1. The study evaluated the repeatability of 3D kinematic measurements of gait and simple upper limb tasks in children with hemiplegic cerebral palsy. 2. 3D gait analysis showed high repeatability in sagittal plane measures and moderate repeatability in frontal and transverse planes. 3. 3D analysis of shoulder and elbow flexion/extension during hand-to-head and hand-to-mouth tasks was highly repeatable, while rotational measures showed moderate repeatability.

1. Gait & Posture 22 (2005) 1–9
www.elsevier.com/locate/gaitpost
Reliability of upper and lower limb three-dimensional kinematics
in children with hemiplegia
Anna H. Mackeya, Sharon E. Waltb, Glenis A. Lobbc, N. Susan Stottd,*
a
University of Auckland Gait Laboratory, Tamaki Campus, Merton Road, Auckland, New Zealand
b
Department of Sport and Exercise Science, University of Auckland Gait Laboratory, Tamaki Campus, Merton Road, Auckland, New Zealand
c
Starship Children’s Hospital, Park Road, Grafton, Auckland, New Zealand
d
Department of Surgery, Faculty of Medicine and Health Sciences, University of Auckland, Room 3432,
Park Road, Auckland, New Zealand
Received 15 December 2003; accepted 1 June 2004
Abstract
The repeatability of both 3D kinematic measurements of arm movement during simple upper limb tasks and lower limb movement during
gait analysis was evaluated in 10 children with hemiplegic cerebral palsy. All tasks were completed on two separate occasions, 1 week apart.
The 3D lower limb gait analysis showed high levels of repeatability in the sagittal plane measures, with mean coefficient of multiple
correlations (CMCs) greater than 0.92 between sessions. Transverse and frontal plane measures had mean CMCs greater than 0.7 between
sessions. A 3D analysis of shoulder and elbow flexion/extension during the two functional tasks (hand to head and hand to mouth) was highly
repeatable between sessions (mean CMCs, 0.87 to 0.95). Rotational measures at the shoulder and the elbow during the same tasks
demonstrated moderate levels of inter-sessional repeatability (mean CMCs shoulder 0.49 to 0.63; elbow 0.63 to 0.74). Overall, the lower limb
3D kinematic analysis had similar levels of repeatability in both the hemiplegic limb and the limb with normal tone. The 3D kinematic
analysis of movement of the hemiplegic upper limb during simple upper limb tasks also had moderate to good repeatability, suggesting it may
be able to be used as an outcome measure in the hemiplegic upper limb.
# 2004 Elsevier B.V. All rights reserved.
Keywords: Kinematics; Hemiplegia; Paediatric; Three-dimensional analysis; Upper limb
1. Introduction everyday functional tasks that involve reaching, grasping
and manipulating objects [2–4].
The term cerebral palsy encompasses a broad group of Therapy and orthopaedic management are considered the
disorders of movement and posture resulting from a static mainstay of interventions for children with cerebral palsy.
insult to the immature brain within the first 2 years of life [1]. Unfortunately one of the major problems in the management
Children with hemiplegic cerebral palsy have varying com- of children with cerebral palsy is the paucity of reliable,
binations of weakness, sensory loss, and spasticity, invol- valid and objective measures to monitor treatment out-
ving the arm and leg on one side of the body [2]. In this comes, particularly for the upper limb. Frequently used
group of children, treatment and intervention is often pri- clinical measures, such as passive range of motion [5,6],
marily focused on the lower limb, to develop and improve measurement of muscle tone [7] and even classification of
the walking ability of the child, with intervention for the types of cerebral palsy have all shown poor reproducibility
upper limb dysfunction being secondary. However, the between observers and sessions, even when tested under
upper limb dysfunction can be equally disabling, affecting standardised conditions [8]. Two recently developed upper
limb therapy measures, Quality Upper Extremity Skills Test
* Corresponding author. Tel.: +64 9 3737599x82861; fax: +64 9 3677159. (QUEST) and Melbourne Assessment of Unilateral Upper
E-mail address: s.stott@auckland.ac.nz (N.S. Stott). Limb function have demonstrated high levels of reliability in
0966-6362/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.gaitpost.2004.06.002

2. 2 A.H. Mackey et al. / Gait & Posture 22 (2005) 1–9
the cerebral palsy population [9,10]. However, both of these 2.2. Upper limb tasks
measures rely on the therapist making a subjective visual
assessment of the child’s range and quality of upper limb The upper limb tasks chosen were required to be both
movement. simple and functional, to represent everyday upper limb
In the lower limb, visual assessments of videoed gait are movement that would have been practised by the child many
not as accurate as 3D gait analysis in detecting and defining times. The two upper limb tasks of taking the ‘hand to head’
gait deviations in children with spastic diplegia [11–13]. and ‘hand to mouth’ met the above criteria and have both
Thus, 3D kinematic gait analysis is considered the gold been described in previous studies of Rau et al. [15] and Rab
standard in movement analysis, providing clinicians with a et al. [18]. In the first task of ‘hand to head’ the child starts
reliable and objective measurement tool that can be used to with the hand on the ipsilateral knee, and is asked to reach
quantify changes in gait in children with cerebral palsy [14]. and touch the top of their head and return the arm to the
Currently this technology is not routinely applied to upper ipsilateral knee. The second task of ‘hand to mouth’ had the
limb movement analysis. Potential problems encountered in same starting position, with the child asked to take their hand
obtaining upper limb kinematics include the large degrees of to their mouth and then return the hand to their knee.
