The femoral nerve arises from the lumbar plexus within the psoas major muscles and is formed from the posterior divisions of the ventral rami of spinal nerves L2 through L4
Ilioinguinal Entrapment Neuropathy
The ilioinguinal nerve is derived
Muscle injuries can result from a variety of causes including poor flexibility, uncoordination, inadequate warm-up, muscle strength imbalance, muscle weakness, fatigue, electrolyte imbalance, poor sports technique, and increased age (3). Some of the most common thigh strains are of the adductor longus, rectus femoris, and iliopsoas.
Adductor longus strain. While the adductor longus, adductor magnus, adductor brevis, and pectineal muscles are all adductors of the hip (figure 3), of these the adductor longus is most often injured in sports (1).
The mechanisms of injury to the adductor longus include acute injury—such as a powerful abduction stress during simultaneous adduction of the leg when performing a cutting movement—or overuse, such as repetitive abduction of the free leg in the skating stride. With a sudden change of direction that occurs with sharp cutting movements, a forceful eccentric contraction of the muscle occurs instead of a concentric contraction, causing the strain. While a forceful muscle contraction in an adult may cause a strain in the muscle-tendon unit, the same action in an immature athlete may cause an avulsion fracture (4).
An acute strain will cause pain that feels like a sudden stab in the groin area. If the injured athlete tries to continue the activity, the intense pain will recur. There may be swelling and bruising localized to the origin of the adductor longus tendon or at the musculotendinous junction. Overall, the patient has the classic musculotendinous injury triad: (1) tenderness to palpation, (2) pain with resisted movement (in this case, adduction), and (3) pain with passive stretching (in this case, abduction).
Imaging procedures are usually unnecessary in simple strains, although images may be obtained to rule out more severe injuries such as avulsion fractures. Ultrasound, though operator dependent, is a cost-effective method to confirm muscle tears.
Treatment of acute groin injuries begins with rest from aggravating activities for 1 to 2 weeks. Icing, compression shorts, and NSAIDs provide symptomatic relief. Physiotherapy should begin as soon as pain allows and should initially include isometric contractions without resistance, followed by isometric contractions against resistance, the limit being pain.
After the initial phase of inflammation has subsided, athletes can begin a stretching program. Heat increases the extensibility of the collagen in tendons and muscles and will be beneficial for the remainder of rehabilitation. Maintenance of cardiovascular fitness with aerobic exercises that do not exacerbate the pain should be greatly encouraged. Preventive training and the correction of predisposing factors (eg, intrinsic muscle tightness, muscle strength imbalances, or muscle weakness) should be included in a complete rehabilitation program.
Rectus femoris strain. The rectus femoris is heavily activated and commonly overused during running, jumping, bicycling, and skating (1). Originating just above the acetabulum and inserting as the patellar tendon at the tibial tuberosity (figure 3), the rectus femoris flexes the hip and extends the knee.
The pain from a rectus femoris strain may be felt from the area anterior to the acetabulum and may radiate to the thigh and inguinal area. Pain can be reproduced by resisted hip flexion or resisted knee extension.
Conservative treatment as outlined for injuries of the adductor longus should be used. The risk of myositis ossificans is increased in cases of significant muscle hemorrhage. Initial bleeding leads to formation of a hematoma, which later calcifies within the substance of the muscle, restricting its flexibility (3). Keeping the muscle in a lengthened position can help decrease further bleeding and subsequent heterotopic bone formation. Wrapping the affected area with ice and an elastic bandage, with the knee in maximum flexion, is optimal therapy in the first 24 hours. Some authors believe that NSAIDs should be avoided in the first 48 hours.
Iliopsoas strain. Strain of this strong hip flexor commonly occurs in weight lifting, uphill running, and sit-ups.
Tenderness associated with this strain is difficult to palpate, since the iliopsoas muscle inserts at the lesser trochanter of the femur. If the site is to be successfully palpated, palpation will be done bimanually over the medial aspect of the femur. Pain can be elicited by having the patient flex the hip 90° and then try to flex it further against resistance or by passive stretching with hyperextension at the hip.
Conservative treatment as outlined for injuries of the adductor longus should be used.
The chief lower abdominal wall injuries in active patients include rectus abdominis strain, inguinal hernia, ilioinguinal neuralgia, and conditions called "sports hernia" and "hockey player's syndrome."
Strain of the rectus abdominis. The rectus abdominis muscle originates on the pubic bone, very close to the origin of the adductor longus. Strain in this muscle is usually caused by overloading, as in weight lifting or doing sit-ups. Pain is localized at the origin and is reproduced by elevating the legs and/or the head with the patient supine.
A rectus abdominis strain can be difficult to differentiate from an intra-abdominal process such as appendicitis. A key diagnostic clue is localized tenderness that is accentuated when the patient contracts the muscle and decreases with muscle relaxation.
Conservative treatment as outlined for injuries of the adductor longus should be used. In chronic, recalcitrant cases, such as significant tears, surgical repair may be necessary.
