Index
It is a main peripheral nerve of the lower limb.
The obturator nerve in human anatomy arises from the ventral divisions of the second, third, and fourth lumbar nerves in the lumbar plexus; the third branch is the largest, while the second branch is often very small.
The obturator nerve is formed by the anterior divisions of the second, third, and fourth lumbar nerves. It is part of the group of nerves called the anterior lumbar plexus .
Obturator nerve anatomy
It descends through the fibers of the psoas major, and emerges from its medial border near the border of the pelvis.
It then passes behind the common iliac arteries, and on the lateral side of the internal iliac artery and ureter, and runs along the lateral wall of the lesser pelvis, up and in front of the obturator vessels, up to the superior part of the obturator foramen.
Here it enters the thigh, through the obturator canal, and divides into an anterior and a posterior branch, which are separated first by some fibers of the external obturator, and further down by the adductor brevis.
The obturator nerve is divided into anterior and posterior branches. The anterior branch provides motor innervation to the superficial adductors and sensory innervation to the hip joint and the medial aspect of the distal thigh.
The articular branches of the obturator nerve supply the hip and knee joints, and therefore pain in one joint may manifest as referred pain in the other.
The posterior branch provides motor innervation to the deep adductors and sensory innervation to the posterior knee joint.
Similarly, pelvic inflammation affecting the obturator nerve can cause referred pain along the medial aspect of the thigh.
In rare cases, it also emits a branch to the pectineus muscle. It then pierces the fascia lata to become the cutaneous branch of the obturator nerve.
Motor function
The obturator nerve innervates all muscles in the medial (adductor) compartment of the thigh, provides motor function to the hip and knee joints, and the abductor and gracilis muscles, except for the hamstring portion of the adductor magnus, which is innervated by the tibial nerve.
Long adductor : thigh adduction.
Short adductor : thigh adduction.
Adductor magnus : the adductor part adheres and flexes the thigh, the thigh part extends the thigh.
Gracilis : adduces thigh.
External obturator : laterally rotate the thigh.
Sensory function
The cutaneous branch innervates the skin of the medial thigh, in other words, it provides sensory perception to the skin on the medial side of the thigh.
Innervation
The obturator nerve is responsible for the sensory innervation of the skin of the medial aspect of the thigh.
The nerve is also responsible for the motor innervation of the adductor muscles of the lower limb (external obturator, adductor longus, adductor short, adductor magnus, gracilis) and the pectineus (inconstant).
In particular, it is not responsible for the innervation of the internal obturator, despite the similarity in name.
Clinical relevance
Persistent pain in the groin and thigh area is a difficult clinical problem to assess. There are many entities that produce pain in the groin, including tendinitis, bursitis, osteitis pubis, stress fracture, sports hernias or athletic pubalgia, nerve entrapment.
Obturator neuropathy is a difficult clinical problem to diagnose. In some cases, a report of compression of the obturator nerve, specifically its anterior division, is a possible cause of pain in the adductor region.
Damage to the obturator nerve
The obturator nerve can be damaged through injury to the nerve itself or to the surrounding muscle tissue. This type of injury can happen during a home or car accident and can also happen accidentally during abdominal surgery.
The obturator nerve can be damaged during surgery involving the pelvis or abdomen. Symptoms include numbness and paresthesia in the medial aspect of the thigh and weakness in the adduction of the thigh.
Alternatively, the patient may have posture and gait problems due to loss of adduction. In a series of 991 patients anesthetized for surgery in the lithotomy position, five developed obturator nerve palsy.
Compression of the obturator nerve can occur against the inferior aspect of the pubic ramus at the level of the obturator foramen in the lithotomy position. Hip abduction more than 30 ° without hip flexion increases stress on the obturator nerve.
There is insufficient scientific evidence to suggest a specific strategy to prevent obturator nerve injury.
Limiting the degree of hip flexion in a patient in the 90 ° lithotomy position can reduce the incidence of neuropathy of the sciatic nerve and its branches, including the obturator nerve.
The obturator nerve can be compressed in the pelvis by a tumor or by a fetus in pregnant women. It can also be compressed against the pubis in highly flexed hip positions.
His injury often occurs with pelvic fractures and may also be related to diseases or injuries related to the hip and sacroiliac joints.
In significant obturator nerve injuries, atrophy along the medial aspect of the thigh, adduction weakness or paralysis of the hip, and sensory disturbances along the distal medial surface of the thigh are common findings.
Obturator neurectomy may be beneficial in spastic conditions.
Obturator nerve block
Obturator nerve block is used to treat pain after lower limb surgery or for chronic hip pain.
