Durometer measurements of skin induration in venous disease

Durometry for the Assessment of Severity of Post-thrombotic Syndrome and Possible Clinical Applications

BACKGROUND

Post-thrombotic syndrome (PTS) impacts the patient's quality of life. Available scales to determine its severity remain controversial, therefore, it is of importance to identify new auxiliary methods for the assessment of this sequelae. Measurement of skin hardness (MSH) might be decisive in tracking PTS. The purpose of this study is to assess if the use of durometry is an objective measure to evaluate prognosis of affected limbs in patients with PTS. We compared MSH of extremities with PTS vs healthy limbs, as well as their variation after 3 months of medical treatment to evaluate if durometry can be used to find differences. We strongly believe that measuring and keeping track of skin changes specifically skin hardness can be a useful factor in the prognosis and treatment of PTS.

METHODS

Prospective cohort study from January 2021 to February 2022 in patients with unilateral PTS. The MSH of the affected limb was compared to the healthy limb. A calibrated durometer was used, 4 measurements were completed at the time of diagnosis and subsequent follow-up were carried out after 3 months of treatment. The percentage of healing (in case of ulcers) and adherence to treatment was carefully monitored. The statistical program R was used.

RESULTS

A total of 1088 durometric measurements were performed on 17 patients, and 34 limbs. The MSH in limbs with PTS was 39.09 and in the control limbs (19.8) (P = <.00001). After 3 months of treatment, the MSH in PTS varied in PTS limbs (39.09 to 30.4) (P = <.000012). Adherence to treatment was 70.5%.

CONCLUSIONS

MSH varied between healthy limbs and the ones with PTS, before and after treatment. Durometry might represent a method for assessing skin changes in patients with PTS.

Use of a novel indentometer to evaluate skin stiffness in healthy and diseased human skin

BACKGROUND

Mechanical behavior of the skin can be evaluated by different non-invasive methods. In this study, we applied a new measurement device based on indentometry to determine the skin mechanical properties in healthy individuals and in patients with systemic sclerosis (SSc).

MATERIAL AND METHODS

Three studies were performed. Study 1 included 100 healthy individuals (46 male and 54 female) divided into four age groups with mean ages of 21.5, 28.9, 51.2, and 69.3 years, respectively. Test sites were located on the center of the forehead and the middle of both volar forearms. Study 2 included 16 healthy individuals (two males and 14 females). Test sites were on both volar forearms. Measurements were made before and after the application of Vaseline and emulsion with 12% urea. Study 3 included 20 patients (one male and 19 females) with SSc and 60 age-matched healthy individuals (23 males and 37 females). Test sites were on the center of the forehead and the middle of both volar forearms. Skin stiffness was measured with skin Indentometer IDM 800 (Courage + Khazaka, Cologne, Germany) equipped with two probes with pin diameters of 3 and 5 mm, respectively. The stiffer the skin, the less deep the displacement by the indenter. The smaller the diameter, the deeper the pin will go into the skin when using the same force. In addition, the Corneometer CM 820 (Courage + Khazaka) was used to determine epidermal water content in study 2.

RESULTS

Indentometric (IDM) values of healthy subjects measured with both probes were lower on the forehead compared to volar forearms. There was no significant difference between both forearms. In all age groups, the IDM values on the male forearms were lower than on the female forearms whereas there was no significant difference on the forehead. In both sex and on all test locations a significant positive correlation between age and IDM values measured with both probes was observed. There was a significant positive correlation between IDM values measured with both probes. The application of moisturizers induced significant changes in epidermal water content whereas the IDM values remained unchanged. At both the forehead and volar forearms, the IDM values in patients with SSc were significantly lower compared to the healthy control skin.

CONCLUSION

The non-invasive indentometric method used can successfully distinguish the changes in normal skin mechanical properties related to age, sex, and anatomical location, as well as in patients with SSc. The method is not appropriate to study the changes related to epidermal hydration.

Recent advances in microsystem approaches for mechanical characterization of soft biological tissues

Microsystem technologies for evaluating the mechanical properties of soft biological tissues offer various capabilities relevant to medical research and clinical diagnosis of pathophysiologic conditions. Recent progress includes (1) the development of tissue-compliant designs that provide minimally invasive interfaces to soft, dynamic biological surfaces and (2) improvements in options for assessments of elastic moduli at spatial scales from cellular resolution to macroscopic areas and across depths from superficial levels to deep geometries. This review summarizes a collection of these technologies, with an emphasis on operational principles, fabrication methods, device designs, integration schemes, and measurement features. The core content begins with a discussion of platforms ranging from penetrating filamentary probes and shape-conformal sheets to stretchable arrays of ultrasonic transducers. Subsequent sections examine different techniques based on planar microelectromechanical system (MEMS) approaches for biocompatible interfaces to targets that span scales from individual cells to organs. One highlighted example includes miniature electromechanical devices that allow depth profiling of soft tissue biomechanics across a wide range of thicknesses. The clinical utility of these technologies is in monitoring changes in tissue properties and in targeting/identifying diseased tissues with distinct variations in modulus. The results suggest future opportunities in engineered systems for biomechanical sensing, spanning a broad scope of applications with relevance to many aspects of health care and biology research.

