Available via license: CC BY-NC 3.0
Content may be subject to copyright.
Clinical Rehabilitation
2014, Vol 28(1) 82 –90
© The Author(s) 2012
Reprints and permissions:
sagepub.co.uk/journalsPermissions.nav
DOI: 10.1177/0269215512465423
cre.sagepub.com
CLINICAL
REHABILITATION
465423CRE28110.1177/0269215512465423Clinical RehabilitationRodby-Bousquet et al.
2012
1 Department of Orthopaedics, Lund University, Skåne
University Hospital, Lund, Sweden
2
Centre for Clinical Research, Uppsala University, Central
Hospital, Västerås, Sweden
3 Rehabilitation Centre of Excellence, Kópavogur,
Iceland
Interrater reliability and
construct validity of the Posture
and Postural Ability Scale in
adults with cerebral palsy
in supine, prone, sitting and
standing positions
Elisabet Rodby-Bousquet1,2, Atli Ágústsson3, Guðný
Jónsdóttir3, Tomasz Czuba4, Ann-Christin Johansson2
and Gunnar Hägglund1
Abstract
Objective: To evaluate reliability, internal consistency and construct validity of the Posture and Postural
Ability Scale for adults with cerebral palsy.
Design: Psychometric evaluation of a clinical assessment tool.
Setting: Rehabilitation centres in Sweden and Iceland.
Subjects: Thirty adults with cerebral palsy aged 19–22 years, six people at each level I–V of the Gross
Motor Function Classification System.
Main measures: The Posture and Postural Ability Scale contains a 7-point ordinal scale for postural
ability in supine, prone, sitting and standing, and items for assessment of posture. Posture and postural
ability was rated from photos and videos by three independent assessors. Interrater reliability was
calculated using weighted kappa. Internal consistency was analysed with Cronbach’s alpha if item deleted
and corrected item–total correlation. Construct validity was evaluated based on known groups, using
Jonckheere Terpstra for averaged values of the three raters relative to the Gross Motor Function
Classification System.
Results: There was an excellent interrater reliability (kappa = 0.85–0.99) and a high internal consistency
(alpha = 0.96–0.97, item–total correlation = 0.60–0.91). Median values differed (P < 0.02) between known
groups represented by the levels of gross motor function, showing construct validity for all items.
Article
4 National Musculoskeletal Competence Centre for Quality Registers,
Lund University, Skåne University Hospital, Lund, Sweden
Corresponding author:
Elisabet Rodby-Bousquet, Department of Orthopaedics, Lund
University, Skåne University Hospital, SE 221 85 Lund, Sweden.
Email: elisabet.rodby_bousquet@med.lu.se
Rodby-Bousquet et al. 83
Conclusion: The Posture and Postural Ability Scale showed an excellent interrater reliability for
experienced raters, a high internal consistency and construct validity. It can detect postural asymmetries
in adults with cerebral palsy at all levels of gross motor function.
Keywords
Posture, postural control, assessment, cerebral palsy, reliability, validity
Received: 28 July 2012; accepted: 2 October 2012
Introduction
There are few assessment tools for posture and pos-
tural ability in lying, sitting and standing for people
with severe physical disabilities, and none of them
has been evaluated regarding its psychometric prop-
erties for adults with cerebral palsy, even though
posture is a key problem in adult cerebral palsy.1
Asymmetric posture is known to cause progres-
sive deformities in immobile people with cerebral
palsy due to the effect of gravity.2–4 However, early
detection and preventive treatment can reduce the
number of severe contractures, hip dislocations,
scoliosis and other fixed deformities.5–8 As tissue
adaptations often occur slowly over time, standard-
ized measurement is crucial to identify the need for
treatment and postural support in order to minimize
progressive deformities and also to evaluate
therapeutic interventions.
The Physical Ability Scale9 for assessment of
postural ability in children with severe disabilities
was developed by Noreen Hare during the 1970s
and 1980s. This inspired Pountney and co-workers
to develop the Chailey Levels of Ability10 to
describe stages of motor development in normal
infants and children with motor impairments. Its
validity has been evaluated for children and youth
with cerebral palsy.10 These instruments form the
basis of the Postural Ability Scale developed by
Pauline Pope in the early 1990s11 to assess both
posture and postural ability in people with severe
physical disabilities regardless of age and diagnosis.