The anesthetic is injected below the pubic tubercle and lateral to the adductor longus tendon. The procedure can also be carried out under ultrasound guidance.
Obturator nerve block is useful in the evaluation and treatment of hip pain and hip adductor spasm believed to be affected by the obturator nerve.
The technique is also useful in providing surgical anesthesia for the lower extremity when combined with lateral cutaneous, femoral, and sciatic nerve blocks.
Obturator nerve block under local anesthesia can be used as a diagnostic tool during differential neural block on an anatomical basis in the evaluation of hip pain.
If destruction of the obturator nerve is being considered, this technique is useful as a prognostic indicator of the degree of motor and sensory impairment that the patient may experience.
Obturator nerve block under local anesthesia can be used to alleviate acute pain emergencies, including postoperative pain relief, while waiting for pharmacological methods to become effective.
Obturator nerve block under local anesthesia is also helpful in treating hip adductor spasm, which can make perineal care or urinary catheterization difficult. This technique is also useful to aid in physical therapy after hip surgery.
Obturator nerve block with local anesthesia and steroids is also useful in the treatment of persistent hip pain when the pain is believed to be secondary to inflammation or entrapment of the obturator nerve.
Destruction of the obturator nerve is occasionally indicated for the alleviation of persistent hip pain after obturator nerve-mediated trauma to the hip.
Surgical anesthesia
The obturator nerve must be blocked for any procedure above the knee or when a pneumatic tourniquet is placed on the thigh. It is blocked with the femoral, cutaneous lateral femoral, and sciatic nerves for this purpose.
One of the most important surgical indications is due to the anatomical relationship of the obturator nerve, as it runs close to the neck of the bladder and the prostate.
Due to the proximity of the nerve to the prostate, this nerve can be electrically stimulated during transurethral resection.
This stimulation can produce significant contraction of the adductors, which can interfere with the surgical procedure and can sometimes even result in perforation of the bladder.
This can occur even with adequate spinal analgesia that blocks the nerve roots near the site of stimulation. Local anesthetic block of the obturator nerve has been well documented to eliminate spasms and facilitate prostate surgery.
Sharp pain
Obturator nerve block with local anesthetics such as bupivacaine is helpful in treating acute pain in the hip and lower medial thigh after pelvic trauma, total hip replacement surgery, and other acute pain emergencies.
Because the involvement or irritation of the obturator nerve can produce a significant spasm in addition to pain.
This technique can be extremely helpful in providing symptomatic relief allowing the patient to comfortably undergo radiographic studies, MRI, or CT scan of the hip or pelvic bones.
Chronic pain
Because the hip joint derives significant innervation from the obturator nerve, blockage of this nerve was one of the main indications in patients with degenerative hip disease.
However, since the advent of total joint replacement, the number of patients requiring this type of block has decreased significantly. It can still be useful as a diagnostic block for a complex pain problem.
Even under these circumstances, a direct hip joint injection provides more valuable diagnostic information than obturator nerve block. Obturator nerve entrapment has been described in athletes and after pelvic surgery.
The obturator nerve has been successfully released surgically. A diagnostic nerve block can help make the diagnosis.
Spasticity
One of the most important non-surgical indications is adductor muscle spasticity. The obturator nerve block is widely used to relieve adductor spasm and improve personal hygiene for patients with spasticity.
Oral dosing and intrathecal injection with baclofen very significantly reduce the use of neurolytic obturator nerve block for this purpose.
But it is still a useful technique for those patients in whom pharmacological methods are not tolerated or do not produce the desired results.
Obturator nerve disorders
Isolated obturator neuropathies are rare. In the series reported by the Mayo Clinic, 22 cases were identified. Most of them were due to surgical procedures: total hip replacement, pelvic surgery, femoral artery procedure, or prolonged tourniquet use.
Two cases were due to pelvic trauma and two cases were due to metastatic disease in the obturator canal. Pelvic tumors can damage the obturator nerve. Obturator nerve injury during gynecologic oncology is rare.
Intra-abdominal surgery can selectively damage the obturator nerve. Other causes include postpartum, lithotomy position, obturator hernia, hypogastric artery aneurysm, acetabular lip cyst, and schwannomas.
Chronic groin pain in athletes may be due to entrapment of the obturator nerve with fascial entrapment of the nerve as it enters the thigh. The relationship between the obturator nerve, the vessels, and the fascia appears sufficient to produce an entrapment syndrome.
Symptoms of damaged obturator nerve
An obturator nerve injury produces weak adduction of the thigh and a tendency to abduct the thigh when walking. There is also weakness of the external rotation of the thigh.
