The Fundamental Principles of Seating
and Positioning in Children and Young
People with Physical Disabilities
Laura Neville
BSc (Hons) Occupational Therapy Student
University of Ulster
Supervised by:
Mrs Jackie Quigg (School of Health Sciences UU)
Dr Alison Porter Armstrong (Health and
Rehabilitation Sciences Research Institute UU)
Commissioned by James Leckey Design Limited
Summer 2005
Project Background
James Leckey Design Limited (Northern Ireland) is a company specialising in
equipment design, manufacture and provision for children with physical disabilities.
As part of a 2 ½ year project, involving the University of Ulster (with Mrs Jackie
Quigg and Dr Alison Porter Armstrong) to research the clinical effectiveness of one
of their product ranges, the company commissioned three BSc (Hons) Occupational
Therapy students (Laura Neville, Linda McNamara and Glenda Alexander) to conduct
critical reviews of the literature in three designated areas:
1) Fundamental Principles of Seating and Positioning in Children and Young
People 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 August
2005 and conducted as part of a steering group comprising of: Mr James Leckey
(James Leckey Design Limited); Mr Noel McQuaid (Technical Director, James
Leckey 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 three
critical reviews commissioned by James Leckey Design reviewing and critically
appraising 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 for
their continued support, direction and guidance in regarding completion of this
review. Thanks also to James, Noel and Clare for providing the opportunity to engage
in this project and thank you to Linda and Glenda for your constant support and
encouragement and making the completion of this review possible.
1
Index of Contents
Introduction
Methods
The relationship between posture, movement, stability and function
Normal posture
The action of sitting
Neutral sitting posture
The 90-90-90 position – how functional?
Functional Sitting Position
Factors affecting positioning
Primitive reflex activity
Structural asymmetries
Abnormal muscle tone
Childhood conditions
Cerebral Palsy
Congenital hip deformity/Developmental Dysplasia
Rett Syndrome
Duchenne Muscular Dystrophy
Spina Bifida
Conclusion
References
Appendices
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2
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 has
evidenced 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) and
facilitation of upper extremity function (Myhr and von Wendt 1991; Myhr et al 1995,
van der Heide 2003). It is imperative that health professionals prescribing and
engineers designing seating equipment are well informed regarding the fundamental
seating principles that dictate the sitting postures of children and young people and
the impact they have on long term health and function.
Traditional emphasis regarding positioning is placed on achieving an upright
symmetrical 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, Hong
2002). Although an important posture to achieve, this upright position is suggested as
non-functional (Engström 2002) and difficult to maintain over time (Howe and
Oldham 2001), resulting in adoption of compensatory postures which may lead to
long term deformity and further deterioration when appropriate external support is
unavailable. Seating solutions may require reaching a balance between an upright
anatomical symmetrical posture and ability to function (Ham et al 1998; Pope 2002).
The focus of this research was to review and critically appraise the literature
regarding the fundamental principles of seating and positioning used with children
and young people with physical disabilities. The report uses evidence from published
studies, and expert opinion to identify seating and positioning principles used with
children and young people with disabilities, the benefits of optimal positioning and
problems which may incur as a result of incorrect positioning. An overview of
normal and abnormal postures is discussed from biomechanical and
neurophysiological viewpoints. Common childhood neuromotor and neuromuscular
conditions 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 and
functional independence.
3
Methods
A literature search was conducted using the following electronic data bases;
AMED (Allied and Complimentary Medicine), ASSIA (Applied Social Sciences
Index 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 relevant
literature 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 words
utilised in the search strategy with respect to the data bases searched. Electronic
database searching was supplemented with hand searches, citation searches of
reference lists, conference proceedings and retrieving relevant literature from
published textbooks. The McMaster critical review forms (Law et al 2002) were used
as 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 in
relation to one another and their orientation in space” (Ham et al, p26). Body
‘segments’ 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 (Hong
2005). Normally, our postures continuously shift and change position to facilitate
movement to engage in functional activities. Pope (2002) identifies that posture is a
prerequisite for movement. Howe and Oldham (2001) also highlight that posture and
movement are inextricably linked, referring to posture as a temporary arrested
movement, which is in a constant state of change. From a neurodevelopmental
perspective Nichols (2001) suggests that the development of postural control and
acquisition of motor milestones are intrinsically linked. Ham et al (1998) support this
assumption highlighting that there is constant neuromotor activity being used to
maintain body balance and posture. Engström (2002) further suggests that biological
and 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 is
required for the spine so that the neck is free to move; shoulder girdle stability is
required 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
4
suggesting that the relationship between proximal stability and distal control is not
necessarily one of cause and effect. This is supported by Case-Smith et al (1989) who
identified weak correlations between proximal control and hand function in typically
developing children as assessed by the Posture and Fine Motor Assessment of Infants
(Case-Smith 1987).
However evidence suggests that clinicians and therapeutic
seating do utilise the principle of achieving pelvic stabilisation to maximise distal
control for function in children with neuromotor dysfunction. This is illustrated in the
literature 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 pelvic
tilt via the use of the functional sitting position in children with cerebral palsy (Myhr
and von Wendt 1990, 1991; Myhr et al 1995. Children with neuromotor and
neuromuscular dysfunction will require external support from seating systems to
accommodate for compromised postural control and postural deficits. Based on
clinical 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 position
6) 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 fatigue
10) Enhance autonomic nervous system function (cardiac, digestive and respiratory
function)
11) Facilitate maximum function with minimum pathology.
(Jones and Gray 2005).
5
Seating and Positioning: Principles and Practice
Normal Posture
Following a review of the literature, it is difficult to define what constititutes
‘normal’ posture. This is because each person is unique regarding their physiological
profile and continually engages in a number of postural variations which may be
attributed to fatigue and emotional state (Howe and Oldham 2001). From a
biomechanical viewpoint, good posture is dependent on the balance of the skeleton
and symmetrical alignment of body segments. Engström (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 and
developmental perspective, normal posture is also dependant on the development of
normal postural control which is described as the control of the body’s position in
space in order to obtain stability and orientation (Brogren et al 1998) and is influenced
by the neuromotor, somatosensory, vestibular and musculoskeletal systems (Nichols
2001). Postural control requires achieving normal developmental milestones and
includes the development of postural reactions (righting, protective and equilibrium
reactions), developmental integration of primitive reflexes (asymmetrical tonic neck
reflex, 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 the
thoracic spine, flexion of the lower extremities, and backwards rotation of the pelvis
towards the rear of the seat. Pelvic rotation in turn dictates the compensatory curves
of 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 trunk
extends, moving towards the backrest. The upper part of the pelvis is in contact with
the lower part of the backrest, thus achieving pelvic stability, with the person now
sitting in an upright neutral position.
6
Neutral sitting posture
Sitting skills emerge in a normally developing child approximately between 7
and 9 months and requires the child to maintain postural control of the head, trunk and
extremities against the pull of gravitational forces (Wandel 2000). The majority of
the 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 pelvis
in anterior tilt, thighs slightly abducted, parallel and horizontal and the iliac crests
aligned and level in the lateral plane (Ham et al 1998). The hips, knees and ankles
are placed at ninety degrees of flexion, the feet are in plantar grade or 0° degrees
flexion (Green and Nelham 1991) and the head is positioned in midline and
maintained in the vertical plane (Erhardt and Merril 1998). The head position in
relation to the spine is important as it has a direct effect on posture. Loss of head
control can therefore affect body position (Ham et al 1998). When the pelvis is in
anterior tilt, the centre of gravity falls anterior to the ischial tuberosities (Ham et al
1998) hence the base of support is provided through the ischial tuberosities and the
upper 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 symmetry
and 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 surface
and allows relaxation of the muscles of the lower extremities (Howe and Oldham
2001). However, there is greater potential for pelvic instability in sitting compared to
standing 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 (Engström
2002).
In the seated posture, it is desirable that as much contact is made with the
chair’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 base
of support surface to allow function (Jones and Gray 2005). However in right angled
seating, 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 of
constant activation of the erector spinae muscles, a person will gain relief from
excessive muscle activity by sacral sitting, resulting in posterior rotation of the pelvis,
accentuation of thoracic kyphosis and cervical lordosis, loss of lumbar lordosis of the
spine (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 pressure
sore development (Jones and Gray 2005). Conflicting opinion exists regarding the
causation 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 gluteal
muscles which promotes flexion of the lumbar spine hence inducing posterior rotation
of the pelvis. (Mayall and Desharnais 1995; Trefler and Taylor 1991; Pynt et al 2001;
Effgen 2005).
Contrary to opinion Engström (2003) attributes the tendency of
thoracic spine collapse (flexion) as influencing the backward rotation of the pelvis and
suggests that seating interventions should aim to improve thoracic extension to block
7
flexion of the spine. Engström (2002) suggests that backward inclination induces
flexion of the thoracic spine whereas a forward inclined seated position promotes
thoracic extension. A study conducted by Miedaner (1990) investigating the effects
of sitting positions on trunk extension for children with motor impairment supports
this 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 a
randomized complete block design a significance level of p=0.001 demonstrated a
true mean difference between the different sitting positions, however small sample
size 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 an
ergonomic perspective (Engström 2001). From an anatomical view point the goal is
to achieve maximum orthopaedic symmetry between left and right sides of the body
via a neutral pelvis to avoid obliquity, rotation and posterior pelvic tilt (Lange 2001).
