Femoral Nerve: Definition, Structure, Functions, Clinical Significance and Associated Lesions

It is a nerve in the thigh that supplies the upper thigh and inner leg, as well as the muscles that extend the knee.

The femoral nerve is one of the main peripheral nerves of the lower extremity.

Motor : innervates the anterior thigh muscles that flex the hip joint (pectineus, iliac, sartorius) and extend the knee ( quadriceps femoris: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius).

Sensory : supplies cutaneous branches to the anteromedial thigh (anterior cutaneous branches of the femoral nerve) and the medial side of the leg and foot (saphenous nerve).

Structure

The femoral nerve is the main nerve that supplies the anterior compartment of the thigh. It is the largest branch of the lumbar plexus, and arises from the dorsal divisions of the ventral branches of the second, third, and fourth lumbar nerves (L2, L3, and L4).

The nerve enters the femoral triangle passing under the inguinal ligament, just next to the femoral artery. In the thigh, the nerve is located in a groove between the iliac muscle and the main psoas, outside the femoral sheath and lateral to the femoral artery.

After a short journey of about 4 cm in the thigh, the nerve divides into anterior and posterior divisions, separated by the lateral circumflex femoral artery. The branches are shown below:

Muscle branches

The Pectineus nerve arises immediately above the inguinal ligament from the medial side of the femoral nerve, and passes behind the femoral sheath to enter the anterior surface of the muscle.

The anterior division supplies the muscle of Sartorius.

The posterior division supplies the rectus femoris, the three vasti (vastus medialis, vastus lateralis, and vastus intermedius), and genu articularis. The genu articularis is supplied by a branch of the nerve to vastus intermedius.

Cutaneous branches

The anterior division emits anterior cutaneous branches: the anterior cutaneous branches are: «intermediate femoral cutaneous nerve» and «medial femoral cutaneous nerve». The posterior division emits only one branch, which is the saphenous nerve.

Articular branches

The hip joint is supplied by the nerve to the rectus femoris.

The knee joint is supplied by nerves to the three vastus. The vastus medialis nerve is particularly thick because it contains the proprioceptive fibers of the knee joint. This is in accordance with Hilton law.

Vascular branches

Branches to the femoral artery and its branches.

Motor functions

The femoral nerve supplies some of the muscles in the front of the thigh.

Hip flexors

Pectineus Muscle : Adducts and flexes the thigh, assists with medial rotation of the thigh.

Iliopsoas : works with the psoas major and psoas minor (forming iliopsoas) to flex the thigh of the hip joint and stabilize the hip joint.

Sartorius muscle : flexes, abducts, and laterally rotates the thigh at the hip joint. Bend your leg at the knee joint.

Knee extensors

Quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius) – Extends the leg at the knee joint.

Sensory functions

The first cutaneous branches of the femoral nerve are the anterior cutaneous branches that arise in the femoral triangle. They supply the skin on the anteromedial thigh.

The last cutaneous branch of the femoral nerve is the saphenous nerve that supplies the skin on the medial side of the leg and foot.

Clinical significance

The signals of the femoral nerve and its branches can be blocked to interrupt the transmission of the pain signal from the area of ​​innervation, performing a regional nerve block.

Some of the nerve blocks that works by affecting the femoral nerve are; femoral nerve block, iliac fascia block and 3-in-1 nerve block.

Saphenous vein detachment

The saphenous vein is often removed in individuals with problematic varicose veins. The long saphenous vein is accompanied in its course by the saphenous nerve.

Damage to the saphenous nerve during this procedure can cause pain, paraesthesia, or complete loss of sensation on the medial side of the lower leg.

Femoral nerve block

The femoral nerve block is useful in the evaluation and treatment of pain in the lower extremities, which is believed to be affected by the femoral nerve.

Femoral nerve block (in combination with a sciatic nerve block) may be indicated in patients requiring lower limb surgery who cannot tolerate a general anesthetic.

