Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel.
Med Biol Eng Comput. 2011 Apr;49(4):473-83. doi: 10.1007/s11517-011-0754-y. Epub 2011 Mar 11.
Spinal cord injury patients are under daily risk for developing deep tissue injury which is a severe pressure ulcer that initiates in soft tissues at the bones' proximity. We aimed to formulate a patient-specific biomechanical model that can continuously monitor internal tissue stresses in real time. We adopted a formulation solving an axisymmetric contact problem of a finite-thickness, elastic layer (soft tissue), and a rigid spherical indentor (ischial tuberosity). We utilized finite element analyses to expand the formulation for large deformations. Sensitivity analyses showed that the soft tissue mechanical properties are the most influential factors in this modeling. We then used synthetic surface pressure data and actual surface pressures recorded under the buttocks of five paraplegic wheelchair users to demonstrate clinical feasibility. Output parameters were designed to be simple so that they can be easily interpreted by the user. Specifically, we calculated peak and average internal von Mises stress and stress dose, under each buttock, and also a time-dependent stress asymmetry index, to account for frequency of posture adjustments. Inter-subject variability was higher than the intra-subject variability. The heaviest subject had the highest maximal and average peak internal soft tissue stress. We believe that this method holds a high potential for clinical applications.
脊髓损伤患者每天都有发生深部组织损伤的风险，深部组织损伤是一种起始于骨骼附近软组织的严重压疮。我们旨在制定一种能够实时连续监测内部组织应力的患者特异性生物力学模型。我们采用了一种求解有限厚度弹性层（软组织）和刚性球形压痕器（坐骨结节）轴对称接触问题的公式。我们利用有限元分析将公式扩展到了大变形的情况。敏感性分析表明，软组织力学性质是该模型中最具影响力的因素。然后，我们使用合成表面压力数据和在 5 名截瘫轮椅使用者臀部下实际记录的表面压力来演示临床可行性。输出参数设计得很简单，以便用户能够轻松解释。具体来说，我们计算了每个臀部下的峰值和平均内部 von Mises 应力和应力剂量，以及一个随时间变化的应力不对称指数，以考虑姿势调整的频率。个体间的变异性高于个体内的变异性。最重的受试者有最高的最大和平均峰值内部软组织应力。我们相信这种方法具有很高的临床应用潜力。