Advantages of this position depicted in the literature include minimisation of
orthopaedic deformity (Ham et al 1998) and promotion of proximal stability which in
turn promotes distal control (Lange 2001). One of the goals of seating is to promoted
relaxation 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) to
investigate the activity of extensor muscles of the lumbar spine in children with
cerebral palsy in different seating positions. Seat surface inclinations of 0° and 15°
combined with backrest inclinations of 75°, 90°, 105° and 120° provided the testing
conditions. Results concluded that electrical activity was least when seat surface
elevation was 0° and backrest inclination was 90°. Caution is advised in generalising
results as testing positions were based on EMG activity recording 60 seconds of
sitting in each position and on a small sample of eleven subjects. A subsequent study
conducted by Nwaobi (1986) regarding the effects of body awareness in space on
tonic muscle activity of patients with cerebral palsy concluded that muscle activity
was lower in the upright position (90-90-90) than the reclined position (30° from
vertical plane), with statistically significant results obtained for back extensors and
hip adductors (p=0.05). One of the goals of seating is to promote increased tolerance
in 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 over
time (Ham et al 1998; Howe and Oldham 2001) and may impede function (Engström
2002). One study however concluded that the upright position was more functional in
comparison with anterior and posterior sitting positions. Nwaobi (1987) investigated
seat orientation of upper extremity function in thirteen children with cerebral palsy
(spastic and athetoid) and concluded that arm movements were significantly faster
8
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 or
decreased abnormal neuromuscular activity in the upright position. The authors also
consider loss of horizontal eye contact and greater effort required to counteract
gravitational 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 back
rest, and their relationship to function. Findings from studies examining the effects of
seat inclination on upper extremity function are mixed. Some authors (Mhyr and von
Wendt 1990, 1991, Myhr et al 1995) concluded that anterior sitting in the ‘functional
sitting position’ improved upper extremity function in children with neuromotor
dysfunction. Other research studies report no effects on upper extremity function
with regard to seat inclination (McClenaghan et al 1992) and no effects regarding
anterior tipped seating on respiratory function in children (Reid and Sochaniwskyj
1991). 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, but
the 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 seating
should extend beyond achieving perfect symmetry, but should focus on providing
external support, at the angles needed by an individual to achieve an upright, stable
and functional position. It is recognised that ideology based on expert opinion and
experience provides important information which may be added to a growing
evidence base however caution must be exemplified when using anecdotal evidence
to justify practice. Shimizu et al (1994) acknowledges that deviation from the optimal
upright position is often required to accommodate for fixed deformities and abnormal
postural tone, yet basic positioning principles should be maintained. This is to provide
equal distribution of weight, for support, stability and comfort. It may be derived that
the 90°/90°/90° position is a useful baseline position to achieve to promote symmetry
with 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 promote
function 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 tasks
and backwards recline for relaxation. Findings from studies regarding the effects of
seat inclination on function and/or postural control are conflicting. Studies identified
for review, focus on the cerebral palsy population and/or typically developing
children. Several authors suggest that forward inclination promotes improved upper
9
extremity function (Myhr and von Wendt 1991, Myhr et al 1995; Reid 1996); trunk
extension (Miedaner 1990) and improved postural efficiency (van der Heide 2003,
Myhr and von Wendt 1990, 1991). Other research studies report no effects of
anterior tipped seating on respiratory function (Nwaobi and Smith 1986, Reid and
Sochaniwskyj 1991, Redstone 2004); upper extremity function (McPherson et al
1991; 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 photographed
and 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 fixation
of hip belt at 45° angle and use of abduction orthoses. Results suggested that the
functional sitting position in comparison to the children’s original sitting position
minimised pathological reflexes, improved postural control and improved upper
extremity function when children sat in forwards inclination (mean 8°, range 0° to
15°), with a firm back rest supporting the pelvis and supported by a cut out level table
to eliminate lateral sway imbalance. Results support previous preliminary findings
investigating the FSP and its impact on reduction of spasticity and enhancement of
postural control (Myhr and von Wendt 1990), although seat inclination alone showed
no identifiable effects, it is subjectively suggested that anterior tilting may stretch the
hamstring muscles when the pelvis is rotated forward hence reducing spasticity. This
is assuming the feet are secured and fixed and the lower extremities are not permitted
to flex under the thighs, however the authors do not provide a specific description
regarding the exact positioning of the feet. A five year follow up study investigating
ten children with cerebral palsy (Myhr et al 1995) concluded that the FSP contributed
to significant improvement (p> 0.05) in head, trunk and foot control and upper
extremity function in eight of the ten children as assessed by the Sitting Assessment
Scale (Myhr and von Wendt 1991).
A study conducted by Reid (1996) utilising a repeated measures experimental
cross over design compared the effects of level or flat benched seating versus saddlebenched seating (15° anterior tilt) on postural control and reaching motions of six
children 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 results
and 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 Heide
et al 2003) suggested that forward tilted seating (15° seat surface inclined) was a more
efficient position for postural efficiency compared to horizontal (0°) and backwards
tilted (15° seat surface reclined) sitting positions. Findings were contrary to the
original hypothesis postulated by the authors, who hypothesised that backward sitting
would have been the most efficient position as it would passively counterbalance the
forward body sway induced by reaching movements. Sitting positions were studied
via surface Electromyograms (EMG) and kinematics, therefore quantifying results.
10
Miedaner (1990) investigated the effects of sitting positions on trunk extension
in fifteen children with motor impairment (cerebral palsy) using the modified Schober
Measurement for Spinal Extension. As previously discussed, results suggested that
the anterior sitting (20° and 30° inclined) tend to increase trunk extension compared
to level bench or floor sitting. Subjective observations suggest that upper extremity
function is not compromised despite increased muscle activity required to maintain
trunk extension when the seat is tilted forward. Further EMG analysis of spinal
muscle activity regarding trunk extension would objectify results.
Contrary to these findings other authors conclude that seat inclination has no
discernable effects. McClenaghan et al (1992) investigated the effects of seat surface
inclination on postural stability and function of the upper extremities of children with
cerebral palsy. Twenty children (ten non-impaired; ten mild cerebral palsy) were
included in the study, with seat surface inclinations depicted as 0° horizontal, 5°
anterior 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 greater
tilting is difficult to tolerate for an extended period with this assumption based on
pilot investigations. Previous research has shown that lumbar spine muscle activity
increases when the seat is tilted forward (Nwaobi 1987).
McClenaghan et al (1992) concluded that significant between-group
differences were observed on most dependent measures (p>0.05) however, suggested
that anterior tilt seating in cerebral palsied children may actually disturb postural
stability, 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 seat
inclinations regarding upper extremity movement. Hadders et al (1999) when
conducting a study to investigate the development of postural adjustments in reaching
in infants in children with cerebral palsy also favoured the reclined position (semirecline 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 turn
actually impedes the use of the upper extremities for function. This would hinder the
carrying out of bilateral activities.
Similar findings have been reported regarding the effects of seat inclination on
respiratory function. Redstone (2004) investigated the respiratory patterns in upright
and semi-reclined seating positions in ten preschool children with cerebral palsy and
ten typically developing children. No significant differences could be attributed to
seat position alone. Reid and Sochaniwskyj (1991) conducted a study to investigate
the effects of anterior tipped seating on respiratory function of normal children and
children with cerebral palsy. Twelve subjects (six normal; six cerebral palsy) were
compared in level (0°) and anterior tipped (10° seat surface inclined) seating, with
respiratory function measured by respitrace transducers. No significant differences in
respiratory function could be attributed to seat inclination alone either in the normal
or cerebral palsy groups, however it is recognised that a larger sample size may have
11
yielded greater power analysis to detect statistical significance. Nwaobi and Smith
(1986) in an earlier study investigated the effect of adaptive seating on pulmonary
function of eight children with spastic cerebral palsy, and concluded that pulmonary
function was more efficient when children were positioned in adaptive seating in the
upright (90-90-90) position.
Continued disparity in the literature exists regarding the direction of seat
inclination for improved function and postural control. Studies reviewed used small
sample sizes, lacked power analysis, and used various seat inclination values and
different assessment times in seated positions and short periods of data analysis
therefore making comparisons difficult. Additionally some studies do not refer to
cerebral palsy as a heterogeneous group. Selection bias was also evident in some
studies therefore questioning the reliability of the findings. Future research should
utilise larger sample sizes and to aid power estimates so that results may be
generalisable to the sample population.
12
FACTORS AFFECTING POSITIONING
Children with neuromotor / neuromuscular dysfunction will have
compromised postural control. This section discusses postural problems and how they
can affect positioning and possible seating solutions that accommodate or prevent
further deviation from normal posture; however consideration regarding the
effectiveness of seating components and their functional use are beyond the scope of
this report. The problems depicted in the literature include a) retention of primitive
reflexes; b) presence of structural asymmetries c) abnormalities of muscle tone.
a) Primitive Reflex Activity
Ø
Ø
Ø
Ø
Ø
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 to
one side. The reflex is characterised by increased extensor tone on the side to which
the head is turned and increased flexor tone on the opposite side. This reflex is
usually integrated between 4-6 months (Lowman 2000). According to Hong (2005)
the continued presence of ATNR after 4-5 months is considered abnormal and
interferes with rolling, bilateral integration, reaching and grasping activities. Due to
the tendency of children to use one hand, continued repetitive movements may lead to
the development of scoliosis (Ham et al 1998). Extensor postures (Levitt 2004), soft
tissue balance and asymmetries in muscle tone may also lead to secondary deformities
including 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 and
the lower extremities extend. When the head extends, the upper extremities extend
and the lower extremities are pulled into flexion. This reflex is normally integrated
13
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 extension
throughout 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 is
usually integrated between 4-6 months.
