Morphological analysis of the connective tissue reaction in linear hypertrophic scars treated with intralesional steroid or silicone-gel sheeting. A light and electron microscopic study.

The linear hypertrophic scar has become the most common type of pathologic scarring. Silicone-gel sheeting is the first line therapy while intralesional steroid is the second. A light and electron microscopic analysis was carried out to reveal differences in tissue reaction following the two different treatments. Two groups of 12 patients each were treated for 4 months. For the first group, diluted Triamcinolone acetonide was injected until an inactive state was achieved. The other group of patients was treated with silicone-gel sheeting. The scars were examined every two weeks and their appearance documented. After reaching the expected therapeutic response, inactive scars were removed. The excised scars were evaluated through light microscopic histopathology and electron microscopy. The light and electron microscopic observations revealed marked differences following treatments. The activity of fibroblasts and the numbers of collagen fibers forming bundles decreased and the orientation of the collagen fibers was more variable in the treated scars. The amount of elastic fibers increased after both steroid and silicone-gel sheeting treatment. Vascularization was also slightly changed, with more capillaries and fewer pre-capillary arteries detected in the treated scars. Both treatments resulted in the same decrease in score but steroid treatment was more rapid in onset. We suggest that the two different treatments work through different mechanisms, although the final functional outcome is similar.