Effects of foot posture and heel padding devices on soft tissue deformations under the heel in supine position in males: MRI studies

Heel ulcers (HUs) are the second most common pressure ulcers (PUs). Despite the significant morbidity and economic cost associated with HUs, there remains a lack of understanding of the basic pathophysiology of PUs because of limited basic research. There are only sparse data regarding the efficacy of prevention aids such as heel padding devices, and these data are based mainly on epidemiological research rather than biomechanical models and deformation measurements. This study was designed to explore the effects of foot posture and support stiffness properties on soft tissue deformations using magnetic resonance imaging (MRI). Subjects were scanned with and without weight bearing, in neutral external rotation position and in 90 degrees to supporting surface and with different heel padding devices. Tissue strains were calculated for skin, subcutaneous tissue, and effective (total) soft tissue. We found skin strains with the foot in external rotation to be significantly greater than when the foot was upright. Heel padding devices have a statistically significant effect on reducing the extent of deformations in both skin and subcutaneous tissues. Furthermore, the design features of heel padding devices have substantial influence on tissue deformations. This study demonstrates how MRI provides convenient, accurate, and quantitative comparison of biomechanical performances of heel padding devices.