The most common presenting symptom is sensory disturbance in the medial thigh. A small area of anesthetic skin on the medial thigh is present. A damaged obturator nerve can cause pain, numbness, and weakness in the thigh.
Patients with motor impairment may complain of problems walking or weakness in the legs. They cannot adduct the hip normally. Some patients have sensory symptoms in the affected medial thigh or groin pain (athletes).
On examinations, the hip adductors are weak and there may be sensory loss in the middle and lower thighs of the medial thigh. When walking, the hip is abnormally abducted.
The obturator nerve can become trapped within the thick fascia that covers the adductor brevis muscle. This is often seen in athletes who report deep pain in the groin and mid-thigh, as well as weakness with exercise.
Pelvic trauma, especially affecting the sacroiliac joint, can damage the obturator nerve, although this nerve is rarely damaged in isolation, and usually affects other nerves, the lumbosacral plexus, or the lumbar nerve roots.
Latrogenic injury has been reported with a number of pelvic surgeries, total hip replacement, and femoral artery procedures.
The lithotomy position has also been implicated in obturator nerve injury, and in prolonged labor, the fetal head may compress the nerve against the lateral wall of the pelvis. Tumors can also compress the nerve within the pelvis.
These symptoms can include paresthesias, sensory loss, or pain. The most common reported symptom in one study was medial thigh or groin pain.
A deep pain can be described in the region of origin of the adductor in the pubic bone and can extend to the medial aspect of the thigh to the knee. The exacerbation of pain can be caused by maneuvers that extend the nerve by extension or by lateral movement of the leg.
Sensation along the medial thigh may also decrease. In some cases, these sensory ailments can extend to the mid calf. However, the obturator nerve rarely provides sensation distal to the knee.
Functionally, patients can demonstrate a circumcised gait. When caused by trauma or surgery, the presentation may initially be masked by pain from pelvic injuries.
Obturator nerve exams
Radiographic images provide limited diagnostic aid. Plain radiographic studies are normal in people with obturator neuropathy.
However, there may be features found on x-ray that can identify a cause of groin pain other than obturator neuropathy.
CT and MRI can detect compressive masses within the pelvis, and MRI can detect atrophy of the adductor and gracilis muscles associated with denervation.
MRI can also be used to obtain the basal anatomical structure of the groin region of patients in whom surgery is a possibility and to exclude other causes of groin pain.
MRI can detect atrophy of the adductor brevis and longus and gracilis suggesting denervation and entrapment of the obturator nerve. However, it cannot detect any abnormalities of the nerve in the thigh or in the fibro-osseous tunnel.
Other images such as computed tomography or ultrasound may be helpful in suspecting massive intrapelvic lesions that entrap the obturator nerve.
Scintigraphic bone scan can demonstrate a mild ipsilateral increase in uptake in the region of the pubic ramus, at the origin of the adductor short or long muscle.
But since obturator neuropathy is primarily a soft tissue problem, MRI is typically of higher performance.
Electromyography is most helpful in detecting obturator neuropathy (with hip adductor needle), and can be confirmed with a local nerve block.
There have been no nerve conduction studies regarding the obturator nerve; however, needle electromyography demonstrates evidence of denervation of the muscles innervated by the nerve.
It is also useful to differentiate it from other entities, such as lumbar plexopathy or upper lumbar radiculopathies.
Bradshaw et al. showed chronic denervation in the short and long adductor muscles of athletes with chronic groin pain attributed to obturator neuropathy.
Obturator foramen nerve block can be diagnostic both to relieve pain with provocative maneuvers and to reproduce exercise-induced weakness.
Most patients with obturator neuropathy have a good recovery with conservative management.
In patients with compression of the obturator nerve in the obturator canal, surgery to release the nerve should be considered in those who do not respond to conservative treatment but respond to diagnostic nerve block, particularly in athletes.
Despite the fact that many muscles used in thigh adduction are interned by nerves other than the obturator nerve. Adduction on the affected side is generally weak. Medial thigh wear can sometimes be seen.
With severe injuries, loss of adduction and internal rotation occur. During ambulation, the hip is externally rotated and abducted abnormally, resulting in a wide circumvallation gait.
Ipsilateral loss of the hip adductor tendon reflex may be present, but is only suggestive, not pathognomonic, of obturator neuropathy.
Because this reflex does not always occur in healthy individuals, the presence of this reflex in the contralateral asymptomatic leg must occur for the finding to be useful.
Obturator nerve treatment
Mild damage to the obturator nerve can be treated with physical therapy. More severe cases may require surgery. The nerve has the ability to regenerate at a rate of about one inch per month.