Retention of TLR interferes with side
turning, rolling, and lying to sitting ability and creeping (Lowman 2000).
Positive Supporting Reaction
The positive supporting reaction is elicited when infants are supported under
the 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 feet
and stand independently (Ham et al 1998). Retention of this response will interfere
with 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 muscles
of the feet when pushing down on foot rests can also elicit an extensor thrust, which
can 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 is
normally integrated between 4-6 months and if retained, interferes with head control,
sitting equilibrium and protective reactions (Lowman 2000), all of which are needed
for postural control.
Seating Interventions
Goals of seating include normalising tone or decreasing abnormal
influences on the body and to facilitate normal movement or pathological activity
(Jones and Gray 2005). Although Wright-Ott and Egilson (2001) suggest that tilt in
space may provide a child with hypotonia (low muscle tone) with greater tolerance for
upright sitting, other authors suggest that tilt in space and/or reclined sitting may
14
increase pathological reflexes (Nwaobi et al 1983; Nwaobi 1986; Myhr and von
Wendt 1990, 1991, Mhyr 1994; Engström 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 overcome
gravity and consequently increased tone. This study also highlighted that asymmetry
of muscle activity in back extensors and prolonged seating in the reclined position
may contribute to development of a scoliosis. Ham et al (1998) also suggest that
tilting of a seat and reclining the backrest can affect eye contact, as well as upper
extremity function and spinal posture. Tilting may therefore reduce functional ability
to 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 and
enhance postural control. Pathological reflex activity increased considerably in the
tilted position. Twenty-two ATNR movements were recorded in the tilted position
compared to one ATNR when in the functional sitting position.
Myhr and von
Wendt (1991) support these findings when investigating the functional sitting position
in children with cerebral palsy. Findings suggest that pathological movements were
significantly reduced (p=0.001) in the functional sitting position compared to
backward tilting. Herman and Lange (1999) suggest that the head should be kept
close to mid line to avoid active neck rotation which may elicit an ATNR.
Levitt (2004) suggests that therapists prevent extensor patterns and
subsequently chair sliding by using tilt in space with hips flexed between 95° and
110°, although adds that it is not a suitable position for those displaying the Moro
response, head and trunk thrust in semi lying or increased athetosis. Engström (2002)
postulates that a constant tilt in space position may contribute to development of
extensor patterns in the cerebral palsy population and suggests that the trunk’s
position in space may change the extensor pattern. Engström suggests that an
individual contoured seating unit which is forward tipped may be beneficial and
highlights that dynamic seating systems may be beneficial as they enable a change of
position between upright and rest.
b) Structural Asymmetries
Ø Spinal deformity (lordosis, scoliosis, kyphosis)
Ø Pelvic Tilt
Ø Windswept deformity / Hip dislocation
15
Spinal deformity:
Lordosis
Lordosis may be defined as an anteroposterior curve of the lumbar spine in
which the concavity is directed posteriorly (Rodgers et al 2001). In normal posture
the lumbar spine should be slightly hollow or lordosed, however muscle imbalance
may result in excessive lengthening and weakening of the abdominal and gluteal
muscles 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 be
secondary to other spinal deformities, anterior pelvic tilt, hip flexion contractures and
is also associated with muscular dystrophy. Treatment usually centres on managing
underlying problems and includes stretching tight hip flexors, strengthening
abdominal 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 often
accompanied by axial rotation of the vertical bodies (Howe and Oldham 2001). The
Scoliosis Research Society defines scoliosis as a lateral curvature exceeding 10° using
the 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 deformity
and 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 postural
tone, hip contractures (Rodgers et al 2001) and compensatory postures resulting from
leg length discrepancy or abnormal pelvic tilt (lateral tilt, obliquity and rotation)
(Howe and Oldham 2001), and increased interface pressure when sitting (Shoham et
al 2004). Scoliosis occurring in combination with pelvic obliquity and hip deformity
is usually convex to the side opposite the dislocated hip and pelvic obliquity
(Gudjonsdottir and Stemmons Mercer 1997). It is recognised that scoliosis is
generally progressive and can contribute to a number of secondary health problems
such as positional pain, respiratory compromise, pressure sores and loss of function
(Holmes et al 2003). Scoliosis may be described as fixed or structural meaning that
there is permanent deformity which cannot be altered by posture, with the vertebral
bodies rotating towards the convexity of the curve and the spinal processes towards
the concavity of the curve (Howe and Olham 2001). In extreme cases, surgical
intervention may be considered. A flexible scoliosis may be passively or actively
corrected via non-surgical intervention including spinal jackets and specialised
seating (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 of
lateral 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 the
kyphotic (flexible) spine. A study conducted by Holmes et al (2003) investigating
the effects of special seating on lateral spinal curvature in the non-ambulant spastic
cerebral palsy population supports this assumption. Holmes et al (2003) concluded
that significant static correction of the scoliotic spine can be achieved by a three point
force arrangement of lateral pads to the sides of the body.
16
Shoham et al (2004) investigated the influence of seat adjustment and a
thoraco-lumbar-sacral orthosis (TLSO) on the distribution of body seat pressure in
fifteen children with scoliosis and pelvic obliquity. Seat adjustments included either
the use of either elevation of the lower side of the pelvis or a wedge insertion beneath
the raised pelvis. Results concluded that the TLSO significantly reduced the spinal
curvature and interface sitting pressure (p<0.05), however seat adjustment had no
significant effect on pressure distribution.
Kyphosis
Kyphosis is characterised by an increased posterior curvature (‘Cshaped’) of the thoracic spine (Howe and Oldham 2001). The kyphosed posture is
apparent during sacral sitting, with the pelvis posteriorly tilted and the thoracic spine
in flexion (Ham et al 1998). Ham et al (1998) further add that a sling back seat and
back support can accentuate kyphosis. The development of kyphosis may be
associated with poor posture, weak erector spinae muscles (required for trunk
extension), compensation to hip deformity (Howe and Oldham 2001), and also occurs
in children with cerebral palsy who demonstrate extensor spasticity in the lower
extremities due to tight hamstrings (Ham et al 1998). Head position is then affected,
resulting in forward flexion or head drop. In order to compensate for head dropping,
the individual will hyperextend their neck in order to visually interact with the
environment, however this will compromise respiratory and swallowing function
(Herman and Lange 1999). Engström (2002) suggests additional problems include
neck pain, flexion contractures of the trunk muscles, restricted arm movement and
increased abdominal pressure.
Several authors (Trefler and Taylor 1991; Ham et al 1998; Engström 2002;
Levitt 2004) suggest tilt in space or opening the seat to backrest angle to
accommodate or support a kyphosis. Engström (2002) suggests the seating unit
should be contoured for equal pressure distribution and the backrest is reclined,
although does not an angle at which recline should occur. Trefler and Taylor (1991)
also suggest the use of a custom contoured back support with a flexible anterior
harness, adding that individuals with a 30° or greater scoliosis may require reclined
seating to accommodate or correct the curve. Tilt in space may also be considered as
it may reduce the effects of gravity acting on the upper body, with the weight of the
body being taken through the backrest (Ham et al 1998, Pope 2002). However, the
advantages of tilting must be considered against the loss of function.
Pelvic Tilt
Posterior pelvic tilt is a major problem in seating as it compromises pelvic
stability (Engström 2002). Problems associated with posterior pelvic tilt include
flattening of lumbar curve, accentuation of thoracic kyphosis (Pynt et al 2001) sacral
sitting, and increased risk of pressure sore development at sacral / coccygeal area
(Ham et al 1998). Causation of posterior of pelvic tilt is attributed to the tension in
17
the hamstrings (Mayall and Desharnais 1995; Trefler and Taylor 1991; Ham et al
1998; Pynt et al 2001) or by flexion of the thoracic spine (Engström 2002). Effgen
(2005) suggests when a child has tight hamstring muscles, footrests must angle under
the seat to accommodate for tightness and allow the pelvis to remain stabilised.
Seating solutions utilize anterior pelvic stabilisation devices to maintain the pelvis in
anterior 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 (Reid
1996), firm back rests and use of an anterior superior iliac spine padded bar acting on
the ischial tuberosities (Ham et al 1998), and anterior tipped seating combined with
use of hip belt and abduction orthosis (Myhr and von Wendt 1990, 1991, Mhyr et al
1995) are other methods used to achieve pelvic stabilisation.