It is used for this indication mainly in patients who would not tolerate the sympathetic changes induced by spinal or epidural anesthesia and who require surgery on the lower extremity.

A femoral nerve block can also be used as pre-operative and post-operative analgesia in patients with a femoral neck fracture who cannot tolerate certain analgesics.

Local anesthetic femoral nerve block can be used diagnostically during differential neuronal block on an anatomical basis in the evaluation of pain in the lower extremities.

If destruction of the femoral nerve is considered, this technique is useful as a prognostic indicator of the degree of motor and sensory impairment that the patient may experience.

Local anesthesia femoral nerve block can be used to alleviate acute pain emergencies, including shaft and femoral neck fractures, and for postoperative pain relief while waiting for pharmacological methods to become effective.

Femoral nerve block with local anesthesia and steroids is occasionally used in the management of persistent lower extremity pain when pain is suspected to be secondary to inflammation or when femoral nerve entrapment is suspected as it passes under the inguinal ligament.

Femoral nerve block with local anesthesia and steroids is also indicated in the palliation of pain and motor dysfunction associated with diabetic femoral neuropathy.

Destruction of the femoral nerve is occasionally used in the palliation of persistent lower extremity pain secondary to an invasive tumor that is mediated by the femoral nerve and has not responded to more conservative measures.

What is femoral neuropathy?

Femoral nerve neuropathy occurs when the femoral nerve is compressed as it passes under the inguinal ligament, anterior to the iliopsoas.

Causes include surgery (hysterectomy, catheterization of the femoral artery, pelvis, hip, arterial bypass, retroperitoneal tumors, diabetes mellitus).

With increased use of anticoagulant agents, femoral neuropathy following spontaneous hemorrhage within the ileo-psoas muscle has become a serious and more frequent clinical problem.

Femoral mononeuropathy can be secondary to direct trauma, compression, stretch injury, or ischemia. The condition predominantly causes weakness in the quadriceps, resulting in difficulty with ambulation.

Compression of the femoral nerve can cause debilitating pain, requiring medical therapy and surgical intervention.

Most patients with femoral mononeuropathy, however, can be managed conservatively with physical therapy, avoiding excessive hip abduction and external rotation, and the patella to prevent knee buckling.

Femoral mononeuropathies account for approximately 1% of all mononeuropathies seen in electrodiagnostic laboratories.

Femoral nerve injury

The femoral nerve supplies the iliac and quadriceps muscles and is sensory to the medial thigh. The nerve is most often damaged after overextension of the hip or knee joints.

Excessive traction in a posteriorly presented fetus wheezing in a locked position is probably the most common cause of traumatic injury to the femoral nerve.

The nerve is rarely damaged by external blows to the limb, but femoral nerve palsy can occasionally be seen in cows below that have repeatedly struggled to get up on slippery surfaces.

Direct injury to the femoral nerve can occur when one or both hind limbs retract caudally, and there is a posterior tear of the iliac and quadriceps femoris muscles through which the femoral nerve passes distal to the hip.

The involvement of these muscles in compartment syndrome and ischemic myopathy in depressed cows provides another opportunity for paralysis of the femoral nerve.

Femoral nerve palsy is associated with the inability to bear weight on the affected limb.

In cases of unilateral nerve injury, flexion of the affected limb flexes, as do all joints of the distal limbs, due to loss of function of the normal stay apparatus.

However, injury to the femoral nerve does not cause the finger to bend to the back of the finger, as would be seen with peroneal nerve palsy. The affected limb cannot bear weight and cannot advance normally.

Complete bilateral femoral nerve palsy causes recumbency and consequently has a poor prognosis in both adult cattle and newborn calves. Occasionally, partial bilateral femoral nerve palsy is seen in descending cows.

The affected animal struggles to stand up with all the hind leg joints in a continuously flexed position, creating a creeping posture.

Femoral nerve palsy lasting more than 2 weeks is associated with significant atrophy of the quadriceps femoris.

