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[Pressure therapy of hypertrophic scar after burns and related research].

OBJECTIVE
To investigate the mechanisms of pressure intervention, and to explore the most effective regime for pressure therapy.


METHODS
Several trials were carried out to study the efficacy and mechanism of pressure therapy, and the development and application efficacy of a smart pressure monitored suit (SPMS) for scar management. (1) Effectiveness of pressure therapy. Forty-five patients suffered burn on extremities were divided into pressure treatment group (n = 36) and control group (n = 9) according to the random number table. Patients in pressure treatment group were prescribed with a regime of wearing custom pressure garment (10% strain rate of pressure + 9 mm thick local pressure padding) more than 23 hours per day, while no active intervention was conducted on patients in control group. Scar conditions were assessed using the Vancouver Scar Scale (VSS), spectrocolorimeter, and tissue palpation ultrasound system. Data were processed with t test or paired t test. (2) Changes in fibroblasts growth rate under pressure. Fibroblasts extracted from scar tissue excised during surgery were loaded with 0, 1.1, 2.8, 5.6 mm Hg (1 mm Hg = 0.133 kPa) pressure respectively to observe the growth rate of fibroblasts. Data were processed with Fisher LSD post-hoc analysis. (3) Scar thickness upon pressure. The changes in scar thickness upon 0, 5, 15, 25, 35 mm Hg pressure were measured at early stage (1 - 6 months), mid-stage (7 - 12 months), and late stage (more than 12 months) using the high frequency ultrasound imaging system. Data were processed with correlation analysis and regression analysis. (4) Study on application of SPMS. Thirty-six patients with hypertrophic scars once treated with the conventional garment were recruited and they were prescribed with the regime of wearing SPMS for one month. Feedback from all participants in rating conventional garment and SPMS was obtained using self-reported questionnaire. The interface pressure of pressure garment was measured using the Pliance X system. Data were processed with Wilcoxon Sign-Ranks test.


RESULTS
(1) Scar thickness, color, and VSS score were significantly improved in pressure treatment group after two-month of pressure intervention. VSS score of the scars in pressure treatment group was lower than that in control group two months after treatment. (2) The growth rate of scar fibroblasts under 5.6 mm Hg pressure was obviously lower than that under 0 mm Hg pressure 2 days after pressure loading (mean deviation = 0.086, P = 0.001). Growth rates of fibroblasts under 2.8 and 5.6 mm Hg pressure were obviously lower than that under 0 mm Hg pressure 3 days after pressure loading (with mean deviation respectively 0.060 and 0.118, P = 0.003, P < 0.001). (3) Scar thickness was significantly reduced upon pressure, and a negative relationship between scar thickness and pressure level was observed (r = -0.96, P < 0.01). (4) The results of SPMS study showed a reduction in both static pressure (19.5%) and dynamic pressure (11.9%) after one month of usage; while there was nearly 50.0% reduction in pressure in conventional garment. SPMS was rated significantly higher than conventional garment in terms of comfort, permeability and clinical efficacy (P ≤ 0.001).


CONCLUSIONS
Pressure therapy can effectively inhibit the growth of hypertrophic scar, while its exact mechanism needs further study for verification. SPMS is convenient to apply for patients. It takes less time to fabricate and adjust when compared to the conventional garment. Its clinical effect is positive and it may expand its application to other medical conditions.