Consideration of the formation and biological significance of hypertrophic scar.

An incision placed at right angles to the direction of skin cleavage lines is susceptible to the development of a haematoma within the sutured wound. Moreover, the edges of the sutured incision are not firmly fixed together by the material and the sutured incision is subjected to direct tension. For these 3 reasons an incision not conforming with the direction of skin cleavage lines may frequently allow stretching and postoperative hypertrophy of a scar. The biological function of a young hypertrophic scar may be an expansion-relaxation movement of the capsule of scar tissue like a bellows, at right angles to the direction of skin cleavage lines in near, though not quite, synchronism with the surrounding dermis. The biological function of a mature scar may be a movement of the scar tissue in exact synchronism with the dermis as activated by the combination of a bellows-like movement of the capsule of scar tissue in the direction at right angles to the skin cleavage lines and an expansion-relaxation movement of the main structure of the scar tissue in the direction parallel with the skin cleavage lines.