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Disability and Rehabilitation: Assistive Technology
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/iidt20
Head support in wheelchairs (scoping review):
state-of-the-art and beyond
Anoek M. Geers, Erik C. Prinsen, Dick J. van der Pijl, Arjen Bergsma, Johan S.
Rietman & Bart F. J. M. Koopman
To cite this article:
Anoek M. Geers, Erik C. Prinsen, Dick J. van der Pijl, Arjen Bergsma,
Johan S. Rietman & Bart F. J. M. Koopman (2021): Head support in wheelchairs (scoping
review): state-of-the-art and beyond, Disability and Rehabilitation: Assistive Technology, DOI:
10.1080/17483107.2021.1892840
To link to this article: https://doi.org/10.1080/17483107.2021.1892840
© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Published online: 17 May 2021.
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REVIEW
Head support in wheelchairs (scoping review): state-of-the-art and beyond
Anoek M. Geers
a,b, Erik C. Prinsen
a,c, Dick J. van der Pijl
b, Arjen Bergsma
a, Johan S. Rietman
a,c,dand
Bart F. J. M. Koopman
aa
Department of Biomechanical Engineering, TechMed Centre, University of Twente, Enschede, The Netherlands;bFocal Meditech B.V, Tilburg, The Netherlands;cRoessingh Research and Development, Enschede, The Netherlands;dRoessingh Centre of Rehabilitation, Enschede, The Netherlands
ABSTRACT
Background: Many wheelchair users experience disabilities in stabilising and positioning of the head. For these users, adequate head support is required. Although several types of head supports are available, fur-ther development of these systems is needed to improve functionality and quality of life, especially for the group of severely challenged users. For this group, user needs have not been clearly established. In this article, we provide an overview of the state-of-the-art in wheelchair mounted head supports and associ-ated scientific evidence in order to identify requirements for the next generation of head support systems. Materials and methods: A scoping review was performed including scientific literature (PubMed/ Scopus), patents (Espacenet/Google Scholar) and commercial information. Types of head support and important system characteristics for future head support systems were proposed from consultations with wheelchair users (n ¼ 3), occupational therapists (n ¼ 3) and an expert panel.
Results: Forty scientific papers, 90 patents and 80 descriptions of commercial devices were included in the scoping review. The identified head support systems were categorised per head support type. Only limited scientific clinical evidence with respect to the effectiveness of existing head support systems was found. From the user and expert consultations, a need was identified for personalised head support sys-tems that intuitively combine changes in sitting and head position with continuous optimal support of the head to accommodate severely challenged users.
Conclusions: This study presents the state-of-the-art in head support systems. Additionally, several important system characteristics are introduced that provide guidance for the development and improve-ment of head supports.
äIMPLICATIONS FOR REHABILITATION
Especially for the group of severely challenged wheelchair users, current head support systems require further development to improve their users’ quality of life.
The desired system characteristics which are discussed in this review are an important step in the definition of requirements for the next generation of head supports.
ARTICLE HISTORY
Received 29 August 2020 Accepted 16 February 2021
KEYWORDS
Assistive devices; orthotic devices; head support; wheelchairs; sitting; head movements; head position
Introduction
Electric and manual wheelchairs provide a means to achieve inde-pendence and increased social participation for users with upper and lower body impairments [1,2]. During wheelchair use and use of additional assistive technology (e.g., wheelchair or environmen-tal control systems), the correct positioning of the head and neck is essential. In fact, a stable, suitable head position is a basic pre-condition to successfully perform daily activities involving the upper extremity [3]. This is especially true for severely physically challenged users.
Head stability provides a stable frame of reference for vision, which is important for independent mobility [4]. It is also a pre-requisite for breathing, eating [5] and swallowing [6]. Additionally, it allows the user to engage in social interaction and communica-tion [7]. Research has shown that an incorrect head position
impairs social interaction with others and may lead to swallowing and breathing [8] disorders, malnutrition [6,9] and fatigue [7]. If no action is taken, over time incorrect positioning can lead to posture deformities and disabilities in the head mobility [10].
Many wheelchair users experience limitations in stabilising and positioning of the head [11–13]. This can be the result of decreased muscle strength or control to keep the head upright against gravity. To compensate for weakness of the neck muscles, wheelchair mounted head supports are used to keep the head in the desired position.
These head support systems are commonly used by persons with progressive neuromuscular disorders such as Duchenne mus-cular dystrophy (DMD) and spinal musmus-cular atrophy (SMA), per-sons with progressive neurological disorders such as amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), persons with
CONTACT Anoek M. Geers a.m.geers@utwente.nl Department of Biomechanical Engineering, TechMed Centre, University of Twente, Enschede, The
Netherlands
Current address: Dutch Research Council (NWO), Applied and Engineering Sciences, The Hague, The Netherlands
ß 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.
spinal cord injury (SCI), persons with cerebral palsy (CP) and per-sons with severe orthopaedic disorders. The frequency of use depends on the medical condition of the wheelchair user. Severely challenged persons are commonly relying on continuous head support during daytime and therefore need support during various daily activities and in rest while being seated.
Adequate support of the head is needed in different sitting postures. Due to a suboptimal head position, users of static head supports may be unable to perform certain activities, and may experience symptoms such as pain, stiffness in the neck and fatigue [7]. Different head support positions with respect to the wheelchair are therefore required during the day to optimally support the body. In addition, especially in the case of severely physically challenged persons for whom the head and neck muscles may be some of the last muscle groups they can still control, it seems undesirable to fixate the head.
A clear overview of available clinical evidence is missing. Especially for the group of severely challenged users, it is appar-ent from daily practice that existing head support systems require further development to improve their quality of life, but user needs have not yet been established.
Hence, the following research question was formulated: what knowledge is available about head support in manual and electric wheelchairs for severely challenged users? To answer this ques-tion, a scoping review [14] was conducted to (1) to systematically map the state-of-the-art in head support systems, (2) to define the available types of head support and (3) to identify important system characteristics for the next generation of head sup-port systems.
The scope of the review was narrowed down to head support systems mounted on manual or electric wheelchairs that are intended for use during daily life by severely challenged users. To synthesise the research results, stakeholder perspectives were gathered by means of interviews with end users and occupational therapists (OTs), and consultation of an expert panel.
Materials and methods
The guidelines from the JBI Manual for Evidence Synthesis (Scoping Reviews) [15] were followed where possible. A scoping review protocol was prepared but not published.
Inclusion criteria
The scoping review was conducted using several information sources in order to obtain a broad view of the relevant literature (Figure 1). To map the state-of-the-art as well as the evidence
available for head support systems, a scientific literature search was performed. Additionally, to identify the number of systems developed and/or available in the market, patent databases and commercial manufacturer and supplier websites were visited.
To include a wide range of sources, no exclusion criteria were set with respect to user group, study design and date. For the sci-entific literature, an inclusion criterion was set with respect to lan-guage, including only scientific papers that are available in English or Dutch.
