Right hip adduction deficit and adolescent idiopathic scoliosis.

Abstract

To determine whether right hip adduction deficit is associated with adolescent idiopathic scoliosis.
102 adolescents (mean age, 14 years) with idiopathic scoliosis were prospectively studied. Their spinal curve pattern (according to Lenke's classification), curve severity (by Cobb's angle), and hip adduction ranges of both sides were recorded. Additional factors that may affect hip adduction range including the preferred leg during standing, the presence of hip flexor tightness, and the side of the dominant leg were also assessed.
The mean Cobb's angle was 27 degrees. The difference in hip adduction range between the right and left hips was 5 degrees (p<0.05). Of 102 patients, 64 had an adduction range deficit of the right hip, 4 of the left hip, and 34 had no difference. Patients with >10 degrees of right hip adduction deficit were associated with a higher proportion of left leg dominance than those with less than or equal to 10 degrees of right hip adduction deficit (18% vs 4%).
Left leg dominance may play a role in right hip adduction deficit and scoliosis.

Full text

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ABSTRACT
Purpose. To determine whether right hip adduction
deficit is associated with adolescent idiopathic
scoliosis.
Methods. 102 adolescents (mean age, 14 years) with
idiopathic scoliosis were prospectively studied.
Their spinal curve pattern (according to Lenke’s
classification), curve severity (by Cobb’s angle), and
hip adduction ranges of both sides were recorded.
Additional factors that may affect hip adduction
range including the preferred leg during standing,
the presence of hip flexor tightness, and the side of
the dominant leg were also assessed.
Results. The mean Cobb’s angle was 27º. The
difference in hip adduction range between the right
and left hips was 5º (p<0.05). Of 102 patients, 64 had
an adduction range deficit of the right hip, 4 of the
left hip, and 34 had no difference. Patients with >10º
of right hip adduction deficit were associated with a
higher proportion of left leg dominance than those
Right hip adduction deficit and adolescent
idiopathic scoliosis
KMC Cheung
Department of Orthopaedics and Traumatology, Queen Mary Hospital, The University of Hong Kong, Hong Kong
ACS Cheng
Department of Physiotherapy, Duchess of Kent Children’s Hospital, Hong Kong
WY Cheung, YS Chooi, YW Wong, KDK Luk
Department of Orthopaedics and Traumatology, Queen Mary Hospital, The University of Hong Kong, Hong Kong
Address correspondence and reprint requests to: Prof Kenneth MC Cheung, Department of Orthopaedics and Traumatology,
Queen Mary Hospital, The University of Hong Kong, Hong Kong. E-mail: cheungmc@hku.hk
Journal of Orthopaedic Surgery 2008;16(1):24-6
with ≤10º of right hip adduction deficit (18% vs 4%).
Conclusion. Left leg dominance may play a role in
right hip adduction deficit and scoliosis.
Key words: adolescent; scoliosis
INTRODUCTION
Adolescent idiopathic scoliosis is a common condition
affecting 3% of most populations.1 Its aetiology
remains unknown. Such patients are more likely to
lean on the right leg during standing and have an
adduction range deficit of the right hip.2 We aimed
to determine whether right hip adduction deficit is
associated with adolescent idiopathic scoliosis.
MATERIALS AND METHODS
Between November 2004 and January 2005, 102
adolescents (mean age, 14 years; standard deviation,
2 years) with idiopathic scoliosis presenting to our