This assessment tool allows postural ability and
posture to be assessed separately. It is in clinical
use for trained professionals but has not been eval-
uated for its psychometric properties. During the
years 2009–2011, the Postural Ability Scale was
developed further by Pope and co-workers (ERB,
AA, GJ). The levels of ability were slightly modi-
fied and items added to the quality of posture to
allow assessment of posture from a sagittal as well
as a frontal view. This modified and expanded
version. called the Posture and Postural Ability
Scale (PPAS) (Table 1), has not previously been
tested for reliability or validity.
There is no universal definition of posture and
postural ability. In this paper, the term ‘posture’,
relates to the shape of the body (i.e. the anatomical
alignment of the body segments in relation
to each other and the supporting surface) and
also to the relationship between the body and the
environment.11–13 ‘Postural ability’ refers to the
ability to stabilize the body segments relative to
each other and to the supporting surface; to get into
the most appropriate body configuration for the
performance of the particular task and environ-
ment. This means control of the centre of gravity
relative to the base of support during both static
and dynamic conditions.11,12
Our purpose was to evaluate the interrater reli-
ability, internal consistency and construct validity
of the Posture and Postural Ability Scale for adults
with cerebral palsy.
Methods
Participants were recruited during a project in the
south of Sweden in October 2009–October 2010 to
expand a National Health Care Program and Quality
Register for cerebral palsy,5,6,14 to include adults
with cerebral palsy. The subjects who agreed to join
the Cerebral Palsy Health Care Program were
examined by a physiotherapist and occupational
84 Clinical Rehabilitation 28(1)
therapist. At the examination the subjects were also
asked if they would agree to participate in the psy-
chometric evaluation of the Posture and Postural
Ability Scale. All subjects who agreed to partici-
pate were included, until six people at each level of
the Gross Motor Function Classification System
had accepted. One additional client with cerebral
palsy was recruited from the Rehabilitation Centre
of Excellence in Kópavogur, Iceland. Written con-
sent was collected from all participants or by proxy
where the participant was unable to give such con-
sent. Ethical approval for the study was granted by
the Medical Research Ethics Committee at Lund
University, number 2009/361.
Cerebral palsy was defined according to
Rosenbaum et al.1 Exclusion and inclusion criteria
Table 1. The Posture and Postural Ability Scale for assessment of postural ability in standing, sitting, supine and
prone, followed by assessment of quality of posture in frontal and sagittal view
Levels of postural ability
Level 1 Unplaceable in an aligned posture
Level 2 Placeable in an aligned posture but needs support
Level 3 Able to maintain position when placed but cannot move
Level 4 Able to initiate flexion/extension of trunk
Level 5 Able to transfer weight laterally and regain posture
Level 6 Able to move out of position
Level 7 Able to move into and out of position
Quality of posture, frontal view, (Yes = 1 point, No = 0 points)
Standing Sitting Supine Prone
Head midline Head midline Head midline Head to one side
Trunk symmetrical Trunk symmetrical Trunk symmetrical Trunk symmetrical
Pelvis neutral Pelvis neutral Pelvis neutral Pelvis neutral
Legs separated and
straight relative to pelvis
Legs separated and
straight relative to pelvis
Legs separated and
straight relative to pelvis
Legs separated and
straight relative to pelvis
Arms resting by side Arms resting by side Arms resting by side Arms resting (elevated,
mid-position)
Weight evenly distributed Weight evenly distributed Weight evenly distributed Weight evenly distributed
Quality of posture, sagittal view, (Yes = 1 point, No = 0 points)
Standing Sitting Supine Prone
Head midline Head midline Head midline Trunk in neutral position
Trunk in neutral position Trunk in neutral position Trunk in neutral position Pelvis neutral
Pelvis neutral Pelvis neutral Pelvis neutral Hips extended
Legs straight, hips/knees
extended
Hips mid-position (90°) Legs straight, hips/knees
extended
Knees extended
Feet mid-position/flat on
floor
Knees mid-position (90°) Feet resting in normal
position
Arms resting (elevated,
mid-position)
Weight evenly distributed Feet mid-position/flat on
floor
Weight evenly distributed Weight evenly distributed
Rodby-Bousquet et al. 85
were in accordance with the Surveillance of Cerebral
Palsy in Europe (SCPE).15 People with motor
impairment and specific neurological signs (ataxia,
dyskinesia and/or spasticity) caused by different
genetic syndromes before the age of 2 without pro-
gressive brain dysfunction were included. Gross
motor function was determined according to the
expanded and revised version of the Gross Motor
Function Classification System, which comprises
five levels I–V.16 The most severe functional limita-
tion is level V, with difficulties controlling head and
trunk posture in most positions, and severely limited
or no voluntary control of movement.
