Meralgia Paresthetica: Lateral Femoral Cutaneous Nerve Entrapment

Figure 1. Paresthesia from meralgia paresthetica is located in the anterior-lateral and lateral thigh regions.

Meralgia Paresthetica is a common clinical condition that an orthopedic or sports acupuncturist will encounter in their practice.

It is a soft-tissue nerve entrapment caused by damage to the lateral femoral cutaneous nerve (LFCN) of the thigh, resulting in pain and paresthesia with possible sensory loss.The patient’s symptoms are reported within the nerve’s cutaneous distribution located in the anterior-lateral and lateral thigh regions involving the area of ST 31 – ST 32 and extending lateral toward GB 31. (Fig. 1).

Meralgia Paresthetica most often occurs in 30 to 40 year old individuals,with a higher rate in adult males than females, but can occur at all ages.¹  It is seen in patients who are involved in various sports and physical activities, including gymnastics, baseball, soccer, body-building, and strenuous exercise.^2-6

Anatomy

Hansen, JT (2017). Netter’s Clinical Anatomy E-Book. Elsevier Health Sciences. Figure 2. A common exit for the LFCN is through the inguinal ligament.

The LFCN functions primarily as a sensory nerve and is a branch that originates from the lumbar plexus at L1 to L3. In the pelvis, it travels from posterior to anterior along the superior aspect of the iliacus muscle to emerge externallythrough the inguinal ligament via anaponeuroticofascial tunnel. ⁷ (Fig. 2)

This anatomical exit for the LFCN is found medial to the anterior superior iliac spine (ASIS) very near GB 28. After the inguinal ligament, the nerve passes lateral to the iliopsoas fibers and over the sartorius muscle and divides into anterior and posterior branches. ⁸

This anatomical course of the LFCN has traditionally been accepted by researchers and clinicians. However, recent research with human dissection has demonstrated variability in the nerve’s course as it exits the pelvis.

Five different variations in the LFCN have been documented Table 1. ⁹

Table 1. Anatomical variations of the lateral femoral cutaneous nerve.

Aszmann et al reported the areas that are most susceptible to mechanical trauma are in Types A, B and C. ¹⁰ Grothhaus et al reported results of 29 cadaver studies and found the lateral femoral cutaneous nerve was potentially at risk along the inguinal ligament as far as 7.3 cm medial to the ASIS and as much as 11.3 cm distal on the sartorius muscle from the ASIS. ⁹

Because of the unique course the LFCN may take, a working knowledge of these potential variations can be useful for the acupuncturist when diagnosing the site of entrapment, the tissues affected and the myofascial channels involved in the condition.

Differential Diagnosis

Meralgia Paresthetica produces similar signs and symptoms as those associated with upper lumbar nerve root (L1‐L3) injury and trochanteric bursitis. These two conditions should be ruled out with the associated exams. When differentiating potential injury diagnosis for anterior thigh pain and/or paresthesia, meralgia paresthetica should be considered especially when particular postures are present and the history includes repetitive activities, which can result in the compression or lengthening of the tissues in the anterior thigh and inguinal regions.

Common postures associated with this condition are increased lumbar lordosis with an anterior pelvic tilt that would compress the region,and an anterior hip shift that lengthens the involved tissues.

Assessment

Because of the variation in regions of nerve entrapment, each patient will have their own unique clinical presentation and distribution of symptoms.

• Patients may complain of pain, burning, numbness, muscle aches, coldness, lightning pain, or buzzing in their lateral or anterolateral thigh.
• The patient may have a history of similar paresthesia, which in the past has resolved quickly but has increased significantly after an increase in a particular activity.
• Patients may report pain with prolonged standing and walking and alleviation with sitting.Sitting may reduce or change the tension in the LFCN or inguinal ligament, thus reducing symptoms.
• Modified Ober’s Test is a provocative test to induce MP symptoms.
• Pelvic Compression Test—This maneuver is used for when symptoms are present. A positive test will decrease the patient’s symptoms.
• Standing Lunge—The tissues of the anterior thigh can be stretched and can increase symptoms.
• Straight Leg Raise Test and Slump’s Test are two exams for radicular pain coming from the lumbar spine that can help rule out MP.
• Tinel’s Sign can be used at the different locations of LFCN entrapment.
• Painful palpation of the trochanteric bursae with matching history to diagnose GT bursitis.
• MP has been related to the following factors: obesity, pregnancy, tight garments such as jeans, military armor and police uniforms, seat belts, direct trauma, muscle spasm and scoliosis. ^11-12 Metabolic factors reported include diabetes mellitus, alcoholism, and lead poisoning. ¹³
• MP has also been reported as a post‐surgical complication after hip joint replacement and spine surgery. ¹⁴

Acupuncture

The primary channel sinews (jingjin) affected are the Spleen and Stomach. The sartorius muscle attachment is part of the Spleen jingjin and the inguinal ligament, especially due to its abdominal connection, belongs to the Stomach jingjin.

The practitioner will need to consider points along these channels to influence their effect on the condition such as with cleft-xi points, connecting-luo and source-yuan points. Myofascial work after acupuncture treatment is necessary for long-lasting results.