Windswept Deformity
Windswept hip deformity is an abduction contracture of one hip resulting in an
adduction contracture of the contralateral hip and may be associated with pelvic
obliquity 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 hip
contractures (Young et al 1998). Seating interventions may utilise a knee block
system 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, via
the abducted femur, to the pelvis on the side that is rotated anteriorly. This is in
addition 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 the
tendencies of adduction of both hips via the use of a pommel. Structural deformity of
the hip joint is a major problem in seating. Developmental Dysplasia or Congenital
Hip Dislocation will be explored in greater depth in the childhood diseases section of
the report.
c) Abnormal Muscle Tone
Normal muscle tone refers to the ability of muscles to maintain the correct
amount of tension and elasticity during movements (Wandal 2000) and may be
defined as resistance to passive elongation or stretch (Harris 1991). Abnormalities of
muscle include hypotonicity, hypertonicity or fluctuating tone (Hong 2002) and have
been associated with deficits in postural control (Nichols 2001). Hypotonia is
18
characterised by decreased muscle tone and results in muscles appearing lax and
floppy (Kohlmeyer 1998) with functional movement and muscle endurance
compromised (Reed 2001). Decreased muscle tone can contribute to the development
of kyphosis or lordosis with increased hip flexion, lower limb contractures (Ham et al
1998), 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 the
muscles (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 that
hypotonicity and hypertoncity often present simultaneously. This is illustrated in the
cerebral palsy population whereby the child may exhibit a hypotonus trunk, rendering
trunk extension difficult, yet present with hypertonicity of the extremities (Westcott
and 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 influence
of hip flexion, orientation of the body contributed to controlling extensor muscle tone.
As previously discussed, this study concluded that spasticity in the lumbar area was
lower 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 hip
adductor muscles were significantly lower (p=0.05) in the upright position compared
to recline. Myhr and von Wendt (1990) suggest that stretching spastic hamstring
muscles 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 extensor
spasticity. Empirical evidence suggests that dynamic seating components may also
accommodate and reduce tone and enhance function (Cooper et al 2001). This
evidence suggests that accommodating abnormal movement and gently returning the
limb to normal alignment is more beneficial than blocking the movement. Some
authors suggest that tilt in space may be required if the child has hypotonus in order to
counteract the effects of gravity (Wright-Ott and Egilson 2001; Ham et al 1998; Pope
2002) yet highlight that advantages of tilt in space must be considered against loss of
function.
19
CHILDHOOD CONDITIONS
Ø
Ø
Ø
Ø
Ø
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 nonprogressive abnormality of the developing brain that results in neurological, motor
and 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 of
tone (hypotonia or spasticity; hypertonia; athetosis; ataxia), degree of involvement
(mild; moderate or severe) and locality of the brain lesion (Westcott and Goulet
2005). It is reported that the incidence rate of cerebral palsy is approximately 2:1000
live 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:
Spastic
This type displays increased muscle tone resulting from an upper motor neuron
lesion, ranges from mild to severe and is categorised according to the part of the body
affected. Erdhardt and Merril (1998) state that spasticity is also accompanied with
persistent primitive reflexes, clonus and hyperreflexia and results in difficulty with
gross and fine motor control.
Athetoid / Dyskinetic
This 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 tone
results in tone rapidly shifting from normal or hypertonic to hypotonic or low tone
(Wandall 2000). It is suggested that athetoid movements are exasberated by
emotional disturbance (Ham et al 1998; Reid 2001; Westcott and Goulet 2005) and
decreased by prone lying, fatigue or increased concentration (Ham et al 1998).
Ataxic
This results from cerebellar dysfunction and is characterised by weakness,
incoordination, intention tremor, unsteady wide based gait, difficulty coordinating
fine 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 child
with ataxic cerebral palsy is at greater risk of developing scoliosis than those with
spastic diplegia or hemiplegic cerebral palsy.
20
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 Merril
1998) proprioceptive, visual and vestibular dysfunction (Westcott and Goulet 2005);
epilepsy (Hare et al 1998); hydrocephalus (McDonald et al 2004); behavioural
disturbances (Ham et al 1998); oral motor dysfunction due to retention of primitive
reflex activity affecting eating and swallowing ability (Erdhardt and Merril 1998);
gastro-oesophageal reflux and speech and language difficulties (McDonald et al
2004). This report focuses on the musculoskeletal impairments of body segments
associated with cerebral palsy.
SPINE
Literature suggests that children with cerebral palsy are likely to develop
spinal deformity (scoliosis, thoracic kyphosis and lordosis) with the highest incidence
occurring in individuals with spastic quadriplegia (Gudjonsdottir and Stemmons
Mercer 1997). Research has evidenced that there is a correlation between tight
hamstrings and hypolordosis in children with cerebral palsy (McCarthy and Betz
2000). Additional contributing factors to spinal deformity include decreased stability
and asymmetrical posture (Westcott and Goulet 2005), primitive reflex activity (Ham
et al 1998), atypical muscle imbalance, tone and weight bearing (Gudjonsdottir and
Stemmons Mercer 1997), leg length discrepancy and pelvic obliquity (Howe and
Oldham 2001).
Consequences of spinal deformity include decreased range of
movement, positional pain, and functional limitations.
PELVIS
According to Lowes and Orlin (2005) pelvic abnormalities in cerebral palsy
include obliquity, posterior and anterior rotation. The relationship between tight
hamstrings 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 al
2004) hip displacement is measured by the migration of the head of femur away from
the acetabulum, with hip subluxation exceeding 33% migration and hip dislocation
exceeding 80% migration. Aetiology is unknown however; contributing factors
include persistence of ATNR, acetabular dysplasia, hypertonicity, hip contractures,
decreased ambulation and muscle imbalance.
Research evidence suggests that
children with tonal asymmetry and severe spasticity appear to be at increased risk of
dislocation, with a windswept deformity on the opposite side (Young et al 1998).
21
Pountney et al (2001) support this assumption by stating that imbalance in muscle
strength and length around the hip leads to dysplasia and subsequent hip subluxation.
Gudjonsdottir and Stemmons (1997) suggest that an important predictor in hip
stability is the age at which a child is able to pull to stand. Cornell (1995) reported
that less than 2% of children who are able to pull to stand before the age of three years
have hip subluxation or dislocation. Hip dislocation, pelvic obliquity and scoliosis are
related problems in cerebral palsy (Gudjonsdottir and Stemmons Mercer 1997), with
Letts et al (1984) reporting that dislocation occurs first, followed by obliquity, then
scoliosis. Research has evidenced that postural management interventions have an
important 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<0.05) compared with other
groups.
FOOT / ANKLE
Lowes and Orlin (2005) suggest that impairments of the foot and ankle include
reduced dorsiflexion resulting from shortened gastrocnemius, plantar flexion during
weight bearing resulting from hypertonicity and ankle instability and the acquisition
of a flat foot position due to breakdown of the arch of the foot resulting from
decreased weight bearing ability.
Seating and Postural Implications
Children with cerebral palsy will have difficulty with stationary postures,
transitionary movements and functional mobility (Westcott and Goulet 2005).
Literature suggests that appropriate seating should aim to normalise tone, inhibit
reflex activity, prevent deformity, promote optimal function, maintain postural
alignment, maintain tissue integrity and maximise stability (Mhyr and von Wendt
1990; Healey et al 1997; Ham et al 1998) with McDonald et al (2004) suggesting that
the provision of adaptive equipment to children with cerebral palsy should be
individualised based on functional and contextual factors. Disparity in the literature
exists regarding the optimal sitting position for a child with cerebral palsy. Some
authors advocate the upright posture (Nwaobi et al 1983; Nwaobi 1986, 1987; Green
and Nelham 1991). Others are in favour of straddled (Reid 1996) and forward
inclined seating (Myhr and von Wendt 1990, 1991; Miedaner 1990; Myhr et al 1995;
van der Heide 2003) and there are those that advocate a reclined posture
(McClenaghan et al 1992; Hadders et al 1999) to enhance postural control. It is
recognised that some of these studies do not refer to cerebral palsy as a heterogeneous
group. Please refer to previous sections reviewing these studies.
22
Congenital Hip Deformity / Developmental Dysplasia
Developmental dysplasia is a condition of pathological hip instability
characterised 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 and
Kernohan 1998).
Rodgers et al (1998) attributes the cause of developmental
dysplasia to both environmental (birth complications) and genetic factors. Ham et al
(1998) support this assumption stating that developmental dysplasia may be due to
hormonal 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 Orlin
2005). This condition is also characterised by poor hip socket development, poor
weight bearing surface and leg length discrepancy if the femur is subluxed from the
acetabulum (Lowes and Orlin 2005). Early diagnosis is imperative as this condition is
treatable in the early stage, however long term permanent damage will incur if left
untreated of if late diagnosis occurs (Cox and Kernohan 1998, Rodgers et al 1998,
Lowes and Orlin 2005). Treatment usually comprises of orthopaedic surgery and
splinting (Cox 1995). Positioning problems include reduced abduction and flexion at
the hip joint, leg length discrepancy, (Lowes and Orin 2005) and if not corrected
early, delayed walking and abnormal gait patterns will be evident (Ham et al 1998).
Two studies identified discuss the seating and mobility issues encountered by children
with developmental dysplasia.
Cox (1995) used a survey method with parents of 11 children who either had
undergone or were undergoing treatment for late diagnosed developmental dysplasia.
Results highlighted that there was insufficient equipment able to accommodate
children in plaster and splints and there was a need to develop seating products, with
emphasis placed on mobility. Small sample size and a response rate of 48% limit the
generalisability of these findings. Cox et al (1998) further researched seating and
mobility in a subsequent study, again utilising a survey method.
To identify
problems, a survey of 113 affected families in England and Northern Ireland was
conducted. Results identified problems in areas of mobility, which creates emotional
and social difficulties in family routines. Regarding mobility, it was found that due to
the child’s loss of mobility, parents resorted to lifting and carrying the child more
frequently, which became problematic as the child increased in age and size. Seating
equipment 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 pushchair
and provide seating in the home environment. Caution must be applied when
generalising results as finding are based on a 38% response rate.
