The formation of friction blisters on the foot: the development of a laboratory-based blister creation model

Age-related variations in stratum corneum hydration in the foot

OBJECTIVE

The aims of the study are to identify which region of the foot has lower hydration according to age, measure the variation in the level of stratum corneum hydration of the foot across the a wide age range, and examine hydration differences of the foot according to gender.

STUDY DESIGN

A descriptive observational study was conducted to assess stratum corneum hydration of the foot among 504 participants recruited between November 2023 and March 2024.

MAIN OUTCOMES MEASURES

Stratum corneum hydration assessment was conducted using a Corneometer 825® probe at 10 specific points on the foot. Data on sociodemographic variables, medical history, foot care habits, and hydration-related factors were collected. Statistical analyses were performed using SPSS v. 24.0.

RESULTS

Stratum corneum hydration of the foot varied significantly across regions, with higher hydration in the digital zone and lower hydration in the heel. An inverse correlation was found between age and hydration, with younger participants exhibiting higher hydration levels. Women showed higher hydration than men. Differences in hydration were observed between the right and left feet.

CONCLUSION

This study highlights the importance of localized assessment of foot skin dehydration. Aging significantly affects stratum corneum hydration of the foot. Gender differences in hydration suggest the importance of personalized approaches to skin care. Differential hydration between feet underscores the influence of mechanical load.

Influence of blistering lesions on foot functionality in hikers

BACKGROUND

Friction blisters are formed by abrasion from frictional forces on the upper layer of the epidermis and can make physical activity an uncomfortable experience. To our knowledge, no previous studies have considered how these injuries affect the functionality of the foot. For this reason, the main aim of this study was to evaluate foot function in hikers, with or without blisters.

MATERIAL AND METHODS

This case-control study examined 298 hikers who walked the Camino de Santiago long-distance trail (in northern Spain); 207 had one or more blistering foot lesions and 91 had no blisters. Sociodemographic and clinical variables were collected, and the number of blisters and their locations on the foot were recorded. All participants self-completed the Foot Function Index (FFI) questionnaire, in their native language.

RESULTS

Pain and disability were significantly greater among the hikers with blisters (pain p=<0.001; disability p = 0.015). However, there were no significant differences in the limitation of physical activity between those with blisters (case group) and the control group (p = 0.144). Neither was there any correlation between the number of blisters and pain, disability or limitation of activity. However, the location of the lesion did influence foot functionality. Blisters on the metatarsal heads were more limiting and caused greater pain (right foot p = 0.009; left foot p = 0.017), greater disability (right foot p = 0.005; left foot p = 0.005), greater limitation of activity (on right foot p = 0.012) and more loss of foot functionality (right foot p = 0.002; left foot p = 0.007).

CONCLUSION

The hikers with blisters experienced reduced foot functionality in terms of pain and disability. The number of blisters was not related to foot functionality. Blisters located on the metatarsal heads caused the greatest increase in pain, disability and limitation of activity.

Tribology of the sock-skin Interface – the influence of different fabric parameters on sock friction

Background

The purpose of this parametric design of experiments was to identify and summarize how the influence of knit structure (single jersey vs. terry), fiber composition (polyester vs. cotton), fiber linear density (30/1 Ne vs. 18/1 Ne & 1/150/34 vs. 2/150/34), and yarn type (filament vs. spun) affected the frictional profile across the sock-skin interface.

Methods

Friction testing trials were completed against both a polypropylene probe and a synthetic skin material (Lorica soft®) to determine if there was a difference in friction based on interface interaction. Friction testing was completed by sliding a probe across the inside bottom surface of the sock (the part that is usually in-contact with the bottom of the foot) while instantaneously measuring the frictional force every tenth of a second.

Results

For both trials (plastic probe and synthetic skin), in the dry condition, knit structure was found to be the most prominent fabric parameter affecting the frictional force experienced at the sock-skin interface. It was also determined that fiber linear density, and yarn type are tertiary factors affecting the frictional force measured at the sock-skin interface. Finally, in the dry state, it was determined that fiber composition had seemingly no effect on the frictional force experienced at the sock-skin interface.