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Vol. 16 No. 1, April 2008 Right hip adduction deficit and adolescent idiopathic scoliosis 25
spinal deformity clinic were prospectively studied.
Their spinal curve pattern (according to Lenke’s
classification3), curve severity (by Cobb’s angle), and
hip adduction ranges of both sides were recorded.
Additional factors that may affect hip adduction
range including the preferred leg during standing,
the presence of hip flexor tightness, and the side of
the dominant leg were assessed by a single senior
physiotherapist blinded to the spinal deformity
information.
The hip adduction ranges of both sides were
assessed using the Ober test; the angle in the side-
lying position was measured using an inclinometer.4
Care was taken to maintain the hip in a neutral
flexion-extension and rotation position.
Patients’ preference to stand on the left or right
leg or both was recorded, as it was hypothesised
that those with a hip adduction deficit of either side
preferred to stand on the deficit leg for stability.2
Hip flexor tightness may reduce hip adduction
range. It was assessed with the hip in a side-lying
position with neutral abduction, adduction, and
rotation, and with 90º of knee flexion. It was defined
as a passive hip extension of <5º.
Patients were asked to walk forward and kick a
stationary ball on the floor. The dominant leg was
defined as the leg kicking the ball.5,6 It was hypothesised
that the dominant leg was related to the preferred leg
during standing and therefore manifested greater
reduction in hip adduction range.2
The differences between right and left hip
adduction range were compared using the paired
t-test. The differences of various parameters
between specific target groups were compared
using the Mann-Whitney U test. The correlations
between various parameters were analysed using
Kendall’s tau. A p value of <0.05 was considered
significant.
RESULTS
The mean difference in hip adduction range between
the right and left hips was 5º (17º vs 22º, p<0.05, paired
t-test). Of 102 patients, 64 (63%) had an adduction
range deficit of the right hip, 4 (4%) of the left hip,
and 34 (33%) had no difference in adduction range
between 2 sides (Table 1).
Patients were subdivided into 2 groups by the
extent of hip adduction deficit. In group A (n=11) the
right hip adduction deficit was >10º, whereas in group
B (n=51) it was ≤10º. In group A, 3 had a single curve
(mean, 27º) and 8 had double curves (mean, 30º and
30º), whereas in group B, 23 had a single curve (mean,
29º), 25 had double curves (mean, 28º and 26º), and 3
had triple curves (mean, 22º, 21º and 25º). There were
no significant differences between the 2 groups in
Cobb’s angles (p=0.82, single curve; p=0.62 and p=0.4,
double curve; independent t-test), right leg preference
during standing (46% vs 45%, p=0.44, Kandall’s tau),
and right hip flexors tightness (55% vs 38%, p=0.43,
Kandall’s tau), but there was significant difference
for leg dominance (18% vs 4%, p=0.02, Kandall’s tau)
[Table 2].
Patients were subdivided into 2 groups according
to Lenke’s classification. The right thoracic major
scoliosis group consisted of 62 patients with Lenke
types 1, 2, 3, and 4, whereas the left lumbar major
scoliosis group consisted of 36 patients with Lenke
types 5 and 6. There were no significant differences
between the 2 groups in the mean right hip adduction
deficits (6º vs 4º, p=0.27, independent t-test) and right
leg preference during standing (40% vs 33%, p=0.36,
Kandall’s tau) [Table 3]. In a separate assessment
between Lenke type 1 (single right-sided thoracic
scoliosis, n=12) and type 2 (single left-sided lumbar
scoliosis, n=17), there were no significant differences
Parameters No. (%) of patients*
Mean (SD) age (years)
Mean (SD) Cobb’s angle
Lenke’s classification
Type 1
Type 2
Type 3
Type 4
Type 5
Type 6
Hip adduction range
Right
Left
Hip adduction range deficit
Right
Left
No difference
Preferred leg during standing
Right
Left
Neither
Hip flexors tightness
Right
Left
Neither
Leg dominant
Right
Left
Neither
14 (2)
27º (12º)
45 (44)
5 (5)
15 (15)
1 (1)
33 (32)
3 (3)
0º–17º (SD, 6º)
0º–22º (SD, 6º)
64 (63)
4 (4)
34 (33)
38 (37)
39 (38)
25 (25)
34 (33)
29 (28)
39 (38)
84 (82)
5 (4)
13 (13)
Table 1
Hip and spine characteristics of patients
* Data are presented as No. (%) unless otherwise stated

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26 KMC Cheung et al.
Journal of Orthopaedic Surgery
Right hip
adduction
deficit
Mean (SD) Cobb’s angle No. (%) of patients
Single curveDouble curveTriple curvePreferred right leg
during standing
Right hip flexors
tightness
Left leg
dominant
Group A (>10º,
n=11)
Group B (≤10º,
n=51)
p value
27º (21º); n=330º (15º), 30º
(18º); n=8
28º (10º), 26º
(10º); n=25
0.62, 0.4
n=05 (46)6 (55)2 (18)
29º (12º); n=2322º (2º), 21º (8º),
25º (1º); n=3
-
24 (45)20 (38) 2 (4)
0.82 0.440.43 0.02
Table 2
Comparison between 2 groups with right hip adduction deficit of >10º versus ≤10º
Lenke’s classificationMean (SD) right hip
adduction deficit
p valueNo. (%) of patients
preferred right leg
during standing
p value
Types 1 to 4 (right thoracic major scoliosis, n=62)
Types 5 and 6 (left lumbar major scoliosis, n=36)
Type 1 (single right thoracic scoliosis, n=12)
Type 5 (single left lumbar scoliosis, n=17)
6º (6º)
4º (5º)
5º (4º)
6º (5º)
p=0.27
25 (40)
12 (33)
7 (58)
6 (35)
p=0.36
p=0.67p=0.09
Table 3
Comparison between groups in terms of Lenke’s classification3
between the 2 groups in the mean right hip adduction
deficits (5º vs 6º, p=0.67, independent t-test) and right
leg preference during standing (58% vs 35%, p=0.09,
Kandall’s tau) [Table 3].
DISCUSSION
Functionally, right hip adduction deficit leads to
a longer right leg and pelvic obliquity and hence
causes scoliosis and the right leg preference during
standing.2 In our study, adolescents with idiopathic
scoliosis had a significant right hip adduction deficit
by a mean of 5º (17º vs 22º). Patients with greater right
hip adduction deficit are more likely to be left leg
dominant. This suggests that left leg dominance may
play a role in right hip adduction deficit and scoliosis.
Whether such a hip adduction deficit exists within
the normal, non-scoliotic population is the subject of
a future study.
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