Search strategy and study selection Scientific literature
The online scientific libraries PubMed and Scopus were used for the literature search. A three-step search strategy was utilised [15]. In both databases, first an initial limited search was per-formed, followed by a second more extensive search including more keywords (e.g., related to device and body segment) (Table 1). As the third step, the reference lists from the included articles were consulted to find additional articles. The scientific literature search was performed by the first author.
The reference manager Mendeley Desktop (Mendeley, United Kingdom) was used to manage the results for the scientific litera-ture search. After removal of duplicates, abstract and title selec-tion was done by the first author. This source selecselec-tion was reviewed by one of the other authors (first reviewer), who noted any disagreements with the selection. Subsequently, in a similar manner, full-text examination was done by the first author and this source selection was reviewed by the first reviewer. In both stages, disagreements were solved either by consensus or if necessary, by the decision of a second reviewer.
Patents
Patent searches were carried out in Espacenet.com and Google Patents using the A61G5/121 classification from the Cooperative Patent Classification system, including current as well as expired patents. Additional searches were performed using device related keywords (i.e., Intervention (A) inTable 1). After removal of dupli-cates, a selection was done based on keywords in the patent title. Subsequently, the eligibility of the remaining patents was manu-ally checked and the patent was either categorised using the
Figure 1. Overview of included information sources and consultation exercises.
Table 1. Utilised search strategy for scientific literature search.
Keywords
Description Search terms Exclusion criteria Intervention (A) Head support Headrest Neck support (B) Assistive Orthotic Self-help Exoskelet Robot Support Treatment Neck brace Neck band Region Head Neck Head-neck Cervical spine Arms Shoulder Hips Context Wheelchair Automotive Search strategy
Limited search Intervention (A) and Context Extended search Intervention (A) OR (Intervention (B)
defined head support types or excluded when not applicable. The patents search and selection was performed by the first author.
Commercial devices
In order to cover the commercially available devices for which no scientific literature or patents are available, the assistive technol-ogy databases AbleData [16] and EASTIN [17] were consulted. Finally, manufacturer websites and product brochures were included in the studied material for an estimation of the number of commercially available head support systems. An estimation was made of the different head support types available for each identified commercial party. This overview included both the entries from the assistive technology databases and other infor-mation available online. The commercial devices search and selec-tion was performed by the first author.
Charting the data
For the results from scientific literature, a data charting form was iteratively developed in Microsoft Excel. This form respectively included author information, year, type of study, study design, type of head support, population, research aim, methods, out-come measures and key findings with respect to head support. A condensed version of this table was created to be included in the article.
Collating, summarising and reporting results
A categorisation of head support types delivered was developed since none existed. The results of the patent and commercial device searches were used to create a quantitative overview of the amount of systems available on the market and/or previously developed, with respect to head support type.
Consultation
To validate and synthesise the research findings, and to go beyond the state-of-the-art, different stakeholders were involved in consultation exercises [14]. This allowed for further investiga-tion of the human-related intended use (HRIU) of head supports (e.g., what tasks should the system allow, take over or enhance, from the viewpoint of the user [18]), and subsequently the identi-fication of important system characteristics for future head sup-port systems. For this purpose, interviews were conducted with three experienced OTs and three fulltime electric wheelchair users. A discussion was held with an expert panel to verify the identified head support types and important system characteristics.
Interviews
The OTs were recruited from different institutions through referral by co-authors. All OTs had over 15 years of relevant work experi-ence, and were specialised in complex seating issues of severely challenged users with a variety of medical conditions (mainly DMD, SMA, ALS and to a lesser extent SCI). The end users were contacted through referral by the co-author affiliated with a com-pany that manufactures and supplies head supports. All partici-pants were sent a short information letter beforehand. After receiving a positive response, an appointment was made for the interview. Participants agreed upon usage of their anonymized responses within the research project.
For the three OTs, the semi-structured interviews included questions about their experiences with current head supports,
including observed limitations, as well as their ideas about the functionalities of future head support systems. Likewise, for the wheelchair users, the semi-structured interviews included ques-tions about their current head support usage, their experiences in daily life as well as desired functionalities of future head support systems. Notes were taken during the interviews and audio was recorded after obtaining permission. A summary of each interview was written. All participants were given the opportunity to review their individual summaries, and agreement on the final version was obtained from all participants. Thereafter, these summaries were analysed by labelling and grouping the citations.
Expert panel
The expert panel consisted of representatives from the different stakeholders, including clinical experts (n ¼ 2, both co-authors), mechanical and design engineers (n ¼ 3, including one co-author) and experts on manufacturing and commercialisation (n ¼ 2, including one co-author).
The categorisation of head support types delivered was dis-cussed with the expert panel and finalised. The set of important system characteristics was discussed with the expert panel and thereafter used as a starting point to categorise the recommenda-tions for further development of the head support in the discussion.
Results
In the scientific literature search, 480 unique records were identi-fied including 17 additional records through reference searching (Figure 2, based on [19]). Of those, 80 records remained after title and abstract selection. Subsequently, 40 records met the inclusion criteria and were analysed. Likewise, 1276 unique records were identified in the patent search (Figure 3), of which 170 records were assessed for eligibility. In the estimation of the number of available systems, 90 records were included.
Types of head support
With respect to the type of support delivered to the user, an overall distinction was made between non-actuated and actuated systems. Additionally, a distinction was made between systems that have the primary function to support the head in a particular position (i.e., static head supports), and systems that have the pri-mary (or additional) function to stabilise the head during inde-pendent movement (i.e., dynamic head supports). Within these categories, the following head support system types were defined (Table 2):
Non-adjustable head supports that support the head only in one position were labelled as static fixed head supports. Static externally adjustable head supports allow for repositioning of the head, however only with the help of others. It should be noted that this label was only used for systems that were described as being able to offer adjustment to several head positions for one user. Systems that were described to only allow reconfiguration to different users were labelled as static fixed head supports. Static independently adjustable head supports allow the user to change their head position independently in response to body repositioning.
A distinction was made between standard dynamic head sup-ports that allow or support movement within a restricted range of motion, and suspended dynamic head supports that use a sus-pending principle to support the head.
Finally, adaptive head supports allow movement in response to user exerted forces on the head support and/or the wheelchair. In general, for protection of the user and the system, these supports absorb and diffuse force and aim to reduce the loss of alignment between the head and the system [20]. They provide support in one position but also allow head support motion in certain direc-tions in response to exerted forces, providing a combination of static and dynamic support.
Scoping review results
Table 3includes the estimated numbers of systems developed for the different head support types. Systems were divided in three categories: commercially available, patents and research. Additionally, the scientific literature column includes the coverage per head support type (as far as specified) for the included papers.