Inguinal hernia. Hernias are common enough that every patient suffering from groin pain should be examined to eliminate this possibility. An inguinal hernia is located above and medial to the pubic tubercle. A femoral hernia, more common in female patients, is below and lateral to the pubic tubercle.
The most common type of hernia is a direct inguinal hernia, which appears as a diffuse bulge at the internal ring, in the medial part of the inguinal canal. An indirect inguinal hernia is congenital in origin and is caused by a failure of the processus vaginalis to close. It therefore appears at the external ring and may extend into the scrotum. In contrast to what some authors have called "groin disruptions" or in contrast to the "sports hernia" described below, inguinal hernias result from a weakness or tear of the posterior wall of the inguinal canal (transversus abdominis) (1,4).
In most cases, activities that significantly increase intra-abdominal pressure or may involve repeated Valsalva's maneuvers, such as weight lifting, cause or exacerbate the hernia. While the pain might initially occur only after activity, it typically will increase in frequency to the point of occurring during activity and even with simple trunk and hip movements. The pain will often radiate into the proximal thigh or the scrotum in males.
Examination for both types of hernia involves invaginating the scrotal skin along the spermatic cord using the index finger in males or direct palpation in females. A palpable mass may or may not be detected. Maneuvers to increase intra-abdominal pressure, such as coughing or tensing the abdominal musculature, may produce a cough impulse (a sign of hernia), or may make a mass more prominent.
Inguinal hernias should be surgically repaired not only to relieve pain and discomfort, but also to prevent incarceration, obstruction, and infarction of the bowel.
Ilioinguinal neuralgia. The ilioinguinal nerve originates from the L1-2 nerve roots and is similar in course and function to the intercostal nerves (figure 4). It innervates the lowest portions of the transversus abdominis and internal oblique muscles, as well as the skin overlying the inguinal ligament.
It transmits sensation from the base of the penis and scrotum (or labium major) along with part of the medial thigh. Direct trauma, intense abdominal muscle training, or inflammatory conditions can lead to entrapment of this nerve as it passes through or close to the abdominal muscle layers. Ilioinguinal nerve entrapment is a well-established cause of chronic inguinal pain in patients who have had lower abdominal surgery (eg, appendectomy or inguinal herniorrhaphy) (5).
Patients will describe a burning or shooting pain in the distribution of the nerve. Light-touch sensation in the inguinal area may be altered, and pain may be exacerbated by hyperextension of the hip. Tenderness may be localized near the anterior superior iliac spine where the ilioinguinal nerve pierces the fascia. The diagnosis can be confirmed by a blockade of the nerve with local anesthetics.
Treatment consists of repeated infiltrations at the confirmed site with anesthetics and/or corticosteroids. Nerve ablation may be indicated in severe cases.
Sports hernia. Athletes in fast-moving sports that involve twisting and turning—like soccer and ice hockey—may be at particular risk of a disruption in the area of the inguinal canal. This injury, often called a "sports hernia," usually involves the posterior wall of the inguinal canal and can appear as a tear of the transversus abdominis muscle or as a disruption to the conjoined tendon, which is the tendon of insertion of both the internal oblique and transversus abdominis muscles (6). A sports hernia may, however, involve the internal oblique muscle and external oblique aponeurosis of the internal inguinal wall (7). It differs from the more common inguinal hernia in that it does not involve a clinically detectable hernia.
A sports hernia typically produces unilateral groin pain during exercise (figure 5). In chronic cases, however, the patient may have symptoms during activities of daily living. Onset of pain is usually insidious but may occur suddenly in some cases. It is typically localized to the conjoined tendon but can involve the inguinal canal laterally. Sudden movements often exacerbate the pain.
Examination for the sports hernia is generally done by inverting the scrotal skin with a finger and palpating for pain over the conjoined tendon, pubic tubercle, and midinguinal region. The pain may be exacerbated by sit-ups. Radiographs are important to rule out other injuries.
Treatment is generally surgical. Rehabilitation includes 6 to 8 weeks of pelvic strength, stability, and flexibility exercises and avoidance of sudden, sharp movements.
Hockey player's syndrome. A subset of the sports hernia has been called "hockey player's syndrome." Since 1989, elite ice hockey players have been referred to our center for an atypical lower abdominal pain syndrome (figure 5: not shown) that resembles but does not clearly correspond to previously described entities. In 1998, colleagues and I published a report (5) on 11 of these professional hockey players, a small subset of the 50 or more patients who have now been treated for this condition at our institution.
This hockey player's syndrome—also referred to as the "slap-shot gut"—involves a tear of the external oblique aponeurosis, associated with inguinal nerve entrapment. The pain is muscular in nature, of gradual onset, and exacerbated by ipsilateral hip extension and contralateral torso rotation. Interestingly, it occurs almost exclusively on the side opposite the player's forehand shot. It is felt mostly during the propulsive phase of skating (the first few strides) and during the slap-shot motion. Inherent abdominal wall weakness, musculoskeletal fatigue, and poorly adapted equipment probably all contribute to this overuse injury of the lower abdominal wall.
Physical examination reveals no overt signs of hernia, although palpation of the superficial inguinal ring may reproduce the pain. Conventional imaging modalities such as bone scan, ultrasound, CT, and MRI all fail to reveal the defect. Surgical exploration is currently the only method to confirm the diagnosis.