Posture and postural ability was recorded by
photos and videos of the participants. Photos of
habitual posture of each individual were taken
from a frontal and sagittal view of the whole body
in supine, prone, sitting and standing position.
Habitual refers to the posture customarily adopted
by the individual when instructed to sit, stand or
lay down in prone or supine as straight as possible
or the posture the body assumes when placed as
straight as possible in any of these positions and
allowed to settle. The positions were: supine lying
on a plinth with arms resting by side; prone lying
on a plinth with the head to one side and arms rest-
ing in an elevated position (flexion in elbows and
abduction, external rotation of shoulders); sitting
on a plinth with feet on the floor; standing on the
floor. Those who were unable to maintain position
independently were provided the manual support
needed to stay in position. People who required
total body support in standing, such as those clas-
sified gross motor function level V, were assessed
in a standing brace or on a tilt table. Videos
recorded the participants’ postural ability, from
the lateral view of the plinth, while instructed to
assume and get out of the four positions. If unable
to do this they were placed in each position.
Assessment of ability was then carried out sequen-
tially corresponding to the points on the Posture
and Postural Ability Scale (Table 1).
The Posture and Postural Ability Scale contains
a 7-point ordinal scale for the assessment of pos-
tural ability in standing, sitting, supine and prone
and six items for assessment of quality of posture in
the frontal plane and another six items in the
sagittal plane (Table 1). Postural symmetry and
alignment gives 1 point for each item while asym-
metry or deviation from midline gives 0 points.
The total score of 0–6 points is calculated sepa-
rately for each position in the frontal and sagittal
plane. Postural ability is rated according to the
ordinal scale ranging from unplaceable (level 1) to
able to move into and out of position (level 7). The
two lower levels of postural ability are in fact a rat-
ing of no ability, that is, they are unable to maintain
or change position by themselves. The difference
between those two levels is whether the person can
(level 2) or cannot (level 1) conform to the position
when placed by another person (i.e in anatomical
alignment when supported). When a person cannot
be placed in prone and standing due to hip disloca-
tion or severe contractures, especially of the hip
flexors, postural ability is scored as level 1 =
unplaceable and posture is scored 0.
Postures and postural abilities of the 30 subjects
were assessed from the photos and videos during
February 2012 by three experienced physiothera-
pists independently using the Posture and Postural
Ability Scale.
Statistical analysis
Interrater reliability for three independent raters
was calculated using weighted kappa scores which
takes the degree of disagreement into account.17 The
magnitude of weighted kappa indicates the agree-
ment beyond chance and was interpreted according
to the method of Fleiss,18 where ≤0.40 signifies
poor agreement, 0.40–0.75 fair to good agreement
and ≥0.75 signifies excellent agreement. The inter-
nal consistency of the assessment tool was evalu-
ated through ‘Cronbach’s alpha if item is deleted’
and ‘corrected item–total correlation’ based on
averaged values for the three raters. Cronbach’s
alpha if item is deleted corresponds to the value
achieved if a specific item is removed.19 The cor-
rected item–total correlation shows the correlation
between each item and the total score of the mea-
surement and any item with a value <0.2 should be
discarded.19 For analysis of reliability and consis-
tency all levels of the Gross Motor Function
Classification System were combined and 95%
86 Clinical Rehabilitation 28(1)
non-parametric bootstrap confidence intervals were
added based on 1000 re-samples.20,21 Construct
validity was evaluated for known groups based on
the five levels of gross motor function with median
and range. Jonckheere-Terpstra was used for analy-
sis of arithmetic average values given by the raters,
and P-values <0.05 were considered significant.