Overall, the majority of head supports are static. Most head supports are fixed to the wheelchair with no opportunity for adjustment. In case head support systems are adjustable, most often these only enable a caregiver to manually change the head support position. Only a few systems allow for independent repo-sitioning of the head support. Although dynamic and adaptive head supports are available, the number of systems is limited (e.g., eleven commercial solutions were identified)
Table 4 presents the results of the scientific literature search. In general, only a few clinical studies have been conducted to evaluate the effectiveness of commercially available static and dynamic head supports with wheelchair users [5,21–23]. Moreover, case studies and case series were found reporting the outcomes after implementation of (customised) head support
solutions or wheelchair systems [24–27], as well as cross-sectional surveys for several user groups [28–30]. Other non-clinical studies describe the development [31–34] and system testing [35–37] of wheelchair mounted head support systems.
Support of head position Static fixed head support
For the static fixed head supports, one case study with a commer-cial device (i2i, Stealth Products) was found [5] for two children with periventricular leukomalacia. With the application of the i2i head support, a more upright posture as well as improved breath-ing and swallowbreath-ing function was observed in both cases. A com-parison of an adaptive wheelchair system and a rigid wheelchair system was done in the clinical study of Cimolin et al. [21], in which the adaptive wheelchair system x:Panda (R82 A/S) had a dynamic backrest with a static head support attached.
In the case series (n ¼ 33) of participants with various impair-ments [25], a headband was applied as additional anterior head support in conjunction with a static head support system. Appliance of a headband was mentioned to be beneficial for users with weak neck extensors in [38], for example persons with SMA, DMD and ALS.
Over the years, static head supports have also been used as direct control interface for driving of the wheelchair. Such control interfaces have been developed in research environments [39,40], and manufactured and applied on an individual basis [24,27,41]. A clinical evaluation was done [42] with the Adremo head/foot steering system (Adremo Revalidatietechniek, The Netherlands).
Another topic that has received considerable attention is the performance of wheelchair mounted head support systems used
Figure 3. Flow diagram study identification for patents search, based on [19].
Table 2. Defined head support (HS) categories and system types.
Intended function Non actuated Actuated
Support of head position (Static) Fixed Externally adjustable Independently adjustable
Non-adjustable HS that supports the head in only one position
Adjustable HS that allows for repositioning with the help of others
Adjustable HS that allows for repositioning by the user
Support of head movement (Dynamic) Standard Suspended
HS that allows for head movement HS that allows for head movement using a suspending principle Support of head position and
movement
Adaptive
HS that allows movement in response to exerted forces on the HS or wheelchair Schematic images of head support types adapted from [83].
during transport in a vehicle. System testing has been performed, comparing head and neck injury risks and loading for manual wheelchairs with and without static fixed head supports [36,37,43,44]. Optimisation of system configuration (e.g., head sup-port position, cushion stiffness) was found to be imsup-port- import-ant [36,45,46].
Adjustable static head support
No clinical studies were found that evaluated the effectiveness of externally adjustable static head supports. However, Turner et al. [28] suggested that the high prevalence of neck pain in persons with a high SCI may be related to the usage of head supports which immobilise the head to a larger extent, and Perr et al. [47] concluded that people would prefer to change the head support position when their position in space changes. Finally, Herman and Lange [12] indicated that optimisation of head support pos-ition can play an important role in normalising movement pat-terns and reducing the risk of spasticity-related deformities for persons with a brain injury.
With respect to independently adjustable static head support, the prototype developed by Geers et al. [32] focussed on provid-ing optimal support accordprovid-ing biomechanical movement trajecto-ries during repositioning of the head and wheelchair seating respectively.
Support of head movement
The commercially available dynamic systems allow for rotation in one or multiple directions, are nonactuated (e.g., passive) and operate within a restricted range of motion. With the exception of the HeadPod (Siesta Systems) [22,23], no clinical evaluations were found for the available commercial devices. The HeadPod was evaluated with severely challenged children (CP, dystonia) as a training device [22] and as an assistive device [23].
Although standard dynamic head supports have been devel-oped by multiple research groups [33,48,49], no clinical evalua-tions of these prototypes were found. A preliminary evaluation with healthy participants was done by Mahmood et al. [49].
Adaptive head support
There are no studies available focussing on the effectiveness of adaptive head support. Multiple studies have focussed on the effectiveness of adaptive integrated wheelchair systems for per-sons with CP [50–52], but as the possible role of head supports remained undiscussed in these studies, these references were not included in Table 4. In research, an adaptive seating system including head support was developed by Togashi et al. [53] with three rotational axes, one of them placed near the head support.
Although in this article in general the definition of adaptive head support in response to user exerted forces is used, Simms
et al. [31,54] developed and tested an adaptive head support that reacts in response to external forces caused by rear impact during transport in a vehicle.
User interviews
User interviews were held with three experienced OTs and three fulltime electric wheelchair users, to further investigate the user needs. The electric wheelchair users, all three diagnosed with SMA, respectively, used static fixed (n ¼ 1) and static independ-ently adjustable (n ¼ 2) head supports.Table 5includes a detailed description of the wheelchair users.
Current usage
All three interviewed OTs indicated that in general, the transition is made from a‘standard’ static fixed head support to a user-spe-cific solution when head balance decreases to an extent that adjustments to the wheelchair seating are necessary to maintain a stable posture. Additionally, customised head support is used when posture deformities occur. Overall, the expert opinions focussed on static head supports (non-adjustable and adjustable), as those were the systems encountered in practice.
Moreover, it was mentioned by all three OTs that changes in seating configuration, e.g., tilt of the seat and recline of the back-rest, result in a different optimal head support position. Therefore, an adjustable head support is necessary, also when a biomechan-ical backrest is present. Another main reason mentioned to have an adjustable head support was the need for adjusting the field of view to enable social and environmental interaction. When fre-quent adjustments of seating position and consefre-quently head support position were needed, the OTs indicated that they prefer to apply an independently adjustable head support to ensure that the user can adjust the position his- or herself. The wheelchair users all underlined the importance of independent adjustability.
In the OT interviews, it was noted that in general along the progression of the disorders (e.g., trunk balance decreases, upright sitting is no longer possible), use of head support increases from incidental to almost continuous. Incidentally, this was also exemplified by the interviewed fulltime wheelchair users (Table 5). User 1 (fixed) indicated that she only incidentally rested her head against the head support, mainly in the car. User 2 (independently adjustable) indicated that she regularly used the head support during the day to rest her head, mainly during head positions that are hard to maintain otherwise. She adjusted the head support position when resting her head for a longer time. User 3 (independently adjustable) indicated that he continu-ously used the head support during daily life. He adjusted the head support position regularly: in response to seating changes, but also to assist during specific activities such as eating. Another example of using the head support adjustments as assistance was
Table 3. Estimated numbers of systems developed for the different head support types.
