It has been suggested that approximately 90% of the estimated 600,000 leg ulcers seen annually in the United States are due to chronic venous disease or mixed arteriovenous insufficiency.1 In addition, 5% to 8% of the world's population is affected by venous disease, making this a costly problem from both an economic and quality-of-life perspective.2,3,4 As individuals age, ulcer prevalence appears to increase exponentially.5 Anderson and associates noted that leg ulcers develop in 1% of the population over 70 years old; this incidence rises to 5% by age 90.6 In patients over age 65, 82% of the leg ulcers seen were secondary to venous insufficiency. These findings correlate well with earlier reports that indicated an 80% to 90% predominance of venous ulceration.7
This chapter presents information about the pathogenesis and management of wounds resulting from venous insufficiency. Because of the complimentary role the lymphatic system plays in venous system function, some aspects of lymphatic system physiology will be included. For a more detailed discussion of lymphatic disease and treatment, however, the reader is referred to Chapter 18.
Overview of Anatomy and Physiology of the Phlebolymphatic System
Blood vessels are composed of five major elements: endothelial cells, basement membranes, elastic tissue, smooth muscle, and collagen. Endothelial cells line all blood vessels and lymphatics.8 Because of their location between the fluid components of blood or lymph and the tissue, endothelial cells are responsible for maintaining vascular homeostasis.9 Integrity of the endothelial lining is essential for normal blood flow. Damage to the lining results in blood cells sticking at the point of injury, subsequently forming a clot.
While veins, like arteries, have intimal, medial, and adventitial layers, the proportions of tissue in each layer vary. Overall, venous walls are much thinner. The smooth muscle and elastic proportions of venous walls are less developed in comparison to arterial walls. The venous adventitia is proportionally thicker.10 Venous walls are much more distensible than arterial walls, however, allowing veins to better accommodate variations in blood volume and serve as a reservoir. In fact, more than 60% of the body's blood volume is contained in veins and venules.11 Unlike arteries, veins contain valves that allow regulating the direction of blood flow toward the heart.
In the leg, perforating veins penetrate the fascia, providing the connection between the deep and superficial veins. Valves direct the flow of blood from superficial to deep veins in the legs. Venous sinusoids within the calf musculature connect to form intramusuclar plexi, which join the peroneal veins. In contrast, the valves in veins of the foot direct blood from deep to superficial veins, thus explaining how the saphenous veins are filled without direct contact with the capillary beds.12
In the legs, because of the valves, blood flow is assisted by contractions ...