(Fig. XXIII, 4.) When the patient is in the dorsal recumbent position, draw a line round the body at the level of the anterior superior iliac spine, and from this line drop a perpendicular to the top of the great trochanter. To complete the triangle, draw a line from the anterior superior iliac spine to the top of the trochanter. When the trochanter is displaced upwards the perpendicular line is diminished in length as compared with the sound side, and when it undergoes a backward displacement the spino-trochanteric line is relatively increased in length.
(b).—Anterior and internal aspect. The lower extremity is demarcated from the abdomen by a well-marked furrow, the inguinal groove. This corresponds to the situation of Poupart's ligament, the recurved lower border of the oblique externus abdominis muscle. This ligament, as it passes from the anterior superior iliac spine to the pubic spine of the same side, forms the upper boundary of Scarpa's triangle, a space which is best demonstrated when the thigh is flexed, abducted, and everted. (Fig. XXV, 3,4)
The sartorius muscle is then thrown into action and the outer boundary of the space so shown. If the hand be now placed on the upper and inner aspect of the thigh and the limb be sharply adducted, a rounded tendon at once becomes noticeable. This is the adductor longus, which forms the inner boundary of Scarpa's triangle.
The outwardly directed adductor longus and the inwardly curving sartorius converge to form the apex of the triangle.
The floor of the space is formed from without inwards by the iliacus, psoas, pectineus and adductor longus muscles. In the superficial fascia which overlies this region, numerous lymphatic glands are situated, and it will here be convenient to briefly discuss their general arrangement. The superficial lymphatic glands are placed in three main groups :
(1) The oblique or inguinal glands, running parallel to and below Poupart's ligament, and draining the anterior aspect of the abdomen below the level of the umbilicus, the lower half of the side and back, the gluteal region, and the upper and outer part of the thigh.
(2) The vertical or femoral glands, running with the long internal saphenous vein, and draining the greater part of the inner aspect of the foot, leg, and thigh.
(3) The pubic glands, situated below and external to the pubic spine, and draining mainly the external genitals, perineum, and anus.
The deep fascia presents an opening, (Fig. XXII, 8., Fig. XXIV, 9.) the saphenous opening, for the transmission of the long saphenous vein to the common femoral vein. This foramen is oval in shape, being 1 inch long and 1/2 to 3/4 inch broad, the long axis vertical. The central point of the opening is situated 1 1/2 inches below and 1 1/2 inches external to the pubic spine.
Beneath the deep fascia overlying Scarpa's triangle, certain important structures are situated, such as the common, superficial femoral, and profunda femoris arteries, the corresponding veins, and the anterior crural nerve. These will all be dealt with later, the femoral ring alone needing here further definition.
The femoral ring, (Fig. XXII, 7., Fig. XXIV, 8.) through which a femoral hernia commonly escapes from the abdominal cavity, lies below the inner part of Poupart's ligament, and external to the pubic spine. A good way to define the ring with precision is that recommended by Holden: " Feel for the pulsation of the common femoral artery, allow 1/2 inch on the inner side for the femoral vein, then comes the femoral ring." The crural or femoral ring presents the following boundaries: To the inner side is Gimbernat's ligament; to the outer side is the femoral vein; in front is Poupart's ligament; behind is the pectineus muscle and the horizontal ramus of the os pubis.
Hunter's canal, (Fig. XXIV, 12.) a more or less triangular muscular channel for the transmission of the superficial femoral artery, occupies the middle third of the antero-internal aspect of the thigh. During forcible contraction of the thigh muscles, Scarpa's triangle may be seen to be continued downwards as a shallow depression between the extensor and adductor muscles, this furrow corresponding to the position of the canal in question. The anatomical boundaries of the canal are
(1) vastus internus externally,
(2) adductor longus and magnus behind,
(3) sartorius and a strong fascial band between the adductors and vastus internus in front and internal.
The canal transmits the superficial femoral vein and artery, the long internus saphenous nerve (anterior crural), and the nerve to the vastus internus (anterior crural).
In order to compare the length of the lower extremities the limbs should be placed parallel to one another, and the tape-measure carried from the anterior superior iliac spine to the tip of the internal malleolus of the tibia of the same side. (Fig. XXIV, 16.) The distance between these two points may be subdivided, if necessary, by marking out, (Fig. XXIV, 17.) on the inner aspect of the knee, the transverse line which indicates the level of the femoro-tibial articulation. The lengths of the femur and of the tibia are thus separately estimated.