Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) deformity of the spine and rib cage1,2 that concerns the vertebral column and whole trunk, including the pelvis.3 It has been estimated that idiopathic scoliosis occurs in 1% to 3% of children aged between 10 and 16 years.4 Despite its unclear origin, several possible etiological factors may be associated with this pathology, such as abnormality in the central nervous system, asymmetry in paraspinal muscle activity, and genetic and endocrinal factors.5–8 Some studies also have indicated that examination of kinetic and kinematic variables in AIS patients may provide useful information to better understanding of the etiology of AIS.9–12
Previous studies have shown that idiopathic scoliosis may alter the relative motion between body segments and produces a pathological gait pattern.12–21 However, in the study of Chen et al.,22 it was concluded that the gait pattern of idiopathic scoliotic patients is similar to that of normal subjects. In this study, gait pathology was assessed based on spatiotemporal gait parameters; angular motion of the shoulders, trunk, pelvis, and lower-limb joints; and ground reaction force components.
Medical management of scoliosis is dependent on the severity of scoliotic curvature and the skeletal maturity of the patient and includes maintenance procedures such as physical therapy, electrical muscle stimulation, exercise, stretching, brace use, and various surgical techniques. Bracing is generally recommended for scoliotic patients with a Cobb angle of between 25° and 45°, primarily to prevent curve progression and also with the aim of achieving some curve correction.4,23,24 The influence of trunk bracing on radiologic curve correction, scoliotic curve pattern in sagittal and coronal planes, compliance, and daily activities of scoliotic patients has been assessed in several studies.25–29 However, there is a lack of information regarding the influence of bracing on gait pattern of scoliotic patients. In some related studies, it was shown that very short-term trunk bracing induced a stiffened gait by reducing shoulder, trunk, pelvic, and hip motions in AIS patients and healthy subjects.30–32 However, Mahaudens et al.33 showed that long-term brace wearing increases frontal pelvis and hip motions despite a slight reduction of the shoulder rotation during gait. Therefore, it does not significantly stiffen the body or deteriorate functional daily walking of scoliotic patients.33
It is controversial whether the use of an orthosis influences the kinetic and kinematic performance of subjects with scoliosis. Therefore, the objectives of this study were to find the immediate effect of bracing on range of motion of lower-limb joints, trunk, and pelvis and to ascertain if trunk bracing affects the symmetry of scoliotic gait or not.
Ten scoliotic patients (eight girls and two boys) aged between 10 and 16 years and ten normal subjects with comparable age, height, and weight were recruited in this study (Table 1). The value of Cobb angle in scoliotic patients was between 24° and 45° and apical vertebra was below T2. All the scoliotic patients were treated with a brace. Eight of them were using Boston and two other were using Milwaukee brace (Table 2).
Subjects with lower-limb dysfunction (e.g., leg-length discrepancy), low back pain, previous spinal surgery, and other orthopedic or neurologic disorders that can affect the gait pattern of subjects were excluded from this study. Scoliotic subjects were tested with and without the brace. A written consent form was signed by the parents of the participants before data collection. This study was approved by the institutional review board of the Isfahan University of Medical Sciences.
INSTRUMENTATION AND PROCEDURE
A 3D motion analysis system (Qualysis motion analysis system) with seven high-speed cameras was used to collect kinematic data during walking. Thirty-eight lightweight reflective markers (with 14-mm diameters) were attached to anatomical landmarks and the middle shank and thigh of the subjects. These markers were attached to right and left anterior superior iliac spine, right and left posterior superior iliac spine, right and left medial and lateral malleolus, right and left iliac crests, right and left acromioclavicular joints, right and left medial and lateral sides of the knee joints, and first and fifth metatarsal heads. Moreover, four marker clusters comprising four markers attached on the rhomboid plates were attached to the anterolateral surface of the leg and thigh by use of extensible Velcro straps (Figure 1).
The subjects were asked to walk with bare feet at their normal speed along a level surface to collect ten successful trials for right and left sides (5 trials for each leg). The trunk section was considered to be a segment embedded between the iliac crest and acromion process. The locations of the markers were recorded by Track-Manager software. The subjects' lower limbs and trunk were modeled by visual 3D software produced by C-motion Company (C-Motion, Inc, Germantown, MD, USA). This program was also used for calculation of range of motion of the trunk, hip, pelvis, knee, and ankle joints during walking. The collected data were filtered with a Butterworth low pass filter with a cutoff frequency of 10 Hz and split to gait cycle interval using heel strike data.
The ranges of motion of the ankle, knee and hip, pelvic, and trunk were evaluated in this study under two conditions. The asymmetry index was also used to evaluate the symmetry of range of motions of right and left sides in two conditions (with and without brace) (Equation 1):
where Xr and X1 are the measured range of motions of the right and left sides, respectively. The normal distribution of the parameters was evaluated by use of Shapiro-Wilk test. The difference between the mean values of the parameters in scoliotic patients in walking with and without orthosis and between normal and scoliotic patients was evaluated using the paired t test and two-sample t test, respectively. Significance value was set at p = 0.05.