freedom at the shoulder; the complexities of defining the
shoulder joint centre using external markers and the lack of a 2.3. Upper limb model
cyclical movement task akin to gait in the lower limb
[15,16]. However, several 3D upper limb kinematic models Twenty-one retro-reflective markers were placed on the
have recently been described in the literature [17,18]. Pre- child’s trunk and upper limbs to create a 3D mathematical
liminary assessments of 3D upper limb kinematic function model for the examination of upper limb movements (Fig. 1)
have been made with two clinical populations, including the [21]. We have previously published details of a comparison
assessment of movement limitations following burn scar of this upper limb model with goniometric measures with a
contracture [19] and the assessment of a child with brachial strong correlation (r = 0.93) found between the mean elbow
plexus palsy [15]. angle measured with the goniometer and the same angle
However, the use and reliability of 3D upper limb kine- measured by the 3D upper limb model [21]. A similar
matics in the hemiplegia, cerebral palsy population has not comparison of frontal and sagittal plane measures at the
been previously studied. The purpose of this study was shoulder has also shown a good correlation (r = 0.74)
therefore to assess the repeatability of 3D joint kinematics between the goniometric measures and the 3D measures
for the upper limb during gait and during two functional (unpublished laboratory data). The 3D upper limb model
tasks of taking hand to mouth and hand to head compared to consisted of seven segments, including right/left trunk; right/
repeatability in the lower limb during gait for hemiplegic left upper arm; right/left forearm and pelvis (Table 1). Each
cerebral palsy. segment is assumed to be a rigid body defined by three
markers, generally representing proximal and distal ends of
the segment plus a third non-collinear marker to allow for
2. Methods rotational orientation [22]. A joint coordinate system was
implemented to describe relative angles between segments
2.1. Subjects [23]. The coordinate system defining each segment is shown
in Fig. 1, with joint flexion-extension measured about the
Ethical approval for the study was granted from the medial-lateral axis (y-axis); joint rotation about the long-
Auckland Ethics Committee, New Zealand. Informed con- itudinal axis (x-axis) and the final perpendicular axis (z-axis)
sent was obtained from all participants and their guardians. determining abduction–adduction at the joint [22].
