The Fundamental Principles of Seating and Positioning in Children and Young People With Physical Disabilities

8/12/2019 The Fundamental Principles of Seating and Positioning in Children and Young People With Physical Disabilities

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The Fundamental Principles of Seatingand Positioning in Children and Young

People with Physical Disabilities

Laura NevilleBSc (Hons) Occupational Therapy Student

University of Ulster

Supervised by:

Mrs Jackie Quigg (School of Health Sciences UU)

Dr Alison Porter Armstrong (Health andRehabilitation Sciences Research Institute UU)

Commissioned by James Leckey Design Limited

Summer 2005


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Project Background

James Leckey Design Limited (Northern Ireland) is a company specialising inequipment design, manufacture and provision for children with physical disabilities.As part of a 2 year project, involving the University of Ulster (with Mrs JackieQuigg and Dr Alison Porter Armstrong) to research the clinical effectiveness of oneof their product ranges, the company commissioned three BSc (Hons) OccupationalTherapy students (Laura Neville, Linda McNamara and Glenda Alexander) to conductcritical reviews of the literature in three designated areas:

1) Fundamental Principles of Seating and Positioning in Children and YoungPeople with Physical Disabilities.(Laura Neville)

2) Postural Management: Components of Specialised Seating Equipment.(Linda McNamara)

3) Early Intervention and the Effects of Adaptive Seating on Function.(Glenda Alexander)

The critical reviews undertaken were completed between June and August2005 and conducted as part of a steering group comprising of: Mr James Leckey(James Leckey Design Limited); Mr Noel McQuaid (Technical Director, JamesLeckey Design Limited), Mrs Clare Wright (Research Occupational Therapist, James

Leckey Design Limited), Mrs Jackie Quigg (UU) and Dr Alison Porter Armstrong(UU), with formal supervision provided on a weekly basis. This is the first of threecritical reviews commissioned by James Leckey Design reviewing and criticallyappraising the literature regarding the fundamental principles of seating and

positioning in children and young people with physical disabilities.

Acknowledgements

I would like to thank Mrs Jackie Quigg and Dr Alison Porter Armstrong fortheir continued support, direction and guidance in regarding completion of thisreview. Thanks also to James, Noel and Clare for providing the opportunity to engagein this project and thank you to Linda and Glenda for your constant support andencouragement and making the completion of this review possible.


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Index of Contents Page

Introduction 3Methods 4The relationship between posture, movement, stability and function 4

Normal posture 6

The action of sitting 6 Neutral sitting posture 7The 90-90-90 position how functional? 8Functional Sitting Position 9Factors affecting positioning 13Primitive reflex activity 13Structural asymmetries 15Abnormal muscle tone 18Childhood conditions 20Cerebral Palsy 20Congenital hip deformity/Developmental Dysplasia 23Rett Syndrome 24Duchenne Muscular Dystrophy 25Spina Bifida 26Conclusion 27References 28Appendices 35


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Principles of Seating and Positioning

Introduction

The prescription of appropriate seating equipment for children and young

people with physical disabilities is important, in order to provide an optimal seated position from which they may engage in functional activities. Research hasevidenced the benefits of adaptive seating to include improved postural alignment(Miedaner 1990; Myhr and von Wendt 1991), development of motor skills (Green and

Nelham 1991), helping the prevention of fixed deformity (Pountney et al 2002) andfacilitation of upper extremity function (Myhr and von Wendt 1991; Myhr et al 1995,van der Heide 2003). It is imperative that health professionals prescribing andengineers designing seating equipment are well informed regarding the fundamentalseating principles that dictate the sitting postures of children and young people andthe impact they have on long term health and function.

Traditional emphasis regarding positioning is placed on achieving an uprightsymmetrical posture utilising the 90-90-90 flexion at the hips, knees and ankles

position (Green and Nelham 1991; Ham et al 1998; Erhardt and Merril 1998, Hong2002). Although an important posture to achieve, this upright position is suggested asnon-functional (Engstrm 2002) and difficult to maintain over time (Howe andOldham 2001), resulting in adoption of compensatory postures which may lead tolong term deformity and further deterioration when appropriate external support isunavailable. Seating solutions may require reaching a balance between an uprightanatomical symmetrical posture and ability to function (Ham et al 1998; Pope 2002).

The focus of this research was to review and critically appraise the literatureregarding the fundamental principles of seating and positioning used with childrenand young people with physical disabilities. The report uses evidence from publishedstudies, and expert opinion to identify seating and positioning principles used withchildren and young people with disabilities, the benefits of optimal positioning and

problems which may incur as a result of incorrect positioning. An overview ofnormal and abnormal postures is discussed from biomechanical andneurophysiological viewpoints. Common childhood neuromotor and neuromuscularconditions are considered with respect to clinical manifestations and resultant

positioning problems which health professionals and engineers must consider when prescribing / designing seating interventions to promote long term health andfunctional independence.


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Methods

A literature search was conducted using the following electronic data bases;AMED (Allied and Complimentary Medicine), ASSIA (Applied Social SciencesIndex and Abstracts), BIDS, British Nursing Index, CINHAL (Cumulative Index of

Nursing and Allied Health Literature), Embase, ISI Web of Science, MEDLINE,

OTDbase, Pubmed, Proquest, Psychinfo and Zetoc. Criteria for considering relevantliterature for review required all articles to be in the English language, and published

between January 1990 up to and including May 2005. On occasions, earlier dated key papers were included for relevance. Tables 1-7 (appendix 1) identify the key wordsutilised in the search strategy with respect to the data bases searched. Electronicdatabase searching was supplemented with hand searches, citation searches ofreference lists, conference proceedings and retrieving relevant literature from

published textbooks. The McMaster critical review forms (Law et al 2002) were usedas a guideline for critiquing relevant studies attained.

The relationship between posture, movement, stability and function

Posture may be defined as, the position of one or many body segments inrelation to one another and their orientation in space (Ham et al, p26). Bodysegments are referred to as the head, thorax, pelvis, lower limbs and feet, whilst the

body linkages are considered as the spinal joints, hips, knees, ankle and shoulder joints (Pope 2002). When considering posture, one should not consider it as static, but as an active and dynamic process which underpins movement and function (Hong2005). Normally, our postures continuously shift and change position to facilitatemovement to engage in functional activities. Pope (2002) identifies that posture is a

prerequisite for movement. Howe and Oldham (2001) also highlight that posture andmovement are inextricably linked, referring to posture as a temporary arrestedmovement, which is in a constant state of change. From a neurodevelopmental

perspective Nichols (2001) suggests that the development of postural control andacquisition of motor milestones are intrinsically linked. Ham et al (1998) support thisassumption highlighting that there is constant neuromotor activity being used tomaintain body balance and posture. Engstrm (2002) further suggests that biologicaland physiological influences affect body position and posture. This is also in addition

to the somatosensory, vestibular and musculoskeletal systems (Nichols 2001).