The kinematics of the hip, knee, ankle, trunk, and pelvis of normal and scoliotic subjects while walking with and without orthosis are shown in Tables 3–7. As can be seen from Table 3, there was no significant difference between the kinematics of ankle joint between normal and scoliotic subjects and between scoliotic subjects walking with and without orthosis (p > 0.05). In contrast, scoliotic subjects had a decreased knee joint range of motion in sagittal plane compared with normal subjects (p = 0.011). The mean value of knee flexion/extension range of motion was 59.46° ± 8.36° and 61.8° ± 7.25° in scoliotic subjects walking without and with orthosis, respectively (p = 0.0311) (Table 4).
The mean values of the hip joint range of motions of normal subjects and scoliotic patients while walking without orthosis and with orthosis were 39.895° ± 9.86°, 38.5° ± 4.82°, and 37.916° ± 5.16°, respectively (p > 0.05). It seems that the hip joint range of motion increased after the use of the orthosis (p = 0.05). Table 5 summarizes the hip joint range of motion of normal and scoliotic subjects.
The range of motion of the pelvis in sagittal plane was 7.08 ± 1.88 in normal subjects, compared with 6.75 ± 1.99 in scoliotic patients (p = 0.356). Use of orthosis significantly influenced pelvic motions in sagittal, coronal, and transverse planes (p < 0.05) (Table 6). There was no significant difference between trunk range of motion in sagittal plane between normal and scoliotic subjects and between scoliotic patients while walking with and without orthosis (p > 0.05). Use of an orthosis significantly influenced the range of motion of trunk in the transverse plane (p = 0.00842) (Table 7).
The asymmetries of ankle, knee, hip, pelvic, and trunk range of motions in scoliotic patients with and without brace situations and in normal subjects are shown in Tables 8 and 9. As can be seen from these tables, trunk bracing significantly increased the asymmetry index of trunk movement in sagittal and ankle joint movement in frontal planes (p ≤ 0.05). However, there was no significant difference between the asymmetry index value of the other lower-limb joints, pelvic, and trunk movements between walking with and without brace conditions. As can be seen from Table 9, the only discrepancy in the gait pattern between scoliotic patients and healthy subjects was in asymmetrical pelvic movement in the frontal plane.
The results of this study showed that scoliosis led to a decrease in range of motion of the hip, knee, pelvis, and trunk in the frontal plane. Moreover, it was shown that scoliotic patients walked with more restricted knee, pelvic, and trunk motions in the sagittal plane. These results agree with the study of Mahaudens et al.,12 which claimed that this motion restriction could be the consequence of increase in the bilateral electrical activity duration of the muscles connected to the pelvis. Moreover, it had been interpreted by 3D structural changes of the spine,19,34–36 pelvis,13,37 and hip components.38–40 Chen et al.22 also claimed that the motion restriction and increase in the activities of pelvic muscles in scoliotic patients is the compensation mechanism used to keep the upper body balance in frontal plane.
In our study, it was shown that trunk bracing reduced the range of motions of pelvic, trunk, hip, and knee joints during walking. However, it was significant for the pelvis in three planes of motion (p < 0.05) and also trunk motion in transverse plane (p = 0.008).These results are in agreement with the findings of the studies of Kramers-de Quarvain et al.,19 Mahaudens et al.,30 and Wong et al.,32 which showed pelvic movement as the main segment significantly influenced by brace wear. The reduction in pelvic motion may be interpreted by the mechanism of trunk bracing action that tries to reduce exaggerated lumbar lordosis and anterior pelvic tilt to better control of the scoliosis curvature. It was also apparent that trunk bracing restricted joints' range of motion by encompassing the trunk and pelvis. However, ankle joint range of motion in scoliotic patients did not change significantly compared with that in normal subjects and compared with the brace condition. Thus, it can be concluded that scoliosis and trunk bracing can affect only proximal joints.
As can be seen from Table 8, trunk bracing also reduced the asymmetry index of sagittal pelvic, knee, ankle, frontal pelvic and hip, and transversal hip and knee ranges of motion during walking. It means that trunk bracing improves the symmetry of gait pattern in scoliotic patients based on kinematic variables. However, statistically, these were not significant (p > 0.05).
There are some limitations that should be acknowledged in this research study, which include the number of subjects and that only one type of orthosis was used by subjects. Therefore, it is recommended that the same study will be done with more number of subjects and also with various types of orthoses.
The results of this study showed that trunk bracing influenced the pelvic range of motion and improved symmetry of range of motion of the pelvis. However, bracing did not significantly influence the kinematics of hip, knee, and ankle joints.
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