Miniaturized electromechanical devices for the characterization of the biomechanics of deep tissue

Evaluating the biomechanics of soft tissues at depths well below their surface, and at high precision and in real time, would open up diagnostic opportunities. Here, we report the development and application of miniaturized electromagnetic devices, each integrating a vibratory actuator and a soft strain-sensing sheet, for dynamically measuring the Young's modulus of skin and of other soft tissues at depths of approximately 1-8 mm, depending on the particular design of the sensor. We experimentally and computationally established the operational principles of the devices and evaluated their performance with a range of synthetic and biological materials and with human skin in healthy volunteers. Arrays of devices can be used to spatially map elastic moduli and to profile the modulus depth-wise. As an example of practical medical utility, we show that the devices can be used to accurately locate lesions associated with psoriasis. Compact electronic devices for the rapid and precise mechanical characterization of living tissues could be used to monitor and diagnose a range of health disorders.

Scalp simulation - A novel approach to site-specific biomechanical modeling of the skin

OBJECTIVES

This study aimed to determine the hardness of the human scalp in vivo in order to identify an appropriate scalp simulant, from a range of commercially available silicone materials, for force impact assessment. Site-dependent variation in scalp hardness, and the applicability of contemporary skin simulants to the scalp were also considered.

MATERIALS AND METHODS

A Shore A-type durometer was used to collected hardness data from the scalps of 30 human participants (five males and five females in each of the three age categories: 18-30, 31-40, 41-50) and four commercially available silicones (light, medium, and heavy-bodied PVS, and duplication silicone). One-sample t-tests were used to compare the mean hardness of simulants to that of the scalp. Site-dependent variation in the hardness of the scalp was assessed using a mixed-model repeated measures ANOVA.

RESULTS

Mean human scalp hardness derived from participants was 20.6 Durometer Units (DU; SD = 3.4). Analysis revealed only the medium-bodied PVS to be an acceptable scalp simulant when compared to the mean hardness of the human scalp (p = 0.869). Scalp hardness varied significantly anteroposteriorly (with an observable linear trend, p < 0.001), but not mediolaterally (p = 0.271). Comparisons of simulants to site-specific variation in scalp hardness anteroposteriorly found the medium-bodied PVS to be only suitable in the central region of the scalp (p = 0.391). In contrast, the duplication silicone (p = 0.074) and light-bodied PVS (p = 0.147) were only comparable to the posterior region.

CONCLUSIONS

Contemporary skin simulants fail to accurately represent the scalp in terms of hardness. There is strong support for the use of medium-bodied PVS as a scalp simulant. Human scalp hardness varies significantly anteroposteriorly, but not mediolaterally, corresponding to regional anatomical variation within the scalp. A number of materials were identified as potential simulants for different regions of the scalp when more site-specific simulant research is required.

Use of durometry in assessment of venous disease

OBJECTIVES

Ulceration of the lower limbs is a common debilitating complication of chronic venous hypertension. Detection of preulcerative skin changes would allow for identification of high-risk patients; early active treatment may prevent ulcer formation.

METHODS

Patients with isolated venous disease and volunteers attending outpatient clinics underwent assessment of their clinical, aetiological, anatomical and pathological (CEAP) classification. We employed an industrial durometer, an instrument that measures the hardness of metals and plastic, to assess skin induration. The durometer probe was rested perpendicular on their skin 15 cm above the medial malleolus in non-ulcerated tissue, with the patient and limb in recumbency. The average of four measurements was derived.

RESULTS

In 107 people, 203 lower limbs (mean age 55.6 years) were assessed. A significant difference in durometry readings was demonstrated between patients with CEAP classes 0, 1 and 2, and those with classes 4, 5 and 6 (P < 0.0005). There was statistically significant evidence that age and CEAP classification correlated with durometry (P < 0.0001).

CONCLUSION

Durometry is of potential value in the assessment and monitoring of preulcerative venous disease, and could help to identify high-risk patients. This would assist in the institution of timely and appropriate treatment.