This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
This occupies approximately the upper third of the thigh. Its base is formed by Poupart's ligament, its outer side by the sartorius muscle, and its inner side by the adductor longus. Its floor is formed by the iliacus, psoas, pectineus, sometimes a portion of the adductor brevis, and the adductor longus muscles. It contains the femoral artery and vein, the anterior crural nerve, the long saphenous vein, and numerous lymphatics (Fig. 533). At its upper and inner part is the saphenous opening, at which femoral hernise make their appearance. Psoas abscesses follow the tendon of the psoas muscle down and make their appearance in Scarpa's triangle, sometimes to one side and sometimes to the other of the artery. Pus from hip-joint disease likewise comes to the front at the upper part of the triangle on one side or the other of the femoral artery. The apex of Scarpa's triangle is a favorite site for ligation of the femoral artery.
The line of the femoral artery is from a point midway between the anterior superior spine and the symphysis pubis (this brings it to the inner side of the middle of Poupart's ligament) to the adductor tubercle at the inner upper part of the internal condyle. Just below Poupart's ligament it gives off four small branches; the superficial external circumflex, superficial epigastric, and superficial and deep external pudic. About 4 cm. (1 1/2 in.) down it gives off the profunda femoris, which is almost as large as the parent trunk. On reaching the edge of the sartorius it passes beneath it to enter Hunter's canal, and at the junction of the middle and lower third of the thigh it pierces the adductor magnus to become the popliteal. At Poupart's ligament the femoral vein lies to the inner side of the artery, but at the apex of the triangle it lies behind it.
In ligating the femoral artery an incision is made in the line given above, and the artery sought for beneath the fascia lata. Ligatures are not placed high up, on account of the proximity of the deep femoral; lower down at the apex of the triangle is the preferred point. The crural branch of the genitocrural nerve lies on the artery for a short distance below Poupart's ligament; it is small in size. Just to the outer side of the artery, and sometimes touching it, is the anterior crural nerve, and running down its outer side are the internal cutaneous and internal saphenous branches. The femoral vein, which above was internal to the artery, at the apex of the triangle lies posterior to it (Fig. 534).
Fig. 532. - Surface anatomy of the thigh.
The profunda femoris artery comes off 4 cm. (1 1/2 in.) below Poupart's ligament. Its branches are the external (lateral) and internal (medial) circumflex, and four perforating. The last perforating is terminal. The external circumflex passes outward over the iliacus and under the sartorius and rectus and divides into three branches; the ascending branch follows the anterior intertrochanteric line and gives off a branch which enters the joint between the limbs of the iliofemoral or Y ligament. The transverse branch goes outward to the upper part of the vastus exter-nus; and the descending branch supplies the muscle lower down. The ascending and transverse branches lie beneath the incision, which is made in operating on the hip-joint anteriorly, and may be cut during the operation. The internal circumflex winds inwardly between the psoas and pectineus, then between the adductor brevis and obturator externus, and then between the adductor magnus and quadratus femoris to anastomose with the external circumflex, sciatic, and superior perforating.
The four perforating arteries wind around close to the bone from within outward and terminate in the hamstring and vastus externus muscles. They perforate the adductor muscles and send large anastomotic branches to one another near the linea aspera. In operations on the femur, when the soft parts are detached from the posterior portion of the bone, the bleeding from these perforating branches is liable to be very free and on account of their depth difficult to control. It is this which renders operations like those for ununited and compound fractures dangerous.