Background

The heel is one of the most common sites of pressure ulcers and the anatomical location with the highest prevalence of deep tissue injury. Several finite element modeling studies investigate heel ulcers for bedridden patients. In the current study we have added the implementation of the calf structure to the current heel models. We tested the effect of foot posture, mattress stiffness, and a lateral calcaneus displacement to the contact pressure and internal maximum shear strain occurring at the heel.

Methods

A new 3D finite element model is created which includes the heel and calf structure. Sensitivity analyses are performed for the foot orientation relative to the mattress, the Young's modulus of the mattress, and a lateral displacement of the calcaneus relative to the other soft tissues in the heel.

Findings

The models predict that a stiffer mattress results in higher contact pressures and internal maximum shear strains at the heel as well as the calf. An abducted foot posture reduces the internal strains in the heel and a lateral calcaneus displacement increases the internal maximum shear strains. A parameter study with different mattress-skin friction coefficients showed that a coefficient below 0.4 decreases the maximum internal shear strains in all of the used loading conditions.

Interpretation

In clinical practice, it is advised to avoid internal shearing of the calcaneus of patients, and it could be taken into consideration by medical experts and nurses that a more abducted foot position may reduce the strains in the heel.

中文翻译：

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卧床患者发生足跟溃疡的危险因素：有限元研究。

背景

足跟是压疮最常见的部位之一，也是深部组织损伤发生率最高的解剖位置。几项有限元建模研究调查了卧床患者的足跟溃疡。在当前的研究中，我们将小腿结构的实现添加到当前的脚跟模型中。我们测试了脚的姿势，床垫的刚度以及跟骨的横向跟骨位移对足跟处产生的接触压力和内部最大剪切应变的影响。

方法

创建了一个新的3D有限元模型，其中包括后跟和小腿结构。对脚相对于床垫的方向，床垫的杨氏模量以及跟骨相对于脚跟中其他软组织的横向位移进行敏感性分析。

发现

这些模型预测，较硬的床垫会导致较高的接触压力以及脚跟和小腿内部的最大剪切应变。外展的脚姿势可减少脚后跟的内部应变，跟骨横向位移会增加内部最大剪切应变。用不同的床垫-皮肤摩擦系数进行的参数研究表明，在所有使用的载荷条件下，低于0.4的系数都会降低最大内部剪切应变。

解释

在临床实践中，建议避免对患者的跟骨进行内部剪切，医学专家和护士可以考虑到，更外展的脚位置可以减少脚跟的拉伤。