The inclusion criteria included ambulatory children with a Upper limb joint centres, at the shoulder, elbow, wrist and
diagnosis of spastic hemiplegia, cerebral palsy aged between neck were defined as virtual markers calculated from offsets
5 and 16 years. Exclusion criteria included any other form of of two external marker positions (Table 1). In accordance with
cerebral palsy or progressive spasticity; any casting or other upper limb models described in the literature [17,18],
botulinum toxin A injections within the last 12 months; assumptions were made for the assessment of shoulder move-
previous upper limb surgery; elbow flexion contracture ment, with both scapulo-thoracic and acromion-calvicular
greater than 208; lack of informed consent and any disabil- motions being discounted. The shoulder joint was therefore
ities that would make it difficult for the child to understand assumed to have only three degrees of freedom. Previous
or cooperate fully with the study. Ten children with hemi- upper limb models have calculated the shoulder joint centre
plegia (seven left and three right) were recruited from as an estimated offset from a single external marker on the
orthopaedic and neurological clinic lists and local schools acromion [17,18]. For this upper limb model, the shoulder
with physical therapy units (six male subjects, mean age 9 Æ joint centre was calculated as the mid point between two
4 years and four female subjects, mean age 12 Æ 3 years). external markers placed on the anterior and posterior aspect of
All subjects were independent ambulators with a Gross the gleno-humeral joint (A1 and A2) (Fig. 1). Marker place-
Motor Functional Classification Scale of level I or II [20]. ment was determined by palpation of bony landmarks, on the

3. A.H. Mackey et al. / Gait & Posture 22 (2005) 1–9 3
Fig. 1. Schematic diagrams (frontal and lateral view) of the upper limb model used for three-dimensional kinematic analysis. (*): Retro-reflective external
markers placed on the skin. ( ): Virtual markers created at the neck; shoulder; elbow and wrist. A1: acromion back; A2: acromion front; C7: cervical spine 7;
SN: sternal notch; UW: upper arm wand; LW: lower arm wand; EL: elbow lateral; EM: elbow medial; WL: wrist lateral; WM: wrist medial; S: sacral; ASIS:
right and left anterior superior iliac spine. The insert of the dorsum scapulae details bony landmarks used for palpation to guide the placement of shoulder
markers (A1 and A2) [37].
inferior aspect of the acromion, anteriorly and the posterior The elbow joint centre was defined as the mid point
aspect of acromion, as it joins the spine of scapula, posteriorly between markers on the outside edge of the medial and
(Fig. 1). The aim of using two bony landmarks to define lateral condyles of the humerus and the wrist joint centre
the shoulder joint centre was to standardise further the joint set as the mid point between medial and lateral wrist
centre position in children of different ages, rather than joint markers [17,18]. A rotational wand was placed on
estimating a set offset from one external marker. both the upper and lower arm segments of each arm. The
upper arm wand was placed in the middle of the upper arm
Table 1 segment, in line with the shoulder joint centre proximally
Segment definitions and joint centre (JC) offsets for the upper limb model and lateral epicondyle of the elbow distally. The forearm
Segment Markers wand was placed on the distal third of the pronated forearm,
Right upper arm Right Shoulder JC Right UW Right elbow JC in line with the lateral epicondyle of the elbow, proximally
Right forearm Right elbow JC Right LW Right wrist JC and wrist joint centre, distally. The distal placement of the
Right trunk Neck JC Right shoulder JC C7 forearm wand was used to represent forearm rotation.
Left upper arm Left shoulder JC Left UW Left elbow JC
Marker location for this upper limb model differed
Left forearm Left elbow JC Left LW Left wrist JC
Left trunk Neck JC Left shoulder JC C7 slightly from those previously described by Schmidt et al.
Pelvis Sacral Right ASIS Left ASIS [17]; Rau et al. [15] and Rab et al. [18]. Rab et al. included
Defining joint centres (JC) Markers (Fig. 1)
external markers on the head and did not use rotational wand
markers [18]. An external head marker was not included in
Shoulder JC A1 A2 Midpoint
Neck JC C7 SN Midpoint
this upper limb model, meaning that specific information on
Elbow JC EL EM Midpoint individual head motion was not obtained from this model.
Wrist JC WL WM Midpoint However, markers placed on the trunk (C7 and sternum) can
ASIS: anterior superior iliac spine; UW: upper arm wand; LW: lower arm provide information on forward or posterior trunk lean,
wand. which may occur during upper limb tasks. Rau et al. [15]

4. 4 A.H. Mackey et al. / Gait & Posture 22 (2005) 1–9
and earlier work from colleagues Schmidt et al. [17] using the method described by Kadaba et al. [24] and
described an upper limb model with marker triads on Steinwender et al. [14]. The adjusted R-squared (R2 ) statistic
a
hand, forearm and upper arm segments, with additional or coefficient of determination was used to assess the
markers placed at the elbow and wrist joint to determine similarity between two representative waveforms for
joint centres. Marker triads were not utilised for our model, within-session analysis, and between mean waveforms for
as preliminary testing in our laboratory with paediatric between-session analysis. Similarity in the waveforms
subjects found that they prevented full comfortable elbow results in the adjusted R-squared value tending towards 1;
movement. dissimilar waveforms result in the adjusted R-square tending
towards 0. The positive square root of the adjusted R-squared
2.4. Testing procedures value, being the r value, or adjusted coefficient of multiple
correlation (CMC), is reported in the text. Comparisons were
Testing was performed in the University of Auckland made in all three planes, frontal, sagittal and transverse and
Gait Laboratory on two occasions, 1 week apart. Children at seven anatomical levels, ankle, knee, hip, pelvis, trunk,
were seen on the same day and time, 1 week apart, to shoulder and elbow.