For functional movement to occur in sitting, literature suggests that stability of proximal body parts (pelvis, spine and shoulders) is a prerequisite for distal control(Green and Nelham 1991; Herman and Lange 1999). For example, pelvic stability isrequired for the spine so that the neck is free to move; shoulder girdle stability isrequired to stabilise the arm for fine motor and hand control. Washington et al (2002)however suggests that there is limited published research to support this hypothesis


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suggesting that the relationship between proximal stability and distal control is notnecessarily one of cause and effect. This is supported by Case-Smith et al (1989) whoidentified weak correlations between proximal control and hand function in typicallydeveloping children as assessed by the Posture and Fine Motor Assessment of Infants(Case-Smith 1987). However evidence suggests that clinicians and therapeuticseating do utilise the principle of achieving pelvic stabilisation to maximise distal

control for function in children with neuromotor dysfunction. This is illustrated in theliterature by the use of anterior pelvic stabilization devices in seating interventions(Reid and Rigby 1996; Reid 1996, Rigby et al 2001) and by promoting anterior pelvictilt via the use of the functional sitting position in children with cerebral palsy (Myhrand von Wendt 1990, 1991; Myhr et al 1995. Children with neuromotor andneuromuscular dysfunction will require external support from seating systems toaccommodate for compromised postural control and postural deficits. Based onclinical and empirical evidence, it is accepted that the general goals of seating and

positioning include the following, and will be considered in the context of this review:

1) Normalise tone or decrease abnormal influence on the body.2) Maintain skeletal alignment.3) Prevent, accommodate or correct skeletal deformity.4) Provide stable base of support to promote function.5) Promote increased tolerance of desired position6) Promote comfort and relaxation.7) Facilitate normal movement patterns or control abnormal movement patterns.8) Manage pressure or prevent the development of pressure sores.9) Decrease fatigue10) Enhance autonomic nervous system function (cardiac, digestive and respiratoryfunction)11) Facilitate maximum function with minimum pathology.

(Jones and Gray 2005).


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Seating and Positioning: Principles and Practice

Normal Posture

Following a review of the literature, it is difficult to define what constititutesnormal posture. This is because each person is unique regarding their physiological

profile and continually engages in a number of postural variations which may beattributed to fatigue and emotional state (Howe and Oldham 2001). From a

biomechanical viewpoint, good posture is dependent on the balance of the skeletonand symmetrical alignment of body segments. Engstrm (2002) states that those who

balance their body in accordance with mechanical rules for human body systems(laws of physics) tend to be more erect. From a neurophysiological anddevelopmental perspective, normal posture is also dependant on the development ofnormal postural control which is described as the control of the body s position inspace in order to obtain stability and orientation (Brogren et al 1998) and is influenced

by the neuromotor, somatosensory, vestibular and musculoskeletal systems (Nichols2001). Postural control requires achieving normal developmental milestones andincludes the development of postural reactions (righting, protective and equilibriumreactions), developmental integration of primitive reflexes (asymmetrical tonic neckreflex, symmetrical tonic neck reflex, tonic labyrinthe reflex), normal muscle tone,normal postural tone and intentional voluntary movements (Wandel 2000).

The action of sitting

It is also useful to understand the interface between the standing and seated posture. Turner (2001) suggests the action of sitting results in flexion of thethoracic spine, flexion of the lower extremities, and backwards rotation of the pelvistowards the rear of the seat. Pelvic rotation in turn dictates the compensatory curvesof the spine, which in turn dictates the position of the remaining body segments(Harms 1990). The pelvis is then placed on the seat against the backrest. The trunkextends, moving towards the backrest. The upper part of the pelvis is in contact withthe lower part of the backrest, thus achieving pelvic stability, with the person nowsitting in an upright neutral position.


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Neutral sitting posture

Sitting skills emerge in a normally developing child approximately between 7and 9 months and requires the child to maintain postural control of the head, trunk andextremities against the pull of gravitational forces (Wandel 2000). The majority ofthe literature refers to the 90-90-90 position as the normal upright neutral seated

posture and considers the head, trunk and extremity positions in relation to each other.Assuming that one is sitting on a flat, right angled chair in a static or neutral position,the upright symmetrical position is characterised by extension of the trunk, the pelvisin anterior tilt, thighs slightly abducted, parallel and horizontal and the iliac crestsaligned and level in the lateral plane (Ham et al 1998). The hips, knees and anklesare placed at ninety degrees of flexion, the feet are in plantar grade or 0 degreesflexion (Green and Nelham 1991) and the head is positioned in midline andmaintained in the vertical plane (Erhardt and Merril 1998). The head position inrelation to the spine is important as it has a direct effect on posture. Loss of headcontrol can therefore affect body position (Ham et al 1998). When the pelvis is inanterior tilt, the centre of gravity falls anterior to the ischial tuberosities (Ham et al1998) hence the base of support is provided through the ischial tuberosities and theupper thighs (Howe and Oldham 2001). Depending on the chair design, weight will

be transferred through the back rest, and the arm rests to the floor through the feet(Pynt et al 2001). The goal of upright positioning is therefore to promote symmetryand alignment of the body segments and linkages (Ham et al 1998). The sitting

position is more relaxing than the standing posture, provides a greater support surfaceand allows relaxation of the muscles of the lower extremities (Howe and Oldham2001). However, there is greater potential for pelvic instability in sitting compared tostanding due to the hip joint position, the anatomical shape of the ischial tuberosities(Reid and Rigby 1996) and the tendency for the pelvis to rotate backwards (Engstrm2002).

In the seated posture, it is desirable that as much contact is made with thechair s support surface in order to provide maximum stability to facilitate function(Green and Nelham 1991), with the goal of seating being able to achieve a stable baseof support surface to allow function (Jones and Gray 2005). However in right angledseating, it is difficult to achieve and often results in a person acquiring a slumped

posture to compensate for fatigue and discomfort. Combined with the effects ofconstant activation of the erector spinae muscles, a person will gain relief fromexcessive muscle activity by sacral sitting, resulting in posterior rotation of the pelvis,accentuation of thoracic kyphosis and cervical lordosis, loss of lumbar lordosis of thespine (Pynt et al 2001) and increased risk of tissue trauma in the sacral area (Han et al

1998). A further goal of seating is to prevent or decrease the occurrence of pressuresore development (Jones and Gray 2005). Conflicting opinion exists regarding thecausation of posterior pelvic tilt. Some authors postulate that the tendency for the

pelvis to rotate posteriorly may be due to tension in the hamstrings and glutealmuscles which promotes flexion of the lumbar spine hence inducing posterior rotationof the pelvis. (Mayall and Desharnais 1995; Trefler and Taylor 1991; Pynt et al 2001;Effgen 2005). Contrary to opinion Engstrm (2003) attributes the tendency ofthoracic spine collapse (flexion) as influencing the backward rotation of the pelvis andsuggests that seating interventions should aim to improve thoracic extension to block


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flexion of the spine. Engstrm (2002) suggests that backward inclination inducesflexion of the thoracic spine whereas a forward inclined seated position promotesthoracic extension. A study conducted by Miedaner (1990) investigating the effectsof sitting positions on trunk extension for children with motor impairment supportsthis assumption. Miedaner concluded that anterior sitting (20 and 30 inclined)compared to level bench or floor sitting increased trunk extension, as measured by the

modified Schoeber Measurement of Spinal Extension (AAOS 1975). Using arandomized complete block design a significance level of p= 0.001 demonstrated atrue mean difference between the different sitting positions, however small samplesize limits the generalisability of this finding.

The 90-90-90 Position How Useful?

The 90-90-90 position may be regarded as an ideal seated position from anergonomic perspective (Engstrm 2001). From an anatomical view point the goal isto achieve maximum orthopaedic symmetry between left and right sides of the bodyvia a neutral pelvis to avoid obliquity, rotation and posterior pelvic tilt (Lange 2001).Advantages of this position depicted in the literature include minimisation oforthopaedic deformity (Ham et al 1998) and promotion of proximal stability which inturn promotes distal control (Lange 2001). One of the goals of seating is to promotedrelaxation and comfort (Jones and Gray 2005). Kangas (2002) suggests the 90-90-90

position can passively and temporarily reduce tone when considered as a resting position. Two studies identified support for this assumption.