The alternative hypothesis of the test is that median
values of the scores decrease with decreasing gross
motor function. For all statistical computing, R soft-
ware environment was used.
Results
Postures and postural abilities of 30 adults (15
males, 15 females) with cerebral palsy born 1988–
1991 (age range 19–22) were recorded with photos
and videos during October 2009–October 2010.
The scores varied between participants at different
levels of the Gross Motor Function Classification
System, with decreasing values at lower levels of
gross motor function such as level IV and V. The
distribution of scores across the 30 participants
were described as median, mean, standard devia-
tion, min, max values, 25th and 75th percentile in
all four positions (Table 2). Since every person was
assessed by three raters, each missing assessment
(photo/position) generated three missing values
(Table 2).
The Posture and Postural Ability Scale showed
excellent interrater reliability for the three indepen-
dent raters with weighted kappa values of 0.85–0.99
(Table 3). There was a high internal consistency for
the Posture and Postural Ability Scale for all items
(Table 4). Cronbach’s alpha if item deleted was 0.97
for sitting posture sagittal and 0.96 for all other
items with a 95% confidence interval of 0.93–0.98
for all items. Corrected item–total correlation varied
between 0.60 and 0.91 with the lowest correlation
for sitting posture in the sagittal view.
The Posture and Postural Ability Scale showed
construct validity based on the ability of the assess-
ment tool to differ between known groups repre-
sented by the gross motor function levels I–V
(Table 5, Figure 1 online). Median values and range
in terms of min and max values are presented
together with P-values (P < 0.02) calculated with
Jonckheere-Terpstra for averaged values (Table 5).
Distribution of scores at each level of gross motor
function in all four positions is provided for all
three raters (Figure 1 online). The Posture and
Postural Ability Scale could not identify differ-
ences in postural ability between individuals at lev-
els I–II but was able to detect postural asymmetries
at all levels.
Table 2. Scores for the Posture and Postural Ability Scale across the 30 participants
Median Mean SD Min/max Percentile Valid/missing
Supine Postural ability 7 5.5 2.1 1 7 4 7 30 0
Posture frontal 1 2.4 2.4 0 6 0 4.3 30 0
Posture sagittal 2 2.7 2.3 0 6 1 5 30 0
Prone Postural ability 6 5.0 2.4 1 7 4 7 29 1
Posture frontal 2 2.4 2.0 0 6 0 4 27 3
Posture sagittal 3 3.2 2.3 0 6 1 5 28 2
Sitting Postural ability 7 5.0 2.4 1 7 2 7 30 0
Posture frontal 2 2.7 2.4 0 6 0 5 30 0
Posture sagittal 3 2.4 1.9 0 6 1 4 30 0
Standing Postural ability 2 4.0 2.7 1 7 1 7 29 1
Posture frontal 1 1.9 2.2 0 6 0 3.3 30 0
Posture sagittal 1 2.2 2.1 0 6 1 4 30 0
Median, mean, standard deviation (SD), min and max values, 25th and 75th percentile, valid and missing values in supine, prone,
sitting and standing.
Rodby-Bousquet et al. 87
Discussion
The Posture and Postural Ability Scale showed an
excellent interrater reliability, a high internal con-
sistency and good construct validity for adults with
cerebral palsy. This is, to our knowledge, the first
study evaluating an assessment tool for posture
and postural ability in lying, sitting and standing
position for adults.
A limitation of the study is that all three raters
participated in the development of the Posture and
Postural Ability Scale; they have long clinical expe-
rience and are specialized in posture management.
Further research is needed to examine interrater
reliability for trained practitioners not involved in
the modification of the assessment tool. A further
limitation is that the ratings were based on photos
and videos. This removes some variability that
arises in clinical practice. Photos provide reflection
of the posture at just one point in time. However, the
condition of people with severe disabilities may
alter during the day due to fatigue, pain, etc. It may
also change over time, making a measurement on
different occasions such as test–retest and intrarater
reliability more difficult to interpret. Therefore we
chose to evaluate agreement between different rat-
ers and used photos and videos to standardize the
occasion and minimize disagreement due to differ-
ent performances and circumstances.
