those using rigid backrests. Discomfort ratings for backrests were significantly higher for those with tetraplegia who used rigid backrests than those with tetraplegia who used sling backrests. The higher discomfort rating among rigid backrest users may be due to sub-optimal shape, fit, adjustment or user preferences due to length of disability. However, backrests are often selected because of their impact on function, adjustability or ability to provide dynamic support. More work is needed to design and develop better rigid backrests that are functional but provide adequate comfort.

Implications for Rehabilitation.

• Development of a measure for long-term seating discomfort is needed.

• Design and development of better rigid backrests that are functional but provide adequate comfort are in need.