Functional analyses of the stratum corneum in scars - Sequential studies after injury and comparison among keloids, hypertrophic scars, and atrophic scars

Objective: To characterize the functional properties of the stratum corneum (SC) of various scars. Design: A prospective cohort study. Setting: University hospital medical center. Patients: Thirty-two consecutive patients surgically treated for various skin diseases and 26 consecutive patients with hypertrophic scars or keloids. Main Outcome Measures: Noninvasive bioengineering measurements of functional properties of the SC, such as transepidermal water loss (TEWL), high-frequency conductance, and SC turnover time. Results: The SC barrier function assessed by TEWL was found to be a better parameter for the functional evaluation of scars than the hydration state of the skin surface measured by high-frequency conductometry. In general, the SC on the scars of deeper wounds in the dermis took longer to normalize functionally than the SC on the scars of superficial wounds, especially on the thigh compared with the abdomen. Thus, elevated levels of TEWL observed on scars at the donor sites of split-thickness grafts normalized between 200 and 400 days in contrast to fewer than 50 days for those of subepidermal erosions. Both TEWL and high-frequency conductance remained high in hypertrophic scars and keloids, and the SC involved showed a faster turnover time than that of adjacent normal skin. Conclusions: Scars, a proliferative change of the dermis, can be objectively evaluated according to functional abnormalities of the SC, because the dermis has a close relationship with the epidermis and with the SC. The functional characteristics of the SC of fresh scars and those of hypertrophic scars and keloids resemble those of retinoid-treated skin, rather than those found in epidermal hyperproliferative conditions such as psoriasis and dermatitis.