minimise environmental changes that might affect range For within-session analysis, we compared the third and
of movement or dynamic muscle tone. The same testing fourth walking trials collected during the gait analysis and
protocol was used in both sessions. The 21 markers the final two repetitions of the upper limb tasks. For the
described above in the upper limb model were first applied between-session analysis, the mean waveform of the four
to the subject’s upper limbs. Each child then completed two walking trials from week 1 was compared to the mean
upper limb functional tasks in sitting (hand to mouth and waveform of the four walking trials at week 2. Correspond-
hand to head). To perform these tasks the children were ingly for the upper limb tasks between session analyses, the
seated on a stool in the centre of the video capture volume mean of the three repetitions from week 1 was compared to
area. A small box was placed in front of the children to rest the mean of the three task repetitions in week 2. The mean
their feet on and ensure they felt secure sitting on the stool. values were utilised for between-session analyses due to the
In an attempt to standardise the upper limb movement, the small variance found within one session.
therapist stood in front of the child demonstrating the task to For the 3D gait analysis, the mean absolute difference
be performed. Each task was carried out three times in a both within and between sessions was determined for step
single session. A 3D gait analysis was then undertaken, length, stride length, cadence and forward velocity for each
using a Cleveland clinic marker set (OrthoTrak 4.2 Refer- subject. The mean absolute difference (degrees) between the
ence Manual, MotionAnalysis Corporation, Santa Rosa, CA, gait kinematic graphs at week 1 and at week 2 was also
USA) to examine lower limb kinematics during gait. The 21 calculated for each subject. This additional information
markers applied to the upper limbs were left in place to highlights the testing variation that can be expected from
obtain a 3D analysis of the arm swing during gait. The child week to week, and is useful for the interpretation of gait
was asked to walk at a self-selected speed along a 10-m analysis results. This information was not determined for the
walkway. At least four walking trials were collected for two upper limb tasks as the starting position for the upper
each participant. All data were collected with an 8-camera limb tasks had not been fully constrained, resulting in
MotionAnalysis video system at 60 Hz (MotionAnalysis variation in the self-selected starting position between ses-
Corporation). sions in some subjects, particularly at the shoulder joint. The
repeatability of the pattern of movement of these tasks was
2.5. Data analysis the main interest of this study, which was best represented by
the previously described CMC statistic.
Processing of the 3D gait analysis data was completed with
EvA software version 6.15 and OrthoTrak software version
5.1 (MotionAnalysis Corporation). OrthoTrak gait analysis 3. Results
software produces graphs normalised to the gait cycle. The
additional markers used to evaluate the 3D position of the arm 3.1. Temporal-spatial parameters
during gait required separate analysis using KinTrak software
version 6 (MotionAnalysis Corporation). Kinematic infor- Kinematic gait patterns may be affected by walking
mation for the two upper limb tasks in sitting was collected velocity [25]. We therefore assessed the inter-sessional mean
using EvA software version 6.15 and analyzed using KinTrak absolute differences in the temporal-spatial parameters to
software version 6 (MotionAnalysis Corporation). define the level of repeatability between walking trials. The
highest variability was found for walking velocity, with a
2.6. Statistical analysis mean absolute difference of 6.8 cm/s within session and
10.3 cm/s between sessions. The lowest variability was
Statistical analysis of the repeatability of the pattern of found for step length, both in the affected and unaffected
upper and lower limb movement waveforms was carried out limb (Table 2).