Surgical treatment involves restoring normal anatomy by repairing the external oblique aponeurosis. Neurectomy of the ilioinguinal nerve is also performed. The patient is advised to refrain from skating or other types of violent twisting and turning motions for 4 weeks postoperatively and is then gradually returned to full activity over the next 6 to 8 weeks. Physiotherapy, pool therapy, stationary cycling, and controlled weight training are the mainstays of rehabilitation (5).
Injuries located within the anatomical area described as the "groin" require astute history-taking and physical-exam skills. Once a careful diagnosis is made, tailored management—often involving conservative measures—will help patients return to full activity as quickly as possible. Judicious use of appropriate diagnostic imaging studies may help focus the large differential diagnosis of these injuries.
Dr Lacroix is director of the Primary Care Sports Medicine Fellowship Program in the Department of Family Medicine at McGill University in Montreal. Address correspondence to Vincent J. Lacroix, MD, McGill University Sport Medicine Clinic, 475 Pine Ave W, Montreal, QB, Canada H2W 1S4; e-mail to firstname.lastname@example.org.
The Iliopsoas Muscle -- The Great Pretender
By Kenneth Rich, DC
The description is appropriate. The iliopsoas muscle is a major body mover but seldom considered as a source of pain. It mimics low back pain, hip pain, and leg pain individually or in combination.
Have you ever had a patient with classic lumbar sprain/strain symptoms that didn't seem to get better in a reasonably short time? No matter what adjustments or therapy you administered, did the condition gradually worsen? Did it seem to spread to surrounding areas in the hips, legs, and thoracic regions? The chances are you were dealing with an iliopsoas muscle spasm. It often accompanies other conditions affecting the low back.
It's very important to understand the anatomy involved. The iliopsoas muscle is comprised of two parts. The iliacus and psoas muscles are joined to each other laterally along the psoas tendon. The iliopsoas originates anterior to the transverse processes of the T12 to L5 vertebrae and inserts into the lesser trochanter of the femur. Both are innervated by the 1st through 3rd lumbar nerve roots. As a combined muscle it is a major flexor of the trunk at the pelvis. In fact, it is considered the most powerful flexor of the thigh. It traverses the body internally, and is only accessible in a very small area in what is known as the femoral triangle, where it inserts into the lesser trochanter of the femur.
This location, major action and inaccessibility account for it being a great pretender. Since it originates anterior to the transverse processes and angles internally there is no therapy which will penetrate deep enough to affect it from the posterior. The lumbar attachment and innervation account for the pain felt in the posterior lumbar region. Because it is a major flexor, if it is in spasm, it will cause many of the regional muscles to compensate and become overused, hypertonic, spasmodic and painful in their own right. Since it is a muscle not known nor understood by most people, it is difficult for most patient to describe the location any more specifically than the low back.
Classic symptoms of an iliopsoas muscle spasm are diffuse achy- type low back pain of a few days onset. The history is generally not specific to an injury which would be considered for low back pain, but it can be. The pain seems to spread to the rest of the low back, lower thoracic and even into the gluteal and lateral hip regions. Most often a key factor is initial pain upon rising from a seated position which may dissipate in a short time. It is difficult to stand upright quickly. Standing, walking and laying down don't seem to affect it badly. Occasionally there may be pelvic discomfort and bowel complications in the history. Relief of pain is often experienced by sitting down. However, extending the leg, as in driving, can make the pain worse. The types of physical actions which seem to cause this condition are standing and twisting at the waist without moving the feet; any action which causes the leg to externally rotate while in normal extension; and even doing too many sit ups (this is the muscle which completes the last half of a sit up).
A few simple tests are in order. Since the action and position are specific, have the person externally rotate their leg and foot 90° and extend it backward with the knee straight and the forward knee flexed and pelvis straight. (Think of kicking a soccer ball with the instep of the foot while doing a fencing forward thrust). This may produce minor pain. Have the person lie on their back and raise and hold both legs 12 inches off the table. This may produce pain, but usually a weakness, especially on the injured side. Have the patient do a sit up against resistance at the 45° position. This should produce some moderate pain in the groin area. The most positive diagnostic test is to have the person flex the knee, hip and externally rotate the leg, such that the lateral malleolus is laying on top of the contralateral knee. Palpate the femoral triangle deeply (press with a single finger 3/4 to 1 inch deep) and look for a reaction. Do this over an area enclosed within the femoral triangle, not just in one spot. If the iliopsoas muscle is in spasm the patient will jump off the table. Believe me, it's that painful. Many patients have said it's worse than childbirth, nonanesthetized root canals or body piercing with a flaming sword.
I've found this to be a very common condition. On the average I see about 8-15% of my patients having this in connection with their low back pain. Because of its major function it is a common muscle to become either overused or injured during extension and external rotation of the leg or flexion of the trunk.