23
Rett Syndrome
Rett Syndrome is a rare neurodevelopmental disorder which predominantly
affects females (Cass et al 2003). It is characterised by progressive loss of intellectual
functioning, loss of fine and gross motor skills, loss of purposeful hand movements
and development of stereotypical hand movements such as hand wringing, washing
and clapping (Parker 2000; Reed 2001), difficulty or inability ambulating (Parker
2000) and marked changes in emotional development and behaviour (Ham et al
1998). Research has evidenced the prevalence of fractures as 20.9% amongst this
population (McDonald et al 2002). Rett syndrome is also classified as a pervasive
developmental disorder as it also characterised by severe and complex impaired social
interaction, communication and behaviour (Rodgers et al 1998) According to Parker
(2000) normal development occurs between the first 6-18 months of life, after which
regression appears to occur. Clinical manifestations also include muscle atrophy,
increased spasticity and seizures (Ham et al 1998), hypotonia, ataxia, and trunk
rocking (Effgen 2005).
Scoliosis is the primary orthopaedic complication of Rett syndrome with onset
associated with stereotypical arm and hand movements, slowing down of righting and
equilibrium reactions, age (McClure et al 1998) alterations in muscle tone, spasticity,
and muscle incoordination (Harrison and Webb 1990). Research has evidenced that
there is a significant relationship between the prevalence of Rett syndrome scoliosis
and 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 of
scoliosis. Cass et al (2003) also suggest that early asymmetry of the pelvis as well as
shoulder protraction and elevation may be a precursor to fixed deformity. Clinical
implications therefore would be to promote bilateral symmetrical muscular balance
through 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 minimise
and 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 are
recommended.
24
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 of
cardiopulmonary compromise (Ham et al 1998). In DMD, muscles break down and
are replaced with fat and scar tissue, (pseudo hypertrophy) resulting in the muscles
appearing bulky, with the calf muscles looking unusually large (Parker 2000).
Impairment of muscle is affected proximally to distally ( Lowes and Orlin 2005) with
Rodgers at al (1998) suggesting involvement begins in the proximal musculature of
the pelvis, proceeding to the shoulder girdle and subsequently to the distal muscle
groups. Thompson et al (1998) add that muscle involvement is bilateral and
symmetrical. To compensate for muscle weakness, the child may resort to using the
upper extremities to assist knee extension by using his hands to ‘walk up’ from floor
to standing (Gower’s sign) (Ham et al 1998; Lowes and Orlin 2005). In addition
hyperextension 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 by
walking 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 in
difficulty in sitting due to unequal weight distribution over the ischial tuberosities.
Bakker et al (2000) suggest that correct positioning and stretching may delay
the development of contractures and spinal deformity. Parker (2000) also highlights
good body alignment is imperative especially with older children for efficient
respiratory function as many may be reliant on ventilators to assist breathing. Due to
the progression of DMD, the child’s postural needs will continually change; hence
seating interventions must be able to accommodate change. Intervention may also be
complex 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; Thompson
et al 1998; Rodger et al 1998; Lowes and Orlin 2005) however a recent systematic
review suggested that although the use of knee ankle foot othoses can prolong assisted
walking 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 regarding
seating is to level the pelvis, with a firm seat base, align the trunk with lateral supports
to facilitate head alignment and support the elbows and forearms on a tray or with arm
supports. Ham et al (1998) highlight that reclining or tilting the seating system may
reduce the load on the spine, however may be contraindicated by the child adopting
an exaggerated lordosed position of the lumbar spine to maintain upright balance and
the head in midline. According to Clark et al (2004) limited research exists regarding
25
the effects of postural support in seating on health and function of young people with
neuromuscular disorders.
Clark et al (2004) conducted a prospective two-period randomised crossover
study to measure the effects of postural support in seating on posture, respiration and
upper limb function for young people with neuromuscular disorders. Nineteen
participants aged 6-22 years old, with a diagnosis of DMD (n=15) or Freidreich’s
Ataxia (n=4) were assessed in wheelchair seating and in adaptive seating via a
standard protocol. Sitting posture, respiration and upper limb function was compared
when sitting in a standard wheelchair and in adaptive seating. Results concluded that
there were no significant differences in respiratory function and no overall
improvement 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 and
difficulty with accurate postural measurements in the clinical setting limit the
generalisability 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 the
spinal column (Rodgers et al 1998) whereby the neural tube fails to unite therefore
exposing a gap over which the skin is defective (Ham et al 1998). Parker (2000)
highlights three spina bifida classifications and includes spina bifida occulta (minor
defect not obvious at the skin surface), meningocele (protruding sac containing
meninges) and myelomeningocele (protruding sac containing meninges and spinal
cord). It is suggested that the cause of spina bifida results from genetic and
environmental factors (Reed 2001; Rodgers et al 1998). Numerous clinical
manifestations are apparent with spina bifida and include the following: fine motor
and hand skill delay (Reed 2001), hydrocephalus (Pountney and McCarthy 1998),
impaired or loss of sensation, paralysis, vasomotor dysfunction (Westcott and Goulet
2005), perceptual dysfunction (visual, auditory, propriceptive, tactile , kinaesthetic
and 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 lesion
determining functional ability. Spinal deformities associated with spina bifida include
scoliosis, 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 the
extremities, poor postural control of trunk, poor coordination and presence of hip
26
dislocation / subluxation (Reed 2001) and flexion contractures of knees and ankle
(Pountney and McCarthy 1998) are factors which must be considered regarding
seating 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 and
improve independence.
One study identified investigated the effect on interface pressure distribution
in a group of children with complete paraplegia due to myelomeningocele and a group
of aged matched controls in different sitting positions (Vaisbuch et al 2000). This
study concluded that the lean forward position (hips flexed to 45°) produced the
largest reduction in interface pressure, however the authors acknowledge the children
felt apprehensive in this posture. The tilt position also reduced interface pressure,
with the authors suggesting that tilting is used to relieve pressure during periods of
non functional activity. No other studies were identified regarding seating principles
with this population.
Conclusion
Following a review of the literature, it is concluded that positioning principles
are based on empirical and evidence and expert opinion regarding children and young
people with neuromotor and neuromuscular disabilities. The majority of research
conducted reflects the impact of seating and positioning with the cerebral palsy
population. Continued disparity in the literature, small sample sizes and short periods
of data collection limit the generalisability of the findings, although are important in
terms of clinical significance. Limited research exists regarding children with
neuromuscular conditions. It is recognised that appropriate positioning in children
with physical disabilities is important to facilitate engagement in functional activity
and enable participation with the environment (Jones and Gray 2005). Research has
evidenced that proper positioning can improve upper extremity function (Mhyr and
von 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 intervention
hence is to provide adaptive seating to create a functional seated position to maintain
health and function as part of a postural management approach.
27
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34
APPENDIX 1
The following tables indicate data bases searched and key words utilized regarding
specific themes.
