The effects of Z plasty on hypertrophic scars.

Hypertrophic scar tissue has been observed to soften and thin following Z plasty without removal of any of the scar tissue. Histochemical studies of tissue before and after Z plasty showed that abnormally sulfated mucopolysaccharides were replaced by normal acid mucopolysaccahrides within 14 days. Collagen in hypertrophic scar appeared in nodules and fibers perpendicular to the surface of the skin rather than as long straight fibers parallel to the skin surface as normally seen. Elastic fibers were reduced and scar was relatively avascular. Following Z plasty the amount of collagen decreased and fibers were oriented in bundles at right angles to each other, parallel to the surface. When tissue was examined by electron microscopy collagen fibers showed marked variation in diameter. Microfibrils were increased and there were aggregates of fibrils with periodicity of 1500 to 1600 A. Following Z plasty, areas which previously contained only microfibrils now had unit collagen fibers with normal periodicity. Urinary excretions of hydroxyproline and hydroxylysine, amino acids found only in collagen, were increased following Z plasty, coinciding with the softening of the scar. Excretion of the disaccharide, glucosylgalactosylhydroxylysine, predominantly found in skin, increased following Z plasty, while excretion of the monosaccharide, galactosyl-hydroxylysine, predominant in bone collagen, remained constant. Amino acid composition of collagen, remained constant. Amino acid composition of collagen isolated from hypertrophic scars was similar to that present in skin and tendon, and unlike that in cartilage or infant dermis. Hydroxyproline content was slightly decreased and hydroxylysine content slightly increased compared to skin or tendon. Histochemical, ultrastructural and biochemical studies of the same specimens suggested that collagen with disordered fibril formation was present in the hypertrophic scar and was degraded following Z plasty. Changes in the molecule which occurred after synthesis of the protein core might be responsible both for the failure of normal maturation of the scar and for its sensitivity to degradative enzymes following Z plasty.