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.
The lymphatic nodes of the groin are frequently the seat of infection necessitating operative measures. They are superficial and deep. For clinical purposes there is no better division of the superficial nodes than into an oblique set along Poupart's ligament and a longitudinal set along the blood-vessels (Fig. 536).
While as a general rule it may be stated that the nodes drain the region they are nearest to, this is frequently not the case. Therefore it is not always possible to infer the source of the infection from the location of the infected lymph node. The nodes of the groin drain the lower anterior half of the abdomen, the genitalia, lower limb, and the anal, gluteal, and lumbar regions.
They vary from 10 to 20 in number, and their efferent vessels either pass through the femoral canal to the nodes inside of the abdomen, or may terminate in the deep lymphatic nodes of the femoral canal.
The deep lymphatics consist of one to three nodes in the femoral canal internal to the femoral vessels. They are not constant, and one which is sometimes found at the upper end of the femoral canal is known as the gland or node of Cloquet. They receive the deep lymphatics of the thigh, as well as sometimes a communication from the superficial lymphatics. They rarely become the seat of infection, but if inflamed may be mistaken for strangulated femoral hernia.
The inguinal nodes frequently become inflamed and swollen (bubo) from infection transmitted from the parts which they drain. For this they are frequently excised. The superficial nodes are located on the fascia lata around the saphenous opening, and at that point are intimately associated with and surround the veins. On this account it is easy to wound the veins, and the hemorrhage may be so free and so hard to control as to endanger the life of the patient. I know of one such fatal case. This accident is to be avoided by freeing the edge of the mass below the saphenous opening and isolating the long saphenous vein, which is then followed up and exposed at its entrance into the femoral vein. The diseased mass is then to be dissected loose from each side, away from the vein, and removed. The femoral vein itself at this point is superficial, and if the saphenous opening is cleaned out it will of necessity be exposed.
The other veins emptying into the femoral at the saphenous opening above the long saphenous - the superficial circumflex iliac, epigastric, and external pudic - are usually too small and easily secured to cause trouble.
The sciatic nerve in its descent crosses a line joining the tuberosity of the ischium and greater trochanter at the junction of its inner and middle thirds. It then descends toward the middle of the popliteal space. It divides into the internal and external popliteal nerves at about the middle of the thigh (Fig. 537). Rarely it divides lower down, but more frequently higher up. It is said that it will bear a weight of 183 lbs., but Symington (Lancet, 1878 - Treves) has pointed out that it will tear out from its spinal attachment before this limit is reached. In exposing it the incision should be made high up at the gluteal fold, to the outer side of the tuberosity of the ischium. At this point it lies to the outer side of the biceps and on the adductor magnus; a little lower down it disappears beneath the biceps, and, if the incision is made here, the muscle must be displaced and it may only be found with difficulty.
Fig. 536. - Superficial lymphatic vessels of lower limb; semidiagram-matic. (Based on figures of Sappey).
At the upper end of the popliteal space it again becomes visible, and can be found between the biceps on the outer side and the semimembranosus on the inner side.
Sciatica may be caused by injury to the sacral plexus in the pelvis, as by labor, or by injury to the nerves as they issue from the spine, as in fractures, luxations, bony outgrowths or tumors. The pain affects the back of the thigh and outer side of the leg.