Now that you've found it, what do you do? Unfortunately because of its location it is not treatable by most normal therapies. Many times even an adjustment will not relieve the condition, because once the adjustment is done the hypertonic muscle will return the joint to subluxation. I've found that in most cases I need to treat the surrounding regions of associated muscle pain, I do trigger point therapy within the femoral triangle to the insertion region of the muscle. This is extremely painful to the patient, but phenomenal in its positive effect. If you are not into causing pain, even for good therapy, send the patient to another doctor or massage therapist who will do this therapy.
Advise the patient that they will feel severe pain, but that it will only last for about 15 to 30 seconds. The patient is to tell you when you hit a spot which feels like a hot knife being stabbed into their muscle. The actual trigger point therapy is performed by applying strong pressure into the femoral triangle. When you find the right spot the patient will react strongly to the pain. Continue to apply the pressure without moving your fingers. Have the patient tell you when the pain begins to become less sharp or begins to subside, not when it's all gone, but only when it begins to subside. Move your finger a fraction of an inch in any direction and look for more trigger points. Generally you will find from 3-6 trigger points within the femoral triangle. Once you have treated each point, go over them one more time to retreat stubborn ones which have come back. This process will take about 2-3 minutes per leg. When the therapy is done apply a stretch to the muscle by pressing down on the bent knee and the contralateral hip against strong patient contraction of the muscle for about 10 seconds. Have the patient relax the leg and apply a little more pressure to the leg to give a small additional stretch to the muscle in a relaxed state.
I have my patients return the next available day for a follow-up. I continue to treat until the trigger points are not there when I palpate for them. The general sensation of pain will subside before this point is reached, but therapy must continue so that the dormant trigger points won't return.
This condition, like many other we repeatedly face, may be overlooked if one isn't looking for it. Often it is the low back pain we notice instead. The next time you have a diffuse low back pain patient who isn't responding as expected, try looking for a different muscle -- the iliopsoas muscle -- the great pretender.
Kenneth Rich, DC
The iliohypogastric nerve arises primarily from the ventral primary rami of L1 and occasionally with a twig from T12. This nerve has a pathway similar to the intercostal nerves in the thoracic region. The iliohypogastric nerve traverses the psoas major muscle to pierce its lateral border anterior to the quadratus lumborum muscle and posterior to the kidney to traverse the lateral abdominal wall. The nerve penetrates the transverse abdominal muscle near the iliac crest coming between it and the internal oblique musculature. The nerve then supplies the lower fibers of the transverse abdominal muscle and the internal oblique, and divides into the lateral and anterior cutaneous branches.
The anterior cutaneous branch continues anteriorly between the internal oblique and transverse abdominal muscle, then pierces the internal oblique and becomes cutaneous through an opening in the fascial aponeurosis of the external oblique muscle approximately 2-3 cm cephalad to the superficial inguinal ring. The distribution of the cutaneous sensation is a small region just superior to the pubis.
The iliohypogastric nerve is rarely injured in isolation. The most common causes of injury are surgical procedures. These include transverse lower abdominal incisions, as in hysterectomies, or injuries from procedures such as inguinal herniorrhaphy and appendectomies. The injuries mainly occur if the incision extends beyond the lateral margin of the inferior rectus abdominis fibers. The damage can result from direct surgical trauma, such as passing a suture around the nerve and incorporating it into the fascial repair, or postoperative entrapment in scar tissue or neuroma formation. Sports injuries such as trauma or muscle tears of the lower abdominal muscles may also result in injury to the nerve. It may also occur during pregnancy due to the rapidly expanding abdomen in the third trimester. This is called the idiopathic iliohypogastric syndrome and is rare.
Symptoms include burning or lancinating pain immediately following the abdominal operation. The pain extends from the surgical incision laterally into the inguinal region and suprapubic region. Discomfort may occur immediately or up to several years after the procedure and may last for months to years. This discomfort is possibly because of the formation of scar tissue in the region. Occasionally, the pain may extend into the genitalia due to the significant overlap with other cutaneous nerves. Loss of sensation is usually minimal and not problematic. Iliohypogastric nerve entrapment causing symptoms similar to trochanteric bursitis refractory to conventional therapy has been reported.
On examination, pain and tenderness are usually present in the area of scarring or entrapment. Hyperesthesia or hypoesthesia may occur in the area supplied by this nerve. Diagnosis is difficult due to the small area of cutaneous supply that this nerve provides. There may be overlap in sensory supply with the genitofemoral and ilioinguinal nerves.
Three major criteria are used to diagnose this nerve injury. The first is a history of surgical procedure in the lower abdominal area, although spontaneous entrapment can occur. Pain can usually be elicited by palpating laterally about the scar margin, and the pain usually radiates inferomedially toward the inguinal region and into the suprapubic and proximal genital area. Second, a definite area of hypoesthesia or hyperesthesia should be identified in the region of supply of the iliohypogastric nerve. Third, infiltration of a local anesthetic into the region where the iliohypogastric and ilioinguinal nerves depart the internal oblique muscle and where symptoms can be reproduced on physical examination by palpation should provide symptomatic relief.