Internal consistency represents the average of
the correlations among all items. The scale dem-
onstrated a high internal consistency for all items,
where Cronbach’s alpha if item deleted was
Table 3. Interrater reliability of the Posture and
Postural Ability Scale
Weighted
kappa
95% CI
Supine Postural ability 0.98 0.93 0.99
Posture frontal 0.94 0.87 0.98
Posture sagittal 0.88 0.79 0.92
Prone Postural ability 0.99 0.98 1.00
Posture frontal 0.89 0.79 0.96
Posture sagittal 0.85 0.71 0.93
Sitting Postural ability 0.99 0.96 1.00
Posture frontal 0.91 0.83 0.95
Posture sagittal 0.87 0.75 0.93
Standing Postural ability 0.99 0.94 1.00
Posture frontal 0.95 0.90 0.97
Posture sagittal 0.95 0.90 0.97
Weighted kappa with 95% confidence interval (95% CI) for
three independent raters.
Table 4. Internal consistency of the Posture and Postural Ability Scale
Cronbach’s α
if item deleted
95% CI Item–total
correlation
95% CI
Supine Postural ability 0.96 0.94 0.98 0.72 0.58 0.85
Posture frontal 0.96 0.93 0.98 0.91 0.84 0.96
Posture sagittal 0.96 0.94 0.98 0.87 0.74 0.95
Prone Postural ability 0.96 0.94 0.98 0.79 0.65 0.89
Posture frontal 0.96 0.93 0.98 0.88 0.76 0.95
Posture sagittal 0.96 0.94 0.98 0.87 0.75 0.96
Sitting Postural ability 0.96 0.94 0.98 0.83 0.73 0.92
Posture frontal 0.96 0.94 0.98 0.84 0.69 0.94
Posture sagittal 0.97 0.94 0.98 0.60 0.32 0.81
Standing Postural ability 0.96 0.93 0.98 0.91 0.84 0.96
Posture frontal 0.96 0.94 0.98 0.82 0.68 0.92
Posture sagittal 0.96 0.94 0.98 0.81 0.66 0.92
Cronbach’s alpha if item deleted and corrected item–total correlation showing the correlation between each item and the total
score when averaged scores for all raters are considered.
88 Clinical Rehabilitation 28(1)
0.96–0.97, which exceeds the 0.8 recommended
by Streiner and Norman.19 Corrected item–total
correlation showed a slightly lower value for sit-
ting posture in the sagittal view compared to the
other items. This is probably explained by the fact
that the height of the plinth was not optimal in
some photos, which affected the ratings of hips
and knees mid-position. An adjustable plinth is
not always available in clinical practice. If the
plinth is not adjustable or if using a chair, it would
be best to provide additional support for the feet
when needed.
Construct validity was evaluated through its abil-
ity to differ between known groups in terms of the
gross motor function levels in cerebral palsy. The
expanded and revised version of the Gross Motor
Classification System has been developed for chil-
dren with cerebral palsy with the oldest age band
12–18 years, but some studies have shown validity
and reliability for use of this classification in adults
with cerebral palsy as well.22–24 According to this
classification, individuals at levels I and II can walk
and stand unsupported. The highest level of the
Posture and Postural Ability Scale is to move into
and out of position and therefore the assessment
tool was not expected to differ between gross motor
function levels I and II in postural ability. The distri-
bution of individuals at maximum and minimum
score showed an anticipated ceiling effect for pos-
tural ability in all four positions for adults at level
I–II, while the floor effect was higher for posture,
indicating a better quantity in terms of ability than
quality of posture. This indicates a need for assess-
ing posture and postural ability separately and as
distinct from gross motor function, in order to detect
postural asymmetries and identify need for postural
support. A strength of the Posture and Postural
Ability Scale is that it identified postural asymme-
tries and deviations at all levels of gross motor func-
tion in this study of adults with cerebral palsy.
The Posture and Postural Ability Scale was sen-
sitive to detect small postural asymmetries and
deviations and is likely to detect postural asymme-
tries at an early stage. The assessment tool has no
grading and cannot differ between a mild, moderate
or severe deviation. The rationale is that any devia-
tion will increase by forces imposed by gravity so it
is clinically relevant to detect asymmetric posture
early in order to apply the appropriate intervention
to minimize progressive deformities.