The practitioner should also prescribe postural and therapeutic exercises to enhance the effect of the treatment and encourage new tissue positioning. For best results, local, adjacent and distal points should be used based on TCM channel theory with the constitution of the patient addressed.

The following is a discussion on local points, target tissue needle technique, moxibustion and a few common therapeutic exercises:

• ST 31 (biguan)—Upper motor point of the rectus femoris and local point for the LFCN entrapment site found distal to the ASIS (Type D).
• Sartorius motor points (proximal and distal)—The sartorius is involved in Types B, C and D nerve entrapment sites. In addition, the sartorius (belonging to the Spleen sinew channel) is fascially connected to the inguinal ligament and tension between these two structures have an influence on the other.
• GB 27 (wushu)—Propagate the needle sensation down the leg following the ST channel or toward the groin.

Inguinal Ligament Needling Technique

This target tissue needle technique, developed by the author, is based on a classical threading needle technique (tou ci). It is specifically used for Types B, C and D but can be used for all types due to its ability to stretch the localized myofascial tissue.

This needle technique can be performed with a 3-inch or 1.5-inch needle. A non-coated Chinese needle is preferred. The intention of this needle technique is to pull on restricted tissues in the inguinal ligament that can open entrapped tissues and help stimulate proprioceptive signaling, i.e. clearing localized obstruction in the channel for proper movement of qi and blood.

The needle insertion site is either directly off the medial border of the ASIS following the course of the inguinal ligament, or the needle can be inserted into the same ligament approximately 3 cun medial from the ASIS. An oblique-transverse angle is best for effective threading of the needle. The practitioner can consider alternating the needle insertion sites based on clinical outcomes.

Caution is advised: The femoral nerve, artery and vein are medial and deep to the medial needle insertion site into the inguinal ligament.

Moxibustion

3-5 direct moxa cones on the painful ashi points located on the area of entrapment.

Exercises

There are many exercises to choose from that are effective for helping to normalize the injured tissue. The practitioner will need to consider the position of the pelvis and femur when prescribing therapeutic exercises for this condition.

The following are common exercises to prescribe for meralgia paresthetica:

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REFERENCES:

1. Martinez‐Salio A, Moreno‐Ramos T, Diaz‐Sanchez M, et al. Meralgia paraesthetica: a report on a series of 140 cases. Rev Neurol. 2009;49(8):405‐408
2. Kho KH, Blijham PJ, Zwarts MJ. Meralgia paresthetica after strenuous exercise. Muscle Nerve. 2005;31(6):761‐763
3. Macgregor J, Moncur JA.Meralgia paraesthetica‐a sports lesion in girl gymnasts. Br J Sports Med. 1977;11(1):16‐19
4. Szewczyk J, Hoffmann M, Kabelis J.Meralgia paraesthetica in a body‐builder. SportverletzSportschaden. 1994;8(1):43‐45
5. Ulkar B, Yildiz Y, Kunduracioglu B.Meralgia paresthetica: a long‐standing performance‐limiting cause of anterior thigh pain in a soccer player. Am J Sports Med. 2003;31(5):787‐789
6. Otoshi K, Itoh Y, Tsujino A, et al.Case report: meralgia paresthetica in a baseball pitcher. Clin OrthopRelat Res. 2008;466(9):2268‐2270
7. Grothaus, M. C., Holt, M., Mekhail, A. O., Ebraheim, N. A., & Yeasting, R. A. (2005). Lateral femoral cutaneous nerve: an anatomic study. Clinical Orthopaedics and Related Research (1976-2007), 437, 164-168.
8. Uzel M, Akkin SM, Tanyeli E, et al. Relationships of the lateral femoral cutaneous nerve to bony landmarks. Clin OrthopRelat Res. 2011;469(9):2605‐2611
9. Grothaus, M. C., Holt, M., Mekhail, A. O., Ebraheim, N. A., & Yeasting, R. A. (2005). Lateral femoral cutaneous nerve: an anatomic study. Clinical Orthopaedics and Related Research (1976-2007), 437, 164-168.
10. Aszmann OC, Dellon ES, Dellon AL. Anatomical course of the lateral femoral cutaneous nerve and its susceptibility to compression and injury. PlastReconstr Surg. 1997;100(3):600‐604
11. Parisi TJ, Mandrekar J, Dyck PJ, et al. Meralgia paresthetica: relation to obesity, advanced age, and diabetes mellitus. Neurology. 2011;77(16):1538‐1542
12. Haim A, Pritsch T, Ben‐Galim P, et al. Meralgia paresthetica: A retrospective analysis of 79 patients evaluated and treated according to a standard algorithm. Acta Orthop. 2006;77(3):482‐486
13. Grossman MG, Ducey SA, Nadler SS, et al. Meralgia paresthetica: diagnosis and treatment. J Am AcadOrthop Surg. 2001;9(5):336‐344
14. de Ruiter GC, Wurzer JA, Kloet A. Decision making in the surgical treatment of meralgia paresthetica: neurolysis versus neurectomy. Acta Neurochir (Wien). 2012;154(10):1765‐1772