Answer:
Chronic venous ulcers are caused by venous insufficiency due to valvular
dysfunction that can be primary or secondary to thrombosis. The consequence
of incompetent perforating veins is exposure of the superficial system
to the high pressures of calf muscular contraction and also gravitational
reflux. This leads to filtration edema, capillary dilation, leakage of
plasma, and red cell. One other effect thought to be important in ulceration
is leukocyte trapping. The activated leukocytes then release oxygen free
radicals and other toxic products such as elastase, tumor necrosis factor,
and collagenase which injure the surrounding tissue. Conservative treatment
involves compression with graded elastic stockings or unna boot. The benefit
is from relief from edema rather than any effect of venous hemodynamics.
The perforating veins can be interrupted to treat the venous insufficiency.
With the advent of endoscopic techniques this has become less morbid a
procedure. Success in covering venous ulcers can be achieved with skin
grafting. When excision of the ulcer bed results in a large soft tissue
defect a free flap may be desirable. Finally in order to prevent recurrences
the patient must be instructed in skin care, avoidance of prolonged standing,
and the permanent use of compression stockings.