HYPERTROPHIC SCAR - AN INTERRUPTION IN THE REMODELING OF REPAIR - A LASER DOPPLER BLOOD-FLOW STUDY

Soft-tissue dermal loss does not regenerate; instead, it is replaced with scar. The extent of scarring is directly related to the severity of tissue loss (in terms of volume and depth). Commonly, an acute dermal loss will heal with excessive scar, hyertrophic scar. A hypertrophic scar is elevated but is contained within the boundaries of the initial injury. Hypertrophic scars have a reddish appearance, indicating an elevated local circulation. A laser Doppler blood flow monitor was employed to measure blood flow changes in healed wounds. It was speculated that local circulation in a developing hypertrophic scar would be elevated. Patients with recently healed wound sites were monitored and exhibited an average blood flow reading of 365 +/- 325 mV (n = 131). This average value, ranging from 98 to 1450 mV, was 18 times greater than the average reading from normal skin, which was 43 +/- 13 mV (n = 212). Blood flow declined to 32 +/- 21 mV (n = 7) at 16 to 18 weeks (74 percent of normal skin values) in healed wounds that developed normal scar. However, a closed wound that developed into a hypertrophic scar had a blood flow reading of 148 +/- 78 mV (n = 59) at 16 to 18 weeks. This value was three times greater than in normal skin and four times greater than in normal scar. At 38 to 50 weeks postinjury, hypertrophic scar remained elevated (102 +/- 34 mV; n = 10). Hypertrophic scars sustain an elevated blood flow. Blood flow patterns recorded from debrided burns, grafts, or donor sites that advanced into hypertrophic scar supported the concept that hypertrophic scar occurs as a consequence of an interruption in the remodeling phase of repair. Blood flow declined in these patients between 7 and 13 week postinjury, indicating the onset of the remodeling phase of repair. However, at 9 to 15 weeks, blood flow began to rise again. The blood flow patterns of hypertrophic scar show an early reduction in blood flow followed by a secondary rise that is sustained for more than a year in some scars.