If no relief is obtained with injection, a different etiology should be sought for the discomfort. Alternate diagnoses include upper lumbar or lower thoracic nerve root pathology or discogenic etiology of the pain. If the iliohypogastric nerve is clearly identified as the source of pain and a favorable response is not obtained to local anesthetic injection, then surgical exploration and resection of the nerve should be considered. No reliable electrodiagnostic techniques are available to define the integrity of this nerve, although needle electromyography (EMG) of the lower abdominal musculature may serve as an adjunct in the diagnosis.
Treatment includes the local injection of an anesthetic as noted above, oral medications, or physical therapy. The oral medications may include antiseizure medications such as gabapentin (Neurontin), carbamazepine (Tegretol), or lamotrigine (Lamictal), as well as nonsteroidal anti-inflammatory drugs (NSAIDs), tricyclic antidepressant medications (amitriptyline [Elavil], doxepin), capsaicin cream, topical lidocaine (Lidoderm patches), or tramadol (Ultram). With physical therapy, cryotherapy or a transcutaneous electrical nerve stimulation (TENS) unit may be tried. When conservative measures are not successful, surgical excision may result in relief of pain with few potential complications. Potential complications include possible neurolysis of the nerve in refractory cases. Surgical excision is more invasive but has had good outcomes in several reports. Krahenbuhl et al reported an endoscopic approach.
The ilioinguinal nerve arises from the fusion of T12 and L1 nerve roots and emerges from the lateral border of the psoas muscle and traverses the anterior abdominal wall to the iliac crest just inferior to the hypogastric nerve. Adjacent to the anterior margin of the iliac crest, it pierces both the transversus abdominus and internal oblique muscles (providing neural branches to these) and sending neural branches to the iliohypogastric nerve. The nerve then supplies sensory branches to supply the pubic symphysis, superior and medial aspect of the femoral triangle and either the root of the penis and anterior scrotum in the male or the mons pubis and labia majora in the female.
Causes of injury include lower abdominal incisions (Pfannenstiel), pregnancy, ileac bone harvesting, appendectomy, inguinal herniorrhaphy, inguinal lymph node dissection, femoral catheter placement, orchiectomy, total abdominal hysterectomy, and abdominoplasty. Nerve injury can also occur idiopathically. The prevalence of injury with surgery has declined due to the use of laparoscopic procedures. Tearing of the lower external oblique aponeurosis may also cause injury to this nerve. This injury has been reported in hockey players.
Symptoms could include hyperesthesia or hypoesthesia of the skin along the inguinal ligament. The sensation may radiate to the lower abdomen. Pain may be localized to the medial groin, labia majora or scrotum, and the inner thigh. The characteristics of the pain may vary considerably. Patients may be able to associate their pain clearly with a traumatic event or with the surgical procedure.
Pain and tenderness may be present with application of pressure where the nerve exits the inguinal canal in up to 75% of patients. Sensory impairment is common in the distribution of the nerve supply noted above. Symptoms usually increase with hip extension (patients walk with a trunk in a forward-flexed posture). Pain may also be reproduced with palpation medial to the anterosuperior iliac spine (ASIS).
The diagnosis can be made on the basis of local infiltration of anesthetic with or without steroid and should result in relief within 10 minutes. Unfortunately, no electrodiagnostic techniques are available to readily test this nerve. Abdominal needle EMG may be helpful in determining the severity of nerve injury, but EMG is not sensitive or specific.
Treatment includes local injection of an anesthetic, physical therapy, or oral medications. Types of medications may include antiseizure medications such as gabapentin (Neurontin), carbamazepine (Tegretol), or lamotrigine (Lamictal), as well as NSAIDs, tricyclic antidepressant medications (amitriptyline [Elavil], doxepin), capsaicin cream, topical lidocaine (Lidoderm patches), or tramadol (Ultram). Ice or possibly a TENS unit may be used with physical therapy. When conservative measures are not successful, surgical excision may result in relief of pain with few potential complications.
The genitofemoral nerve or its branches (genital or femoral branches) can be entrapped throughout its course. Nerve injury occurs most commonly as a complication of lower abdominal surgeries.
The genitofemoral nerve arises from the L1 and L2 ventral primary rami, which fuse in the psoas muscle. The nerve then pierces the anterior surface of the psoas major muscle at the level of L3-4 and descends on the fascial surface of the psoas major muscle past the ureter. It then splits into the genital and femoral branches near the inguinal ligament.
The genital branch continues along the psoas major to the deep inguinal ring and enters the inguinal canal. It supplies the cremaster muscle, spermatic cord, scrotum, and adjacent thigh in males. In females, it travels with the round ligament of the uterus and provides cutaneous sensation to the labia majora and adjacent thigh. The femoral branch lies lateral to the genital on the psoas major and travels lateral to the femoral artery and posterior to the inguinal ligament to enter the proximal thigh. There, it pierces the sartorius muscle distal to the inguinal ligament and supplies the proximal portion of the thigh about the femoral triangle just lateral to the skin that is innervated by the ilioinguinal nerve.
Nerve injury may result from hernia repair, appendectomy, biopsies, and cesarean delivery. Injury may also occur due to intrapelvic trauma to the posterior abdominal wall, retroperitoneal hematoma, pregnancy, or trauma to the inguinal ligament. Fortunately, injury to this nerve is rare, even with open herniorrhaphy.
