Levy Ayelet, Gefen Amit
Ostomy Wound Manage. 2017 Oct;63(10):48-55.
The sacrum is the most susceptible anatomical site for developing pressure injuries, including deep tissue injuries, during supine lying. Prophylactic dressings generally are designed to reduce friction, alleviate internal tissue shear, manage the microclimate, and overall cushion the soft tissues subjected to sustained deformations under the sacrum. Using computational modeling, the authors developed a set of 8 magnetic resonance imaging-based, 3-dimensional finite element models of the buttocks of a healthy 28-year-old woman for comparing the biomechanical effects of different prophylactic sacral dressing designs when used during supine lying on a standard hospital foam mattress. Computer simulation data from model variants incorporating an isotropic (same stiffness in every direction) multilayer compliant dressing, an anisotropic (directionally dependent stiffness properties) multilayer compliant dressing, and a completely stiff dressing were compared to control (no dressing). Specific outcome measures that were compared across these simulation cases were strain energy density (SED) and maximal shear stresses in a volume of interest (VOI) of soft tissues surrounding the sacrum. The SED and shear stress measurements were obtained in pure compression loading of the buttocks (ie, simulating a horizontal supine bed rest) and in combined compression-and-shear loads applied to the buttocks (ie, 45˚ Fowler position causing frictional and shear forces) on a standard foam mattress. Compared to the isotropic dressing design, the anisotropic dressing facilitated more soft tissue protection through an additional 11% reduction in exposure to SED at the VOI. In this model, use of the anisotropic compliant dressing resulted in the lowest exposures to internal tissue SED and shear stresses. Research to examine the clinical inference of this modeling technique and studies to compare the effects of prophylactic dressings on healthy volunteers and patients in different positions are warranted.
骶骨是仰卧位时发生压力性损伤（包括深部组织损伤）最易感的解剖部位。预防性敷料通常旨在减少摩擦、减轻内部组织剪切力、调节微气候，并总体上缓冲骶骨下方承受持续变形的软组织。作者利用计算建模，开发了一组基于磁共振成像的、三维有限元模型，模拟一名28岁健康女性的臀部，以比较不同预防性骶骨敷料设计在仰卧于标准医院泡沫床垫上时的生物力学效应。将包含各向同性（各方向刚度相同）多层顺应性敷料、各向异性（刚度特性与方向有关）多层顺应性敷料和完全刚性敷料的模型变体的计算机模拟数据与对照组（不使用敷料）进行比较。在这些模拟案例中进行比较的具体结果指标是骶骨周围软组织感兴趣体积（VOI）内的应变能密度（SED）和最大剪切应力。SED和剪切应力测量是在臀部的纯压缩加载（即模拟水平仰卧卧床休息）以及在标准泡沫床垫上对臀部施加的压缩与剪切联合载荷（即45˚福勒位，会产生摩擦力和剪切力）下获得的。与各向同性敷料设计相比，各向异性敷料通过使VOI处SED暴露量额外降低11%，从而促进了更多的软组织保护。在该模型中，使用各向异性顺应性敷料导致内部组织SED和剪切应力的暴露量最低。有必要开展研究以检验这种建模技术的临床推断，并开展研究比较预防性敷料对处于不同体位的健康志愿者和患者的影响。