TABLE 1: Seating
Data Base
Key Words
CINAHL
exp seating/ AND Child
exp equipment design AND child
exp seating/ AND child
dynamic seating
BIDS
seating
Pubmed
seating
seating principles
seating and positioning
Proquest
adaptive seating
seating
seat$ AND children AND position
Embase
exp seat/ AND child
dynamic seating
AMED
exp seating/ AND child
exp equipment design/ AND exp seating
AND child
dynamic seating
Medline (Ovid)
dynamic seating
seating and positioning
OTDbase
seating
ASSIA
positioning and seating
Psychinfo
seating
British Nursing Index
seating
Seat$
Zetoc
seating
pe*diatric seating
35
ISI Web of Science
seating
TABLE 2: Positioning / Posture
Data Base
Key Words
CINAHL
patient positioning
BIDS
posture
positioning
Pubmed
seating and posture
Proquest
seating and positioning
Embase
positioning
AMED
exp positioning/
patient positioning AND exp pelvis/
Medline (Ovid)
seating and positioning
OTDbase
positioning
ASSIA
seating and positioning
Psychinfo
positioning
British Nursing Index
patient positioning
Zetoc
seating and positioning
ISI Web of Science
seating and positioning
seating and posture
positioning and posture
36
TABLE 3: Cerebral Palsy
Data Base
Key Words
CINAHL
exp cerebral palsy/ AND posture/ AND
child
BIDS
cerebral palsy
Pubmed
cerebral palsy and seating
Proquest
cerebral palsy and positioning
cerebral palsy and seating
spastic cerebral palsy and posture
spastic cerebral palsy and position
Embase
exp cerebral palsy/ AND child
exp cerebral palsy/ AND posture/ AND
child
AMED
exp cerebral palsy/ AND seating
Medline (Ovid)
cerebral palsy and seating
OTDbase
cerebral palsy
ASSIA
cerebral palsy and positioning
cerebral palsy and posture
Psychinfo
cerebral palsy and posture
British Nursing Index
Exp cerebral palsy/ AND seating
Zetoc
cerebral palsy and seating
ISI Web of Science
Cerebral palsy
cerebral palsy and positioning
cerebral palsy and posture
37
TABLE 4: Duchenne Muscular Dystrophy
Data Base
Key Words
CINAHL
exp duchenne muscular dystrophy/ AND
child
BIDS
muscular dystrophy
Pubmed
duchenne muscular dystrophy and seating
duchenne muscular dystrophy and
posture
exp duchenne muscular dystrophy/ AND
exp child/
Proquest
Embase
duchenne muscular dystrophy/ AND exp
child/
AMED
duchenne muscular dystrophy
Medline (Ovid)
duchenne muscular dystrophy and seating
OTDbase
duchenne muscular dystrophy
ASSIA
duchenne muscular dystrophy
duchenne muscular dystrophy AND
posture
Psychinfo
duchenne muscular dystrophy
British Nursing Index
duchenne muscular dystrophy
Zetoc
duchenne muscular dystrophy and seating
duchenne muscular dystrophy and child
duchenne muscular dystrophy and
posture
ISI Web of Science
Duchenne muscular dystrophy
38
TABLE 5: Congenital Hip Deformity / Developmental Dysplasia
Data Base
Key Words
CINAHL
exp hip deformity congenital/ AND child
BIDS
congenital hip deformity
developmental dysplasia
Pubmed
congenital hip deformity and seating
congenital hip deformity and posture
Proquest
developmental dysplasia
Embase
exp hip dislocation congenital/
Medline (Ovid)
Congenital hip deformity AND child
AND hip dislocation
AMED
exp hip dislocation congenital/
OTDbase
developmental dysplasia
ASSIA
developmental dysplasia
Psychinfo
developmental dysplasia
British Nursing Index
exp congenital abnormality/ AND exp
developmental dysplasia/
Zetoc
congenital hip
developmental dysplasia
developmental dysplasia and seating
developmental dysplasia and child
ISI Web of Science
developmental dysplasia
39
TABLE 6: Rett Syndrome
Data Base
Key Words
CINAHL
rett syndrome
BIDS
rett syndrome
Pubmed
rett syndrome and posture
Proquest
rett syndrome and posture
Embase
exp rett syndrome/ AND exp child
AMED
exp rett syndrome/ AND exp child
Medline (Ovid)
rett syndrome and child
rett syndrome and posture
rett syndrome and posture
rett syndrome and child development
OTDbase
rett syndrome
ASSIA
rett syndrome
Psychinfo
rett syndrome
British Nursing Index
rett syndrome
Zetoc
rett syndrome
ISI Web of Science
rett syndrome
40
TABLE 7: Spina Bifida
Data Base
Key Words
CINHAL
spina bifida and seating
spina bifida and positioning
BIDS
spina bifida
Pubmed
spina bifida and seating
spina bifida and posture
Proquest
spina bifida and seating
AMED
exp child/ AND exp abnormalities/ AND
exp spina bifida/
exp child/ AND exp meningomyelocele
Medline (Ovid)
spina bifida and posture
spina bifida and children
OTDbase
spina bifida
ASSIA
spina bifida and posture and seating
Psychinfo
spina bifida and children
British Nursing Index
spina bifida and seating
Zetoc
spina bifida and seating
spina bifida and posture
spina bifida
ISI Web of Science
spina bifida and child
spina bifida and posture
spina bifida and seating
41
Findings from a multidisciplinary
clinical case series of females with
rett syndrome.
Cass H, Reilly, Owen L, Wisbeach
A, Weekes L, Wigram T &
Charman T (2003).
To gather systematic data
from a multidisciplinary
clinical assessment case load
of females with rett
syndrome, to allow clinical
manifestations of the disorder
to be statistically validated in
order to discuss implications
regarding management of the
condition and directions for
future research.
To investigate the
relationship between
proximal and distal motor
control using the Postural
Fine Motor Assessment Scale
for Infants (PFMAI)
Case-Smith J, Fisher AG & Bauer
D (1989).
An Analysis of the Relationship
between Proximal and Distal Motor
Control.
Purpose
Author / Date / Title
Case-Series design
Cas-series design
Study Design
87 participants ( 2yeras 1 month
– 44 years 10 months) with a
confirmed diagnosis of rett
syndrome seen between 1993
and 2000.
n= 76 (classic rett syndrome)
n=11 (atypical presentation of
disorder)
60 normal infants (2-6 months:
mean 4.4 months) from day care
facility tested as measured by
the PFMAI.
Participants
All participants seen in
multidisciplinary tertiary health
clinic (paediatrician, PT, SLT.
OT and music therapist).
Assessment areas included:
oralmotor skills, feeding
problems, growth, breathing
problems , pos tural
abnormalities and joint
deformities, epilepsy,
stereotypies and hand
movements, self-care, and
cognitive and communication
skills. Areas assessed by
parental/carer reports, direct
observation, multidisciplinary
examination, clinical reports,
video taped assessment sessions
and assessment tools e.g.
Schedule for Oral Motor
Assessment.
Posture and fine motor control
were measured by the PFMAI,
with testing conducted by J
Case-Smith and 4 undergraduate
students trained in PFMAI
administration. Posture observed
by the infants ability to
independently sustain movement
against gravity when in prone
and supine. (postural reactions
encouraged by attracting infants
attention to developmentally
appropriate toys. Fine motor
skills assessed by eliciting
various grasping and hand
positions by presenting children
with 3 objects. Infants position
ed in semi recline. Four minutes
of testing allocate d for reach and
manipulation of each object
Methodology
Previously reported trends in
presentation confirmed:
↑ poor growth, fixed
deformity and scoliosis in
adulthood.
↑ mobility in adolescence,
follwed by decline in
adulthood.
High dependency level.
Limited
cognition/communication
skills.
Slight improvement in ANS
function in adulthood.
Feeding difficulties ↑ into
middle childhood, reachinf a
plateau. Findings confirm
that Rett Syndrome is not
degenerative and suggests
that intervention and support
to maintain and increase
motor skills, daily living
skills and cognitive and
communication is
appropriate.
Results suggest in normal
children, there is a significant
but weak correlation
between proximal control and
the development of distal
skill, suggesting that
[proximal-distal principle
may not be an appropriate
postulate on which to base
treatment / intervention.
Significant relationship to
support a functional
relationship between
proximal and distal motor
functions.
Results and Conclusions
1
Problems of seating and mobility
encountered by children with
developmental dysplasia of the hip.
Cox SL & Mollan RAB (1995)
To confirm the clinical
suspicion that significant
problems are encountered by
children and their care -givers
in coping the treatment of
splinting resulting from late
diagnoses developmental
dysplasia of the hip (DDH).
2) To compare children ’s and
parents’ paediatric pain
ratings to determine whether
or not concordance exists
between the two.
1) To investigate the nature
and prevalence of pain in
children and adolescents with
spina bifida.
Clancy CA, McGrath PJ & Oddson
BE (2005).
Pain in adolescents with spina
bifida.
Purpose
Author / Date / Title
Questionnaire focuses on
seating and mobility problems.
Questions generated from
analysis of the literature and
information obtained from
detailed semi-structured
interviews with surgeons and
staff involved in treatment.
3 questionnaires sent to patient s
in Northern Ireland; 2 in the
republic of Ireland; and 6 in
Engalnd.
Questionnaire (pilot study)
(semi structured and open)
Prospective study.
Study Design
Parents of 11 children (2 boys;
9 girls) who were either
undergoing or had undergone
treatment for late diagnosed
DDH, were surveyed by
questionnaire.
Parents (mean age 43 years 4
months)
For comparison purposes
sample divided into 2 groups
n= 68 children with spina bifida
(30 males, 38 females)
Mean age 12 years 8 months
(range 8-19 years).
n=59 (myelomeningocele)
n= 6 lipomyelomeningocele
n= 3 lipomeningocele.
n= 49 shunted hydrocephalus
n=26 ambulated full time
Children able to communicate in
English and had no significant
cognitive limitations.
Recruited from regional
children’s centre.
Participants
Questionnaires either distributed
by post or through parental
support groups and were
completed by parents.
24 questionnaires distributed, of
which 11 were returned (48.8%
response rate).
Measures administrated by one
of two trained Masters level
volunteer in separate area from
clinic to ensure independent
rating.
Data collected via parental
report questionnaires (The
Pediatric Pain Questionnaire)
and child report questionnaire
(Visual Analogue Scale) and,
from t medical records to
investigate ain intensity,
location, frequency and
duration.
Methodology
This pilot study confirmed
need for future focused
research to provide products
suggested.
Results suggest there is a
deficiency in equipment
available to cope with and
manage children in plaster,
including products to help in
seating. Special emphais is
placed on mobility.
56% reported experiencing
pain once a week or more
often; Pain occurred more
frequently in the head, neck,
back, abdomen, shoulders,
legs and hands.
43∕49 with hydrocephalus
reported headaches.
15∕19 without hydrocehalus
reported headaches..
Children reporting intense
pain, also report ↑ frequency
and ↑ pain locations.
Parenta most reliable st
reporting locality of
children’s pain.
Findings conclude children
with soina bifida report
clinically significant, under
recognised & untreated pain.
Results and Conclusions
2
Development of postural
adjustments during reac hing in
infants with cerebral palsy.
Hadders-Algra M, van der Fits
IBM, Stremmelaar EF & Touwen
BCC (1999).
To analyse the early
development of postural
adjustments accompanying
reaching movements in
children with cerebral palsy.
Physical, emotional and
social problems are the focus
of the report.
To identify problems related
to the treatment (splintage) of
DDH in order of priority in
families of hildren with
DDH.
Cox SL & Kernohan WG (1998 ) .
They cannot sit properly or move
around: seating and mobility during
treatment for developmental
dysplasia of the hip in children.