Injury to the femoral branch causes hypesthesia over the anterior thigh below the inguinal ligament, which is how it is distinguished from the iliohypogastric and ilioinguinal nerve. Groin pain is a common presentation of neuralgia from nerve injury or entrapment. The pain may be worse with internal or external rotation of the hip, prolonged walking, or even with light touch. Differential diagnoses include injury to the ilioinguinal and genitofemoral nerves as well as L1-2 radiculopathies. Some anatomic overlap may exist with the supply of the ilioinguinal and genitofemoral nerves, which makes the diagnosis somewhat difficult to establish.
Unfortunately, no reliable electrodiagnostic test exists that can be used for diagnosis of injury to this nerve. S.J. Oh has discussed a side-to-side sensory comparison study, but this test is technically difficult to perform. Diagnosis is typically made using anesthetic nerve blocks. By injecting the ilioinguinal and iliohypogastric nerves anteriorly, the pain or abnormal sensation should remain unchanged. The lumbar roots for L1 and L2 are then blocked, which should result in relief and help with determining the diagnosis and preventing unnecessary surgical exploration of an uninjured nerve.
The above-mentioned blocks are both diagnostic and therapeutic. Avoidance of aggravating activities should be emphasized. Treatment also may consist of antiseizure medications such as gabapentin (Neurontin), carbamazepine (Tegretol), or lamotrigine (Lamictal), as well as tricyclic antidepressant medications (amitriptyline [Elavil], doxepin). Other medications include capsaicin cream, topical lidocaine (Lidoderm patches), NSAIDs, or, possibly, tramadol (Ultram). A trial with a TENS unit may also be beneficial.
If conservative treatment fails, surgical excision of the nerve is the treatment of choice. Some authors describe a transabdominal approach to the nerve (Magee and Lyon) with satisfactory results. The complications of this procedure include hypoesthesia of the scrotum or labium majus, the skin over the femoral triangle, and loss of cremasteric reflex. It will usually not result in notable morbidity. According to Harms et al, an extraperitoneal approach should result in fewer operative complications.
Injury or entrapment of the lateral femoral cutaneous nerve is also known as meralgia paresthetica. It is derived from the Greek word, meros, meaning thigh, and algo, meaning pain. It is a syndrome of paresthesia and pain in the lateral and anterolateral thigh. This syndrome is most commonly seen in individuals aged 20-60 years, but it can occur in people of all ages.
This nerve arises from the ventral primary rami of L2-4 where they divide into anterior and posterior branches. The dorsal portions fuse to form the lateral femoral cutaneous nerve in the midpelvic region of the psoas major. The nerve then courses over the iliacus toward the ASIS. The nerve travels posterior to the inguinal ligament and superior to the sartorius muscle at the iliac crest region and divides into anterior and posterior branches. The anterior branch comes off 10 cm distal to the inguinal ligament on line with the ASIS and supplies cutaneous sensation to the lateral thigh including just proximal to the patella. It then communicates with cutaneous branches of the femoral nerve and saphenous nerve to form the patellar plexus. The posterior branch pierces the fascia lata posterior and lateral and divides into multiple small branches that supply the skin from the greater trochanter to the mid thigh.
Entrapment usually occurs at the inguinal ligament. The peak incidence for this condition is in middle age. Differential diagnoses include lumbar radiculopathies and discogenic or nerve root problems at L2 and L3. The entrapment may be from intrapelvic causes, extrapelvic causes, or mechanical causes. Intrapelvic causes would include pregnancy, abdominal tumors, uterine fibroids, diverticulitis, or appendicitis. Injury has been described in cases of abdominal aortic aneurism. Examples of extrapelvic causes include trauma to the region of the ASIS (eg, a seatbelt from a motor vehicle accident), tight garments, belts, girdles, or stretch from obesity and ascites. Mechanical factors include prolonged sitting or standing and pelvic tilt from leg length discrepancy. Diabetes can also cause this neuropathy in isolation or in the clinical setting of a polyneuropathy.
Symptoms include anterior and lateral thigh burning, tingling, and/or numbness that increases with standing, walking, or with hip extension. Symptoms may also increase with lying prone. Symptoms usually are unilateral but may be bilateral in rare cases. The symptoms usually improve with sitting unless compressive forces, such as tight belts or garments, remain.
Physical examination findings may be completely normal. Findings may include hyperesthesia over the lateral thigh (usually in a smaller area than the symptoms). Pain can be produced by pressure medial to the ASIS. A positive Tinel sign may be present over the ASIS or inguinal ligament.
Diagnosis of this entrapment may again be based on an injection of local anesthetic near the inguinal ligament or ASIS. Spontaneous recovery is usually expected. Electrodiagnostic testing may be performed for diagnosis. With nerve conductions studies, the technique includes using a bar electrode for recording and reference. This can be performed with either antidromic (conduction against the sensory fibers) or orthodromic (conduction with the direction of the nerves) methods. The antidromic study is usually easier, although it may be absent bilaterally on occasion. The response is small and difficult to obtain in obese patients.