Category Commercial Patent Research prototypes Scientific literature Support of head position (Static)
Fixed 32 42 5 23
Externally adjustable 35 35 2
Independently adjustable 2 2 1 1
Support of head movement (Dynamic)
Standard 2 6 3 3
Suspended 2 2 3
Support of head position and movement (Static and dynamic)
Adaptive 7 3 2 3
Table 4. Charting table with included articles from scoping review. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Bekteshi et al. [ 42 ] CS (Repeated measures) FS, CI Adremo head/ foot system Dyskinetic CP, GMFCS IV-V (n ¼ 10, 6-21 yr) To evaluate the presence and severity of DCP-related movement disorders during PWC mobility To investigate the relation between DCP related movement disorders, PWC mobility performance, and participants ’ characteristics To explore DCP-related movement disorders and PWC mobility performance during different PWC mobility tasks Two time points (two weeks break in between) Four mobility tasks with own PWC Data collected by video recording Dyskinesia Impairment mobility scale (DIMS) Time used to perform mobility task Number of errors during performance Mobility training with head/foot-steering WC in DCP solely based on clinical expertise, lack of evidence-based knowledge exists Negative relationship between proximal arm overflow movements and PW mobility driving experience may imply that over time DCP children adopt deliberate strategies to minimise impact of arm overflow movements to increase control of the head Future research with bigger sample size and additional outcome measures recommended to further explore the head/foot driving strategies in DCP Belcher and Frank [ 30 ] C S (C ro ss -s ec ti o n al ) Unknown (n ¼ 203) To determine the extent to which electric wheelchair users travel in vehicles, their concerns about safety, their knowledge about clamping procedures, their use of head rests and any problems encountered Survey Descriptive statistics and thematic content analysis HS used by 69 participants of 170 users who used transport; 33 participants used WC attached HS, 3 participants used car HS and 2 had extended backrests HS usage considered too low, as without HS user is more susceptible to injuries Dynamic crash testing of HS needed Unclear whether HS were attached to WC or to car (unless explicitly mentioned) Brown et al. [ 22 ] CS (Repeated measures) SD HeadPod Neurologic diagnosis with multiple impairments, GMFCS-V (n¼ 14, 3– 11 years) To determine the feasibility of HeadPod use as home-based intervention to improve head control in children with CP Three time points (baseline, 3, 6 months) Testing daily usage of HeadPod (3 15 min/ day) Video recording Daily recording of device use Global rate of change (GROC) scale survey (n ¼ 5) Active time head held upright Number of head bobs in five minutes Study adherence Perceived improvement (GROC survey) No significant changes observed after 3 months After 6 months, some of the children showed improvement in active time head held upright Respectively strong and moderate nonsignificant relationship between total minutes of HS use and active time, head bobs Hard to specifically attribute observed changes to intervention alone HeadPod as training device possibly is a suitable intervention for part of the population to improve head control, execution of a larger RCT is needed (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Cimolin et al. [ 21 ] C S (C ro ss -s ec ti o n al ) FS x:Panda CP, GMFCS-V (n¼ 10, 6– 10 years) To develop an experimental setup for the acquisition of 3D kinematics and pressure distribution during extensor thrusts To apply this procedure in a group of children with CP comparing an adaptive seating system versus a rigid seating system One time point Testing adaptive and rigid seating system (fixed HS) Noise disturbance Kinematic data (body and seat) Pressure distribution data (seatback, head support) Data collected by video recording Diff. between initial (before) and end positions (after) of head, trunk Diff. between initial positions and max. values of head, trunk, wrist Average wrist jerk Peaks of force on seatback, HS Fo r rig id se at ing , la rg e fo rc es ca n b e ex er te d o n H S and se at in g A d ap ti ve sy st em h ad a p o si ti ve inf lu en ce , im p ro ving h ea d and tr u n k sta b ili ty an d re d u ci n g ex te n sor tr u st Si gn ifi ca n t lar ge r h ea d exc u rs io n o cc u rr ed fo r the ad ap ti ve in an te ri o r-p o st eri o r d ire ct io n , in ve rt ic al d ir ec tio n n o sig ni fic ant di ffe re n ce s fo u n d B ac kr est p re ssu re d ist ri b u ti on d at a sh o w ed si g n ific an t lo w er p ea k fo rc es fo r ada p ti ve , n o si g n ifi ca n t di ffe re n ce s fo r H S R ed u ct io n o f fo rce s as so ci at ed w ith a re d u cti on of p ai n an d to im p ro ve m en t o f m ai nt ai ni ng p o si ti on ov er ti m e Ekiz et al. [ 26 ] C S (Case series) Unknown SCI (n ¼ 27, mean 33 years) To determine the WC appropriateness for persons with SCI Evaluation of WC and WC parts Functional independence measure (FIM) American spinal Injury association scale impairment scale (AIS) Appropriateness of dimensions HS deemed necessary for persons with upper level of cervical SCI All HS except one (missing, 1/27) marked as appropriate Elfenbein and Logemann [35 ] ST FS Unknown To evaluate the acoustic impact of three different HS and subsequently describe any intervention needed Audio signal transmission WC seated hearing aid dummy Testing with three HS and without HS Measurements of signal level at different angles (0 –360 degrees, interval of 45 degrees) HS interfere with the transmission of sound to the ears HS tested (3 ) created different patterns of shadow and baffle effects, magnitude of effects increased with signal frequency Magnitude of the head support effects increased with signal frequency Recommended that audiologists evaluate HS effects Fuhrman et al. [ 37 ] ST FS Single-pad modified To quantify and establish the potential benefit or harm of HS use for WC-seated children travelling in motor vehicles during rear impact Crash test dummy in paediatric WC Sled test at 26 km/h (11 g) rear impact Testing with (3 ) and without (3 )H S Four-point strap-type surrogate tie downs (WC) and three-point occupant restraint system Dummy instrumentation for head accelerations, neck axial forces and bending moments High speed video recording Maximum linear head acceleration Rotational head velocity and acceleration Normalized axial loads and bending moments Head injury criteria values at different time intervals (calculated) Neck injury criteria values (calculated) Lo w er h ea d an d n ec k in ju ry ri sk s in re ar im p ac t su g g es ted fo r W C -se at ed ch ild ren u si n g H S as co m p ar ed to no n-H S u se rs Hi gh er p ea k ac ce le ra ti o n s an d lo n g er d u ra ti o n s o f th e ac ce le ra ti on s o b se rv ed for te sts wi th o u t H S H S re du ce d ro ta ti o n al effe ct s o n th e h ea d in al l te st s H S ca n m ai n ta in str u ctu ra l int eg ri ty in rea r im p ac t Al l n ec k and h ea d inj u ry o u tc o m e m ea su res im p ro ved b y 34 –70 % fo r te sts w ith H S (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Fuhrman et al. [ 44 ] ST FS Single-pad modified To characterise WC kinematics and WC tie down and occupant restraint system (WTORS) loading for manual paediatric wheelchairs and to evaluate the effects of HS use during rear impact Crash test dummy in paediatric WC Sled test at 26 km/h (11 g) rear impact Testing with (3 ) and without (3 )H S Altered seatback level (1 , n o HS) Fo u r-po in t st ra p-ty pe su rr og at e tie d o w n s (W C ) an d th re e-p o in t oc cu p an t re str ai n t sy st em B elt an d ro d -e n d lo ad ce lls H ig h -s p eed vi d eo rec o rd ing Front, rear wheelchair tie down loads Kinematics of the wheelchair and seat HS increased WTORS loading and seatback deflections WC with HS had greater rearward WC rotations, vertical caster excursions and greater seatback deflections followed by greater rebound Fo r H S te st s, m ea n p ea k fr o n t an d rea r tie d o w n lo ad s g re at er , le ss lo ad in g o f th e la p b el t G re ate r se atb ac k re ar w