5. A.H. Mackey et al. / Gait & Posture 22 (2005) 1–9 5
Table 2
Mean absolute difference in temporal-spatial parameters within and between sessions
Temporal/spatial parameters Within session Between sessions
Mean absolute difference (S.D.) Range Mean absolute difference (S.D.) Range
Step length (cm)
Affected 2.7 (2.3) 1.0–7.3 2.3 (1.1) 1.0–4.4
Unaffected 2.5 (2.2) 0.0–7.4 2.0 (1.6) 0.2–6.0
Stride length (cm) 4.9 (4.1) 0.0–12.4 3.8 (2.6) 1.0–9.0
Cadence (steps/min) 4.2 (2.9) 0.0–9.5 8.9 (11.3) 0.1–35.0
Velocity (cm/s) 6.8 (6.3) 0.0–20.0 10.3 (11.3) 0.5–34.0
Table 3
Mean adjusted coefficient of multiple correlation (CMC) for lower limb measures during gait analysis
Kinematics Within session CMC (S.D.) Between session CMC (S.D.)
Normal limb Hemiplegic limb Normal limb Hemiplegic limb
Sagittal plane
Ankle dorsi/plantar flexion 0.96 (0.0) 0.98 (0.0) 0.98 (0.0) 0.96 (0.0)
Knee flexion/extension 0.99 (0.0) 0.98 (0.0) 0.99 (0.0) 0.99 (0.0)
Hip flexion/extension 0.98 (0.0) 0.99 (0.0) 0.99 (0.0) 0.99 (0.0)
Pelvic tilt 0.88 (0.2) 0.82 (0.3) 0.92 (0.2) 0.93 (0.1)
Trunk tilt 0.84 (0.2) 0.82 (0.2) 0.92 (0.1) 0.94 (0.1)
Frontal plane
Foot progression 0.87 (0.2) 0.89 (0.2) 0.76 (0.2) 0.81 (0.3)
Knee varus/valgus 0.86 (0.2) 0.89 (0.2) 0.70 (0.2) 0.85 (0.1)
Hip abduction/adduction 0.93 (0.1) 0.92 (0.2) 0.91 (0.1) 0.95 (0.1)
Pelvic obliquity 0.95 (0.1) 0.88 (0.2) 0.92 (0.2) 0.91 (0.2)
Trunk obliquity 0.86 (0.2) 0.91 (0.1) 0.93 (0.1) 0.89 (0.1)
Transverse plane
Foot rotation 0.89 (0.1) 0.92 (0.1) 0.91 (0.1) 0.92 (0.1)
Knee rotation 0.91 (0.1) 0.89 (0.2) 0.80 (0.1) 0.82 (0.2)
Hip rotation 0.89 (0.1) 0.88 (0.2) 0.78 (0.2) 0.86 (0.1)
Pelvis rotation 0.91 (0.1) 0.90 (0.1) 0.95 (0.1) 0.87 (0.1)
Trunk rotation 0.88 (0.2) 0.81 (0.3) 0.97 (0.0) 0.83 (0.3)
CMC: coefficient of multiple correlation.
3.2. Lower limb kinematics normal limb and the hemiplegic limb (Fig. 2). The frontal
and transverse plane measures had slightly lower levels of
High levels of repeatability were observed across all three repeatability; however the mean CMC was still 0.7 or greater
planes in the lower limb (Table 3). Sagittal plane kinematics for these measures. The lowest CMCs between sessions
at the hip, knee and ankle were the most reliable, with CMC were found for foot progression and knee varus/valgus
values of 0.96–0.99 within and between sessions for both the position in the frontal plane and correspondingly for hip
Fig. 2. Representative frontal, sagittal and transverse plane kinematic graphs of hip range of motion during gait in a child with hemiplegia, derived from data
collected at time 0 (session one) and 1 week later (session two). The x-axis represents 0–100% of the gait cycle, beginning with Right Heel Strike (RHS).
Laboratory normative data is shown as a broad grey band, while the solid line indicates data from session one and the dotted line indicates data from session two,
1 week later. The waveforms are very similar for the two testing sessions (LTO, Left Toe Off; LHS, Left Heel Strike; RTO, Right Toe Off).

6. 6 A.H. Mackey et al. / Gait & Posture 22 (2005) 1–9
Table 4 Table 4. 3D kinematics in the frontal and sagittal plane were
Mean absolute differences in lower limb kinematics between sessions most repeatable with mean absolute differences of four
Kinematics Mean absolute differences in degrees (S.D.) degrees or less from week 1 to week 2.
