Assessment of the Biomechanical Effects of Prophylactic Sacral Dressings on Tissue Loads: A Computational Modeling Analysis

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.