Ultrastructure of active versus passive contracture of wounds

Myofibroblast populations in skin scar contracture due to wound contraction and in joint contracture due to passive position were compared in male New Zealand rabbits. Active contraction was produced by removal of full thickness back skin, with healing by contraction and epithelization. Joint contracture was produced by forced knee flexion for nine weeks by means of Steinman pin fixation. Electron microscopy revealed complete absence of myofibroblasts in the contracture due to position in contrast to prominent myofibroblasts in contracted skin scars. Contracture due to position is, thus, due to collagen remodeling alone, without an active contraction process. This suggests that the potential use of drugs for biochemical control of contracture will have to take into account how the contracture formed.