Normal limb Hemiplegic limb
Sagittal plane 3.3. Upper limb position during gait
Ankle dorsi/plantar flexion 2 (1) 1 (0)
Knee flexion/extension 4 (2) 2 (1) A 3D analysis of the upper limb position in gait found
Hip flexion/extension 4 (1) 3 (1)
moderate repeatability both within and between sessions
Pelvic tilt 2 (1) 2 (1)
Trunk tilt 2 (1) 3 (1) (Table 5). Repeatability was highest at the shoulder in the
sagittal and frontal planes with CMC values of 0.52 to 0.87.
Frontal plane
Foot progression 1 (0) 1 (0)
Transverse plane elbow supination and pronation had the
Knee varus/valgus 4 (2) 2 (1) lowest repeatability within and between sessions, with CMC
Hip abduction/adduction 3 (1) 3 (1) values of 0.42 to 0.61. The repeatability of the elbow flexion
Pelvic obliquity 2 (1) 2 (1) position during gait was similar for the affected (CMC, 0.58)
Trunk obliquity 3 (1) 3 (1) and unaffected upper limb (CMC, 0.60) between sessions.
Transverse plane
Foot rotation 8 (1) 5 (1) 3.4. Upper limb kinematics—hand to mouth and hand to
Knee rotation 10 (3) 7 (2)
head tasks
Hip rotation 7 (2) 5 (2)
Pelvis rotation 3 (1) 3 (2)
Trunk rotation 3 (1) 4 (2) Simple hand to head and hand to mouth tasks were used
to assess the repeatability of a simple motor task in the upper
Table 5
Mean adjusted coefficient of multiple correlation for upper limb position during gait
Kinematics Within Session CMC (S.D.) Between Session CMC (S.D.)
Unaffected limb Affected limb Unaffected limb Affected limb
Sagittal plane
Elbow flexion 0.58 (0.3) 0.60 (0.2) 0.60 (0.3) 0.58 (0.3)
Shoulder flexion 0.80 (0.2) 0.67 (0.3) 0.87 (0.1) 0.68 (0.3)
Frontal plane
Shoulder abduction/adduction 0.52 (0.3) 0.65 (0.3) 0.66 (0.3) 0.54 (0.3)
Transverse plane
Elbow supination/pronation 0.48 (0.2) 0.61 (0.3) 0.49 (0.3) 0.42 (0.3)
Shoulder rotation 0.58 (03) 0.67 (0.3) 0.57 (0.3) 0.57 (0.2)
CMC: coefficient of multiple correlation.
and knee rotation in the transverse plane. Similar values of limb (Fig. 3). Table 6 shows the mean and standard deviation
repeatability were found for both the normal and hemiplegic of the CMC values comparing waveforms within and
limb, and in the within-day and between-day variability. The between sessions. Moderate to high levels of repeatability
mean absolute differences, in degrees, between gait kine- were found for the upper limb kinematics of these two
matic graphs from session one to session two are shown in functional tasks. Sagittal plane elbow and shoulder kine-
Elbow Flexion / Extension Elbow Supination / Pronation
60
Joint Angle (degrees)
160
Joint Angle (degrees)
Sup / Pron
120
40
Ext / Flex
80
20
40
0 0
0 100 0 100
Fig. 3. Representative kinematic graphs of elbow flexion/extension and forearm supination/pronation for one subject carrying out hand to mouth task using the
hemiplegic arm. The x-axis represents time, normalised to 100% from the start to the end of the movement. Three repetitions of elbow movement during the
same testing session are shown with the solid line representing the first trial and the two dotted lines indicating the second and third trials. Although the pattern of
movement is similar in the three trials, there are changes in the starting point between the three trials.

7. A.H. Mackey et al. / Gait & Posture 22 (2005) 1–9 7
Table 6
Mean adjusted coefficient of multiple correlation (CMC) for affected upper limb movements during hand to head and hand to mouth task
Kinematics Task 1: Hand to head Task 2: Hand to mouth
Within session CMC (S.D.) Between session Within session CMC (S.D.) Between session
CMC (S.D.) CMC (S.D.)