When examining a calf with absent patellar reflexes, clinicians must differentiate between femoral nerve palsy and thrombosis of the aorta or iliac arteries.

Calves with bilateral thrombosis have cold extremities that lack sensation on the dorsal and lateral aspects of the extremity.

Mechanism of injury

The femoral nerve can be injured due to compression on the pelvic edge by retractors as seen in abdominopelvic surgery and due to ischemia associated with aortic cross-clamp.

Stretching and compression of the femoral nerve can occur during gynecologic surgery below the inguinal ligament with external rotation of the hips and abduction of the thighs.

It is also associated with invasive procedures to access the femoral vessels and hip replacement.

However, there is no evidence for adopting a particular hip position in order to reduce the occurrence of femoral nerve injury.

Warner, Martin, et al. found four femoral nerve injuries in a series where appropriate precautions were taken to prevent perioperative peripheral nerve injury (PPNI).

Femoral nerve palsy

Femoral nerve palsy and lateral patellar dislocation are closely related in young calves after dystocia or assisted delivery. In both conditions, the quadriceps muscle is biomechanically ineffective with the inability to extend the knee.

Therefore, the clinical signs are similar, and it is somewhat difficult to differentiate from each other. The femoral nerve is damaged by overstretching, while the extended hind limbs insert into the pelvic canal over the cranial border of the pelvic border.

The nerve is damaged as it enters the quadriceps muscle. The experimental sections of the femoral nerve reproduced the clinical conditions.

The patellar luxation is lateral in the calves. Its origin is not yet clear. Femoral nerve palsy, trauma, or congenital weakness of the surrounding patellar ligaments have been evoked as the cause of the dislocation.

Patella laxity is found in calves with femoral paralysis. However, spontaneous dislocation rarely occurs in calves with femoral nerve palsy.

The gait of affected animals is typical. The knee bends and collapses rapidly when the animal tries to bear weight due to the weakness of the quadriceps femoris.

At the same time, the hock is also flexed with the leg slightly delayed. Hypometry is also observed. While standing, the hip of the affected limb is lower and the lower joints flex. There are no fetlock knuckles.

Muscle atrophy appears faster, and is more severe in calves with femoral nerve palsy.

Research has shown experimentally and in clinical cases that atrophy can appear as early as 2 days after nerve injury and significant atrophy after 6 days.

Lack of sensation of the skin may be present on the medial aspect of the tibia if the saphenous nerve has been involved in the trauma. In a study of 30 calves suffering from femoral nerve trauma, 57% lacked skin sensation.

The right leg is more commonly affected than the left for unknown reasons. Chronically affected animals have a prominent femur due to atrophy. After a while, neurogenic atrophy can lead to patellar luxation.

A complete physical examination should be performed to identify other traumatic injuries related to dystocia (eg, long bone fractures). Calves with bilateral femoral paralysis have a poor prognosis.

Calves with unilateral femoral nerve palsy need help standing and nursing. After a few days they will adapt their posture. The final result cannot be predicted based on clinical signs.

Depending on the severity of the nerve damage, clinical signs may improve in 2 weeks to 6 months. Muscle atrophy will improve over time, but it rarely returns to normal.

Patella luxation is treated surgically under epidural or general anesthesia. If the main cause is femoral nerve palsy, surgery may also be done.

It will improve the biomechanics of suffocation and the speed of recovery while the nerve heals and the muscles are strengthened.

Different surgical stabilization techniques have been described for lateral patellar luxation. Medial patellar ligament prosthesis combined with a joint capsule imbrication can be easily performed without invading the knee and without specialized orthopedic equipment.

Another technique is to shorten the intermediate patellar ligament and use a prosthesis between the patella and the tibial crest to keep it aligned on the trochlear crest.

Sulcoplasty is a technique of choice in other species and can also be used in calves. However, knowledge and special orthopedic equipment are necessary to achieve this technique.

Finally, in some rare cases, the lateral connective tissues must be released to allow reduction of the lateral patellar dislocation. If the femoral nerve is normal, postoperative clinical improvement is rapid.