Nwaobi et al (1983) conducted a study using electromyography (EMG) toinvestigate the activity of extensor muscles of the lumbar spine in children withcerebral palsy in different seating positions. Seat surface inclinations of 0 and 15combined with backrest inclinations of 75, 90, 105 and 120 provided the testingconditions. Results concluded that electrical activity was least when seat surfaceelevation was 0 and backrest inclination was 90. Caution is advised in generalisingresults as testing positions were based on EMG activity recording 60 seconds ofsitting in each position and on a small sample of eleven subjects. A subsequent studyconducted by Nwaobi (1986) regarding the effects of body awareness in space ontonic muscle activity of patients with cerebral palsy concluded that muscle activitywas lower in the upright position (90-90-90) than the reclined position (30 fromvertical plane), with statistically significant results obtained for back extensors andhip adductors (p = 0.05). One of the goals of seating is to promote increased tolerancein the desired position (Jones and Gray 2005). Findings from this study suggest that

extensor tone is increased in the reclined position.

Literature also identifies that the 90-90-90 position is difficult to maintain overtime (Ham et al 1998; Howe and Oldham 2001) and may impede function (Engstrm2002). One study however concluded that the upright position was more functional incomparison with anterior and posterior sitting positions. Nwaobi (1987) investigatedseat orientation of upper extremity function in thirteen children with cerebral palsy(spastic and athetoid) and concluded that arm movements were significantly faster


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when positioned in 90-90-90 compared to anterior (15) and posterior (15 and 30)orientations. The authors attribute this outcome to either improved control of ordecreased abnormal neuromuscular activity in the upright position. The authors alsoconsider loss of horizontal eye contact and greater effort required to counteractgravitational effects in the posterior orientation as impeding upper extremity function(Nwaobi 1987). Other studies identified compare the upright neutral position to

alternative sitting positions e.g. inclined/reclined seat base, inclined/reclined backrest, and their relationship to function. Findings from studies examining the effects ofseat inclination on upper extremity function are mixed. Some authors (Mhyr and vonWendt 1990, 1991, Myhr et al 1995) concluded that anterior sitting in the functionalsitting position improved upper extremity function in children with neuromotordysfunction. Other research studies report no effects on upper extremity functionwith regard to seat inclination (McClenaghan et al 1992) and no effects regardinganterior tipped seating on respiratory function in children (Reid and Sochaniwskyj1991). These studies will be reviewed in the next section.

Several authors advocate the idea of bypassing the 90-90-90 position. Kangas(2002) argues that for functional performance, movement and tone are required, butthe 90-90-90 position prevents functional performance as it is essentially a resting

position and too restrictive. Minkel (2001) postulates that the goal of adapted seatingshould extend beyond achieving perfect symmetry, but should focus on providingexternal support, at the angles needed by an individual to achieve an upright, stableand functional position. It is recognised that ideology based on expert opinion andexperience provides important information which may be added to a growingevidence base however caution must be exemplified when using anecdotal evidenceto justify practice. Shimizu et al (1994) acknowledges that deviation from the optimalupright position is often required to accommodate for fixed deformities and abnormal

postural tone, yet basic positioning principles should be maintained. This is to provideequal distribution of weight, for support, stability and comfort. It may be derived thatthe 90/90/90 position is a useful baseline position to achieve to promote symmetrywith further seating adaptations / components being utilised to facilitate function.

Functional Sitting Position

A major goal in seating is to provide and stable base of support to promotefunction and to enhance autonomic nervous system function (Jones and Gray 2005).Pain et al (2003) suggests that alternative sitting positions to 90-90-90 are being

proposed and include forward inclination to permit engagement in functional tasksand backwards recline for relaxation. Findings from studies regarding the effects ofseat inclination on function and/or postural control are conflicting. Studies identifiedfor review, focus on the cerebral palsy population and/or typically developingchildren. Several authors suggest that forward inclination promotes improved upper


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extremity function (Myhr and von Wendt 1991, Myhr et al 1995; Reid 1996); trunkextension (Miedaner 1990) and improved postural efficiency (van der Heide 2003,Myhr and von Wendt 1990, 1991). Other research studies report no effects ofanterior tipped seating on respiratory function (Nwaobi and Smith 1986, Reid andSochaniwskyj 1991, Redstone 2004); upper extremity function (McPherson et al1991; McClenaghan et al 1992) and postural stability (McClenaghan et al 1992).

Myhr and von Wendt (1991) conducted a study to find a functional sitting position for children with cerebral palsy. Twenty-three children were photographedand video filmed in six different sitting positions, including the functional sitting

position (FSP). The FSP required the pelvis to be anteriorly tilted, with the upper body anterior to the fulcrum at the ischial tuberosities to allow an upright posture.Symmetrical weight bearing through the ischial tuberosities was achieved via fixationof hip belt at 45 angle and use of abduction orthoses. Results suggested that thefunctional sitting position in comparison to the children s original sitting positionminimised pathological reflexes, improved postural control and improved upperextremity function when children sat in forwards inclination (mean 8, range 0 to15), with a firm back rest supporting the pelvis and supported by a cut out level tableto eliminate lateral sway imbalance. Results support previous preliminary findingsinvestigating the FSP and its impact on reduction of spasticity and enhancement of

postural control (Myhr and von Wendt 1990), although seat inclination alone showedno identifiable effects, it is subjectively suggested that anterior tilting may stretch thehamstring muscles when the pelvis is rotated forward hence reducing spasticity. Thisis assuming the feet are secured and fixed and the lower extremities are not permittedto flex under the thighs, however the authors do not provide a specific descriptionregarding the exact positioning of the feet. A five year follow up study investigatingten children with cerebral palsy (Myhr et al 1995) concluded that the FSP contributedto significant improvement (p> 0.05) in head, trunk and foot control and upperextremity function in eight of the ten children as assessed by the Sitting AssessmentScale (Myhr and von Wendt 1991).

A study conducted by Reid (1996) utilising a repeated measures experimentalcross over design compared the effects of level or flat benched seating versus saddle-

benched seating (15 anterior tilt) on postural control and reaching motions of sixchildren with cerebral palsy assessed by the Sitting Assessment for Children with

Neuromotor Dysfunction (Reid 1995). Small sample size rendered insufficient power analysis to detect statistically significance differences, however group resultsand single subject data analysis suggest that saddle sitting may potentially improve

postural and reaching movements.

An investigation regarding the development of postural adjustments during

reaching in twenty-nine typically developing children, and ten adults (van der Heideet al 2003) suggested that forward tilted seating (15 seat surface inclined) was a moreefficient position for postural efficiency compared to horizontal (0) and backwardstilted (15 seat surface reclined) sitting positions. Findings were contrary to theoriginal hypothesis postulated by the authors, who hypothesised that backward sittingwould have been the most efficient position as it would passively counterbalance theforward body sway induced by reaching movements. Sitting positions were studiedvia surface Electromyograms (EMG) and kinematics, therefore quantifying results.


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Miedaner (1990) investigated the effects of sitting positions on trunk extensionin fifteen children with motor impairment (cerebral palsy) using the modified SchoberMeasurement for Spinal Extension. As previously discussed, results suggested thatthe anterior sitting (20 and 30 inclined) tend to increase trunk extension comparedto level bench or floor sitting. Subjective observations suggest that upper extremityfunction is not compromised despite increased muscle activity required to maintain

trunk extension when the seat is tilted forward. Further EMG analysis of spinalmuscle activity regarding trunk extension would objectify results.