Session 1 Session 2 Session 1 Session 2
Sagittal plane
Elbow flexion/extension 0.96 (0.0) 0.94 (0.0) 0.92 (0.1) 0.93 (0.1) 0.96 (0.1) 0.95 (0.0)
Shoulder flexion/extension 0.95 (0.0) 0.90 (0.1) 0.87 (0.2) 0.90 (0.1) 0.94 (0.1) 0.91 (0.0)
Frontal plane
Shoulder abduction/adduction 0.71 (0.2) 0.77 (0.1) 0.76 (0.2) 0.74 (0.2) 0.74 (0.1) 0.62 (0.3)
Transverse plane
Elbow supination/pronation 0.90 (0.1) 0.88 (0.1) 0.63 (0.3) 0.76 (0.2) 0.90 (0.1) 0.74 (0.3)
Shoulder rotation 0.72 (0.2) 0.63 (0.3) 0.63 (0.3) 0.67 (0.3) 0.72 (0.2) 0.49 (0.3)
CMC: coefficient of multiple correlation.
matics had the highest levels of repeatability for both tasks and extension. Three-dimensional upper limb kinematic ana-
within and between sessions, with CMC values ranging from lysis has been used by several pilot studies as an assessment
0.87 to 0.96. However, some variation was seen in the tool, particularly for burns patients and a patient with brachial
starting position of the arm when the task was repeated plexus palsy [15,17–19]. However, this is the first reported
both within and between sessions (see Fig. 3). Lower levels study to assess the reliability of 3D upper limb kinematics in a
of repeatability were found for frontal and transverse plane paediatric population with hemiplegia, cerebral palsy.
kinematics, with shoulder rotation having the lowest values We found a high degree of reproducibility in the pattern
of repeatability in both tasks with CMC values of 0.49–0.63. of sagittal plane movement during hand to head and hand to
mouth tasks across the two testing sessions, suggesting that
3D kinematic analysis can be used reliably to assess sagittal
4. Discussion plane motion at the elbow and shoulder in an individual
carrying out such a task. However, there was some varia-
In this study we were interested in the reliability of 3D bility in the starting position of the arm used to achieve the
kinematic analysis in the upper limb compared to 3D task, both between subjects and between sessions. This is
kinematic analysis of lower limbs in children with hemi- similar to the data found by Rab et al. which showed
plegia, cerebral palsy, to understand better the usefulness of between subject standard deviations of up to 25 degrees
3D kinematic analysis as an outcome measure in the hemi- for elbow and shoulder motion in normal children during a
plegic upper limb. As expected, the lower limb 3D kine- hand to head task [18]. Greater standardisation of both the
matics had excellent repeatability, both within and between starting and the finishing points for the task would be
sessions. Similar to previous studies [14,24], the repeatabil- required to improve the repeatability of the starting and
ity was highest in the sagittal plane and lower in the frontal ending points of this type of movement.
plane (foot and knee) and transverse plane (hip and knee). The repeatability of upper limb motion in the frontal and
Small changes in marker placement at the knee and ankle transverse planes was lower than that in the sagittal plane.
can result in significant changes in transverse plane kine- Even within one session, the repeatability was less suggest-
matics [24], and this may have accounted for the lower ing that this was not related to variations in marker place-
repeatability in the transverse plane seen in this study. We ment or camera position but rather to differences in patterns
found that 3D kinematic analysis of arm movement during of movements between each trial. In the lower limb, the
simple functional tasks also had moderate to high levels of motor strategies that can be used to complete a task are
repeatability within and between measurement sessions, limited. In contrast, a large number of different motor
particularly in the sagittal plane. Surprisingly, arm swing strategies can be used to achieve the same motor task in
during gait had only moderate levels of repeatability in both the upper limb. Bernstein has described the anatomical
the normal limb and the hemiplegic limb. redundancy present in the upper limb as the ‘degrees of
Two-dimensional (2D) forms of movement analysis have freedom’ or ‘motor equivalence’ problem [31]. The large
been widely used to investigate the motor control strategies number of degrees of freedom in the upper limb exceeds that
involved in reaching and grasping in both normal paediatric required for performance of a task and thus the position of
populations [26,27] and in the paediatric hemiplegic popula- the hand in space can be determined by an infinite number of
tion [28–30]. However, the kinematic information obtained joint angles [32–34]. The explanation for this joint redun-
from these studies is limited to sagittal plane elbow motion dancy is not fully understood, but it has been proposed that
only, with measures more accurately reflecting relative posi- this flexibility permits a better response to random changes
tion of arm and forearm segments rather than elbow flexion in the final target position [34].

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The New Zealand Neurological Foundation and the
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School of Medicine Foundation, University of Auckland [20] Palisano R, Rosenbaum P, Walter S, Russell D, Wood E, Galuppi BE.
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Biostatistics Unit at the University of Auckland; Nicola
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