Applied Surgical Anatomy of the Thigh ‌

Overview

Muscle Groups

There are three major muscle groups in the thigh (Figs. 9-47 to 9-49):

1. The adductors of the hip are supplied by the obturator nerve and occupy the medial segment of the thigh. The adductor magnus both adducts and
   extends the hip, and it has a dual nerve supply, the obturator and sciatic nerves.

2. The extensors of the knee are supplied by the femoral nerve and occupy the anterior segment of the thigh.

3. The flexors of the knee (which also extend the hip) are supplied by the sciatic nerve and lie in the posterior segment of the thigh.

The knee extensors are separated from the hip adductors by the thin medial intermuscular septum and from the knee flexors by the tough lateral intermuscular septum. The adductors and flexors are not separated by an intermuscular septum.

Nerves

Three major nerves run down the thigh. The obturator nerve, which arises from the lumbar plexus (L2-4), runs in the adductor group, supplying all these muscles.

The sciatic nerve, which arises from the lumbosacral plexus (L4-5, S1-3), lies in the posterior segment of the thigh, supplying the hamstrings and the extensor portion of the adductor magnus. Running deep to the long head of the biceps and lying on the adductor magnus, it ends medial to the biceps as the muscle crosses from the ischial tuberosity toward the head of the fibula (see Fig. 9-53).

Figure 9-47 The superficial musculature of the lateral aspect of the thigh. The iliotibial band (tract) overlies the vastus lateralis proximally.

Figure 9-48 The tensor fasciae latae, the vastus lateralis, and a portion of the vastus intermedius have been resected to reveal the femur and the lateral intermuscular septum. Note the perforating vessels as they pierce the septum. Note that the vastus lateralis bulges posteriorly.

Figure 9-49 The superficial musculature of the anterior aspect of the thigh.

Rectus Femoris. Origin. Reflected head from just above acetabulum and anterior capsule of hip joint; straight head from anterior-inferior iliac spine. Insertion. Upper border of patella, tibial tubercle. Action. Powerful extensor of knee and weak flexor of hip. Nerve supply. Femoral nerve (L2-L4).

The femoral nerve, which is a branch of the lumbar plexus (L2-4), divides into its branches soon after entering the thigh and supplies all the extensors of the knee and the sartorius and pectineus (Fig. 9-50).

Vessels

The femoral artery is the artery of transit through the thigh. Its major branch, the profunda femoris artery, is the main blood supply of the thigh musculature. After the femoral artery gives off the profunda femoris artery in the femoral triangle, it gives off no other major branches of importance in the thigh (Fig. 9-51).

The femoral artery actually enters the thigh under the inguinal ligament at the midinguinal point, directly over the head of the femur, which is why the femoral pulse is the surface marking of the femoral head. The artery then travels distally on the iliopsoas and the pectineus muscle and disappears at the bottom of the femoral triangle beneath the sartorius muscle, running on the adductor longus muscle. There, the artery lies in a depression known as the subsartorial canal of Hunter. The canal runs between the extensor and adductor compartments of the thigh and is roofed by a thick fascial layer and the sartorius muscle. The posterior wall is formed by the adductor muscles (the adductor longus superiorly and the adductor magnus inferiorly), and the anterior wall is formed by the vastus medialis muscle. Running with the artery in the canal is the saphenous nerve (a cutaneous nerve that is derived from the femoral nerve), the femoral vein, and, in the upper half, the nerve to the vastus medialis muscle.

The femoral artery ultimately pierces the adductor magnus muscle one handbreadth above the knee to join the sciatic nerve in the popliteal fossa before entering the posterior compartments of the thigh. There, it lies deep and medial to the sciatic nerve (Fig. 9-53).

The femoral artery is lateral to the femoral vein in the femoral triangle, but medial to it in the popliteal fossa, perhaps as a result of the rotation of the limb that occurs during fetal development.