Contrary to these findings other authors conclude that seat inclination has nodiscernable effects. McClenaghan et al (1992) investigated the effects of seat surfaceinclination on postural stability and function of the upper extremities of children withcerebral palsy. Twenty children (ten non-impaired; ten mild cerebral palsy) wereincluded in the study, with seat surface inclinations depicted as 0 horizontal, 5anterior tilt, and 5 posterior tilt, with seat to back inclination maintained at 90.Previous authors (Myhr and von Wendt 1990, 1991; Miedaner 1990; Myhr et al 1995;Reid 1996; van der Heide 2003) used seat surface inclinations of greater than 5(range 8- 30); however McClenaghan justifies 5 inclination by stating that greatertilting is difficult to tolerate for an extended period with this assumption based on

pilot investigations. Previous research has shown that lumbar spine muscle activityincreases when the seat is tilted forward (Nwaobi 1987).

McClenaghan et al (1992) concluded that significant between-groupdifferences were observed on most dependent measures (p>0.05) however, suggestedthat anterior tilt seating in cerebral palsied children may actually disturb posturalstability, without improving performance of the upper extremities and suggested

posterior tilt as a more efficient position during periods of upper extremity function.Although only applicable to the adult cerebral palsy population, McPherson et al(1990) also concluded that no significant differences could be attributed to seatinclinations regarding upper extremity movement. Hadders et al (1999) whenconducting a study to investigate the development of postural adjustments in reachingin infants in children with cerebral palsy also favoured the reclined position (semi-recline at 45) as opposed to lying in supine, long leg sitting and upright sitting).McClenaghan (1992) also argues that the use of a table in Myhr and von Wendt(1991) study may result in weight bearing on the support surface, which in turnactually impedes the use of the upper extremities for function. This would hinder thecarrying out of bilateral activities.

Similar findings have been reported regarding the effects of seat inclination onrespiratory function. Redstone (2004) investigated the respiratory patterns in upright

and semi-reclined seating positions in ten preschool children with cerebral palsy andten typically developing children. No significant differences could be attributed toseat position alone. Reid and Sochaniwskyj (1991) conducted a study to investigatethe effects of anterior tipped seating on respiratory function of normal children andchildren with cerebral palsy. Twelve subjects (six normal; six cerebral palsy) werecompared in level (0) and anterior tipped (10 seat surface inclined) seating, withrespiratory function measured by respitrace transducers. No significant differences inrespiratory function could be attributed to seat inclination alone either in the normalor cerebral palsy groups, however it is recognised that a larger sample size may have


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yielded greater power analysis to detect statistical significance. Nwaobi and Smith(1986) in an earlier study investigated the effect of adaptive seating on pulmonaryfunction of eight children with spastic cerebral palsy, and concluded that pulmonaryfunction was more efficient when children were positioned in adaptive seating in theupright (90-90-90) position.

Continued disparity in the literature exists regarding the direction of seatinclination for improved function and postural control. Studies reviewed used smallsample sizes, lacked power analysis, and used various seat inclination values anddifferent assessment times in seated positions and short periods of data analysistherefore making comparisons difficult. Additionally some studies do not refer tocerebral palsy as a heterogeneous group. Selection bias was also evident in somestudies therefore questioning the reliability of the findings. Future research shouldutilise larger sample sizes and to aid power estimates so that results may begeneralisable to the sample population.


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FACTORS AFFECTING POSITIONING

Children with neuromotor / neuromuscular dysfunction will havecompromised postural control. This section discusses postural problems and how theycan affect positioning and possible seating solutions that accommodate or preventfurther deviation from normal posture; however consideration regarding theeffectiveness of seating components and their functional use are beyond the scope ofthis report. The problems depicted in the literature include a) retention of primitivereflexes; b) presence of structural asymmetries c) abnormalities of muscle tone.

a) Primitive Reflex Activity

Asymmetrical Tonic Neck Reflex Symmetrical Tonic Neck Reflex Tonic Labyrinthine Reflex Positive Supporting Reaction Moro Reflex

Asymmetrical Tonic Neck Reflex (ATNR)

According to Ham et al (1998) ATNR is elicited when the head is turned toone side. The reflex is characterised by increased extensor tone on the side to whichthe head is turned and increased flexor tone on the opposite side. This reflex isusually integrated between 4-6 months (Lowman 2000). According to Hong (2005)the continued presence of ATNR after 4-5 months is considered abnormal andinterferes with rolling, bilateral integration, reaching and grasping activities. Due tothe tendency of children to use one hand, continued repetitive movements may lead tothe development of scoliosis (Ham et al 1998). Extensor postures (Levitt 2004), softtissue balance and asymmetries in muscle tone may also lead to secondary deformitiesincluding subluxed hips and, contractures mainly affecting the hip flexors and

adductors (Hong 2005).

Symmetrical Tonic Neck Reflex (STNR)

STNR is elicited when the head is flexed or extended (Lowman 2000).According to Ham et al (1998) when the head is flexed, the upper extremities flex andthe lower extremities extend. When the head extends, the upper extremities extendand the lower extremities are pulled into flexion. This reflex is normally integrated


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between 4-6 months. Retention of STNR interferes with reciprocal creeping, walking(Lowman 2000) and upper limb function (Ham et al 1998.)

Tonic Labyrinthine Reflex (TLR)

TLR is elicited when in supine or being moved into flexion or extension(Lowman 2000). In supine or with the head extended, there is increased extensionthroughout the body. In prone or when the head is forward of the upright position,there is an increase in flexion throughout the body (Ham et al 1998). This reflex isusually integrated between 4-6 months. Retention of TLR interferes with sideturning, rolling, and lying to sitting ability and creeping (Lowman 2000).

Positive Supporting Reaction

The positive supporting reaction is elicited when infants are supported underthe shoulders and held upright with feet flat on the floor (Ham et al 1998)Proprioceptive stimuli via the feet induce extension of the lower extremities and

plantar flexion of the feet (Lowman 2000). This response is usually integrated between 1-2 months and disappears when the child learns to weight bear through feetand stand independently (Ham et al 1998). Retention of this response will interferewith walking patterns and may lead to walking on toes (Lowman 2000). In addition,Ham et al (1998) suggest that proprioceptive stimuli applied to the intrinsic musclesof the feet when pushing down on foot rests can also elicit an extensor thrust, whichcan lead to sacral sitting and the development of extension contractures of the hip.

Moro Reflex

Ham et al (1998) suggest the Moro reflex is elicited when the head extends backwards, which results in an extension pattern of the body, with the arms extended,abducted and externally rotated followed by a flexion posture. This reflex isnormally integrated between 4-6 months and if retained, interferes with head control,sitting equilibrium and protective reactions (Lowman 2000), all of which are neededfor postural control.

Seating Interventions

Goals of seating include normalising tone or decreasing abnormalinfluences on the body and to facilitate normal movement or pathological activity(Jones and Gray 2005). Although Wright-Ott and Egilson (2001) suggest that tilt inspace may provide a child with hypotonia (low muscle tone) with greater tolerance forupright sitting, other authors suggest that tilt in space and/or reclined sitting may


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increase pathological reflexes (Nwaobi et al 1983; Nwaobi 1986; Myhr and vonWendt 1990, 1991, Mhyr 1994; Engstrm 2002).

