Scoliose idiopathique ::évidences scientifiques et implications cliniques

Les déformations du rachis chez l'enfant en croissance représentent la majorité des demandes de prise en charge thérapeutique dans le cadre des pathologies musculosquelettiques pédiatriques. La plus commune de ces pathologies est la scoliose idiopathique, qui a une prévalence de deux à trois enfants sur 100. Alors que dans la majorité des cas la déformation rachidienne se stabilise en fin de croissance, certains cas plus sévères nécessitent le recours à la chirurgie. Un dépistage plus précoce et une meilleure compréhension de l'étiopathogénie ainsi que des conséquences de la scoliose, à la lumière des études récentes, permettent de mieux appréhender le traitement dans son approche bio-psycho-sociale afin de rendre plus efficace la prise en charge kinésithérapeutique. Les connaissances des hypothèses étiologiques (asymétrie de croissance osseuse, biomécanique de la station érigée, anomalies des tissus conjonctifs et myofasciaux, facteurs neurologiques, environnementaux et hormonaux) ouvrent la voie à des techniques thérapeutiques mieux inscrites dans un modèle d'« evidence based practice ». Cet article offre une large revue des évidences scientifiques et de leurs implications cliniques, articulée autour des hypothèses étiologiques de la scoliose idiopathique, des facteurs évolutifs et du pronostic, des troubles associés et des enjeux diagnostiques. Il servira de base scientifique à un second article plus orienté sur les principes de prise en charge kinésithérapeutique

Gait in adolescent idiopathic scoliosis: energy cost analysis

Walking is a very common activity for the human body. It is so common that the musculoskeletal and cardiovascular systems are optimized to have the minimum energetic cost at 4 km/h (spontaneous speed). A previous study showed that lumbar and thoracolumbar adolescent idiopathic scoliosis (AIS) patients exhibit a reduction of shoulder, pelvic, and hip frontal mobility during gait. A longer contraction duration of the spinal and pelvic muscles was also noted. The energetic cost (C) of walking is normally linked to the actual mechanical work muscles have to perform. This total mechanical work (Wtot) can be divided in two parts: the work needed to move the shoulders and lower limbs relative to the center of mass of the body (COMb) is known as the internal work (Wint), whereas additional work, known as external work (Wext), is needed to accelerate and lift up the COMb relative to the ground. Normally, the COMb goes up and down by 3 cm with every step. Pathological walking usually leads to an increase in Wtot (often because of increased vertical displacement of the COMb), and consequently, it increases the energetic cost. The goal of this study is to investigate the effects of scoliosis and scoliosis severity on the mechanical work and energetic cost of walking. Fifty-four female subjects aged 12 to 17 were used in this study. Thirteen healthy girls were in the control group, 12 were in scoliosis group 1 (Cobb angle [Cb] ≤ 20°), 13 were in scoliosis group 2 (20° < Cb < 40°), and 16 were in scoliosis group 3 (Cb ≥ 40°). They were assessed by physical examination and gait analysis. The 41 scoliotic patients had an untreated progressive left thoracolumbar or lumbar AIS. During gait analysis, the subject was asked to walk on a treadmill at 4 km h−1. Movements of the limbs were followed by six infrared cameras, which tracked markers fixed on the body. Wint was calculated from the kinematics. The movements of the COMb were derived from the ground reaction forces, and Wext was calculated from the force signal. Wtot was equal to Wint + Wext. Oxygen consumption \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\dot{V}{\text{O}}_{2} } \right)$$\end{document} was measured with a mask to calculate energetic cost (C) and muscular efficiency (Wtot/C). Statistical comparisons between the groups were performed using an analysis of variance (ANOVA). The external work (Wext) and internal work (Wint) were both reduced from 7 to 22% as a function of the severity of the scoliosis curve. Overall, the total muscular mechanical work (Wtot) was reduced from 7% to 13% in the scoliosis patients. Within scoliosis groups, the Wext for the group 1 (Cb ≥ 20°) and 2 (20 ≤ Cb ≤ 40°) was significantly different from group 3 (Cb ≥ 40°). No significant differences were observed between scoliosis groups for the Wint. The Wtot did not showed any significant difference between scoliosis groups except between group 1 and 3. The energy cost and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document} were increased by around 30%. As a result Muscle efficiency was significantly decreased by 23% to 32%, but no significant differences related to the severity of the scoliosis were noted. This study shows that scoliosis patients have inefficient muscles during walking. Muscle efficiency was so severely decreased that it could be used as a diagnostic tool, since every scoliosis patient had an average muscle efficiency below 27%, whereas every control had an average muscle efficiency above 27%. The reduction of mechanical work found in scoliotic patients has never been observed in any pathological gait, but it is interpreted as a long term adaptation to economize energy and face poor muscle efficiency. With a relatively stiff gait, scoliosis patients also limit vertical movement of the COMb (smoothing the gait) and consequently, reduce Wext and Wint. Inefficiency of scoliosis muscles was obvious even in mild scoliosis (group 1, Cb < 20°) and could be related to the prolonged muscle contraction time observed in a previous study (muscle co-contraction)

Very Short-Term Effect of Brace Wearing on Gait in Adolescent Idiopathic Scoliosis Girls

PURPOSE: Adolescent idiopathic scoliotic (AIS) deformity induces excessive oxygen consumption correlated to a bilateral increase of lumbo-pelvic muscles timing activity (EMG) during gait. Wearing a brace, the usual treatment for AIS, by supporting the spine and the pelvis, would generate lumbo-pelvic muscular relaxation and consequently reduce excessive oxygen consumption. The purpose of this study was to evaluate the short-term effect of bracing on gait biomechanics in scoliotic spine when compared with normal braced spine. METHODS: Thirteen healthy volunteers were compared to 13 AIS girls. In both samples, gait analysis was assessed using a three-dimensional motion analysis, including synchronous kinematic, electromyographic, mechanical and energy measurements, first without brace, then wearing a brace. RESULTS: For scoliotic patients, comparison of in-brace and out-brace situations revealed a significant decrease of frontal pelvis (p < 0.001), hip (p < 0.001) and shoulder (p = 0.004) motion in brace associated with a significant reduction of pelvis rotation (p = 0.003). However, the brace did not change significantly the lumbo-pelvic muscle activity duration (EMG) or the mechanical and energetic parameters. Transversal pelvis motion was reduced by 39 % (p = 0.04), frontal hip and shoulder motions by 23 % (p = 0.004) and 30 % (p = 0.01) respectively, and energy cost of walking remained increased by 37 % in braced AIS girls relatively to braced healthy subjects. Mechanical and electromyographic variables were not significantly different between the two braced populations during gait except for the gluteus medius muscle that showed bilaterally an increase of duration of electrical activity in healthy subjects and contrarily a decrease in AIS patients (healthy: −3.5 ± 9.6 % of gait cycle vs. scoliotic: 3.7 ± 7.7 % of gait cycle; p = 0.04). CONCLUSIONS: Bracing changed neither the oxygen consumption nor the timing of the lumbo-pelvic muscles activity in both groups during gait. However, in brace the timing activity of bilateral gluteus medius muscles tended to decrease in AIS patients and increase in healthy subjects. Moreover, braced AIS patients had more restricted frontal hips and shoulder motion as well as pelvis rotation than braced healthy subjects