A needle stimulation electrode may need to be used. The sensory response is absent in 71% and prolonged in 24% of patients with meralgia paresthetica. EMG testing results with needle are normal in patients with this diagnosis, which may help differentiate it from an upper lumbar radiculopathy. Technically, the sensory test is a difficult study and a response must be present on the opposite side to determine entrapment. It may be nearly impossible to obtain a response in an obese patient or a patient with a large abdomen without using a needle for stimulation. Unfortunately, the test may be difficult for the patient to tolerate because of the large amount of current (with respect to more peripheral nerves) that is required to stimulate a nerve that lies under adipose tissue.
Treatment may include injection of local anesthetic agents as noted above. A steroid can also be used to prolong the effects and reduce the inflammation. Oral medications such as NSAIDs, antiseizure medications (gabapentin [Neurontin]), tricyclic antidepressants, capsaicin cream, topical lidocaine, and tramadol can be used. One must also instruct patients on ways to prevent further irritation of the nerve. This may include avoiding hip extension, prolonged standing, and compressive garments. The use of ice and a TENS unit may also be helpful. Surgical exploration may be required if the above treatment options are not helpful. This includes transection of the nerve or decompression with or without neurolysis. Anatomical variations of the nerve and neuromas can occur and lead to recurrence.
The femoral nerve arises from the posterior divisions of the ventral primary rami of L2, L3, and L4 within the psoas major muscle. These nerves join to form the largest branch of the lumbar plexus. The nerve emerges from the lateral border of the psoas muscle and courses inferiorly in the intermuscular groove between this muscle and the iliacus muscle. It then passes under the inguinal ligament lateral to the femoral artery and vein. It then divides into multiple branches within the femoral triangle. It divides into sensory branches in the proximal thigh to innervate the upper and anterior thigh and muscular branches to the quadriceps muscle. One of the major branches is the lateral femoral cutaneous nerve as discussed above.
It also divides into the medial femoral cutaneous nerve, which originates just distal to the inguinal ligament to descend on the sartorius muscle and penetrates the deep fascia about the distal third of the thigh to split into 2 terminal nerve branches. One branch innervates the skin covering the medial aspect of the distal thigh and knee joint region. The second branch supplies the skin superior to the patella and shares several communicating branches with the saphenous nerve. The posterior branch of the medial cutaneous nerve travels along the medial border of the sartorius muscle and pierces the deep fascia about the knee to also communicate with the saphenous nerve in providing cutaneous sensation to the patellar region. The best-known cutaneous nerve arising from the femoral nerve is the saphenous nerve, which is discussed below.
The femoral nerve can have several entrapment locations or causes of injury, including intrapelvic injury or injury in the inguinal region. Diabetic amyotrophy is the most common cause of femoral nerve neuropathy. Open injuries can occur from gunshots, knife wounds, glass shards, or needle puncture in some medical procedures. The most worrisome complication of major trauma to the femoral triangle region is an associated femoral artery injury. The nerve can be injured at the time of the trauma or inadvertently sutured during repair of this injury. Large-blade, self-retaining retractors used during pelvic operations can cause injury the nerve due to compression.
Most entrapment neuropathies occur below the inguinal ligament. After passing beneath the inguinal ligament, the femoral nerve is in close proximity to the femoral head, tendon insertion of the vastus intermedius, psoas tendon, hip, and joint capsule. The femoral nerve does not have significant protection in this area.
Heat developed by methylmethacrylate in a total hip arthroplasty can injure the femoral nerve. Pelvic procedures that require the lower extremity to be positioned in an acutely flexed, abducted, and externally rotated position for long periods can cause compression by angling the femoral nerve beneath the inguinal ligament. The nerve may be compromised by pressure from a fetus in a difficult birth. Pelvic fractures and acute hyperextension of the thigh may also cause an isolated femoral nerve injury. Pelvic radiation, appendiceal or renal abscesses, and tumors can cause femoral nerve injuries as well. The nerve can also be injured by a compartment-like compression from a hemorrhage from hemorrhagic disorders or anticoagulant use.
The symptoms of a femoral neuropathy may include pain in the inguinal region that is partially relieved by flexion and external rotation of the hip and dysesthesia over the anterior thigh and anteromedial leg. Patients complain of difficulty with walking and knee buckling depending on the severity of the injury. The nerve gives rise to the saphenous nerve in the thigh; therefore, numbness in this distribution can be present. Anterior knee pain may also be present due to the saphenous nerve supply to the patella.
On examination, patients may present with weak hip flexion, knee extension, and impaired quadriceps tendon reflex and sensory deficit in the anteromedial aspect of the thigh. Pain may be increased with hip extension and relieved with external rotation of the hip. If compression occurs at the inguinal region, no hip flexion weakness is present. Sensory loss may occur along the medial aspect of the leg below the knee (saphenous distribution).
Electrodiagnostic testing is typically performed for diagnosis but is also important to determine the extent of the injury and to determine prognosis of recovery. With electrodiagnostic testing, either surface or needle electrodes lateral to the femoral artery in the inguinal region is used for stimulation. The stimulation can be performed above and below the inguinal ligament. Disk electrodes from the vastus medialis are used to record stimulation.