Conclusion

This parametric design of experiments has further enhanced the understanding of the tribology at the sock-skin interface. Through strategic design, four different textile parameters have been investigated, measured, and justified as to how each influence the friction measured between the two interfaces. This knowledge can be used to develop socks that mitigate the risk of friction blisters formation.

Our contemporary understanding of the aetiology of pressure ulcers/pressure injuries

In 2019, the third and updated edition of the Clinical Practice Guideline (CPG) on Prevention and Treatment of Pressure Ulcers/Injuries has been published. In addition to this most up‐to‐date evidence‐based guidance for clinicians, related topics such as pressure ulcers (PUs)/pressure injuries (PIs) aetiology, classification, and future research needs were considered by the teams of experts. To elaborate on these topics, this is the third paper of a series of the CPG articles, which summarises the latest understanding of the aetiology of PUs/PIs with a special focus on the effects of soft tissue deformation. Sustained deformations of soft tissues cause initial cell death and tissue damage that ultimately may result in the formation of PUs/PIs. High tissue deformations result in cell damage on a microscopic level within just a few minutes, although it may take hours of sustained loading for the damage to become clinically visible. Superficial skin damage seems to be primarily caused by excessive shear strain/stress exposures, deeper PUs/PIs predominantly result from high pressures in combination with shear at the surface over bony prominences, or under stiff medical devices. Therefore, primary PU/PI prevention should aim for minimising deformations by either reducing the peak strain/stress values in tissues or decreasing the exposure time.

The Variation of Plantar Temperature and Plantar Pressure during Shod Running with Socks or not

Foot temperature can be affected by friction and contact pressure, in this study, we explored the specific changes of foot temperature under different friction conditions, running with socks versus no socks. The relationship between vertical loading force and foot temperature will also be investigated at the same time. Ten male recreational runners wore the same shoes and socks and were tested running 8km/h on a treadmill. The plantar temperature during running was recorded every 3 minutes for a total of 45 minutes. Post-run temperature change was recorded every 3 minutes for 12 minutes. The plantar pressure was recorded before running and at the first 15 minutes during running. The subjects with socks and no socks were tested on separate occasions. There were no significant differences found between the socks and no socks conditions. However, central metatarsal head, lateral metatarsal head, medial rearfoot and lateral rearfoot regions exist differences were reflected at the first 6minutes-12minutes of running. The foot temperature became more stable after 15minutes of running. Also, plantar pressure increased significantly in the hallux, other toes, first metatarsal head and central metatarsal regions. It also could conclude that lower initial temperature had a greater increase trend during the running start stage. When the ankle in plantarflexion stage, toe and forefoot regions showed a higher rise in temperature and also presented higher plantar pressure correspondingly.

Plantar Pressure and Foot Temperature Responses to Acute Barefoot and Shod Running

Purpose. Increased contact pressure and skin friction may lead to higher skin temperature. Here, we hypothesized a relationship between plantar pressure and foot temperature. To elicit different conditions of stress to the foot, participants performed running trials of barefoot and shod running. Methods. Eighteen male recreational runners ran shod and barefoot at a self-selected speed for 15 min over different days. Before and immediately after running, plantar pressure during standing (via a pressure mapping system) and skin temperature (using thermography) were recorded. Results. No significant changes were found in plantar pressure after barefoot or shod conditions (p > 0.9). Shod running elicited higher temperatures in the forefoot (by 0.5-2.2°C or 0.1-1.2% compared with the whole foot, p < 0.01) and midfoot (by 0.9-2.4°C, p < 0.01). Barefoot running resulted in higher temperature variation in the rearfoot (0.1-10.4%, p = 0.04). Correlations between skin temperature and plantar pressure were not significant (r < 0.5 and r > -0.5, p > 0.05). Conclusions. The increase in temperature after the shod condition was most likely the result of footwear insulation. However, variation of the temperature in the rearfoot was higher after barefoot running, possible due to a higher contact load. Changes in temperature could not predict changes in plantar pressure and vice-versa.