Purpose
Author / Date / Title
Longitudinal
Questionnaire (semi structured
and open)
Study Design
7 children (age range 4-18
months). 3 boys; 4 girls
38 questionnaires returned (3 4%
response rate.
113 affected families surveyed
Participants
Reaching movements were
assessed via simultaneous
recording of video data and
surface EMG of arm, neck,
trunk and leg muscles during
reaching in various positions
(lying supine, semi -recline
(45°), upright and long leg
sitting).
10 questionnaires distributed in
England; 3 obtained via
interview with parents in
childrens ward in hpspital in N.
Ireland: 100 distributed to those
undergoing or had undergone
treatment at the hospital.
Questionnaire developed based
on the activitied of daily iving
that were established for
families with children between 3
months and 3 years old.
Methodology
Results suggest basic
orientation of postural
adjustments of childr en
developing spastic CP was
intact, with main problems
being ↓ ability to modulate
postural adjustment to task
specific constraints. The
child with spastic athetosis
showed distinct abnormalities
in basic organisation of
postural adjustments.
Reaching movements were
favoured in semi recline as
opposed to upright, supine
and long leg sitting
5 developed spastic
hemiplegia
1developed spastic
tetraplegia
1 developed spastic
tetraplegia with athetosis.
Such problems may be
alleviated by provision of
specialised devices that
would permit mobility by car,
in a pushchair and provide
seating in the home.
Reslults suggested that
parents idenfied social,
emotional and physical
problems. Problems included
size and shape of splint,
transporting ans seating
problems and disruption of
family routines.
Results and Conclusions
3
The relationship between tight
hamstrings and lumbar hypolordosis
in children with cerebral palsy.
McCarthy JJ & Betz RR (2000)
To assess the influence of
tight hamstrings on the
saggital alignment of the
thoracic and lumbar spine in
children with cerebral palsy.
To investigate the effects of
special seating on lateral
spinal curvature in the non ambulant spastic cerebral
palsy population with
scoliosis.
Holmes KJ, Michhael SM & Thorpe
(2003).
Management of scoliosis with
special seating for the non -ambulant
spastic cerebral palsy population – a
biomechanical study.
Purpose
Author / Date / Year
Retrospective clinical and
radiographic review.
Prospective study: matched
pairs design
Study Design
21 participants
Mean age: 9.4 years old
Inclusion criteria reuired
subjects to be non-ambulant,
have a scoliosis and require
special seating within their
wheelchair,.
16 subjects with spastic cerebral
palsy
9 boys: 7 girls
Man age: 14.7 years (range 6.5 20.8).
Participants
The popliteal angle was
measured to assess hamstring
tightness.
The Cobb method was used to
measure lumbar and thoracic
kyphosis. Standing and sitiing
lateral spine films were
obtained.
Shape of spine measured
(spinous process angle in an
assessment chair (CAPS II).
Exerted forcs on chair measured
by electrical transducers
attached to lateral support pads
and seat base. Measurements
were taken in 3 alternative
arrangements: 1) unsupported
upper body 2) two lateral pads at
the same height 3) body
supported by 3-point force
system.
Methodology
Study concludes that there is
a correlation between tight
hamstrings and decreasing
lumbar lordosis, esp ecially in
the seated postion in children
with cerebral palsy.
A statistical significant
correlation was obtained
(p<0.01) between the sitting
lumbar curve and the
popliteal angle. This
correlation was less when
standing.
Significant static correction
of the spine (scoliotic) may
be achieved via an
arrangement of lateral pads
on a seating system applying
a 3-point force system to the
sides of the body.
Results and Conclusions
4
The relationship of cumulative
motor asymmetries to scoliosis in
rett syndrome.
McClure MK, Battaglia C &
McClure RJ (1997).
To investigate the
interrelationships between
rett syndrome scoliosis and
symmetric, asymmetric
motor pull, ambulation and
advancement of age in order
to provide a treatment
rationale for slowing the
progression of a scoliosis.
To investigate the inter relationship of seat -surface
inclination on postural
stability and functional use of
the upper extremities in
children with cerebral palsy.
McClenagahan BA, Thombs L &
Milner M (1992).
Effects of seat -surface inclination
on postural stability and function of
the upper extremities of children
with cerebral palsy.
Purpose
Author / Date / Title
Questionnaire
Quasi-experimental design
Study Design
Findings based on 57% response
rate.
262 questionnaires completed
by International Rett Syndrome
Association families.
Able to comprehend simple
instructions.
Screened for visual problems.
20 children (10 non -impaired:
10 mild-moderate spastic
cerebral palsy.
Age range: 4-15 years.
CP children able to sit
independently and ambulate
with or without mobility aids.
Participants
Responses were scored
independently by two
investigators..
400 questionnaires were
distributed via post, 262 were
completed and returned (66%).
228 were suitable for statistical
analysis (57%).
Seat surface inclinations of 0°,
5° (anterior tilt), 5° posterior
tilt) with seat to backrest angle
at 90° were compared within
and between groups, with leg
rest position at 90° from the seat
surface for all experimental
conditions.
Methodology
A significant relationship was
found between the prevalence
of rett syndrome scoliosis and
orthopaedic risk factors. The
findings suggest a treatme nt
approach focusing on
balancing bilateral muscle
pull.
Significant between group
differences were observed on
most dependent measures.
No significant difference a
could be attributed to seat
inclination, however authors
suggest anterior tilt may
disturb postural stability,
without improving upper
extremity function..
Results and Conclusions
5
To compare arm movements
of persons with and without
cerebral palsy and to
determine if the alteration of
the seat angle of a chair affect
quality of movements.
To identify a reliable,
objective and clinically
useful measure for assessing
changes in trunk alignment
and to evaluate which of five
different seated positions was
the most effective in
encouraging trunk extension.
McPherson JJ, Schild R, Spaulding
SJ, Barasamian P, Transon C &
White SC (1991).
Miedaner JA (1990).
The effects of sitting positions on
trunk extension for children with
motor impairment.
Analysis of upper extremity
movement in four sitting positions:
a comparison of persons with and
without cerebral palsy.
Purpose
Author / Date / Title
Quasi-experimental
Study Design
15 children
Age range (2-6 years)
Diagnosis of developmental
delay and/or severe hypotonic or
hypertonic cerebral palsy
(diplegia or quadriplegia).
Age range; 18-21 years
Right hand dominant
Able to follow instructions
12 subjects
3 men: 3 women with mild moderate spastic cerebral palsy;
3 men and 3 women with no
known pathological conditi on.
Participants
Tested in 5 random positions
during 30 min session (floor
sitting in tailor like fashion,
level sitting with hips and knees
at 90°, bench sitting with bench
tilted forward (20°and 30°) and
sitting in a commercial chair.
Trunk extension measures by
the modified Schober
Measurement of Spinal
Extension (1975).
Each child rated on a scale of 1 4 to document trunk control,
rated by an experienced
paediatric physiotherapist.
Arm movements were compared
between groups and within
groups in four different
positions (neutral, wheelchair,
posterior tillt (15°) and anterior
tilt (15°). Four conditions
presented in counterbalanced
order. EMG activity recoreded.
Methodology
Significant differences
observed among the five
conditions. Study suggests a
anterior sitting posture is the
preferred position to facilitate
increased trunk extension.
Quantifiable and qualitative
between group differences in
reaching. No significant
differences could be
attributed to the seating
positions.
Results and Conclusions
6
Improvement of functional sitting
position for children with cerebral
palsy.
Myhr U & von Wendt (1991).
To find a functional sitting
position for children with
cerebral palsy and to compare
this position with the
children’s original sitting
positions with various
experimental positions.
To create a functional sitting
position (FSP) by identifying
the essential factors required
to reduce spasticity as well
as enhancing postural control
in children with cerebral
palsy.
Myhr U & von Wendt (1990).
Reducing spasticity and enhancing
postural control for the creation of a
functional sitting position in
children with cerebral palsy: a pilot
study.
Purpose
Author / Date / Title
Quasi-experimental
Pilot study (single case design)
Study Design
23 children (8 female, 15 male)
Age range (2-16 years)
Child A: 7 years old, spastic
diplegia
Child B: 15 years old , spastic
tetraplegia.
2 children with severe cerebral
palsy.
Participants
Head control, pathological
movements, postural control
were measured via observation
and Sitting Assessment Scale.
Children were filmed and
photographed in 6 positions
(adapted chair; adapted chair
and cut out level table in font of
child,; FSP without abduction
orthosis; adapted chair and
abduction orthosis,;FSP without
table; FSP with table and
abduction orthosis). In FSP seat
was forward inclined.
Both children filmed and
photographed individually in six
positions on the same occasion,
including sitting in their own
adapted chairs and in the
proposed FSP. Testing
conditions were altered by
changing the seat inclination,
use/non-use of abduction
orthosis and with.without a table
in front of them. Total time for
postural control was recorded
and pathological movements
were counted.
Methodolgy
Results suggest pathological
movements are minimised
and postural control and
upper extremity function are
more 3efficient in a forward
tipped seat, with a firm
backrest supporting pelvis,
arms supported against a
table and feet permitted to
move backward.
Greatest reduction of
spasticity gained and postural
control enhanced when three
factors were combined:
symmetrical fixation of belt
under seat, use of an
abduction orthosis and
placement in the FSP. This is
in addition to seat inclined
forwards and arms supported
on a table. No discernable
effects were identified by seat
inclination alone.