The artery also changes position in relation to the femur; it is anterior to it at its upper end, medial to it in its middle portion, and behind it at its lower end. These changes influence not only the planning of approaches, but also the insertion of skeletal pins for traction and the application of external fixators.

The profunda femoris artery supplies the thigh musculature. It arises from the femoral artery in the femoral triangle, coming off its lateral side before passing behind it quickly. The two arteries then leave the femoral triangle. The profunda femoris artery passes behind the adductor longus muscle, whereas the femoral artery passes anterior to it. Thus, the muscle is sandwiched between the two arteries (Fig. 9-50; see Fig. 9-51).

Four of the perforating branches of the profunda femoris artery pass posteriorly through the medial compartment of the thigh. They wind around the femur just as the medial femoral circumflex artery does and enter the anterior compartment again by piercing the lateral intermuscular septum. They must be ligated at that point in the posterolateral approach to the femur (see Fig. 9-51).

The medial femoral circumflex artery passes between the iliopsoas and pectineus muscles to lie on the upper border of the adductor longus muscle. From there, it winds around the interval between the quadratus femoris and adductor magnus muscles, where it divides. The ascending branch runs along the superior border of the quadratus femoris, where it may be cut in posterior approaches to the hip, causing troublesome bleeding. The horizontal branch passes between the quadratus femoris and the adductor magnus to form one limb of the cruciate anastomosis (see Fig. 9-51).

The lateral femoral circumflex artery passes lateral to the rectus femoris muscle, where it appears in the upper part of the anterolateral approach. There, it divides into three branches:

1. The ascending branch runs upward toward the anterior-superior iliac spine in the intermuscular interval between the sartorius and tensor fasciae latae muscles. There, it requires ligation in the anterior approach to the hip.

2. The transverse branch continues to wind around the femur and joins the transverse branch of the medial femoral circumflex, contributing to the cruciate anastomosis.

3. The descending branch passes along the interval between the vastus intermedius and vastus lateralis muscles, where it is encountered in the

anterolateral approach to the femur (see Fig. 9-51).

The saphenous vein arises on the dorsum of the ankle at the medial end of the dorsal venous arch. Passing anterior to the medial malleolus (where it can be found during cutdown for the insertion of intravenous lines), it passes behind the knee before spiraling forward on the medial side of the thigh into the femoral vein. The saphenous vein is the major superficial vein of the thigh, but although it frequently is the object of general surgical procedures, it has little importance for the orthopedic surgeon.

Landmark and Incisions

Landmark

Most of the femur is cloaked deeply in muscle; only the greater trochanter and the femoral condyles are easily palpable. The femur has a natural anterior bow, which is important for the design of intramedullary rods.

The angle between the femoral shaft and the femoral neck varies but is usually about 130 degrees. The femoral neck is displaced about 15 degrees in anteversion on the femoral shaft. These angles should be borne in mind when pins or nails are inserted up the femoral neck.

Figure 9-50 The sartorius, the rectus femoris, the tensor fasciae latae, the vastus lateralis, and the vastus intermedius have been resected to reveal the course of the femoral and profunda femoris arteries; note the relationship of the arteries to the quadriceps and the adductor muscles.

Vastus Lateralis. Origin. Upper half of intertrochanteric line. Vastus lateralis ridge, lateral lip of linea aspera, and upper two-thirds of lateral supracondylar line of femur. Also from lateral intermuscular septum. Insertion. Lateral border of patella and tibial tubercle. Action. Extensor of knee. Nerve supply. Femoral nerve (L2-L4).

Vastus Intermedius. Origin. Anterior and lateral aspect of upper two-thirds of femoral shaft. Insertion. Tibial tubercle. Action. Extensor of knee. Nerve supply. Femoral nerve (L2-L4).

Vastus Medialis. Origin. Medial lip of linea aspera and spiral line of femur. Insertion. Tibial tubercle and medial border of patella. Action. Extensor of knee. Nerve supply. Femoral nerve (L2-L4).