The Posture and Postural Ability Scale does not
require any special equipment and is easy to use in
Table 5. Construct validity of the Posture and Postural Ability Scale
GMFCS
I II III IV V P-value
Supine Postural ability 7 (7–7) 7 (7–7) 7 (6–7) 4 (3–7) 1.5 (1–4) <0.001
Posture frontal 6 (2–6) 4 (2–5) 1 (0–6) 0 (0–1) 0 (0–1) <0.001
Posture sagittal 6 (4–6) 4 (1–6) 2.5 (0–6) 0.5 (0–3) 1 (0–3) <0.001
Prone Postural ability 7 (7–7) 7 (7–7) 6 (5–7) 4 (1–6) 1 (1–3) <0.001
Posture frontal 5 (2–6) 4 (2–5) 2 (0–5) 1 (0–3) 0 (0–3) <0.001
Posture sagittal 6 (2–6) 5 (2–6) 3 (0–6) 1 (0–4) 0 (0–4) <0.001
Sitting Postural ability 7 (7–7) 7 (7–7) 7 (2–7) 2 (2–6) 2 (1–2) <0.001
Posture frontal 6 (4–6) 4 (1–6) 3 (0–6) 0 (0–2) 0 (0–4) <0.001
Posture sagittal 3.5 (2–6) 2 (0–5) 3.5 (0–6) 0 (0–4) 1 (0–5) 0.019
Standing Postural ability 7 (7–7) 7 (7–7) 4 (1–7) 1.5 (1–2) 1 (1–2) <0.001
Posture frontal 6 (3–6) 3 (0–5) 0 (0–3) 0 (0–2) 0 (0–2) <0.001
Posture sagittal 5 (4–6) 2 (0–6) 1 (0–4) 0 (0–3) 0 (0–3) <0.001
Median values and range (min–max values) for levels I–V of the Gross Motor Function Classification System (GMFCS) and P-values
calculated with Jonckheere-Terpstra of averaged values for the three raters.
Rodby-Bousquet et al. 89
a clinical setting. It provides important information
of the need for postural support and where it needs
to be applied. Although the instrument has been
used in clinical practice for different client groups,
further research to evaluate its psychometric prop-
erties for people with diagnoses other than cerebral
palsy is desirable. All assessment tools for posture
and postural ability currently used in clinical prac-
tice require additional training of the professional
intending to use them.
In conclusion, the Posture and Postural Ability
Scale shows an excellent interrater reliability for
experienced raters, a high internal consistency and
good construct validity. It can detect postural asym-
metries at all levels of gross motor function in adults
with cerebral palsy. The results show an anticipated
ceiling effect for postural ability at gross motor
function level I–II. Further research is needed to
examine interrater reliability for trained profession-
als not involved with modification of the assess-
ment tool, as well as its application to other client
groups.
Clinical messages
•This evaluation is based on photos and
videos of posture and postural ability in
adults with cerebral palsy.
•The Posture and Postural Ability Scale
shows excellent interrater reliability, high
internal consistency and construct validity.
•It can detect postural asymmetries at all
levels of gross motor function in adults
with cerebral palsy.
Authors’ contributions
ERB designed the study, developed the instrument, col-
lected the data, rated the subjects, analysed the results and
wrote the manuscript. AA and GJ developed the instru-
ment, rated the subjects and revised the manuscript. TC
made the statistical calculations, analysed the data, pro-
vided the dot plots and revised the manuscript. ACJ
revised the manuscript. GH designed the study and
actively improved and revised the manuscript. All authors
approved the final draft.
Acknowledgements
The authors would like to thank Pauline Pope, London, for
her endless work and support in developing and modifying
the PPAS and for proof-reading the manuscript.
Conflict of interest
The authors declare that they have no conflicts of
interests.
Funding
This study was supported by the Faculty of Medicine,
Lund University, Stiftelsen för bistånd åt rörelsehindrade
i Skåne, the Linnea and Josef Carlsson Foundation and
the Norrbacka Eugenia Foundation.
References
1. Rosenbaum P, Paneth N, Leviton A, et al. A report: the
definition and classification of cerebral palsy April 2006.
Dev Med Child Neurol Suppl 2007; 49: 8–14.
2. Brown K. Positional deformity in children with cerebral
palsy. Physiother Theory Pract 1985; 1: 37–41.