ar d d ef lec ti o n an d h ea d to h ea d su p p or t in te ra cti on ab sor b ene rg y an d m ay th er ef o re red u ce th e loa d in g on th e la p b el t Gakopoulos et al. [ 84 ] D, CS (Case report) FS, CI Adremo head/ foot system Healthy (n ¼ 1, age unknown) To develop a data logger to capture data from human-wheelchair interaction for the head-foot steering system On/off switches/sensors installed on HS and foot support(s) Real-time visualisation on PC Data logger interface to multiple IMUs placed on user body (5 ) and wheelchair (1 ) and WC control inputs (7 ) One mobility task Current drawn, power consumption Bluetooth transmission latency Cross-correlation IMU data and control input Task completion time Number of activations in wheelchair sensors Fo r the le ft /r ig ht st ee ring o f th e w h ee lc h air , D C P p at ien ts ta ke lo ng er th an he al th y an d h av e d iff ic u lti es ap p ly ing co n st ant p re ss u re to H S as in te rr u p tion s oc cu r A n al ys is o f co nt ro l si g na ls m ig h t b e ob je ct iv e tool fo r th e m ea su rem en t o f PW C d riv in g sk ills an d p er fo rm an ce asse ssm en t Gakopolous et al. [ 77 ] D FS, CI Dyskinetic CP (N/A) To quantify the effect on sensor readings when force sensor arrays are integrated into a H S Non-integrated force sensor array (16 10 sensels) Four different sensor integration approaches (support materials, textile integration) Data logger from [10] Calibrated force gauge Force applied to single sensels Force applied to multiple sensels Curve mean voltage versus applied force Responses of force sensor arrays are impacted by the support material and textiles, especially at higher loads decreases in mean voltage were observed Support material and textiles caused changes in the pattern when force was applied to multiple sensels Influence of other control algorithms can be tested Geers et al. [ 32 ] D IS Papillon modified To develop an independently adjustable HS that can be steered by a joystick in 3D along biomechanical movement trajectories Position control on actuated HS (DOF ¼ 4) Proportional joystick Motion curve dependent on PWC backseat angle (DOF ¼ 1) Absolute encoders on HS (4 ) and WC (1 ) Step inputs to test controller End effector positions and orientations H S p rototy p e foc u sse d o n re p o si ti on in g ac cor d in g b io m ec ha ni ca l m o ve m en t tr aj ec to ries Pos iti on co n tr o l o n ac tu ate d H S (D O F ¼ 4) u si n g fo rce to rq u e se n so r as jo ys ti ck H S re p o si ti o n in g al o n g cu rv e th at es ti m ate s fle xi on -e xt en si on h ea d mo ti o n Fi rs t ve rs io n o f au to ma ti c ad ap ta ti on to b ac ks ea t an g le , re in it ia lizi n g h ea d p o si ti on to ch an g in g se at se tt in g s (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Fu rt he r d ev el o p m ent ad vi se d w it h re sp ec t to ra n g e o f m o ti o n , ro b u st n ess an d u se r in te rf ac e Hamzah et al. [ 33 ] D D CP (N/A) To design an adjustable 3D-printed head support CAD model of head support Static FEM analyses to find the optimal HS thickness and to check loading deformation Fabrication by 3D printer Maximum displacement of head support Displacement distribution Design allows for head rotation from left to right and is adjustable in height Simulation results suggest that increasing thickness of head support results in decreasing deformation Maximum displacement occurs with head support at maximal angle when load is applied Heitmann et al. [ 40 ] D, CS (Case series) FS, CI Healthy (n ¼ 3 and n ¼ 4, age unknown) To develop a H S mounted control interface for proportional WC control Force sensor array embedded into HS (16 1) Control of wheelchair direction and speed via HS Pilot test (n ¼ 3) with pressure distribution map on screen Five mobility tests (n ¼ 4) with HS prototype interface on WC Position, shape contact spot (PT) De via tions from reference trajectory Collision with obstacles Initial prototype tests showed that participants could drive the wheelchair accurately after a few minutes of practice Prototype does not cause limitations on head movements and does not obstruct field of view Future work will likely include quantitative measurements of the WC speed and de via tion from reference trajectories, outdoor tests and testing with disabled users Hunt Herman and Lange [ 12 ] C S (E xp er t o p in io n ) Brain injury (N/A) To describe specific principles and techniques used to manage spasticity after brain injury Classification based on seating and user characteristics HS can provide intermittent rest to prevent muscle fatigue Some clients with brain injuries have an adverse reaction to posterior tactile stimulation at their occiput Clients with flexor tone may need anterior support, such as a forehead strap, a soft collar or cervical orthosis, unfortunately, these are often poorly tolerated. Some clients may benefit from a HS to block excessive neck hyperextension (related to STNR) Undesirable head movements can be blocked with pads against the temporal, parietal, or frontal bones, but never against the mandible or temporomandibular joints, care should be taken to protect the ear from impingement (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Hoffer et al. [ 85 ] C S (E xp er t o p in io n ) FS, SD CP (N/A) To describe concepts in orthotics for CP Classification based on prognosis and function Short description of head support devices attached to body braces (resp. fixed and (dynamic) suspended HS) For sitting patients, simple body braces with HS (when necessary) are suggested to improve body position Howard et al. [ 34 ] D, ST FS Type G To fabricate a H S using 3D scanning, CAD and 3D printing To test fabricated HS against commercial HS in static loading conditions 3D scan of head from volunteer Fabrication by 3 D printer (4 , different configurations and materials) Posterior force on inner rear surface (1 ) and lateral force on the side (commercial, 3 ) Calibrated loading machine Video recording Force and displacement of loading pad Maximum force Maximum displacement Force versus displacement Amount of elastic and permanent deformation Additive manufacturing could be appropriate method to produce lighter weight, highly customised, cost-effective and safe HS for WC users Limited standardised methods for the provision of custom postural support accessories for wheelchairs available Lateral force resulted in plastic deformation of commercial HS and elastic deformation of the fabricated HS Future research is needed on design and manufacturing process parameters, clinically relevant loading conditions and parameters, financial implications of 3 D printing techniques on seating services Huhn et al. [ 41 ] C S (Case report) FS, CI Unknown CP, GMFCS Level V (n ¼ 1, 9 year) To describe the physical therapist ’s clinical decision making related to power mobility for a child with multiple disabilities Head array with switches (3 ) o n W C and PWC Training sessions over multiple years (1 / week) Mobility tasks (3 ) with RWD (2 ) and MWD 1 Separate time points Number of collisions (evaluation) Startle-like reflex caused extension of the trunk, head, and arms, thus the user was unable to stop and avoid collisions due to the persistent contact of the head with the control array User seemed to experience difficulties with timing head movements with movement of the chair (RWD), therefore trials with MWD MWD showed a decrease in collisions compared to RWD Karg and Sprigle [ 36 ] ST FS, ES Multiple (AEL, Danmar, Miller ’s, Otto Bock, Techni Seat) To develop a test methodology to statically determine the crashworthiness of WC HS To subject several commercially available HS to the test methodology FMVSS test conditions Quasi-static test procedure with increasing HS loads Tests (2 ) at min. and max. HS height settings Photography of permanent deformation Rearward angular, horizontal displacement Load-displacement curve Horizontal slip Mode of deformation Energy associated with critical deformation of HS Several head supports capable of providing adequate restraint in an impact situation At min. height, threshold load and energy requirement for displacement met by