As previously discussed, Nwaobi (1986) concluded that children with cerebral palsy have better postural control in the upright rather than the reclined or tilted position. In testing conditions Nwaobi (1986) found that increased extensor tone

resulting from TLR was elicited by the position of the head in the reclined position,adding that loss of horizontal eye contact resulted in a greater effort to overcomegravity and consequently increased tone. This study also highlighted that asymmetryof muscle activity in back extensors and prolonged seating in the reclined positionmay contribute to development of a scoliosis. Ham et al (1998) also suggest thattilting of a seat and reclining the backrest can affect eye contact, as well as upperextremity function and spinal posture. Tilting may therefore reduce functional abilityto participate or interact with others and the environment.

Similarly Myhr and von Wendt (1990) in their pilot study concluded that the backward tilted position was the most inefficient position to reduce spasticity andenhance postural control. Pathological reflex activity increased considerably in thetilted position. Twenty-two ATNR movements were recorded in the tilted positioncompared to one ATNR when in the functional sitting position. Myhr and vonWendt (1991) support these findings when investigating the functional sitting positionin children with cerebral palsy. Findings suggest that pathological movements weresignificantly reduced (p=0.001) in the functional sitting position compared to

backward tilting. Herman and Lange (1999) suggest that the head should be keptclose to mid line to avoid active neck rotation which may elicit an ATNR.

Levitt (2004) suggests that therapists prevent extensor patterns andsubsequently chair sliding by using tilt in space with hips flexed between 95 and110, although adds that it is not a suitable position for those displaying the Mororesponse, head and trunk thrust in semi lying or increased athetosis. Engstrm (2002)

postulates that a constant tilt in space position may contribute to development ofextensor patterns in the cerebral palsy population and suggests that the trunk s

position in space may change the extensor pattern. Engstrm suggests that anindividual contoured seating unit which is forward tipped may be beneficial andhighlights that dynamic seating systems may be beneficial as they enable a change of

position between upright and rest.

b) Structural Asymmetries

Spinal deformity (lordosis, scoliosis, kyphosis) Pelvic Tilt Windswept deformity / Hip dislocation


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Spinal deformity:Lordosis

Lordosis may be defined as an anteroposterior curve of the lumbar spine inwhich the concavity is directed posteriorly (Rodgers et al 2001). In normal posturethe lumbar spine should be slightly hollow or lordosed, however muscle imbalance

may result in excessive lengthening and weakening of the abdominal and glutealmuscles and tightening of the iliopsoas and spinal erector muscles which results in the

pelvis being tilted anteriorly and further increasing the curvature of the lumbar spine.This results in a lordotic posture (Howe and Oldham 2001). Lordosis may besecondary to other spinal deformities, anterior pelvic tilt, hip flexion contractures andis also associated with muscular dystrophy. Treatment usually centres on managingunderlying problems and includes stretching tight hip flexors, strengtheningabdominal muscles and in severe cases bracing may be required (Rodgers et al 2001).

Scoliosis

Scoliosis is a lateral curvature of the lumbar and/or thoracic spine oftenaccompanied by axial rotation of the vertical bodies (Howe and Oldham 2001). TheScoliosis Research Society defines scoliosis as a lateral curvature exceeding 10 usingthe Cobb method (Scoliosis Research Society 2002). According to Rodgers et al(2001) curves of less than 20 are mild, curves over 40 result in permanent deformityand curves of 65 and over may result in compromised cardiopulmonary function.The development of scoliosis has been associated with asymmetrical muscle tone(Young et al 1998), retention of primitive reflexes (Ham et al 1998), poor posturaltone, hip contractures (Rodgers et al 2001) and compensatory postures resulting fromleg length discrepancy or abnormal pelvic tilt (lateral tilt, obliquity and rotation)(Howe and Oldham 2001), and increased interface pressure when sitting (Shoham etal 2004). Scoliosis occurring in combination with pelvic obliquity and hip deformityis usually convex to the side opposite the dislocated hip and pelvic obliquity(Gudjonsdottir and Stemmons Mercer 1997). It is recognised that scoliosis isgenerally progressive and can contribute to a number of secondary health problemssuch as positional pain, respiratory compromise, pressure sores and loss of function(Holmes et al 2003). Scoliosis may be described as fixed or structural meaning thatthere is permanent deformity which cannot be altered by posture, with the vertebral

bodies rotating towards the convexity of the curve and the spinal processes towardsthe concavity of the curve (Howe and Olham 2001). In extreme cases, surgicalintervention may be considered. A flexible scoliosis may be passively or activelycorrected via non-surgical intervention including spinal jackets and specialisedseating (Holmes et al 2003).

The literature suggests that management of scoliosis is achieved via a three point force system to the sides of the body. Ham et al (1998) suggests the use oflateral supports, which involves forces acting from anterior to posterior at the pelvis,anterior to posterior at the shoulders and posterior to anterior at the apex of thekyphotic (flexible) spine. A study conducted by Holmes et al (2003) investigatingthe effects of special seating on lateral spinal curvature in the non-ambulant spasticcerebral palsy population supports this assumption. Holmes et al (2003) concludedthat significant static correction of the scoliotic spine can be achieved by a three pointforce arrangement of lateral pads to the sides of the body.


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Shoham et al (2004) investigated the influence of seat adjustment and athoraco-lumbar-sacral orthosis (TLSO) on the distribution of body seat pressure infifteen children with scoliosis and pelvic obliquity. Seat adjustments included eitherthe use of either elevation of the lower side of the pelvis or a wedge insertion beneaththe raised pelvis. Results concluded that the TLSO significantly reduced the spinal

curvature and interface sitting pressure ( p


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the hamstrings (Mayall and Desharnais 1995; Trefler and Taylor 1991; Ham et al1998; Pynt et al 2001) or by flexion of the thoracic spine (Engstrm 2002). Effgen(2005) suggests when a child has tight hamstring muscles, footrests must angle underthe seat to accommodate for tightness and allow the pelvis to remain stabilised.Seating solutions utilize anterior pelvic stabilisation devices to maintain the pelvis inanterior tilt to prevent backward rotation (Reid and Rigby 1996). Approaches used

include ramped cushions (15 inclined) in conjunction with a pelvic belt, sacral pad,knee blocks and foot support (Green and Nelham 1991). Straddle seating (Reid1996), firm back rests and use of an anterior superior iliac spine padded bar acting onthe ischial tuberosities (Ham et al 1998), and anterior tipped seating combined withuse of hip belt and abduction orthosis (Myhr and von Wendt 1990, 1991, Mhyr et al1995) are other methods used to achieve pelvic stabilisation.

