A New Skin Tensiometer Device: Computational Analyses To Understand Biodynamic Excisional Skin Tension Lines

Abstract

One of the problems in planning cutaneous surgery is that human skin is anisotropic, or directionally dependent. Indeed, skin tension varies between individuals and at different body sites. Many a surgeon has tried to design different devices to measure skin tension to help plan excisional surgery, or to understand wound healing. However, many of the devices have been beset with problems due to many confounding variables - differences in technical ability, material (sutures) used and variability between different users. We describe the development of a new skin tensiometer that overcomes many historical technical issues. A new skin tension measuring device is presented here. It was designed to be less user-dependent, more reliable and usable on different bodily sites. The design and computational optimizations are discussed. Our skin tensiometer has helped understand the differences between incisional and excisional skin lines. Langer, who pioneered the concept of skin tension lines, created incisional lines that differ from lines caused by forces that need to be overcome when large wounds are closed surgically (excisional tension). The use of this innovative device has led to understanding of skin biomechanics and best excisional skin tension (BEST) lines.

Are Incisional and Excisional Skin Tension Lines Biomechanically Different? Understanding the Interplay between Elastin and Collagen during Surgical Procedures

“…The images demonstrating a typical finding (Fig.1) show that for incisional lines (low tension wounds) elastin stretches and collagen buckles, and for excisional wounds (after removal of skin lesions) it is predominantly collagen at play with very little elastin involvement. This not only confirms our contention regarding biodynamic excisional skin tension (BEST) lines (20) that we must view skin lines differently for incisions and excisions, but we see this as the starting point for more research into wound, scar and skin dynamics after excisional surgery. This is why this study set out to look at the roles of elastin and collagen in surgical wounds when closing incisions (inherently low-load) or excisions (higher-loads due to larger defects).…”

“…(20) Human skin, when viewed as a mere physical membrane ends up with skin lines and wrinkles because a keratinocyte-stiffened epidermis drapes a softer and thicker dermis. Of course, anatomical sites like knees and elbows have wrinkles that can be considered 'tension' wrinkles (two-dimensional, due to geometry, pretension and joint action) and in other areas like the forehead, muscle action causes 'compression' wrinkles (one-dimensional due to muscle action only), but in our view, BEST lines for surgical excisions may not be along these lines.…”

The Epistemology of Wrinkles: From Geology and Anatomy to Physiology

“…when skin is excised and tension created, as is done after skin cancer surgery, different dynamics apply and wrinkle lines no longer have the least wound tension. [7] More recently, it has come to light that wrinkles can be caused due to aging and oxidative stress -and indeed increased wrinkling may be a sign of impending heart disease, metabolic disorders, osteoporosis or degenerative disorders. [8] And, while photo-damage from sunlight is one of the most common causes in Caucasian skin, recent studies have shown that UV light also damages lymphatic channels.…”

The Golden Spiral Flap: A New Flap Design that Allows for Closure of Larger Wounds under Reduced Tension – How Studying Nature’s Own Design Led to the Development of a New Surgical Technique?

“…While understanding that the tensile strength of a wound is important for wound closure (3), there has been poor scientific correlation between cutaneous wrinkle lines and wound tension. A team led by this author has used computational analyses to understand biodynamic excisional skin tension (BEST) lines, i.e., the best lines of wound closure, after tissue has been removed by excision of skin lesions (4). The study began on skin of the scalp for two reasons – it is relatively untethered to underlying tissues, and scalp whorls that appear to confirm to nature’s golden spiral pattern are unique to human beings – and were thought to occur due to the rapid expansion of the brain during intrauterine life.…”