Miller ’s (2) and Ottobock (2) and only energy criterion by Dan Mar (2); at min. and max. height, criteria met by AEL (1) Functional integrity criterion met at min. height by AEL, Miller ’s (2), Otto Bock (1) (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS HS tested (except AEL) should not be adjusted to their max. height during transport More height adjustments should be tested to determine relationship with failure loads Dynamic testing of wheelchairs with head support is necessary to determine the influence of wheelchair seatbacks and HS loads in a rear end collision Commercially available head supports, with a few design improvements, can be effective in preventing neck injury in rear-end collisions Karg et al. [ 45 ] C S (E xp er t o p in io n ) FS Unknown To present guidelines and recommendations for postural support devices used on WC that also serve as seats in motor vehicles Development of guidelines and best practices WC user might need additional supports in order to maintain a seated posture during incidental movements, vibrations, turns and accelerations of the vehicle in addition to crash protection Concerns about individual supports generally related to interference with proper positioning of seatbelts; appliance of pressure, injury of a vulnerable part of the body; potential of support to break loose and cause injury Support use may be critical to respiratory and other basic functions for some WC users, and use should be continued during travel Posterior HS may limit rearward head/neck movement and thus reduce whiplash injuries Potential for whiplash injury may be decreased when a posterior HS is used and positioned behind and close (< 50 mm gap) to the back of the head HS that do not provide posterior support may increase the risk of neck hyper-extension injuries by limiting the rearward motion of the upper neck and not the head Use of an anterior forehead band is strongly discouraged (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Kenyon et al. [ 27 ] CS (Case report) FS, CI CP, GMFCS Level V (n ¼ 1, 18 years) To describe the development and implementation of an intervention program with a H S controlled mobility trainer Motorized platform with WC mounted Switches on HS (3 ) Intervention plan (12 weeks) with multiple sessions (2 ) Pre-intervention and post- intervention scores Goniometric assessment of passive ROM of upper and lower extremities, functional motor skills and active head/trunk control Gross Motor Function Measure-88, CPCHILD Power mobility screen scales Number of independent switch activations, stops, movements in preferred direction Independent switch activations by the participant steadily increased throughout the intervention period Progress from using seemingly unintentional switch activation to intentionally moving the trainer down hallways and through doorways Participant demonstrated improved test scores and power mobility skills following participation Kerst et al. [ 23 ] C S (Repeated measures) SD HeadPod Hypotonia and cortical vision impairment, GMFCS Level V (n ¼ 4, 4-5 yr) To investigate whether subjects with hypotonia near the cervical spine develop muscle strength and control while using the HS Force sensor attached to the base of the HS Observations by occupational and physical therapists Observations by teachers on day of recording Measurements during 4 months (2 3 weeks break) Force vectors, maximum force Number of times, time stamps exceeding force threshold Seat placement relative to teacher Class activities, engagement and behaviour of participants All subjects showed increased time exerting forces greater than the head in later weeks Magnitude of forces increased in later weeks, indicating improved muscle strength All subjects showed more activity in at least one direction where they previously showed minimal activity Performance level varied according to their interest or preference in the activities Therapists concluded head control improved for subjects, more active, precise and purposeful head movements Kupetz et al. [ 39 ] D FS, CI Quadriplegics (N/A) To develop a control system for quadriplegics with head and neck mobility Head movement measured using infra-red LED array Control of speed, direction via head Control of braking system via HS Design of PW that can be manoeuvred by head tracking No results available Lathem et al. [ 86 ] C S (E xp er t o p in io n ) FS Quadriplegics (N/A) To describe occupational therapy programs for C1 to C4 quadriplegics Description of occupational therapy programs Limitation in neck range of motion may hinder user ability to perform activities Appliance of support to stabilise the head during typing with tongue/mouth stick Semi-reclining or full-reclining back manual WC are suggested that can optionally be equipped with HS Head positioners fabricated for transport in vehicle (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Lin et al. [ 38 ] C S (E xp er t o p in io n ) Progressive NMD (N/A) To provide an overview of mobility assistive technology in progressive NMD Classification by mobility device, supports, control system Example of a non-proportional control system is the head array system, a 3-piece HS with switches activated by head movement Patients with weak neck extensors, such as SMA, DMD, congenital MD, or ALS, may require anterior or lateral HS such as a headband or an anterior forehead pad Swallow function must be taken into consideration during placement of anterior HS Lozac ’h et al. [ 24 ] D, CS (Case series) FS, CI SCI (n ¼ 3, 20 –22 years) To develop a control system for quadriplegics Standard potentiometric joystick behind WC Control of direction and speed (with limit) Introductory session and training (1 week, 1– 2h ) Feedback from patients during 9– 16 months Configuration helped and improved lateral stability of user ’s body as pressure against HS needed to be maintained Accurate positioning was fundamental for usage of the HS Positive user evaluations Mahmood et al. [ 49 ] C S (C ro ss -s ec ti o n al ) D Healthy (n ¼ 10, mean 27 years) To evaluate the effect of a passive neck orthosis that provides gravity compensation One time point Discrete head movements with and without HS EMG recordings (neck muscles) Inertial sensors (2 ) EMG activity level Head position variability Time required to perform task HS that compensates gravitational forces while allowing motions could help to maintain function and slow down muscle weakening HS showed potential in tests to reduce the activity level of the upper trapezius level HS had no impact on time required to perform task Manary et al. [ 43 ] ST FS Unknown To determine the performance of forward-facing commercial WC during transport in vehicles when subjected to rear-impact test conditions To gain experience with the test methods and performance criteria set forth in a proposed voluntary standard for forward facing wheelchairs in rear-impact loading Crash test dummies (M 8 ;F1 )i nW C Sled tests at 25 –32 km/h (12 –14 g) rear impact Testing with (2 ) and without (7 )H S Four-point strap-type surrogate tie downs (WC) and three-point occupant restraint system High-speed video recording Post-test inspection Performance criteria according FFRI draft Results of sled tests show structural failures in all WC tested One of the two HS did not meet the recommended height The allowed limit for peak horizontal excursion was exceeded in all tests, including the test with HS of sufficient height (1 ), suggesting that HS present on wheelchairs are not designed to provide rear impact protection Peeters et al. [ 67 ] C S (C ro ss -s ec ti o n al ) Healthy (n ¼ 25, 6– 20 years) To obtain more insight in the interaction of trunk, head and arm movements in healthy children with a specific One time point Participants seated in chair without back-or armrests Testing of max. range of trunk and head Range of motion Movement of body segments Pelvis, trunk segment, neck angles Instant of task execution Head movement opposite to trunk movement was observed in sagittal and transverse planes (except when reaching laterally in the transverse plane) and variable in the (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS focus on the