Windswept Deformity

Windswept hip deformity is an abduction contracture of one hip resulting in anadduction contracture of the contralateral hip and may be associated with pelvicobliquity and secondary scoliosis (Young et al 1998). Pelvic obliquity results in

pelvic rotation in the transverse plane and pelvic tilt in the saggital plane(Gujonsdottir and Mercer 1997). Aetiology of windswept deformity is unknown;however contributing factors include acetabular dysplasia, femoral anteversion,spasticity, retention of ATNR (Reese et al 1990), muscle imbalance and hipcontractures (Young et al 1998). Seating interventions may utilise a knee blocksystem to help correct windswept hips (Levitt 2004). According to Ham et al (1998),the knee blocks should be adjusted so that a force is applied anterior to posterior, viathe abducted femur, to the pelvis on the side that is rotated anteriorly. This is inaddition to the use of lateral supports and a sacral pad to help de-rotate the pelvis.Trefler and Taylor (1991) suggest positioning in abduction may discourage thetendencies of adduction of both hips via the use of a pommel. Structural deformity ofthe hip joint is a major problem in seating. Developmental Dysplasia or CongenitalHip Dislocation will be explored in greater depth in the childhood diseases section ofthe report.

c) Abnormal Muscle Tone

Normal muscle tone refers to the ability of muscles to maintain the correctamount of tension and elasticity during movements (Wandal 2000) and may bedefined as resistance to passive elongation or stretch (Harris 1991). Abnormalities ofmuscle include hypotonicity, hypertonicity or fluctuating tone (Hong 2002) and have

been associated with deficits in postural control (Nichols 2001). Hypotonia is


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characterised by decreased muscle tone and results in muscles appearing lax andfloppy (Kohlmeyer 1998) with functional movement and muscle endurancecompromised (Reed 2001). Decreased muscle tone can contribute to the developmentof kyphosis or lordosis with increased hip flexion, lower limb contractures (Ham et al1998), joint immobility, instability and subluxation due to large range of movement(Hong 2002), weakness, hyperextended knees and valgus or flat feet (Levitt 2004).

Hypertonicity or spasticity is characterised by increased tension or contraction in themuscles (Ham et al 1998). Increased muscle tone may also contribute to scoliosis,muscle contractures, extensor/flexion synergies (Ham et al 1998), clonus,hyperreflexia (exaggerated stretch reflex) patterns (Reed 2001) and persistent

primitive reflexes (Erhardt and Merill 1998). Hong (2002) highlights thathypotonicity and hypertoncity often present simultaneously. This is illustrated in thecerebral palsy population whereby the child may exhibit a hypotonus trunk, renderingtrunk extension difficult, yet present with hypertonicity of the extremities (Westcottand Goulet 2005).

Research has highlighted that spasticity is decreased when the hips are flexed(Nwaobi et al 1983). Nwaobi et al (1983) also found that in addition to the influenceof hip flexion, orientation of the body contributed to controlling extensor muscle tone.As previously discussed, this study concluded that spasticity in the lumbar area waslower in the upright position (90/90/90), compared to a backward tilted position.

Nwaobi (1986) also concluded that tonic muscle activity of the back extensor and hipadductor muscles were significantly lower (p=0.05) in the upright position comparedto recline. Myhr and von Wendt (1990) suggest that stretching spastic hamstringmuscles can only be achieved by rotating the pelvis anteriorly, with a straight back.Research has evidenced enhanced postural control via the use of the functional sitting

position which puts the pelvis into anterior tilt (Myhr and von Wendt 1990, 1991;Myhr et al 1995, van der Heide 2003).

Based on expert opinion, Herman and Lange (1999) suggest that knee flexion past 90 and ankles in dorsiflexion with slight eversion may reduce extensorspasticity. Empirical evidence suggests that dynamic seating components may alsoaccommodate and reduce tone and enhance function (Cooper et al 2001). Thisevidence suggests that accommodating abnormal movement and gently returning thelimb to normal alignment is more beneficial than blocking the movement. Someauthors suggest that tilt in space may be required if the child has hypotonus in order tocounteract the effects of gravity (Wright-Ott and Egilson 2001; Ham et al 1998; Pope2002) yet highlight that advantages of tilt in space must be considered against loss offunction.


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CHILDHOOD CONDITIONS

Cerebral Palsy Congenital Hip Deformity / Developmental Dysplasia Rett Syndrome Duchenne Muscular Dystrophy Spina Bifida

Cerebral Palsy

According to Rodgers et al (2001), Cerebral palsy may defined as a non- progressive abnormality of the developing brain that results in neurological, motorand postural deficits in the developing child. Perceptual, cognitive, sensory and

psychosocial dysfunction may also co-exist with this disorder (Ham et al 1998).Classification of cerebral palsy may be according to topographical distribution(monoplegia; diplegia; hemiplegia; paraplegia; tetraplgia or quadriplegia), quality oftone (hypotonia or spasticity; hypertonia; athetosis; ataxia), degree of involvement(mild; moderate or severe) and locality of the brain lesion (Westcott and Goulet2005). It is reported that the incidence rate of cerebral palsy is approximately 2:1000live births (ref) and may be attributable to pre-natal, perinatal and post-natal factors(Erdhardt and Merril 1998). Reed (2001) describes four main groups of cerebral

palsy syndromes:

SpasticThis type displays increased muscle tone resulting from an upper motor neuronlesion, ranges from mild to severe and is categorised according to the part of the bodyaffected. Erdhardt and Merril (1998) state that spasticity is also accompanied with

persistent primitive reflexes, clonus and hyperreflexia and results in difficulty withgross and fine motor control.

Athetoid / DyskineticThis results from basal ganglia dysfunction and is characterised by slow, jerky,writhing involuntary movements which may affect the extremities (athetosis) or

proximal parts of the trunk and limbs (dyskinesis). Athetosis or fluctuating toneresults in tone rapidly shifting from normal or hypertonic to hypotonic or low tone(Wandall 2000). It is suggested that athetoid movements are exasberated byemotional disturbance (Ham et al 1998; Reid 2001; Westcott and Goulet 2005) and

decreased by prone lying, fatigue or increased concentration (Ham et al 1998).AtaxicThis results from cerebellar dysfunction and is characterised by weakness,incoordination, intention tremor, unsteady wide based gait, difficulty coordinatingfine motor skills (Reed 2001) and difficulty maintaining stable alignment of the head,trunk, shoulders and pelvis Wandall (2000). According to Ham et al (1998) a childwith ataxic cerebral palsy is at greater risk of developing scoliosis than those withspastic diplegia or hemiplegic cerebral palsy.


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Clinical Manifestations

In addition to motor impairment, a multitude of clinical problems co-exist with

cerebral palsy and include cognitive and learning disabilities (Ham et al 1998);sensory deficits including hyperresponsivity or hyporesponsivity (Erhardt and Merril1998) proprioceptive, visual and vestibular dysfunction (Westcott and Goulet 2005);epilepsy (Hare et al 1998); hydrocephalus (McDonald et al 2004); behaviouraldisturbances (Ham et al 1998); oral motor dysfunction due to retention of primitivereflex activity affecting eating and swallowing ability (Erdhardt and Merril 1998);gastro-oesophageal reflux and speech and language difficulties (McDonald et al2004). This report focuses on the musculoskeletal impairments of body segmentsassociated with cerebral palsy.

SPINE

Literature suggests that children with cerebral palsy are likely to developspinal deformity (scoliosis, thoracic kyphosis and lordosis) with the highest incidenceoccurring in individuals with spastic quadriplegia (Gudjonsdottir and StemmonsMercer 1997). Research has evidenced that there is a correlation between tighthamstrings and hypolordosis in children with cerebral palsy (McCarthy and Betz2000). Additional contributing factors to spinal deformity include decreased stabilityand asymmetrical posture (Westcott and Goulet 2005), primitive reflex activity (Hamet al 1998), atypical muscle imbalance, tone and weight bearing (Gudjonsdottir andStemmons Mercer 1997), leg length discrepancy and pelvic obliquity (Howe andOldham 2001). Consequences of spinal deformity include decreased range ofmovement, positional pain, and functional limitations.

PELVIS

According to Lowes and Orlin (2005) pelvic abnormalities in cerebral palsyinclude obliquity, posterior and anterior rotation. The relationship between tighthamstrings and hypolordosis may also contribute to the posterior rotation of the

pelvis.

