Applied Surgical Anatomy of the Medial Approach

Overview

The anatomy of this approach is the anatomy of the adductor compartment of the thigh. The adductors do not cover the hip joint, since they all originate below the level of the joint itself.

The adductor compartment of the thigh consists of three layers of muscles, with the two divisions of the obturator nerve running between each pair of layers. The superficial layer consists of the adductor longus and the gracilis; the middle layer, the adductor brevis; and the deep layer, the adductor magnus.

Landmarks and Incision

Landmarks

The adductor longus is the only muscle of the adductor group that is easily palpable at its tendinous origin. Its structure is considered in detail in the superficial surgical dissection.

The pubic tubercle is the most lateral part of the body of the pubis.

Easily palpable, it marks the medial attachment of the inguinal ligament (Fig. 8-70).

Figure 8-70 Osteology of the medial approach to the hip.

Incisions

A longitudinal incision crosses the relaxed skin tension line obliquely, since they run down and medially cross the front of the thigh. A transverse insertion made in the groin, used for release of the adductors, is parallel with the lines and should heal with minimal scar formation. Meticulous closure of the deep fascia minimizes ugly depressed scars.

Superficial Surgical Dissection

The approach runs between the adductor longus and the gracilis. Both muscles are supplied by the anterior division of the obturator nerve, but the nerves enter them close to their pubic origins, leaving the intermuscular plane available for surgical use (see Fig. 8-68).

The gracilis is extremely long and thin, with long parallel-running fibers. Its aponeurotic origin, a thin sheet of tendinous fibers arising from the pubis, lies in an anteroposterior plane.

The adductor longus arises by a strong tendon which accounts for its involvement in the relatively high incidence of avulsion fractures. The origin may ossify in those who, like horseback riders, use their hip adductors excessively. This ossification is known as rider’s bone. Calcification and ossification are also seen in soccer players in whom the lesion may give rise to chronic pain and loss of function.

Given the size and relative “weakness” of these two muscles, it is difficult to understand why they were once given the name of custodes virginitatis.21

The obturator nerve is derived from anterior divisions of the L2-L4 nerve roots. The nerve divides in the obturator notch into anterior and posterior divisions. The anterior division passes over the upper border of the obturator externus and descends on the medial side of the thigh behind the adductor longus, on the anterior surface of the adductor brevis. It supplies sensory fibers to the hip joint.

The nerve is commonly transected in cases of adduction contractures of the hip caused by spasticity of the adductor muscles. To find it, define the interval between the adductor longus and the adductor brevis, the point at which the nerve is available for section. The nerve lies on the anterior surface of the adductor brevis, bound to it by a thin areolar covering. There, it may divide into three or even four bundles. Therefore, when performing an anterior obturator neurectomy, dissect the nerve bundles proximally as far as possible to avoid overlooking branches coming off higher up.

The anterior branch gives cutaneous distribution to the medial side of the knee, perhaps the reason hip pain is often referred to the knee, especially in cases of slipped upper femoral epiphysis. (A second pain commonly referred to the inside of the knee, originating in the ovary, is thought to be due to direct irritation of the obturator nerve by ovarian pathology, because the nerve runs adjacent to the ovary in the pelvis.)

Deep Surgical Dissection

The intermuscular interval used in deep surgical dissection lies between the adductor brevis and the adductor magnus (see Fig. 8-69).

The adductor brevis runs down the thigh sandwiched between the anterior and posterior divisions of the obturator nerve.

In certain animals, the adductor magnus inserts into the tibia. In humans, the superficial medial ligament of the knee is thought to have arisen as the degenerative tendon of the adductor magnus and is sometimes referred to as the fourth hamstring muscle.

The posterior division of the obturator nerve runs distally on the surface of the adductor magnus supplying it. It gives off a fine terminal branch which runs with the femoral artery through the hiatus in the adductor magnus muscle to the popliteal fossa where it supplies part of the knee joint capsule.