Detailed knowledge of the lower limbs venous penetrating system is essential for both differential diagnostics and treatment of venous diseases. Veins differ from arteries in terms of wall structure, blood flow conditions and internal pressure. It leads to significant alteration in endothelial function and blood coagulation. A surgeon handling venous diseases must be aware of this. Veins are web-like blood vessels, and blood is collected into bigger and bigger vessels. Unlike arterial branches, veins have tributaries. The venous system of the limbs may be divided into epi – and subfascial due to the presence of fascia. Both systems are connected with about 150 penetrating veins which create a web-like structure. Deep veins play the most important role in blood outflow from the limbs. Superficial and perforating veins are subsidiary. Lower limb muscles play a crucial role in creating a peripheral venous pump. Perforator veins connect superficial and deep veins penetrating the muscular fascia. They are guarded with valves which facilitate the blood flow from the superficial to the deep circulation. During the 1979 congress, the name “connecting veins” was proposed for lateral veins constituting connections within one circulation: superficial or deep. The name “penetrating veins” was suggested for all the veins interconnecting both circulations [5
]. Perforating veins possess valves whose closure prevents the backward flow of the blood. They consist of 2, and sometimes 3 folds with edges pointing in the direction of the lumen of the vessel. Just next to the valve, the venous wall is usually dilated into a sinusoidal bulge.
The valve is usually located below the orifice of the venous tributary, and the lumen of the vein is usually wider above, not below the valve. Such morphological presentation is described as telescopic Hach's symptom. It has a huge diagnostic value of venous flow [5
]. Sometimes before crossing the fascia, perforating veins form a small, s-shaped loop. It prevents light refraction and excessive vein stretching, when the skin and tissue move along the fascia. Valveless, perforating veins with bidirectional blood flow were also described [10
]. According to Linton, the normal perforating vein diameter may vary from 1 mm to 2 mm [11
]. Mozes observed that only 1/4 of normal perforating veins have a diameter exceeding 2 mm [10
]. In 1867 Le Dentu introduced a division, classic today, of perforating veins into direct and indirect. Others believe that such division was made several dozen years later by Warwick [10
]. Direct perforating veins connect big, superficial veins – the saphenous vein, small saphenous vein and their collateral branches – with major deep veins. They are short, transverse, sometimes slightly rising or falling when crossing the fascia. These large diameter veins show a relatively constant anatomical distribution. Cockett and Jones proved that they play the main pathophysiological role in the so-called post-thrombotic syndrome [12
]. Indirect perforator veins, on the other hand, have a small diameter and are large in number. They are characterized by a meander-like flow and ramifications at either one end or along their whole length. They communicate deep veins with superficial veins via one or more intramuscular veins. Dodd and Cockett showed that the perforator veins do not play any significant role in CVI pathology [13
]. Due to diversity of appearance it is impossible to describe precisely all perforating veins’ topography. Regarding the CVD, Cockett's veins are the most significant. Their incompetence is connected with varied clinical presentations. These should be treated as a direct cause of both CVI and all the complications arising from the condition including arthrogenic congestive syndrome and chronic syndrome of intrafascial tibial hypertension. Less frequently, Cockett's perforators’ insufficiency is an autonomic clinical presentation [11
]. Three sets of Cockett's perforators, located in the interior part of the distal tibia, have been identified – the upper, middle and lower. They connect the posterior arch vein with the posterior tibial veins.
At times, a perforator comes out directly from the saphenous vein. The characteristic cutaneous projection of crural fascia diminution agrees with so-called virtual Hach's positional lines [11
]. The lower Cockett's perforator is located near the medial malleolus, while the middle Cockett's perforator is a general idea, which includes 3 sets of vessels: anterior, medial and posterior. Their identification, which is related to muscular septum topography, may be performed clinically and intraoperatively, but it is not possible during USG or phlebological examination. The anterior vessel is located directly on the periosteum of the posterior part of the tibial bone. The medial vein runs next to the intramuscular septum. The topography of the upper Crockett's veins shows similar characteristics, but it lacks the posterior vessel. Typical incompetent perforating veins of the lower limb are presented in .
Figure 1 The schematic of the most important: A) on the medial side, B) behind the limp