静脉皮瓣

Venous flow through flaps are thin and pliable with vessels similar in size to those of the hand. Their harvest results in minimal donor site morbidity. These flaps are

composed of skin, subcutaneous tissue, and a plexus of veins. Unlike conventional

flaps where the nutrient capillary beds are supplied by an inflow artery and drained by an outflow vein, the VFTF has no native arterial inflow circuit. All flow proceeds into and out of the flap via the venous plexus.

静脉皮瓣其对供区破坏很小，仅由皮肤、皮下组织和静脉丛组成，传统皮瓣都是由动脉系统供血静脉系统回流血液，而静脉皮瓣由于没有自带动脉，所有血液进出都靠静脉系统。

The exact physiology of VFTF survival has not been determined. Three theories have been proposed:

静脉皮瓣存活的生理学基础还没有完全明确，有三个理论支持

1.逆分流 Reverse Shunting

2.逆流 Reverse Flow

3.毛细血管旁路 Capillary Bypass

In the conventional flap, nutrient capillary beds are supplied by an inflow artery and are drained by an outflow vein. The conventional flap tends to be thicker, and is usually well defined in terms of both inflow and outflow by a named artery and its venae commitans.

在传统皮瓣，毛细血管床靠动脉供血，静脉流出，其通常较厚，有知名血管及其伴行静脉（如下图是）。

In the venous flap, a vein delivers inflow of blood and outflow of blood. The flap tends to be thinner, can be designed over numerous veins, and often does not have a specific anatomically named inflow and outflow vein.

静脉皮瓣，血液靠静脉流入并流出，皮瓣更薄，可以找出很多静脉，一般没有知名静脉（下图示）。

The physiology of the VFTF places unique restrictions on its design. The tissue furthest away from the venous plexus is prone to congestion and necrosis. Larger flaps require a more extensive venous plexus for complete survival. Studies have shown that VFTFs designed with a central venous plexus with two or more efferent veins have a survival pattern similar to that of a conventional flaps which have an inflow artery and an outflow vein.

A fine network of veins extending throughout the flap is not the only factor in the VFTF's survival. Characteristics of the donor site also play a role. There are several potential VFTF donor sites:

静脉皮瓣可选择供区：

?前臂远端掌侧Distal Volar Forearm

?前臂近端掌侧Proximal Volar Forearm

?指/趾背Dorsum Digit/Hand

?足背 Dorsal Foot

?大腿/臂内侧 Medial Thigh/Leg

?上肢Upper Arm

?

Direct visualization of the venous plexus through the thin skin of the distal

extremities allows precise design of the VFTFs. The flap can not only be centered over the most appropriate plexus, but creative inflow and outflow circuits can also be designed in the branching venous system. The donor sites of small and moderate sized flaps can usually be

closed primarily.

通过皮肤直视其下方的静脉系统，根据其走形设计皮瓣，不仅可以

根据主干走形设计也可以根据分支分布设计皮瓣，供区一般可以直接缝合。

VFTFs harvested from the leg and upper arm are nourished by the saphenous and basilic vein respectively. These flaps are useful when long vascular conduits or a larger soft tissue paddle is required. These flaps are associated with increased subcutaneous tissue between the nourishing vein and overlying skin. The smaller venous systems cannot be visualized and their extent cannot be determined at the time of flap design. These flaps are usually designed over the main vein. Their maximum width is restricted to insure optimal survival.

大腿或上肢静脉皮瓣通过隐静脉和贵要静脉营养，这些皮瓣可以设计成大皮瓣以适应大软组织缺损应用，由于其小静脉在皮瓣设计的时候不能确定，因此皮瓣的宽度要根据主干静脉走形设计以确保成活。

Another limiting factor in the survival and success of VFTFs is the recipient bed. Areas with ongoing infection can prolong healing time and delay neovascularization of the VFTF. This can prolong the time the flap has to rely on

venous physiology and potentially decrease flap survival. In addition, factors such as infection can result in activation of platelets and increase thrombosis potential.

另一个限制皮瓣成活的因素是受区情况，感染将影响愈合，减缓新生血管化进程，增加血小板积聚和血栓形成机会。

The VFTF can be harvested with additional tissues creating a composite VFTF. This composite flap is more difficult to design because success is dependent on spatial distribution of multiple components rather than just inflow and outflow circuits. Sensory nerves such as the brachial cutaneous and saphenous nerves have been included to create a sensate flap or to graft nerve defects at the recipient site. Tendon has been included to reconstruct tendons, ligaments, and joints capsules. One author has reported inclusion of tibial bone with a saphenous venous flap for reconstruction of soft tissue and bony defects in the hand. Theoretically, these are vascular grafts. Composite VFTFs have been reported sporadically but no series has evaluated the efficacy of their components as vascularized grafts.