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The anterior branches of anterior parts of the L2, L3 and L4 nerves in the lower back area (also known as the lumbar plexus), connect to form the obturator nerve. The brain provides sensation and function to certain parts of the body through this nerve, including the front of the upper leg and the knee. The most important muscles, in relation to this nerve, are the psoas muscle, the internal obturator muscle, the pectineus and adductor longus muscles and the adductor brevis muscle. The obturator nerve ends near the adductus longus muscle by joining the femoral and saphenous nerves. At this point the nerve gives off branches that provide function to the surrounding muscles and the hip joint.
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Causes of Impingement
- Pelvic injury and fractures
- Nerve trapped between the head of the fetus and the bones of the pelvis during delivery
- Nerve compressed between a tumor and the pelvis
- Trauma during abdominal or pelvic surgery
- Total hip arthroplasties
- Keeping the lower limbs in an incorrect position for long periods of time
- Nerve trapped in the adductor magnus muscle, in athletes
- Nerve impinged due to incorrect positioning of an infant’s lower limb during delivery
- Spontaneous impingement on fetal exit from the pelvis
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Symptoms of Impingement
The symptoms caused by the impingement of the obturator nerve affect the structures and functions of the lower back, hip and knee areas. The symptoms include an aching pain in the groin, which radiates from the groin to the inner thigh and to the knee; weakness of the leg, especially after exercise; numbness of the inner thigh; an abnormal walking pattern and posture; and the inability to move the affected leg close to the other leg.
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Diagnosis of Impingement
Impingement of the obturator nerve can be mistaken for a number of conditions involving the lower back and limb area, such as adductor muscle strain, osteitis pubis, stress fracture of the pelvis, inguinal ligament enthesopathy, entrapment of the lateral cutaneous nerve of the thigh and inguinal hernia.
After assessment of the clinical features, the area is examined for further information to help with diagnosis. For a patient with obturator nerve impingement, examination typically points to wasting of the adductor muscles of the thigh and lowered sensation in the inner thigh. A needle examination will be performed on patients who have had groin pain for more than three months in whom this injury is suspected. Ellectrodiagnosis may also be performed.
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If the nerve is inflamed and swollen following entrapment, pain can be controlled by pain killers and other drugs, such as non steroidal anti-inflammatants.
If the condition is recognized at an early stage, impingement is of the anterior nerve can be treated with electrical stimulation applied to adductor and hip flexor muscles, along with stretching and massage of the limb.
If symptoms of obturator nerve impingement and subsequent signs of nerve degeneration are seen in athletes, surgery may be performed, involving cutting the fascia over the pectineus and adductor longus muscles, and then using the space between these muscles to show the anterior part of the obturator nerve under another layer of fascia. This fascia is cut along the nerve, and the muscles will then be closed in a loose fashion.
If nerve impingement symptoms are very troubling for the patient, a steroid injection can be given to control them. This is called obturator nerve block, and it is done mainly to control the pain and inflammation that occurs in response to impingement.
Recovery can take several months to a year, because the healing process of nerves is very slow.
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"Nerve Entrapment Syndromes of the Lower Extremity (Obturator Nerve Entrapment)," http://emedicine.medscape.com/article/1234809-overview#aw2aab6b3
"Obturator Nerve Injury and Entrapment," http://www.med.nyu.edu/neurosurgery/pns/conditions/injuries/obturator.html
"What is the Obturator Nerve?," http://www.wisegeek.com/what-is-the-obturator-nerve.htm