Symptoms of femoral nerve damage

The femoral nerve (n. femoralis) is formed from the fibers of the dorsal branches of the anterior primary division of the LII-LIV spinal nerves, and sometimes LI. Beginning at the level of LI, it is initially located behind the psoas major muscle, then emerges from under its outer edge. Further, the nerve is in the groove (groove) between the iliac and psoas major muscles. Here it is covered from above by the iliac fascia. The fascial sheets located above the femoral nerve are divided into four plates: iliac, preiliac, transverse, and peritoneal. Between these plates there may be up to three bursae containing a small amount of connective and fatty tissue. Since the femoral nerve is located in a tight and fixed space between the pelvic bones and the iliac fascia, in this place it can easily be compressed during hemorrhage with the formation of a hematoma. The nerve leaves the pelvic cavity, passing through an osteofibrous tunnel formed by the inguinal ligament (in front), branches of the pubic bone and the ilium. Under the ligament, the nerve passes through a muscular lacuna. Upon exiting the thigh, the nerve is located under the sheets of the broad fascia of the thigh, covering the iliac and pectineal muscles. Here it is located in the femoral triangle, limited at the top by the inguinal ligament, outside by the sartorius muscle and inside by the long adductor muscle. On the lateral side of the femoral triangle, the deep sheet of the broad fascia of the thigh passes into the iliacus fascia covering m. iliopsoas. The femoral artery is located medial to the nerve. At this level, the femoral nerve can also be compressed by a hematoma.

Above the inguinal ligament, the femoral nerve sends branches to the iliac, large and small lumbar muscles. These muscles flex the thigh at the hip joint, rotating it outward; with the thigh fixed, they flex the lumbar part of the spinal column, tilting the torso forward.

Tests to determine the strength of these muscles:

1. in a supine position, the subject raises the straightened lower limb upward; the examiner resists this movement by pressing his palm into the middle of the thigh area;
2. in a sitting position on a stool, the subject bends the lower limb at the hip joint; the examiner prevents this movement by providing resistance at the level of the lower third of the thigh;
3. From a position lying on the back (on a hard surface), the subject is asked to sit up without the help of the upper limbs with the lower limbs fixed to the bed.

Below the inguinal ligament or distally, the femoral nerve divides into motor and sensory branches. The former supply the pectineus, sartorius, and quadriceps muscles, the latter the skin, subcutaneous tissue, and fascia in the region of the lower two-thirds of the anterior and anterointernal surface of the thigh, the anterointernal surface of the leg, and sometimes the inner edge of the foot at the medial malleolus.

The pectineus muscle (m. pectineus) flexes, adducts and rotates the thigh outward.

The sartorius muscle (m. sartorius) flexes the lower limb at the hip and knee joints, rotating the thigh outward.

Test to determine the strength of the sartorius muscle: the subject is asked to moderately bend the lower limb at the knee and hip joints and rotate the thigh outward in a supine position; the examiner resists this movement and palpates the contracted muscle. A similar test can also be performed with the subject sitting on a chair.

The quadriceps femoris muscle (m. quadriceps femoris) flexes the thigh at the hip joint and extends the leg at the knee joint.

Quadriceps Strength Test:

1. in a lying position on a splint, the lower limb is bent at the hip and knee joints, the person being examined is asked to straighten the lower limb; the examiner resists this movement and examines the contracted muscle;
2. Sitting on a chair, the subject extends his lower limb at the knee joint; the examiner resists this movement and palpates the contracted muscle.

The presence of hypotrophy of this muscle can be determined by measuring the circumference of the thigh at strictly symmetrical levels (usually 20 cm above the upper edge of the patella.

The femoral nerve is damaged by trauma (including traumatic and spontaneous hematomas along its course, for example, in hemophilia, treatment with anticoagulants, etc.), inguinal lymphadenitis, appendicular abscess, etc.

The clinical picture of femoral nerve damage in the groove between the iliac and lumbar muscles or in the femoral triangle is almost identical. Initially, pain occurs in the groin area. This pain radiates to the lumbar region and the thigh. The intensity of the pain increases quite quickly to a strong and constant level.

The hip joint is usually held in a position of flexion and external rotation. Patients assume a characteristic position in bed. They often lie on the affected side, with the lumbar spine, hips and knees bent - flexion contracture in the hip joint. Extension of the hip joint increases pain, but other movements are possible if the lower limb remains in a flexed position.

In case of hemorrhage at the level of the iliac muscle, paralysis of the muscles supplied by the femoral nerve occurs, however, this does not always happen. When a hematoma forms, usually only the femoral nerve is affected. In very rare cases, the lateral cutaneous nerve of the thigh may also be involved. Damage to the femoral nerve, as a rule, manifests itself as pronounced paresis of the flexors of the hip and extensors of the lower leg, loss of the knee reflex. Standing, walking, running and especially climbing stairs become difficult. Patients try to compensate for the loss of function of the quadriceps muscle by contracting the muscle that tenses the broad fascia of the thigh. Walking on a flat surface is possible, but the gait becomes peculiar; the lower limb is excessively extended at the knee joint, as a result of which the lower leg is excessively thrown forward and the foot lands on the floor with the entire sole. Patients avoid bending the lower limb at the knee joint, since they are unable to straighten it. The patella is not fixed and can be passively moved in different directions.

The neuralgic variant of femoral nerve damage is characterized by the Wasserman symptom: the patient lies on his stomach; the examiner lifts the straightened limb upwards, causing pain along the anterior surface of the thigh and in the groin area. The same will happen when bending the knee joint (Matskevich symptom). The pain also increases in a standing position when bending the body backwards. Sensitivity disorders are localized in the lower two-thirds of the anterior and anterointernal surface of the thigh, the anterointernal surface of the shin, and the inner edge of the foot. Vasomotor and trophic disorders may join in.

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