Skin Hardness Measurement in Hypertrophic Scars

Introduction Hypertrophic scars and keloids represent the abnormal result of cutaneous tissue repair after an acute injury and are characterized by an excessive synthesis of collagen due to the increased activity of different types of fibroblasts. Hypertrophic scars develop within the boundary of the original wound and may spontaneously regress over time, while keloids extend beyond the wound boundary and tend to remain elevated. Other differences between keloids and hypertrophic scars include histologic morphology, cellular response to growth factors, and scar appearance. These cutaneous fibrotic conditions can be caused by minor insults to the skin, such as ear piercing, abrasions, or tattooing, or by major trauma, such as severe burns.[1] Despite the defect, symptoms, and psychological impact of these abnormal wound responses, the literature offers little consensus about appropriate therapy. It has been difficult to assess the efficacy of the existing treatment modalities, because they have been limited to numbers of controlled, comparative studies on the effectiveness of various treatment methods in improving the appearance or symptoms of such scars.[2] The main objectives in managing keloids and hypertrophic scars include restoration of the functional utility of the affected anatomic site, relief of symptoms, and prevention of recurrence. In terms of keloids and hypertrophic formation, the most important point is prevention. The best therapeutic choices appear to be surgery[3] plus adjuvants, such as intralesional steroids,[4] silicone gel sheeting,[5,6] pressure,[7] radiotherapy,[8] collagen, and mucopolysaccharides creams.[9] In the present study, the authors considered that objective quantification of skin hardness through noninvasive techniques is an essential way to control hypertrophic scarring and the efficacy of related treatments. Several methods, including transcutaneous oxygen tension measurement,[10] ultrasonography,[11] tonometry,[12] and laser Doppler[13] evaluation, have been used for appropriate assessment of physical parameters in burn scars. In this preliminary study, the authors used a durometer, a new hand-held engineering instrument that is the international standard for measuring the hardness of plastic, rubber, and other nonmetallic material, to assess skin hardness of hypertrophic scars derived from burn wounds, to compare the numeric data with a clinical scoring, and to monitor scar maturation during treatment over time. Methods Patients entering the study were recruited from those undergoing post-burn follow up at the Burn Unit of the Department of Dermatology, University of Pisa, Italy, and who had clinical evidence of hypertrophic scars of less than one month duration. Fifty-eight patients (aged 18–64 years, mean age 54.5) participated in this study, and a total of 72 anatomic sites of hypertrophic scarring were scored by a blinded observer using the following clinical skin hardness severity score: 0 = normal, 1 = mild, 2 = moderate, 3 = severe. This scoring system is based on one widely used for assessing skin hardness in patients with systemic sclerosis.[14] Skin sites where clinical scoring was done were circled with a skin marker in order to ensure that clinical and instrumental evaluation used the same sites during the study. Sites with hypertrophic scarring over bony prominences were avoided. Patients were instructed to wear customized pressure garments 24 hours a day and to report any significant side effects that occurred during treatment. Clinical scoring and durometer readings were taken monthly for six months. All patients were informed about the aims and methodology of the study, and informed consent was elicited before any evaluation was performed. The study had previously obtained the approval of the local ethics committee. Skin Hardness Evaluation We used a Rex Durometer Max Hand model 1700, type 0, without a foot attachment (Rex Gauge Company Inc., Glenview, Illinois). This instrument is the international standard for measuring the hardness of plastic, rubber, and other nonmetallic material. Model 0, as used in this study (Figure 1), is for soft materials, such as animal tissue, in which the amount of creep is minimal. The durometer is provided with a calibrated gauge that registers linearly the relative degree of hardness. This feature is the result of a spring-loaded interior that senses hardness by application of an indentation load on the specimen. At the bottom of the durometer, there is a small, dull, inferior indenter that is retractable and is responsible for the measurements registered on the gauge. For measurements, the durometer was used at 25°C room temperature and rested by gravity against the skin (Figure 1); four consecutive readings were taken at the same site. Between readings the durometer was reset to 0. The investigator performing the durometer measurements was not aware of the skin severity score assigned to each patient. Control measurements were made on 36 normal subjects matched for age, sex, and anatomic site. Statistical Analysis The mean of quadruplicate determinations for each patient and control was used for analysis. The nonparametric ANOVA test was used to compare between patients and controls and between patients with different skin severity scores. Statistical significance was considered to be a p value less than 0.05. Results At baseline, the durometer readings for hypertrophic scars and control subjects contrasted with their skin severity scores as shown on Figure 2. Values of increased skin severity score were associated with higher durometer readings (p