3. Fulford FE and Brown JK. Position as a cause of defor-
mity in children with cerebral palsy. Dev Med Child Neurol
1976; 18: 305–314.
4. Porter D, Michael S and Kirkwood C. Is there a relationship
between preferred posture and positioning in early life and
the direction of subsequent asymmetrical postural deformity
in non ambulant people with cerebral palsy? Child Care
Health Dev 2008; 34: 635–641.
5. Hägglund G, Andersson S, Duppe H, Lauge-Pedersen H,
Nordmark E and Westbom L. Prevention of severe contrac-
tures might replace multilevel surgery in cerebral palsy:
results of a population-based health care programme and
new techniques to reduce spasticity. J Pediatr Orthop B
2005; 14: 269–273.
6. Hägglund G, Andersson S, Duppe H, Lauge-Pedersen H,
Nordmark E and Westbom L. Prevention of dislocation of
the hip in children with cerebral palsy. The first ten years
of a population-based prevention programme. J Bone Joint
Surg Br 2005; 87: 95–101.
7. Pountney T, Mandy A, Green E and Gard P. Management
of hip dislocation with postural management. Child Care
Health Dev 2002; 28: 179–185.
8. Persson-Bunke M, Hägglund G and Lauge-Pedersen H.
Windswept hip deformity in children with cerebral palsy. J
Pediatr Orthop B 2006; 15: 335–338.
9. Hallett R, Hare N and Milner A. Description and evaluation
of an assessment form. Physiotherapy 1987; 73: 220–225.
10. Pountney TE, Cheek L, Green E, Mulcahy C and Nelham
R. Content and criterion validation of the Chailey levels of
ability. Physiotherapy 1999; 85: 410–416.
90 Clinical Rehabilitation 28(1)
11. Pope PM. Severe and complex neurological disability: man-
agement of the physical condition. Edinburgh: Butterworth-
Heinemann/Elsevier, 2007.
12. Bouisset S and Do MC. Posture, dynamic stability,
and voluntary movement. Neurophysiol Clin 2008; 38:
345–362.
13. Shumway-Cook A and Woollacott MH. Motor control:
translating research into clinical practice. Philadelphia,
PA: Lippincott Williams & Wilkins, 2011.
14. Westbom L, Hagglund G and Nordmark E. Cerebral palsy
in a total population of 4–11 year olds in southern Sweden.
Prevalence and distribution according to different CP clas-
sification systems. BMC Pediatr 2007; 7: 41.
15. Surveillance of Cerebral Palsy in Europe (SCPE). Sur-
veillance of cerebral palsy in Europe: a collaboration of
cerebral palsy surveys and registers. Dev Med Child Neu-
rol 2000; 42: 816–824.
16. Palisano RJ, Rosenbaum P, Bartlett D and Livingston MH.
Content validity of the expanded and revised Gross Motor
Function Classification System. Dev Med Child Neurol
2008; 50: 744–750.
17. Conger AJ. Integration and generalization of kappas for
multiple raters. Psychol Bull 1980; 88: 322–328.
18. Fleiss JL (ed.). Statistical methods for rates and propor-
tions, second edition. New York: John Wiley & Sons
Inc., 1981.
19. Streiner DL and Norman GR. Health measurement scales:
a practical guide to their development and use. Oxford:
Oxford University Press, 2008.
20. DiCiccio TJ and Efron B. Bootstrap confidence intervals.
Statist Sci 1996; 11: 189–212.
21. Davison AC and Hinkley DV (eds). Bootstrap methods and
their application. Cambridge: Cambridge University Press,
1997.
22. Jahnsen R, Aamodt G and Rosenbaum P. Gross Motor
Function Classification System used in adults with cerebral
palsy: agreement of self-reported versus professional rating.
Dev Med Child Neurol 2006; 48: 734–738.
23. McCormick A, Brien M, Plourde J, Wood E, Rosenbaum
P and McLean J. Stability of the Gross Motor Function
Classification System in adults with cerebral palsy. Dev
Med Child Neurol 2007; 49: 265–269.
24. Sandstrom K, Alinder J and Oberg B. Descriptions of func-
tioning and health and relations to a gross motor classifica-
tion in adults with cerebral palsy. Disabil Rehabil 2004; 26:
1023–1031.