Pharmacological pain management and physical therapy may be helpful in the acute phase of the injury (to improve strength and preserve mobility and ambulation). Obturator neuropathy can be treated by laparoscopic neurolysis.
Medication may include non-steroidal anti-inflammatory drugs (NSAIDs) or other pain relievers such as acetaminophen. Rest, modifying the activities that initially caused the event, or substituting them for other activities can offer relief.
Physiotherapy, massage, or nerve blocks can be tried. However, conservative management may not be an adequate alternative to the high-level athlete or in those with refractory treatment.
There may be a temporal relationship between nerve injury, therapy, and recovery. Therefore, athletes with diagnosed obturator neuropathy should try only a limited course of conservative therapy.
Sorenson et al. stated that patients with acute-onset obturator neuropathy had a good recovery with conservative treatment. In contrast, people with chronic neuropathy are less likely to get better and therefore result in a worse outcome.
In entrapment syndromes, conservative treatment is used for the first time, but in high-level athletes it may not be appropriate and surgery should be considered.
Surgery should be considered in those with pain and weakness resistant to conservative therapy and documented electromyographic changes or response to nerve block.
Surgical nerve decompression should be considered for injuries documented by electromyography or local nerve block, for those with predisposing risk factors (previous surgery, pelvic trauma, or hematoma), and with prolonged or severe injuries.
Good results are reported after surgical release along the nerve. A physical therapy rehabilitation plan should be implemented with a gradual return to activities after surgery, with an expected return to activity at 3-6 weeks.
Restorative function of the obturator nerve
The obturator nerve emerges from the medial side of the psoas muscle, crosses the lesser pelvis, and passes through the obturator foramen into the medial thigh, innervating the adductor longus, short, and magnus; gracilis; external shutter; and pectineal muscles, whose action is to adduct the thigh.
Traumatic injury to the obturator nerve is rare; however, iatrogenic injury has been described in the context of radical or retroperitoneal surgery for gynecologic malignancy, urologic or orthopedic procedures, such as radical prostatectomy and total hip replacement.
Different strategies have been described to treat obturator nerve injuries, depending on the type of injury and the surgeon’s preference. Immediate repair with direct end-to-end coaptation or interpositional nerve graft has been used with success.
However, the obturator nerve is not easily mobilized on its intrapelvic path and, in the context of pelvic surgery, the nerve is often difficult to identify as it is heavily encapsulated in scar tissue.
In these scenarios, the use of conventional techniques can become a significant challenge.
Furthermore, because nerve disruption frequently occurs very proximal from the muscle end organ, the results of local repair at the injury site may be less favorable.
Therefore, nerve transfer would be considered a good option to restore the function of the obturator nerve in those patients in whom the proximal stump is not available, or in cases where the predicted result using conventional graft is poor.
There is only one report in the literature that describes a nerve transfer technique to restore the function of this nerve:
Spiliopoulos and Williams (2011) performed the transfer of a redundant motor branch from the femoral nerve to the obturator nerve in a patient in whom the injury occurred during major pelvic surgery for ovarian neoplasia.
The authors reported that, 1 year after surgery, the patient had a full M5 strength in thigh adduction with normal gait and electromyographic signs of recovery of the right adductor muscle, suggesting almost complete regeneration. of the functional obturator nerve.
The obturator nerve and athletes
The obturator nerve is rarely injured in isolation. Several authors have described a nerve injury after tumor surgery, hemorrhage, or compression. However, the discussion of sports-related injuries is also important.
Bradshaw et al. described obturator neuropathy in athletes as a result of fascial entrapment as the nerve enters the thigh, specifically in the adductor compartment.
Exercise-induced, the pain had a characteristic clinical pattern of medial thigh pain beginning in the region of the origin of the adductor muscle and radiating distally along the medial thigh, with strenuous exercise.
An anatomical study of cadaver limbs by Harvey and Bell reinforced the concept that obturator neuropathy is caused by an entrapment syndrome due to the relationship between nerves, vessels, and fascia.
Brukner and Khan state that there may be “associated weakness or a sense of lack of propulsion of the limb during running, but numbness is very rarely reported.”
Denervation of the adductor muscles was demonstrated by needle electromyography. Conservative medical management has had limited success.
Conservative treatment included rest, physical therapy (such as ultrasound and interference therapy), soft tissue massage, pelvic and adductor muscle strengthening exercises, oral anti-inflammatory therapy, corticosteroid injection, and groin stretches.
In contrast, surgical neurolysis provides better results with athletes returning to competition within several weeks of treatment. At surgery, the entrapment of the obturator nerve by a thick fascia covering the adductor brevis muscle was described.
However, the reproduction of this entrapment neuropathy postulated by other researchers has yet to be found.
