Biophysical skin properties of grade 1 pressure ulcers and unaffected skin in spinal cord injured and able-bodied persons in the unloaded sacral region.

AIM OF THE STUDY: To examine biophysical skin properties in the sacral region in spinal cord injury (SCI) patients suffering from a grade 1 pressure ulcer (PU) defined as non-blanchable erythema (SCI/PU), SCI patients in the post-acute phase (SCI/PA) and able-bodied participants (CON). Also, for SCI/PU patients, both the affected skin and healthy skin close to the PU were examined. STUDY DESIGN: An experimental controlled study with a convenience sample. SETTING: A Swiss acute care and rehabilitation clinic specializing in SCIs. MATERIALS AND METHODS: We determined hydration, redness, elasticity and perfusion of the unloaded skin in the sacral region of 6 SCI/PU patients (affected and healthy skin), 20 SCI/PA patients and 10 able-bodied controls. These measures were made by two trained examiners after the patients were lying in the supine position. RESULTS: The affected skin of SCI/PU patients showed elevated redness: median 595.5 arbitrary units (AU) (quartiles 440.4; 631.6) and perfusion: 263.0 AU (104.1; 659.4), both significantly increased compared to the healthy skin in SCI/PA patients and CON (p < 0.001). Similarly, healthy skin of SCI/PA patients showed elevated redness (p = 0.016) and perfusion (p < 0.001) compared to CON. On the other hand, differences in redness and perfusion between the affected and unaffected skin in SCI/PU patients were not significant. The results for skin hydration and skin elasticity were similar in all groups. CONCLUSIONS: Skin perfusion and redness were significantly increased in grade 1 PUs and for healthy skin in both SCI/PA patients and CON participants; thus, these are important in understanding the pathophysiology of PUs and skin in SCI.

Challenges to measure hydration, redness, elasticity and perfusion in the unloaded sacral region of healthy persons after supine position.

AIM OF THE STUDY: To combine measurement methods of biophysical skin properties in a clinical setting and to measure baseline values in the unloaded sacral region of healthy persons after lying 30 min in supine position. METHODS: Hydration (Corneometer® CM 825), redness (Mexameter® MX 18), elasticity (Cutometer® MPA 580) and perfusion (PeriFlux System 5000) of the skin in the sacral region of 10 healthy participants (median age: 26.9 years) were measured consecutively in the laying position by two trained examiners. RESULTS: The assessment duration for all four parameters lasted about 15 min. Intra-class correlation coefficients were overall moderate to strong (hydration r = 0.594, redness r = 0.817, elasticity r = 0.719, perfusion r = 0.591). Hydration (median 27.7 arbitrary units (AU)) mainly indicated dry skin conditions. Redness (median 158.5 AU) was low. Elasticity (median 0.880 AU) showed similar values as in the neck region. Perfusion (median 17.1 AU) showed values in the range of results reported in the literature. CONCLUSION: Biophysical skin properties in the sacral region after supine position can be measured within periods of 15 min. The results provide baseline data for the skin of healthy persons as well as insights into skin-physiological variations. But it remains challenging to optimize measurement procedures and test protocols when transferring preclinical tests in a clinical application.

Development of a new design of hip protectors using finite element analysis and mechanical tests.

The rate of hip fractures due to falls increases with age. External hip protectors placed over the greater trochanter can prevent hip fractures, but the willingness to wear such protective devices is rather low. Most of the commercially available hip protectors consist either of an energy-absorbing foam pad or of a hard shell that distributes the load to the surrounding tissue. In the present study, a fibre-reinforced shell composed of three curved strips bonded with a ring, was designed and lined with shock absorbing foam. The development of the new shell design was based on quasi-static and impact tests of manufactured shells in combination with finite element simulations. The results of the numerical analysis showed the potential protection effect of the shell and indicated how the design can be further improved. First impact tests on an anatomical hip model showed promising results of the new protector shell in combination with a foam pad.

In vivo confirmation of hydration-induced changes in human-skin thickness, roughness and interaction with the environment.

The skin properties, structure, and performance can be influenced by many internal and external factors, such as age, gender, lifestyle, skin diseases, and a hydration level that can vary in relation to the environment. The aim of this work was to demonstrate the multifaceted influence of water on human skin through a combination of in vivo confocal Raman spectroscopy and images of volar-forearm skin captured with the laser scanning confocal microscopy. By means of this pilot study, the authors have both qualitatively and quantitatively studied the influence of changing the depth-dependent hydration level of the stratum corneum (SC) on the real contact area, surface roughness, and the dimensions of the primary lines and presented a new method for characterizing the contact area for different states of the skin. The hydration level of the skin and the thickness of the SC increased significantly due to uptake of moisture derived from liquid water or, to a much lesser extent, from humidity present in the environment. Hydrated skin was smoother and exhibited higher real contact area values. The highest rates of water uptake were observed for the upper few micrometers of skin and for short exposure times.

Anatomical hip model for the mechanical testing of hip protectors.

An anatomical hip model has been developed to simulate the impact load on the hip of a falling person wearing a hip protector. The hip consists of an artificial pelvis made of aluminium, linked by a ball-and-socket joint to an anatomically shaped steel femur (thigh bone). The femur is embedded in silicone material with a hip-shaped surface to allow realistic positioning of the protectors with accessory underwear. Additionally, the silicone simulates the damping and load-dispersal effect of soft tissue. A triaxial load sensor is integrated in the neck of the femur to measure the axial and cross-sectional force components in response to external impact forces on the hip. The performance of the hip model was investigated in drop tests and validated against biomechanical data. In a first series of measurements, the shock absorption of 10 different hip protectors, including both energy-absorbing and energy-shunting systems, was analysed. To determine the importance of hip protector placement, each protector was tested in the correct anatomical alignment over the hip and anteriorly displaced by 3 cm. Considerable differences were found between individual hip protectors in their effectiveness to reduce impact forces on the femur. Position of the hip protector also influenced the forces applied to the femur.