A histomorphometric study on the change of hypertrophic scar after steroid injection in rabbits

ABSTRACT

Hypertrophic scar, occurred from the skin injury or surgical operation causes esthetic, psychologic, and functional problems to both the patients and the surgeon. The drug of choice for the treatment of hypertrophic scar is steroid. The purpose of this study was to evaluate the effects of several kinds of steroid injection on the hypertrophic scar in the rabbit model. Adult male white rabbits, weighing about 2.5kg, were used. After three full-thickness wounding over the ventral surface of each ear, either saline (control group), or triamcinolone(0.8mg), dexamethasone(0.1mg) and prednisolone(0.8mg) was injected on day 16. The rabbits were sacrificed on 1, 2, 3, 4 and 8 weeks after injection, and the specimens were retrieved en bloc. Histologic and histomorphometric examinations of tissue samples were done. The results obtained were as follows In control group, cartilage proliferation and soft tissue hypertrophy were seen on 1 week and 2 weeks after saline injection. Collagen fibers were thickened in diameter, and arranged in irregular manner. After 3 weeks, cartilage proliferation was markedly decreased. Irregular collagen fibers and soft tissue thickening were also observed. After 4 and 8 weeks, soft tissues were consist of loose connective tissue, and still thickened. In experimental groups, collagen fiber thickness were arranged in somewhat irregular manner, and small amount of blood vessel proliferation were observed in 1, 2 and 3 weeks after injection. After 4 weeks, blood vessels and inflammatory cells were decreased, and collagen fibers were arranged in parallel manner. In 8 week-group, small amount of loose connective tissues were observed. After 2 weeks of injection, hypertrophic index of the experimental groups was significantly decreased than the control group. In the experimental group, dexamethasone seemed more potent than triamcinolone and prednisolone. These results suggest that hypertrophic scar was markedly decreased after steroid injection and triamcinolone, dexamethasone, and prednisolone are effective for treatment of hypertrophic scar.