HIP

Hip displacement (dislocation or subluxation) is a major disability in cerebral

palsy and can cause difficulties in sitting, positioning (Hankinson and Morton 2002),ambulation and perineal hygiene (Scrutton et al 2001). According to McDonald et al2004) hip displacement is measured by the migration of the head of femur away fromthe acetabulum, with hip subluxation exceeding 33% migration and hip dislocationexceeding 80% migration. Aetiology is unknown however; contributing factorsinclude persistence of ATNR, acetabular dysplasia, hypertonicity, hip contractures,decreased ambulation and muscle imbalance. Research evidence suggests thatchildren with tonal asymmetry and severe spasticity appear to be at increased risk ofdislocation, with a windswept deformity on the opposite side (Young et al 1998).


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Pountney et al (2001) support this assumption by stating that imbalance in musclestrength and length around the hip leads to dysplasia and subsequent hip subluxation.Gudjonsdottir and Stemmons (1997) suggest that an important predictor in hipstability is the age at which a child is able to pull to stand. Cornell (1995) reportedthat less than 2% of children who are able to pull to stand before the age of three yearshave hip subluxation or dislocation. Hip dislocation, pelvic obliquity and scoliosis are

related problems in cerebral palsy (Gudjonsdottir and Stemmons Mercer 1997), withLetts et al (1984) reporting that dislocation occurs first, followed by obliquity, thenscoliosis. Research has evidenced that postural management interventions have animportant role in preventing dysplasia of the hip in children with cerebral palsy(Pountney et al 2001). A retrospective study of 59 children with bilateral cerebral

palsy concluded that children using all Chailey Adjustable Postural Support Systems(CAPS) maintained significantly more hip integrity (p


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Congenital Hip Deformity / Developmental Dysplasia

Developmental dysplasia is a condition of pathological hip instabilitycharacterised by dislocation or subluxation of the femoral head from the acetabulum(Lowes and Orlin 2005) with incidence being reported at 2:1000 live births (Cox andKernohan 1998). Rodgers et al (1998) attributes the cause of developmentaldysplasia to both environmental (birth complications) and genetic factors. Ham et al(1998) support this assumption stating that developmental dysplasia may be due tohormonal joint laxity, genetically determined joint laxity and delivery in the breech

position. Limited hip abduction and asymmetry are manifestations of this condition,with typical neonates displaying 75 and 90 abduction in each hip (Lowes and Orlin2005). This condition is also characterised by poor hip socket development, poorweight bearing surface and leg length discrepancy if the femur is subluxed from theacetabulum (Lowes and Orlin 2005). Early diagnosis is imperative as this condition istreatable in the early stage, however long term permanent damage will incur if leftuntreated of if late diagnosis occurs (Cox and Kernohan 1998, Rodgers et al 1998,Lowes and Orlin 2005). Treatment usually comprises of orthopaedic surgery andsplinting (Cox 1995). Positioning problems include reduced abduction and flexion atthe hip joint, leg length discrepancy, (Lowes and Orin 2005) and if not correctedearly, delayed walking and abnormal gait patterns will be evident (Ham et al 1998).Two studies identified discuss the seating and mobility issues encountered by childrenwith developmental dysplasia.

Cox (1995) used a survey method with parents of 11 children who either hadundergone or were undergoing treatment for late diagnosed developmental dysplasia.Results highlighted that there was insufficient equipment able to accommodatechildren in plaster and splints and there was a need to develop seating products, withemphasis placed on mobility. Small sample size and a response rate of 48% limit thegeneralisability of these findings. Cox et al (1998) further researched seating andmobility in a subsequent study, again utilising a survey method. To identify

problems, a survey of 113 affected families in England and Northern Ireland wasconducted. Results identified problems in areas of mobility, which creates emotionaland social difficulties in family routines. Regarding mobility, it was found that due tothe child s loss of mobility, parents resorted to lifting and carrying the child morefrequently, which became problematic as the child increased in age and size. Seatingequipment in the home often had to be adapted and improvised to accommodate the

size of the splint, therefore compromising safety. Lack of mobility and seating problems were found to restrict the child s movement and restricted parental activity.The authors (Cox et al 1998) suggest problems could be improved in this population

by provision of special devices that would allow mobility in the car, in a pushchairand provide seating in the home environment. Caution must be applied whengeneralising results as finding are based on a 38% response rate.


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Rett Syndrome

Rett Syndrome is a rare neurodevelopmental disorder which predominantlyaffects females (Cass et al 2003). It is characterised by progressive loss of intellectualfunctioning, loss of fine and gross motor skills, loss of purposeful hand movementsand development of stereotypical hand movements such as hand wringing, washingand clapping (Parker 2000; Reed 2001), difficulty or inability ambulating (Parker2000) and marked changes in emotional development and behaviour (Ham et al1998). Research has evidenced the prevalence of fractures as 20.9% amongst this

population (McDonald et al 2002). Rett syndrome is also classified as a pervasivedevelopmental disorder as it also characterised by severe and complex impaired socialinteraction, communication and behaviour (Rodgers et al 1998) According to Parker(2000) normal development occurs between the first 6-18 months of life, after whichregression appears to occur. Clinical manifestations also include muscle atrophy,increased spasticity and seizures (Ham et al 1998), hypotonia, ataxia, and trunkrocking (Effgen 2005).

Scoliosis is the primary orthopaedic complication of Rett syndrome with onsetassociated with stereotypical arm and hand movements, slowing down of righting andequilibrium reactions, age (McClure et al 1998) alterations in muscle tone, spasticity,and muscle incoordination (Harrison and Webb 1990). Research has evidenced thatthere is a significant relationship between the prevalence of Rett syndrome scoliosisand orthopaedic risk factors. McClure et al (1998) concluded that rett scoliosis may

be due orthopaedic asymmetries rather than a neurological form of scoliosis, with age,abnormal upper body positioning, and non-ambulation as significant predictors ofscoliosis. Cass et al (2003) also suggest that early asymmetry of the pelvis as well asshoulder protraction and elevation may be a precursor to fixed deformity. Clinicalimplications therefore would be to promote bilateral symmetrical muscular balancethrough proper sitting and lying positions (McClure et al 1998). Ham et al (1998)suggest that in the early stages, weight bearing should be encouraged to help minimiseand delay the onset of deformity, as well as the use of spinal jackets. Ham et al(1998) also suggest that soft moulded seats with supports at the backrest arerecommended.


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Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a genetic disorder characterised by progressive proximal muscle weakness (Reed 2001). This disorder only affects boys,with few surviving beyond 20-30 years old and mortality as a consequence ofcardiopulmonary compromise (Ham et al 1998). In DMD, muscles break down and

are replaced with fat and scar tissue, (pseudo hypertrophy) resulting in the musclesappearing bulky, with the calf muscles looking unusually large (Parker 2000).Impairment of muscle is affected proximally to distally ( Lowes and Orlin 2005) withRodgers at al (1998) suggesting involvement begins in the proximal musculature ofthe pelvis, proceeding to the shoulder girdle and subsequently to the distal musclegroups. Thompson et al (1998) add that muscle involvement is bilateral andsymmetrical. To compensate for muscle weakness, the child may resort to using theupper extremities to assist knee extension by using his hands to walk up from floorto standing (Gower s sign) (Ham et al 1998; Lowes and Orlin 2005). In additionhyperextension or lordosis of the lumbar spine may be apparent as a compensatory

posture in order to maintain an upright position and head in midline (Ham et al 1998).Early signs of DMD are evident when the child displays increased plantar flexion bywalking on their toes at approximately 1 year old (Parker 2000). Brown (2002)suggests that loss of ambulation may occur between 8-11 years, with Lord et al (1990)reporting wheelchair dependence at 6-15 years. As muscle weakness progresses,flexion contractures (Reed 2001) and scoliosis (Lowes and Orlin 2005) will occur.Research highlights that pain is related to spinal deformity (Lui et al 2003). Brown(2002) highlights that pelvic obliquity will coincide with scoliosis resulting indifficulty in sitting due to unequal weight distribution over the ischial tuberosities.