segmental nature of the trunk movement, reaching (6 ), daily tasks (4 ) Optical motion capture Video recordings Relative movement between head and trunk Movement onsets of head and trunk frontal plane in most tasks As head is often moving in the opposite direction of the trunk, it is important that HS allow for head rotations independent of trunk movement Trunk and head movements onset were earlier compared to arm movement onset When performing max. head movements, interactions between trunk and head could already be seen Perr [ 47 ] C S (C ro ss -s ec ti o n al ) ES Head support (LaBac) Healthy (n ¼ 37, age unknown) To examine whether an adjustable HS might be useful to WC users One time point Tilt-in-space seating system HS (2 ) with depth adjustments Wheelchair positioned in three orientations (0, 10, 20 deg) Preferred HS position HS angle in relation to vertical With tilt-in-space or changing orientation, change of head position might be desired People do not prefer the same HS angle when compared with other people People would prefer to change the HS when their position in space changes Significant difference between 0 and 10 and 0 and 20 deg., no significance between 10 and 20 deg. Further investigation should be conducted to determine the effects of the interaction of changes in height, depth and angle of the HS Richardson and Frank [ 10 ] CS (Case-control) MD (n ¼ 29, mean 25 years) To identify the areas of difficulty encountered by a regional specialist wheelchair service in providing electrical wheelchairs in its early years, focussing on posture, pain and deformity Retrospective review of wheelchair service records Form recording issues at initial assessment, < 12 months and 13 –24 months following chair delivery Descriptive statistics Subject characteristics and impairments Functional issues Wheelchair driving skills 41% of users had weakness in the head or neck at first assessment, 21% experienced progressive weakness of the head or neck within 1 year At first assessment, 2 users needed HS, while after 24 months 6 users needed HS Spinal pain commonest pain site noted over time Transport issues are important and associated risks need to be minimised, including also adequate HS Simms et al. [ 31 ] D, ST A Unknown To test the rear-impact injury risks of adult WC users with and without HS To develop a H S Crash test dummy in WC Rear-impact sled tests with and without HS (16 km/h 10 g IIWPG pulse) Light and heavy gauge version of prototype Spring loaded mechanism Neck hyperextension Injury risk (Neck Injury Criterion and Nkm) Onset of seatback failure seriously reduces seat -integrated HS effectiveness regardless of HS design Tests without HS exposed WC users to a very high chance of neck injury, with HS showed successful withstanding of impact and prevented (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS hyperextension of the neck Both HS versions show large reductions in injury scores compared to baseline, albeit still somewhat about threshold (NIC) Cushions can be altered to improve the NIC score Attachment to commercial wheelchairs remains problematic Simms et al. [ 54 ] ST FS, A Head support (Rolko) To develop a H S To test the rear-impact injury risks of adult wheelchair users with and without HS To test effectiveness of developed HS compared with commercially available HS Prototype from [32] Crash test dummy in WC Rear-impact sled tests (16 km/h 10 g IIWPG pulse) with (6 ) and without HS (3 ) Tests with prototype (4 ) and commercial HS (2 , 1 50 mm gap) Neck hyperextension Injury risk (Neck Injury Criterion and Nkm) NIC test scores with HS (no gap) showed approx. 20 –30% chance of neck injury symptom s> 1 month, compared to 95% for without HS Nkm test scores with HS (no gap) showed approximately 5% chance of neck injury, compared to 45% for without HS Horizontal gap between head and HS should be as small as possible Prototype and commercial HS performed similarly Further research is needed on combination of HS with yielding seat back to reduce injury risks further Outcomes to be considered as trends rather than absolute predictions because of small number of tests Steenbergen et al. [ 48 ] D, ST, CS (Case study) D SMA-II (n ¼ 1, age unknown) To design a H S based on a compliant mechanism Static balancing to support the mass of the head Static tests with tilting of HS (10, 20, 30 deg) Dynamic tests during vehicle transport (50 km/h) Observations and accelerometer measurements Tests in different positions (0-90-180-270 deg) Interview and fitting of HS to subject Accelerations in vehicle Analysis showed that flexion-extension and lateral flexion-extension have to be supported, rotation of the head almost no influence on head stability HS was able to withstand accelerations 3– 5.5 m/s 2, depending on position in car HS resisted left-right accelerations not as well as forward-backward accelerations Fitting of HS proved to be difficult, compliant parts were deemed too stiff and restrictive CS (Case series) FS (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Taylor et al. [ 25 ] Neck collar (Otto Bock) CP, brain stem injury, SCI (n ¼ 33, age unknown) To design a headband that can be used in conjunction with seating system Headband used in conjunction with Otto Bock neck collar, HS Headband has stayed in place and provided upright or neutral head positioning for 30 persons Fluctuating tone and head confinement reasons for unsuccessful appliance (n ¼ 3) When providing headband, therapist has to make sure there is sufficient occipital support from the HS Togashi et al. [ 53 ] D A CP (N/A) To develop an adaptive seating system with three-degrees rotational axis Rotational axis in reclining (actuated), twist of hip and neck Variable compliance control Angle Angular velocity Torque Test trial with variable compliance control With current information not possible to evaluate applicability for children, further clinical testing needed Trail et al. [ 29 ] C S (C ro ss-se ct io n al ) A LS (n ¼ 42, 32 –75 years) To determine WC types and features that are most beneficial to persons with ALS To ascertain at what stage of disease and disability persons benefit from WC use To pinpoint the differences in user characteristics between the users of WC and PWC Survey Open questions, multiple choice, attitude scales Individual disease severity and limb function (AALS) WC type, style, features Self-perceived feelings of well-being Ability to perform ADL AALS score Extra comfort including HS was one of the most desirable wheelchair features 26% of the participants reported having difficulty holding their head upright, 17% of the participants reported aches and pains in the neck In later stages of ALS, a PWC with neck, shoulder, arm, and leg supports will allow the patient independent mobility for longer time periods When neck and shoulder weakness place the patient in a stooped, forward drooping head posture, a high back wheelchair with tilt features and HS helps in user positioning Turner et al. [ 28 ] C S (C ro ss-se ct io n al ) SC I (n¼ 384, 18 –84 years) To investigate, in a community sample of persons with SCI, chronic pain prevalence, associated factors, sites, characteristics, interference with daily functioning, treatments received and treatment helpfulness Survey Comparison to NWRSCIS database Chronic Pain Grade questionnaire Short-Form MCGill Pain questionnaire Pain sites Treatments Individuals with tetraplegia significantly more likely to have neck and shoulder pain than those with paraplegia Neck pain significantly more present in persons with cervical and T1-5 injuries than in those with T6-12, more present in C1-4 than in L1-S4/5 High rate of neck pain in the C1-4 group indicates possibility that immobilisation is a cause as persons are likely to use HS on WC (continued )
