Functional anatomy of the semi-membranosus muscle: main thigh pump and derivative route of the Hunter's canal

Introduction: Our objective is to highlight the role of the semi-membranosus muscle, which is surprisingly not described in the major books of anatomy, as main thigh pump in the venous return [ 1 ]. Material and methods: Latex injection of fresh cadavers followed by anatomical dissection and colored segmentation of the whole venous network of 300 lower limbs, 3D reconstructions by CT venography of 1000 CVD patients are at the basis of this study. Results: The venous arcades of the semi-membranosus muscle constitute a main deep collateral route by-passing the narrowed area of the Hunter's canal. This anatomical study clearly shows that these venous arcades are regularly connected:( Figure 1 ) * By their 2 lower branches to the popliteal vein * By their 2 higher branches to the deep femoral vein. Consequently, they constitute a derivative route of the femoral axis, explaining their dilatation in case of stenosis of the Hunter's canal outlet. Similarly, in a physiological situation, the whole amount of blood ejected by the powerful calf pump through the popliteal vein cannot always reach the femoral vein through the Hunter's canal: the arcades then play the role of a safety valve. Moreover, the veins of the semi-membranosus muscle constitute a main thigh pump: they push up the blood towards the femoral crossroad at the root of the limb. Discussion and conclusion: The veins of the semi-membranosus should be systematically investigated by USD : their dilatation is the witness of venous outlet syndrome of the Hunter's canal which is a major cause of femoral vein thrombosis. USD investigation should be systematically carried out at that levels to prevent future deep vein obstruction.