Liu X C, Fabry G, Molenaers G, Lammens J, Moens P
University Hospital Pellenberg, Belgium.
J Pediatr Orthop. 1998 Mar-Apr;18(2):187-9.
The symmetry index (SI), as one of methods to evaluate gait pattern in patients with leg-length discrepancy (LLD), helps to estimate the acceptable range of inequality and to determine symmetry in the kinematic and kinetic data before and after a heel lift, although this parameter has a large standard deviation that undermines its accuracy. Thirty patients with LLD were studied by a motion-analysis system and a force plate. Joint motion of the lower extremity in the sagittal plane, back movement in the coronal plane, and three-dimensional ground-reaction forces (GRFs) were registered. From a linear-regression analysis, a mean value of inequality of 2.33 cm (range, 2.12-2.54) was found to correspond to an acceptable gait symmetry. After a heel lift, the SI of the pelvic tilt at midstance and of the vertical GRF at initial contact increases significantly, but the SI of the medial GRF at terminal stance decreases. Patients with an inequality of a mean value of 0.51 cm determined by palpating bilaterally the top of the iliac crest (the TIC1 subgroup) showed a lesser value of the SI of the center of pressure in the forward direction during stance compared with the group with a mean value of inequality of 1.39 cm (the TIC2 subgroup). As a result of our findings, we conclude that the effect of the amount of correction by a heel lift on gait symmetry is unpredictable.
对称指数（SI）作为评估下肢长度不等（LLD）患者步态模式的方法之一，有助于估计可接受的不等距范围，并确定足跟抬高前后运动学和动力学数据的对称性，尽管该参数的标准差较大，会影响其准确性。通过运动分析系统和测力板对30例LLD患者进行了研究。记录了下肢在矢状面的关节运动、冠状面的背部运动以及三维地面反作用力（GRF）。通过线性回归分析发现，平均不等距值为2.33厘米（范围为2.12 - 2.54厘米）对应于可接受的步态对称性。足跟抬高后，站立中期骨盆倾斜的SI以及初始接触时垂直GRF的SI显著增加，但终末站立时内侧GRF的SI降低。通过双侧触诊髂嵴顶部确定平均不等距值为0.51厘米的患者（TIC1亚组）在站立期间向前方向的压力中心SI值低于平均不等距值为1.39厘米的组（TIC2亚组）。根据我们的研究结果，我们得出结论，足跟抬高的矫正量对步态对称性的影响是不可预测的。