Table 4. Continued. Ref. Study design Type of HS Comm. device Population (no. subjects, age) Research aim Methods Outcome measures Key findings with respect to HS Uyama and Hanaki [ 5 ] CS (Case series) FS i2i, x:Panda PVL (n ¼ 2, 6-9 years) To investigate the effect of the i2i HS Comparison between x:Panda and i2i Posture and respiratory function (0, 15, 30 degrees tilt) Photography and respirometer Evaluation of scoliosis (User 1) Powered wheelchair driving competence test (User 2) Four segment lines in frontal plane, respiratory function (User 1 and 2) Cobb angle on X-ray (User 1) PMP test (User 2) i2i able to provide a more upright posture on WC; respiratory and swallowing function, upper extremity ADL improved i2i provided direct application of force to the head/neck rather than indirectly to the pelvis Limitations of i2i include lack of flexibility, need for expert adjustment, possible restriction of upper limb mobility Young et al. [ 47 ] ST FS To present MADYMO model of WC with deformable seatback and additional HS MADYMO model including seatback, HS Parameter optimisation on configuration Comparison to experimental data and model [ 87 ] Neck Injury Criterion (NIC) Predicted seatback frame angular deflection Predicted trajectories for dummy head and shoulders, top of seatback frame Predictive ability of the final model improved compared to baseline model [ 87 ] For NIC reduction, minimising the horizontal gap between head and HS is most important, followed by increasing cushion stiffness A stiff HS cushion should be used when attaching a H S to aW C Zisserman and Cole [ 88 ] CS (Case report) FS Unknown CP (n ¼ 1, 54 year) To describe rainwater covers for a three-piece HS Three-piece head array on HS Covers do not reduce contact sensitivity Clinical studies (CS), development (D), system testing (ST) fixed static (FS), externally adjustable static (ES), independently adjustable stati c (IS), adaptive (A), standard dynamic (D), suspended dynamic (SD), control inter-face (CI); head support (HS), wheelchair (WC), power wheelchair (PWC).
given by one of the OTs as she mentioned that several of her cli-ents with ALS adjusted head position to improve their breathing.
The users with an externally adjustable system as well as two OTs emphasised that there is only a narrow bandwidth in which the optimal head support position for a certain sitting position can be found. Small adjustments have a large impact on per-ceived comfort level. This was further illustrated by User 3 who mentioned that compared to his sporting wheelchair with static fixed head support, his independently adjustable head support significantly helped to prevent pain and fatigue.
Limitations of current head supports
Although the currently available independently adjustable head supports do provide opportunity to adjust the head support to an optimal position, several limitations were discussed. Firstly, both the OTs and the two independently adjustable head support users agreed that for the system currently often delivered in the Netherlands (i.e., independently adjustable Papillon, Focal Meditech B.V.), the possibility to individually adjust head support position is strongly valued, however in general many adjustment steps are needed to come to the desired head support position. Especially together with significant changes in seating configur-ation, many steps are needed as the head support position needs to be adjusted in parallel. Secondly, currently it is hard to provide adequate head support in active postures in which the head is placed more forward. A commonly applied solution is the usage of a headband, however all participants mentioned their dislike (respectively perceived dislike by clients) of this solution and described it as uncomfortable and unappealing in appearance. Thirdly, two of the OTs mentioned that the fixation of the head in the head support systems is somewhat undesirable, as it further restricts the possibilities for head movement for users who still are mobile to a certain extent. This was especially regarded as important considering the field of view (e.g., looking left and right), for example during driving. Finally, one of the OTs, as well as User 3, mentioned the occurrence of unwanted dynamical dis-turbances during driving.
Future
The recommendations from the OTs and end users regarding independent repositioning in future head supports can be sum-marised as follows: (1) the repositioning should be done more efficiently (2) the repositioning should appear and feel more nat-ural and (3) the control interface should be more intuitive. From a user perspective, a reduction of effort and time required for mak-ing adjustments is desired. To lower the number of adjustments needed, all OTs underlined the need for integration of the head support position with the wheelchair seating (especially in the sagittal plane), introducing for example parallel adjustment of the seat and head support. With respect to the control interface, all OTs also mentioned that integration with wheelchair control inter-face is desired, such that users do not need to use an add-itional interface.
The following desired functionalities were identified by the OTs and wheelchair users: (1) improved support of the head in active postures (2) support of head motions and (3) reduction of external disturbances experienced during wheelchair driving. There is room for improvement with respect to the head support in more active postures, e.g., improvements of, alternatives for the headband could be considered. Additionally, the support of small head motions was identified as a desired functionality, mainly to widen the field of view of the user in addition to eye movements. Moreover, it was noted that supporting movements may help in maintaining head mobility for a longer time. Furthermore, possibly future head supports could take into account the minimisation of unwanted effects of vibrations and other disturbances encountered during wheelchair driving.
Application of (automatic) adaptive behaviour as a means to improve the efficiency and the intuitiveness of user interface was introduced by the interviewer during the interviews as a possible solution. The wheelchair users perceived this concept as a pos-sible way to reduce the input required to come to an optimal head position. However, by all users it was regarded as essential that the position of the head support was ultimately controlled by his- or herself, as sitting postures vary every day and through the day, and accurate positioning is essential. It was noted that the design of the head support system, possibly including shared control between the user and the system, also needs to take into account the different needs of the user depending on the task being executed and the (dynamic) environment the user is oper-ating in, as the desired output is not always the same.
Finally, several remarks from the OTs as well as the wheelchair users illustrated that it is important that an individual match is made between user and device. Especially the personalisation of the interface to the (progressive) medical condition of the user and his- or her additional limitations should be considered. As expressed by two of the OTs, adaptive behaviour of the head sup-port system needs to be considered carefully and on an individual basis, as unwanted side effects such as destabilisation of posture or aggravation of posture deformities should be avoided.
Discussion
Although a significant number of studies (n ¼ 40) was included in the scoping review, only a very limited amount of clinical evi-dence was found for the effectiveness of wheelchair mounted head support systems. Overall, there was a high clinical and meth-odological heterogeneity between studies. Based on the literature review, the user interviews and the input from the expert panel, the following important system characteristics were formulated: 1. Independent repositioning of the head support in relation to
upper- and lower body support 2. Biomechanical support of head motions
3. Integration with seating system and potentially other assist-ive devices to provide total body support
4. Adaptation to dynamic environments
Table 5. Description of interviewed end users (N ¼ 3).
User Gender Age Disease Impairments (self-described)
Head support
Usage
Type System
1 F 34 SMA Limited muscle force and range of motion
Static fixed Standard Incidental
2 F 28 Static independently
adjustable
Papillon, Focal Meditech B.V.
Regular 3 M 24 No independent balancing of the
head, severely limited mobility and range of motion
