Valvular density alone cannot account for sites of chronic venous insufficiency and ulceration in the lower extremity.

摘要

OBJECTIVE: Class 6 chronic venous stasis is associated with abnormal venous hemodynamics and ulceration. Ulcers primarily occur over bones and tendon prominences but very rarely over muscular compartments. We hypothesized that the anatomical distribution of venous stasis ulcers in the lower extremity is related to a lower density of venous valves. METHODS: The venous vasculature of six normal human legs was cast with resin, and their microvenous valvular anatomy was examined. Skin samples were obtained from the skin overlying the 1) Achilles' tendon, 2) anterior tibia, 3) medial malleolus, 4) lateral malleolus, 5) dorsal surface of the foot, 6) planta pedis, 7) dorsal aspect of the great toe; and from the skin regions overlying the 8) gastrocnemius, 9) tibialis anterior, and 10) peroneus muscles. The valvular and venous densities were determined in a scanning electron microscope, normalized to the size of specimens, and the valvular index was calculated. Analysis of variance with Bonferroni t-test was used to compare the valvular index between the regions. RESULTS: Venous valves were observed in all tissue regions. The diameter of veins with valves ranged from 18 microm to 803 microm. The valvular index for regions overlying bones/tendons (i.e., regions 1-7) was significantly higher versus those overlying muscular regions (i.e., regions 8-10) (p < 0.05). The valvular index was not different (p = 0.51) when regions 1 and 2 (where ulcers almost never occur) were compared to regions 3, 4, 5, 6, and 7 (where ulcers frequently occur); nor were there differences between the vascular indexes of regions overlying muscle. The largest venous valves were observed in the plantar region, and the smallest-sized ones were present in the peroneal region. CONCLUSIONS: This study shows that the density of venous valves is actually higher in regions of the human lower extremity overlying bones and tendons, where venous stasis ulcers are common, than those overlying muscular areas, where ulcers are rarely seen. Thus, valvular quantity alone cannot account for the higher clinical incidence of ulceration. It is likely that muscular pumping and/or valvular quality are important factors in preventing the development of venous stasis and ulceration in the lower extremity.