Computer Modeling Studies to Assess Whether a Prophylactic Dressing Reduces the Risk for Deep Tissue Injury in the Heels of Supine Patients with Diabetes.

Heels are susceptible to pressure ulcer (PU) development. Some evidence suggests dressings may provide mechanical cushioning, reduce friction with support, and lower localized internal tissue loading, which together may minimize the risk for heel ulcers (HUs). To examine the effect of dressing application on pressure ulcer prevention, 20 computer simulations were performed. Volumetric exposure of soft tissues to effective and shear strains and stresses, with and without a multilayered foam dressing, were assessed, with the extent of tissue exposure considered as measures of the theoretical risk for PUs. The simulations, conducted using the finite element method, provided the mechanical strain and stress magnitudes and distributions in the weight-bearing tissues of the heel, which were visualized and analyzed post-hoc for comparing diabetic to healthy tissue loads with/without prophylactic dressings and at different foot (plantar flexion) postures. The volumetric exposure of the soft tissues of the heel to elevated strains and stresses was considerably reduced by the presence of the dressing, whether diabetic or nondiabetic tissue conditions existed, and for the entire range of the simulated plantar flexion positions. Further, greater plantar flexion, which occurs with elevation of the head of the bed, reduced the volumetric exposure of subcutaneous fat to increased effective strains and stresses, again, particularly when the dressing was on. Specifically, peak (maximum of raw data) effective strains in the soft tissues of the heel decreased by 14.8% and 13.5% with the use of the dressing for healthy persons and persons with diabetes, respectively. Additionally, volumetric exposures of the soft tissues to large effective strains, defined as exposures to >50% strain, decreased substantially, by at least a factor of 2, with the angle of plantar flexion and with respect to a neutral foot posture. Volumetric exposures to midrange (less than 50%) strains were more mildly affected by the foot posture (ie, less than 10% difference was noted across plantar flexion angles). The differences in tissue exposures to strains and stresses between the dressing and nondressing models suggest this dressing provides an important biomechanical protective effect, specifically when diabetic tissue conditions exist. In addition, the data suggest alleviating shear by repositioning the heels after elevating the head of the bed may be critical in order to limit the increase in tissue stress and subsequent PU risk. Randomized, controlled clinical studies to examine the efficacy of dressings for the prevention of heel PUs are warranted.