A saphenous nerve sensory study may also be performed (continuation of the sensory portion of the femoral nerve over the medial aspect of the leg and ankle). Needle examination should be completed for the paraspinal muscles as well as the iliopsoas (also L2-3) and hip adductors supplied by the obturator nerve to determine the presence of root or plexus injury versus peripheral nerve injury. The needle EMG is usually the most revealing portion of the electrodiagnostic test. The examiner must look not only for denervation potentials, but also for any active motor units.
Treatment may be based on symptoms only, or it may be more invasive and include surgical intervention depending upon the severity of the injury. Quadriceps weakness may be treated with a locking knee brace to prevent instability, and the patient may require an assistive device for walking. Good recovery has been reported in up to 70% of patients with a femoral neuropathy and may take up to a year. The recovery may even occur in the setting of a fairly severe injury as determined both on electrodiagnostic testing and by physical examination. Patients with severe axonal loss have some recovery of function, although it is usually incomplete.
The saphenous nerve is the longest, and the terminal, branch of the femoral nerve. It is a pure sensory nerve that is made up of fibers from the L3 and L4 spinal segments. It can become entrapped in multiple locations from the thigh to the leg, because of its long course. It branches from the femoral nerve just distal to the inguinal ligament and courses with the superficial femoral artery to enter Hunter canal in the distal third of the thigh. This canal extends proximally from the apex of the femoral triangle to inferomedial aspect of the thigh in the adductor magnus tendon just proximal to the femoral condyle. The canal is somewhat triangular and lies between the vastus medialis laterally and the adductor magnus and longus muscles medially.
The roof is a dense bridge of connective tissue extending between these muscle groups. The saphenous nerve exits the canal by piercing the bridge of tough connective tissue and becomes subcutaneous about 10 cm proximal to the medial epicondyle of the femur. The nerve also may pierce the sartorius muscle. Once it becomes subcutaneous, the nerve branches to form the infrapatellar plexus, while the main branch continues along the medial leg and foot.
The saphenous nerve can become entrapped where it pierces the connective tissue at the roof of Hunter canal, resulting in inflammation from a sharp angulation of the nerve through the structure and the dynamic forces of the muscles in this region. This results in contraction and relaxation of the fibrous tissue that impinges the nerve. The nerve also can be injured from an improperly protected knee or leg support during operation. It may be injured due to neurilemoma, entrapment by femoral vessels, direct trauma, pes anserine bursitis, varicose vein operations, and medial knee arthrotomies and meniscus repairs.
Symptoms of entrapment may include a deep aching sensation in the thigh, knee pain, and possibly paresthesias in the cutaneous distribution of the saphenous distribution in the leg and foot. The infrapatellar branch may also become entrapped on its own. This is because it passes through a separate foramen in the sartorius muscle tendon, or it may course horizontally across the prominence of the medial femoral epicondyle, where it may be exposed to trauma. Patients report paresthesias and numbness about the infrapatellar region that is worse with flexion of the knee or compression from garments and braces.
Saphenous nerve entrapment is a frequently overlooked cause of persistent medial knee pain that occurs in patients who experience trauma or direct blows to the medial aspect of the knee. As this is a purely sensory nerve, weakness should not be noted with an isolated injury of this nerve. If weakness is present, look for an injury of the femoral nerve or possibly an upper lumbar radiculopathy, particularly if thigh adduction is present (obturator nerve).
Deep palpation proximal to the medial epicondyle of the femur may reproduce the pain and complaints. Some weakness may be present because of guarding or disuse atrophy from the pain, but no direct weakness will result from the nerve impingement. Sensory loss in the saphenous distribution may be present on examination. No weakness should be present in the quadriceps muscles or in the hip adductors.
The diagnosis may be made on the basis of injection of local anesthetic along the course of the nerve and proximal to the proposed site of entrapment. Nerve conduction techniques are available to assess neural conduction in the main branch of the saphenous nerve or the terminal branches. The routine tests may be disappointing with persons with subcutaneous adipose tissue or swelling. A side-to-side comparison of the nerve should be made and must demonstrate a lesion consistent with the patient's complaints. A somatosensory evoked potential (SSEP) test can also be performed and the results compared with those of the contralateral side for diagnosis, although this test may be cumbersome and time-consuming.
No findings should be present on needle examination of the muscle during EMG. Needle examination should include the quadriceps muscles and the adductor longus to assess for both femoral and obturator nerve injury. If findings are present in both of these muscles, then paraspinal muscles definitely should be examined to rule out radiculopathy.
Entrapment in Hunter canal is usually treated conservatively with an injection of anesthetic with or without corticosteroid at the point of maximal tenderness (usually 10 cm proximal to the medial femoral condyle). The injection may need to be repeated periodically. Avoiding aggravating activities and using proper body mechanics will also be helpful. If this approach fails, surgical decompression may be needed. In patients with a direct blow to the medial knee who have persistent medial knee pain despite conservative trials for treatment, a neurectomy or neurolysis of the infrapatellar branch may be helpful.