Stefano Ricci
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Abstract One hundred limbs of 50 non-embalmed cadaveric subjects (mean age of 82) were studied by injection of the venous system of the lower limbs with green neoprene latex. A realistic 3D reconstruction of the whole venous network with an accurate morphological description was obtained by 200 phlebographies and 100 CT venograms. The outlet of the Hunter’s canal, located at the medial aspect of the lower thigh, is narrowed by a tendinous band, the vastoadductor membrane, joining the vastus medialis to the adductor longus. The roof of the canal is made by the vastus medialis muscle, the floor by the adductors, and it is closed medially by the sartorius muscle. A musculotendinous band, the vastoadductor membrane, arose from the adductor magnus muscle, joining the adductor tendon to the vastus medialis. The vascular pedicle being tightened inside this small fibrous space changes its direction to go from the thigh to the popliteal fossa: this explains the frequent kink or plication of the vein, compressed at the posterior aspect of the canal, while the artery is located at the anterior aspect of the canal. The saphenous nerve is located deeply next to the collateral canal and perforates the muscular fascia at the lower third of the thigh. It runs subcutaneously parallel to the tendon of the adductor longus. The femoral vein is located more posteriorly and is frequently narrowed at this level by the edge of the vastoadductor membrane. The reason for venous compression is the reduced width and stiffness of this part of the canal, surrounded by fibrous stiff structures. The vein at this level could be easily compressed in the posterior angle of the hiatus, commonly tightened by a calcified artery. Physiological hypothesis: The cadaveric simulations demonstrated that contraction of the adductor longus closes the hiatus, and contraction of the adductor magnus opens it. During the impulsion phase of the step (extension of the thigh), the systole of the calf muscle pump pushes the blood up into the femoral vein. At this time, the adductor longus is relaxed and the adductor magnus contracts, which opens the Hunter’s hiatus. During thigh flexion, at the beginning of the step (suspension phase), the calf is relaxed and the adductor longus is in tension, which closes the Hunter’s hiatus. This event could be important for the prevention of venous thrombosis of the femoropopliteal axis. In the sitting position, the adductor longus muscle relaxes and the adductor magnus is shortened, which closes the outlet of the Hunter’s canal, leading to venous compression. Different possible derivative routes in case of stenosis of the Hunter’s canal are possible: i) the axial vein located along the ischiatic nerve; ii) the deep femoral vein with a low popliteal communicating branch; iii) the venous arcades of the vastus medialis; iv) and especially the dilated arcades of the semimembranosus muscle. These act like a safety valve, derivating the blood of the popliteal vein to the deep femoral vein, bypassing the Hunter’s canal stenosis. In clinical practice, a venous examination should systematically include an evaluation below the semimembranosus muscle at the posteromedial aspect of the thigh, 10 cm up to the knee joint, close to the midline: the presence of dilated arcades is a sign of stasis, and probably of femoral compression of the Hunter’s outlet. |
Comment by Stefano Ricci
This interesting paper should be considered as the sequel of the one, from the same authors, just analyzed in this same Bibliolab: Anatomy of the veno-muscular pumps of the lower limb - Phlebology Online First, published on January 10, 2014. In that instance the adductors canal’s possible obstruction (functional or organic) was only recalled, while in this paper it is described at great length. Very clear images are supplied that greatly help in understanding this difficult and scarcely attended subject. After this lecture it comes natural to suspect an adductors canal obstruction in many unexplained clinical situations that we often encounter in our clinical practice. The one that is the most intriguing as far as superficial venous network is concerned, is the case when a reflux at the sapheno-poplitel junction (SPJ) is transmitted to the Giacomini vein (in a centripetal direction) and consequently to the great saphenous vein (GSV). Often in these cases the GSV is incompetent as a consequence of the overload. Typically, the SPJ reflux is present also during muscles contraction (the so called systolic phase) giving evidence of an insufficient draining capacity of the deep system, the Giacomini acting like a derivative route, although not mentioned in the paper’s bypassing routes. Probably a complete dynamic (but not easy) study of the Hunter’s canal in these cases would reveal, at least, a relative obstruction. The same anatomical presence of the Giacomini vein (GV) could be (inversely) correlated to the deep veins system efficiency: the GV is present only in subjects with deep veins relatively difficult drainage. Finally, some SPJ interruption recurrences and popliteal fossa perforator post op. appearances could be explained in the same way.
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