Results and Conclusion
7
Five year follow-up of functional
sitting position in children with
cerebral palsy.
Myhr U, von Wendt L, Norrlin S &
Radell U (1995).
To re-examine the reliability
of the Sitting Assessment
Scale.
To re-assess children who
were previously introduced to
and tested in the FSP five
years previously.
To obtain a baseline
comparison with
measurements of children
with cerebral palsy.
To determine the
spontaneous positioning of
the lower extremities relative
to the movement axis at the
knee joint, and to determine
thre extent of spontaneous
use of the arms for support in
different sitting positions, in
a group of non-disabled
children.
Myhr U (1994).
Influence of different seat and
backrest inclinations on the
spontaneous positioning of the
extremities of non -disabled
children.
Purpose
Author / Date / Title
Retrospective
Case Study
Study Design
10 children with CP
10 non-disabled children
(7 girls; 3 boys)
Mean age 6.7 years (range: 4 -9
years).
Participants
Head, trunk, foot control, arm
and hand function were assessed
by the Sitting Assessment Scale
Ten children were filmed and
photographed after the
introduction of the FSP and
subsequently five years later.
The children were filmed and
photographed whilst performing
standardised tasks in 5 different
sitting positions (backrest
vertical and seat surface
inclination varying between 0°
10° forward inclined, 10°
backward reclined, and also in
reclined positions in with seat
and backrest lean backward
from the horizontal plane and
vertical plane, respectively
(15 °).
Methodology
Study concludes that the FSP
contributes to improved
ability to use the upper
extremities (hand and arm
function).
8 out of the 10 children
assessed, who used the FSP
over the five year period,
showed slight but significant
improvement, the remaining
two children had deteriorated.
Results revealed that in
positions with the backrest
vertical and with the use of a
hip belt, all children held
their feet posterior to the
knee joint axis regardless of
seat inclination.
Results and Conclusions
8
Electromyographic investigation of
extensor activity in cerebral -palsied
children in different seating
positions.
Nwaobi OM, Brubaker CE, Cusick
B & Sussman (1983).
To determine if the
myoelectric activity of the
extensor muscles of the
lumbar spine is affected by
positions of the seat surface
and seat back, or by their
positions relative to one
another.
To compare the effects of
adaptive and non adaptive
seating on pulmonary
function.
Nwaobi OM & Smith (1986).
Effect of adaptive seating on
pulmonary function of children with
cerebral palsy.
Purpose
Author / Date / Tilte
Experimental
Quasi-Experimental
Study Design
11 children (7 boys: 4 girls)
with spastic CP.
Age range: 4-8 years
8 children with spastic CP
Age range: 5-12.
Non-ambulant
No apparent evidence of
intrinsic lung disease.
Participants
Using surface electrodes EMG
activity was recorded for the
lumbar extensor spinae muscles
in seven different testing
conditions. Seat surface
inclinations of 0° and 15°
combined with backrest
inclinations of 75°, 90°, 105°,
and 120°..
Children were positioned in
90-90-90 in both seating units.
Vital capacity, forced expiratory
volume in one second, and
expiratory time as measure by a
spirometer , of children with CP
were measured in a typical sling
back wheelchair and in a
wheelchair with modular inserts.
Methodology
Results highlighted that
extensor activity was lowest
when backrest inclination
remained at 90° and the seat
surface at 0° (upright sitting).
Preliminary finding from
study suggests that the
orientation of the head
/neck/body in relation to
gravity may play an
important role in controlling
extensor activity.
Results suggest implications
for speech, sitting for
prolonged periods and the
prevention of pulmonary
hypertension.
Results of the study suggest
that pulmonary function was
higher in adaptive seating
compared to non -adaptive
seating.
Results and Conclusions
9
Seating orientations and upper
extremity function in children with
cerebral palsy.
Nwaobi OM (1987).
To measure the performance
time of a prescribed upper
extremity activity in four
different seating orientations
relative to the ve rtical plane
to determine the effect of
body orientation on voluntary
motor function.
To determine if tonic activity
of these muscles change in
response to body orientation,
and which body orientation
provides the lowest level of
muscle activity.
To measure the tonic
myoelectric activity of the
low back extensors, hip
adductors and ankle plantar
flexors in two body
orientations.
Nwaobi UM (1986).
Effects of body orientation in space
on tonic muscle activity of patients
with cerebral palsy.
Purpose
Author / Date / Title
Quasi-experimental
Experimental
Study Design
13 children with CP
3 athetoid CP
10 spastic CP
Age range: 8-16 years
Unable to ambulate
independently
Require adaptive seating for
upright positioning
Fair-poor gross upper extremity
control.
Fair head and trunk con trol
Poor fine motor skills.
12 children (8 boys: 4 girls)
Age range: 6-18 years
Diagnosis of mild-moderate
spastic diplegia.
Fair head and trunk control
Fair to poor fine motor skills
No fixed deformity.
Participants
The children were placed
randomly in different seating
orientations (30°, 15°, and 0°
posterior inclination and
15°anterior inclination).
The seating positions were 0° in
vertical plane and 30° from the
vertical plane. Each participant
was position ed in 90-90-90 with
the use of a pommel prior to
testing.
Surface electrodes were used to
measure myoelectric activity if
the low back extensors, hip
adductors and ankle planta r
flexor muscles in two seating
positions.
Methodology
Results conclude orientation
of the body in space affects
upper extremity function.
The level of upper extremity
performance was highest in
the upright position.
Results demonstrated that
muscle activity was affected
by body orientation, with
tonic muscle activity lower in
the upright position with
statistically significant
differences for the hip
adductors and back extensors.
Extensor tone may increase
in the reclined position.
Results and Conclusions
10
Effects of anterior tipped seating on
respiratory function of normal
children and children with cerebral
palsy.
Reid DT & Sochaniwskj (1991).
To investigate the effects of
using an anterior inclined seat
base on tidal volume,
respiration rate and minute
ventilation function of
normal children and children
with cerebral palsy.
To evaluate postural control
and upper extremity
movement control in children
with cerebral palsy using a
saddle seat.
Reid DT (1996)
The effects of the saddle seat on
seated postural control and upper
extremity movement in children
with cerebral palsy.
Purpose
Author / Date / Title
Experimental
Repeated-measures
experimental cross -over design.
Study Design
Children with CP able to
ambulate either with or without
mobility aids
12 children (6 non-impaired,
mean age 9.7 ; 6 with spastic
CP), mean age 6.0)
Able to sit on a flat bench
without holding on.
Independently mobile via use of
walker or manual wheelchair.
6 children with mild-moderate
spastic CP.
Participants
Respiration parameters of tidal
volume, respiration rate and
minute ventilation are
compared in response to two
seated positions 1) flat seating
2) anterior seating (10° forward
tipped). Respiratory inductance
plethysmography used to record
respiratory function.
Clinical assessment of seated
postural control was measured
by the Sitting Assessment for
Children with Neuromotor
Dysfunction.
The two experimental conditions
were the saddle seat (15°
forwards inclination) and a flat
wooden bench.
Methodology
Results suggest however that
increased tidal volume and
minute ventilation may
increased in anterior tipped
seating, although are not
statistically significant.
Results conclude that no
significant differences in
respiratory parameters were
attributed to seat inclination
in either the normal group or
those with CP.
Saddle bench allowed
improved postural control as
measured by the Sitting
Assessment for Children with
Neuromotor Dysfunction.
The saddle seat has the
potential to modify the
quality of seating posture and
reaching movements in
children with cerebral palsy.
Results and Conclusion
11
To investigate the
development of postural
adjustments accompanying
reaching movements in
sitting children.
To determine the prevalence
of windswept hip deformity
and hip dislocation, and their
relationship to asymmetry of
muscle tone.
Van der Heide JC, Oten B, van
Eykern LA & Hadders -Algra
(2003).
Young NL, Wright JG, Lam TP,
Rajaratnam K, Stephens D, &
Wedge JH (1998).
Windswept deformit y in spastic
quadriplegic cerebral palsy.
Developmental of postural
adjustments during reaching in
sitting children.
Purpose
Author / Date / Title
Cross-sectional study
Experimental
Study Design
103 subjects with spastic CP
recruited from two study
institutions.
10 young adults (mean age
23.6±2 years)
29 healthy children, age range
2-11.
Participants
Data gathered form me dical
records and physical
examination (standardised)
29 children and 10 adults studies
via EMG and kinematics during
reaching in 4 different
conditions: sitting with seat
surface horizontal, with and
without task load, 15° forward
of seat surface and 15 °
backwards tilt of seat surface
Methodology
Results show that tonal
symmetry is related to
windswept deformity alone,
whereas increased age, severe
spasticity, and direction of
tonal asymmetry were
associated with windswept
deformity and hip
dislocation.
Prevalence rates included
52% (windswept hips), 25%
(tonal asymmetry), in hip
subluxation (63%) and hip
surgery (63%). The side with
the strongest tone was more
frequently dislocated of held
in fixed adduction.
Results conclude
development of postural
adjustment during reaching is
non-linear and not finished
until 11 years old.
Anticipatory postural muscle
activity , consistently present
in adults, was basically
absent between 2 -11 years.
Findings suggest that the
forward tilted sitting position
is the most efficient regarding
postural control.
Results and Conclusion