Injuries to animals

Bilateral femoral nerve injury has been seen in dogs after extreme hip extension. With femoral nerve injuries, the knee cannot be fixed (extended) for weight bearing and the animal usually carries the affected limb.

Lesions involving the peripheral femoral nerve cause anesthesia in areas innervated by the saphenous nerve. Selective lesions involving the gray matter of the spinal cord produce motor dysfunction only.

The patellar reflex is absent or diminished; however, the flexor reflex is normal, except for decreased hip flexion. The jumping reaction is greatly diminished in the affected limb because weight bearing is inhibited.

However, if the weight of the animal is compatible, proprioceptive placement should be normal when only the femoral nerve is affected.

Femoral neuropathy can be associated with iliopsoas muscle pathology. The injury may be secondary to bleeding disorders, neoplasia, or primary iliopsoas muscle injury.

Muscle pathology can be detected by ultrasonography or computed tomography (CT), but magnetic resonance imaging (MRI) can provide better visualization. Muscle insertion tectomy can relieve signs of hip pain.

In large animals, femoral nerve palsy produces severe monoparesis. The affected limb is poorly advanced and collapses during weight lifting. In calves and foals, femoral nerve palsy results from trauma during delivery.

Forced removal from the “hip lock” position can hyperextend the hip and overstretch the nerve where it enters the quadriceps muscle. The incidence increases in muscular cattle breeds.

Treatment for femoral neuropathy

Mild cases of femoral neuropathy generally respond to conservative therapy, and surgery should be reserved for more severe cases.

The initial treatment of femoral neuropathy should consist of treatment with simple analgesics, non-steroidal anti-inflammatory agents, or cyclooxygenase-2 inhibitors.

If diabetes is thought to be the etiology of the patient’s femoral neuropathy, strict control of blood sugars is mandatory.

Avoiding repetitive activities that are believed to be responsible for exacerbating femoral neuropathy (for example, repetitive extension and flexion of the hip) will also help improve the patient’s symptoms.

If the patient does not respond to these conservative measures, a reasonable next step is injecting the femoral nerve with a local anesthetic and steroids.

Diagnosing femoral neuropathy

Conditions to consider in the differential diagnosis of femoral mononeuropathy include the following:

  • Vasculitic neuropathy.
  • Lumbar plexopathies.
  • Lumbosacral disc syndromes.

Patients who complain of radiating pain and associated symptoms are commonly seen in chiropractic offices. Although peripheral nerve entrapments of the lower extremity are rare conditions, clinicians should be aware of their existence.

Peripheral mononeuropathy of the lower limb nerve can be associated with confusing clinical manifestations and ineffective patient management. The test may show that you have:

Weakness when straightening the knee or bending at the hip. Sensation changes in the front of the thigh or in the front leg. An abnormal knee reflex. Smaller than normal quadriceps muscles in the front of the thigh.

Tests that can be done include:

Electromyography (EMG). Nerve conduction tests (NCVs), usually done at the same time as an electromyogram. Magnetic resonance imaging (MRI) to detect masses or tumors.

Muscle pathology can be detected by ultrasonography or computed tomography, but magnetic resonance imaging can provide better visualization. Muscle insertion tectomy can relieve signs of hip pain.

Femoral nerve stretch

Femoral nerve stretch is a neural tension test used to place tension on the femoral nerve to diagnose nerve root compression of the mid-lumbar nerve roots (L2-L4).

Femoral nerve stretch is performed with the prone patient. The physician first passively extends the patient’s hip and then passively flexes the knee.

If the familiar symptoms of the patient’s anterior thigh are reproduced or intensified by these maneuvers, the test is considered positive.

It is important to distinguish between the reproduction of the patient’s family symptoms caused by tension on the femoral nerve and stretching of the rectus femoris muscle.

Your provider may order additional tests, based on your medical history and symptoms. Tests may include blood tests, X-rays, and other imaging tests.