Development of an in-vivo method to estimate the personalized 3D mass moment of inertia of the scoliotic trunk

本提案的总体目标是：1)开发一种临床方法，用于使用逆动力学方法估计脊柱侧凸干的体内个性化三维惯性矩；2)验证该方法。在青少年特发性脊柱侧凸（AIS）中，脊柱和胸腔的变化逐渐发展导致严重的躯干畸形。由于脊柱畸形经常进展，每次临床就诊时转动惯量不断变化。这对躯干的移动性和刚性有影响。目前还没有临床方法来估计不断变化的脊柱侧凸躯干的体内个性化惯性矩，尽管已经提出了不同的方法来估计体段惯性特性。来自尸体的人体测量表不能真正代表青春期女性人口或脊柱侧凸女孩，也不能适应改变躯干形状。第一个具体目标是利用我们的三维逆动态摆模型来估计受试者心甘情愿地绕脚踝摆动时全身的转动惯量。通常，在反动力计算中，肌肉力矩是未知值，但可以使用代换法消除，只留下惯性矩作为未知值。平行轴定理可以用来估计脊柱侧弯躯干的转动惯量，因为整个身体的转动惯量和未变形的身体部分的转动惯量是已知的。第二个具体目标是用角动量方程应用类似的方法。第三个具体目标是将我们的结果与其他公认的方法进行比较，如基于视频的系统，我们的宇宙摆法或振荡表法等。这项工作首次解决了个性化的体内质量惯性矩的脊柱侧凸。因为脊柱侧凸是脊柱的三维变形，导致躯干的变化，身体形态强烈影响站立稳定性和躯干的活动。我们有理由认为，脊柱侧凸患者的惯性矩改变可能与站立不平衡有关。

The general objectives of this proposal are to 1) develop a clinical method for estimating the in vivo personalized three-dimensional (3D) moment of inertia of the scoliotic trunk using an inverse dynamic approach and to 2) validate it. In adolescent idiopathic scoliosis (AIS), changes in the spine and rib cage develop progressively leading to a serious trunk deformity. Since spinal deformity often progresses, the moment of inertia is constantly changing at each clinical visit. This has a repercussion on the mobility of the trunk and its rigidity. Presently there is no clinical method for estimating the in vivo personalized moment of inertia of the ever changing scoliotic trunk though different methods have been proposed to estimate the body segment inertial properties. Anthropometric tables derived from cadavers do not truly represent the adolescent female population or scoliotic girls and can not be adapted for changing trunk shape. The first specific objective is to adapt our 3D inverse dynamic pendulum model to estimate the moment of inertia of the whole body when the subject willingly oscillates about the ankles. Normally, the muscle moment is the unknown value in an inverse dynamic calculation but can be eliminated using substitution leaving only the moment of inertia as the unknown. The parallel axis theorem can then be used to estimate the moment of inertia of the scoliotic trunk since that of the whole body and that of the un-deformed body segments are known. The second specific objective is to apply a similar approach using the angular momentum equation. The third specific objective is to compare our results with other accepted methods such video-based systems, our universe pendulum method or that of an oscillating table, etc. This work addresses for the first time the personalized in vivo mass moment of inertia of the scoliotic spine. Because scoliosis is a 3D deformation of the spine leading to changes in the trunk and that body morphology strongly affects standing stability and trunk mobility. It is reasonable to advance that modifications in the moment of inertia may be link to standing imbalance in scoliotic patient.