Skin tension or skin compression? Small circular wounds are likely to shrink, not gape

The final appearance of a scar may be influenced by tension or mechanical factors [Borges AF. Scar prognosis of wounds. Br J Plast Surg 1960;13:47-54; Arem AJ, Madden JW. Effects of stress on healing wounds. J Surg Res 1976;20:93-102; Burgess LP, Morin GV, Rand M, et al. Wound healing. Relationship of wound closing tension to scar width in rats. Arch Otolaryngol Head Neck Surg 1990;116:798-802; Meyer M, McGrouther DA. A study relating wound tension to scar morphology in the pre-sternal scar using Langer's technique. Br J Plast Surg 1991;44:291-4] Karl Langer suggested that information could be gained about the tension inherent in skin, in all directions, by observing the wound edge retraction that occurred after making circular skin incisions [Langer K. On the anatomy and physiology of the skin II. Skin tension. Br J Plast Surg 1978;31:93-106]. Circular wounds may be used to demonstrate the orientation of the dominant axis of 'tension' in the skin but is this always a tensile stress as opposed to a compressive stress? This is the second article in a series documenting the mechanical properties of circular punch biopsy wounds. The aim of this study was to make detailed observations of the dimensional distortions of circular wounds on the face and neck, from which deductions could be made with regard to mechanical stress. One hundred and seventy-five benign head and neck lesions were excised from 72 volunteers using circular dermal punch biopsies. The distortions of the resulting wounds were observed to be elliptical in most cases. Measurements were taken of the maximum and minimum diameters of the wound and expressed as ratios of the size of the punch biopsy used for excision. The change in area from the area of the punch biopsy to that of the wound was also calculated. The maximum diameter of the wound was smaller than the diameter of the punch biopsy in 40.6% of cases, the minimum diameter of the wound was smaller in 97.7% of cases and the area of the wound was smaller than that of the punch biopsy in 90.3%. These dimensional changes varied between sites (P=0.0005, P=0.0001 and P<0.0001, respectively). We conclude that the reported rhomboidal or lattice structure [Ridge MD, Wright V. The directional effects of skin. A bioengineering study of skin with particular reference to Langer's Lines. J Invest Dermatol 1966;46:341-6] of skin has individual components which are under tensional force due to elastic retraction. Wounds smaller than the rhomboidal unit will reduce in area, due to the intact tensional forces in the individual dermal components, giving an appearance of the skin overall being under compression. Larger wounds, disrupting more of the lattice structure, will gape.