Bakker et al (2000) suggest that correct positioning and stretching may delaythe development of contractures and spinal deformity. Parker (2000) also highlightsgood body alignment is imperative especially with older children for efficientrespiratory function as many may be reliant on ventilators to assist breathing. Due tothe progression of DMD, the child s postural needs will continually change; henceseating interventions must be able to accommodate change. Intervention may also becomplex as proximal stabilisation is one of the first functions to diminish in DMD,therefore external stabilisation with adaptive seating is required (Clark et al 2004).Intervention involves the use of knee-ankle-foot orthoses (Ham et al 1998; Thompsonet al 1998; Rodger et al 1998; Lowes and Orlin 2005) however a recent systematicreview suggested that although the use of knee ankle foot othoses can prolong assistedwalking and standing, it is uncertain whether they can prolong functional walking(Bakker et al 2000). Ham et al (1998) also highlight that the success of seating

systems is variable as it cannot prevent the onset of scoliosis in this population.Initially a light-weight self-propelling chair may be required, progressing onto a powered wheelchair. Clark et al (2004) suggest common clinical practice regardingseating is to level the pelvis, with a firm seat base, align the trunk with lateral supportsto facilitate head alignment and support the elbows and forearms on a tray or with armsupports. Ham et al (1998) highlight that reclining or tilting the seating system mayreduce the load on the spine, however may be contraindicated by the child adoptingan exaggerated lordosed position of the lumbar spine to maintain upright balance andthe head in midline. According to Clark et al (2004) limited research exists regarding


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the effects of postural support in seating on health and function of young people withneuromuscular disorders.

Clark et al (2004) conducted a prospective two-period randomised crossoverstudy to measure the effects of postural support in seating on posture, respiration andupper limb function for young people with neuromuscular disorders. Nineteen

participants aged 6-22 years old, with a diagnosis of DMD (n=15) or Freidreich sAtaxia (n=4) were assessed in wheelchair seating and in adaptive seating via astandard protocol. Sitting posture, respiration and upper limb function was comparedwhen sitting in a standard wheelchair and in adaptive seating. Results concluded thatthere were no significant differences in respiratory function and no overallimprovement in upper limb function when compared in the two seating systems,however suggested that adaptive seating can improve the posture of this client group

by changing body alignment of young people in the chair. Small sample size anddifficulty with accurate postural measurements in the clinical setting limit thegeneralisability of these findings. The proposed protocol used in the study has not yet

been tested for reliability and validity.

Spina Bifida

Spina bifida, is described as a congenital defect of the vertebral arches in thespinal column (Rodgers et al 1998) whereby the neural tube fails to unite thereforeexposing a gap over which the skin is defective (Ham et al 1998). Parker (2000)highlights three spina bifida classifications and includes spina bifida occulta (minordefect not obvious at the skin surface), meningocele (protruding sac containingmeninges) and myelomeningocele (protruding sac containing meninges and spinalcord). It is suggested that the cause of spina bifida results from genetic andenvironmental factors (Reed 2001; Rodgers et al 1998). Numerous clinicalmanifestations are apparent with spina bifida and include the following: fine motorand hand skill delay (Reed 2001), hydrocephalus (Pountney and McCarthy 1998),impaired or loss of sensation, paralysis, vasomotor dysfunction (Westcott and Goulet2005), perceptual dysfunction (visual, auditory, propriceptive, tactile , kinaestheticand hypo- or hyperresponsitivity), learning disability (Reed 2001), pressure sores(Vaisbuch 2000) and psychosocial problems (Pountney and McCarthy 1998).Evidence also suggests that children with spina bifida frequently report clinically

significant yet under recognised and untreated pain (Clancy et al 2005). Neurological dysfunction will also contribute to the onset of orthopaedic

problems posing problems for seating and positioning, with the level of the lesiondetermining functional ability. Spinal deformities associated with spina bifida includescoliosis, kyphosis or kyphoscoliosis (Reed 2001), with deformity being present at

birth or occurring as the child develops (Pountney and McCarthy 1998). Retention of primitive reflexes, abnormal muscle tone, limited range of movement in theextremities, poor postural control of trunk, poor coordination and presence of hip


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dislocation / subluxation (Reed 2001) and flexion contractures of knees and ankle(Pountney and McCarthy 1998) are factors which must be considered regardingseating intervention. Ham et al (1998) suggest that seating objectives with this

population are to provide a stable base of support, maintain alignment of the spine,relieve discomfort over pressure areas, encourage cardiopulmonary function andimprove independence.

One study identified investigated the effect on interface pressure distributionin a group of children with complete paraplegia due to myelomeningocele and a groupof aged matched controls in different sitting positions (Vaisbuch et al 2000). Thisstudy concluded that the lean forward position (hips flexed to 45) produced thelargest reduction in interface pressure, however the authors acknowledge the childrenfelt apprehensive in this posture. The tilt position also reduced interface pressure,with the authors suggesting that tilting is used to relieve pressure during periods ofnon functional activity. No other studies were identified regarding seating principleswith this population.

Conclusion

Following a review of the literature, it is concluded that positioning principlesare based on empirical and evidence and expert opinion regarding children and young

people with neuromotor and neuromuscular disabilities. The majority of researchconducted reflects the impact of seating and positioning with the cerebral palsy

population. Continued disparity in the literature, small sample sizes and short periodsof data collection limit the generalisability of the findings, although are important interms of clinical significance. Limited research exists regarding children withneuromuscular conditions. It is recognised that appropriate positioning in childrenwith physical disabilities is important to facilitate engagement in functional activityand enable participation with the environment (Jones and Gray 2005). Research hasevidenced that proper positioning can improve upper extremity function (Mhyr andvon Wendt 1991, Mhyr et al 1995), postural alignment (Washington et al 2002), and

prevent the development of deformity (Pountney et al 2002). Children and young people who lack postural control and are unable to maintain appropriate postures

therefore will require external support from seating systems. The goal of interventionhence is to provide adaptive seating to create a functional seated position to maintainhealth and function as part of a postural management approach.


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APPENDIX 1

The following tables indicate data bases searched and key words utilized regardingspecific themes.

TABLE 1: Seating

Data Base Key Words

CINAHL exp seating/ AND Childexp equipment design AND childexp seating/ AND childdynamic seating

BIDS seating

Pubmed seatingseating principlesseating and positioning

Proquest adaptive seatingseatingseat$ AND children AND position

Embase exp seat/ AND childdynamic seating

AMED exp seating/ AND childexp equipment design/ AND exp seatingAND childdynamic seating

Medline (Ovid) dynamic seatingseating and positioning

OTDbase seating

ASSIA positioning and seating

Psychinfo seating

British Nursing Index seatingSeat$

Zetoc seating p

Documents

The Fundamental Principles of Seating and Positioning in Children and Young People With Physical Disabilities