Thigh nerve entrapment syndrome - Meralgia paraesthetica
The lateral femoral cutaneous nerve wraps around the pelvic iliac crest

Definition

Thigh nerve entrapment is a neuropathy caused by the compression of the lateral femoral cutaneous nerve, which provides sensation to the outer thigh. The condition is also termed meralgia paraesthetica (from ancient Greek: meros = thigh; algos = pain) or Bernhardt-Roth Syndrome as firstly described by Bernhardt in 1878.

The lateral femoral cutaneous nerve originates at the lumbar spine and runs beneath the inguinal ligament drawn in red

Pathology

The lateral femoral cutaneous nerve arises at the lumbar spine from the innervations of the lumbar nerve roots (L2, L3). It runs from these vertebrae to the pelvis under the inguinal ligament to innervate the upper thigh. The lateral femoral cutaneous nerve has sensorial and no motor function. This nerve is mostly compressed by the inguinal ligament extending diagonally from the iliac crest to the pubis. The pathology results into partial damage to the nerve with loss of the protective myelin sheath. Its compression leads to typical sensory symptoms on the skin of the upper, lateral thigh like a burning sensation, tingling and numbness. A neuropathy of the lateral femoral nerve can also arise following trauma or as an injury during surgery at the groin area (e.g. inguinal hernia). 

Colles' fracture with bone displacement seen before (left) and after closed reduction (right) in a cast

Classification

The fractures of the distal radius are defined with various classification systems including the AO (Arbeitsgemeinschaft fuer Osteosynthese) system. They relate to the mechanisms of injury and bone fracture characteristics and provide a guideline towards suitable treatments. The most frequent types of distal radius fracture are:

No 1.

Colles’ fracture is the most common type of fracture in which the distal bone of the radius tilts upwards following an outer bending of the wrist as it happens when falling on the hand

Smith’s fracture or reversed Colles’ fracture occurs when the distal portion of the radius tilts downwards following the inward bending of the wrist

Barton fracture is an intra-articular fracture of the distal radius with dislocation of the radiocarpal joint

Chauffeur fracture is an intra-articular fracture of the radial styloid process, also known as Hutchinson fracture or backfire fracture.

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

Compression of the seatbelt caused by a suddent car impact can lead to the pathology

Causes

The compression of the lateral femoral nerve can be caused by a number of factors:

Intensive sport activity involving the abdominal musculature (gymnastics, baseball, soccer, weight-lifting)

Trauma (seat belt compression of lower abdomen in car accidents)

Standing, walking or cycling for prolonged periods of time

Tumor growths of the pelvic area compressing the nerve

Neuroma or benign tumors of the nerves

Diabetes neuropathy (affecting several nerves)

Wearing heavy tool belt or tight pants is a risk factor for meralgia paraesthetica

Risk factors

Leading risk factors for the development of compression lateral femoral cutaneous nerve are:

Age between 30 and 60 years

Male gender

Intensive physical training

Obesity: pressure on the nerve of excessive weight

Medical conditions: diabetes, thyroid disorders

Alcoholism

Pregnancy increased weight in the groin area

Iatrogenic injury during surgery in the lower abdomen (hip replacement, iliac crest bone grafting)

Wearing tight clothes

Use of heavy tool belt

Inguinal scars

The upper/outer side of the thigh is the region where symptoms are felt

Symptoms

The symptoms of lateral femoral cutaneous nerve compression mostly involve the upper and outer side of the thigh causing altered sensation with stimuli such as heat and touch. Symptoms may increase with movement (e.g. hip extension: legs moved backwards) and subside by lying down with the knees flexed.  Most common symptoms are:

Tingling/pins/needles

Numbness

Burning sensation

Pain in the groin area and buttocks (seldom)

Clinical examination is usually sufficient for the diagnosis of meralgia paraesthetica

Diagnosis

Clinical examination is usually sufficient for the diagnosis of lateral femoral cutaneous nerve entrapment. Medical history is critical to pinpoint physical activities, chronic diseases or changes in body weight that may have leaded to the neuropathy.

Clinical examination is performed to acquire information on the type, location and intensity of sensory symptoms that have arisen.

X-ray is only performed to exclude other pathologies of the pelvis and hip (avulsion fracture of anterior superior iliac spine) 

Electromyography is a test to assess muscle and nerve function through electric stimulation with an electrode implanted in the thigh muscle and recording neural activity. The function is usually unchanged in thigh nerve entrapment.

Nerve conduction study is similar to the previous although the electrodes are located onto the skin and the stimulation only triggers the nerve and not the muscle.

Nerve blockade via injection of anaesthetic into the lateral femoral cutaneous nerve confirms the diagnosis of entrapment when the symptoms subside with the injection.

Other investigations include:

Blood tests for diabetes and thyroid dysfunction

Identifying tumours or metastases to the iliac crest, uterine fibroids, chronic appendicitis

Treatment

Local steroid injection is recommended with prolonged symptoms

Nonoperative treatment

Conservative treatment is usually successful to relieve the symptoms of a femoral cutaneous nerve entrapment. The prognosis lasts between few weeks to months. In pregnancy this condition is usually transitory. 

Rest

Anti-inflammatory therapy with NSADs

Local injection of steroids (severe symptoms)

Pain killers (analgesics)

Antidepressants

Anti-seizure medications (gabapentin, pregabalin, phenytoin)

Life style changes

Reducing intense sport training

Avoid prolonged standing and walking

Weight loss

Wearing loose clothes and belts

Physiotherapy

Lateral cutaneous femoral nerve entrapment is resolved by decompressing the nerve with an incision of the inguinal ligament

Surgical treatment

Surgery is only performed in case of severe and ongoing symptoms. It consists of nerve release or decompression with or without transposition of the nerve or nerve repair in case of injury. It usually results in poorer prognosis. A 2-3-cm incision along the inguinal ligament is achieved followed by dissection of the soft tissues (fascial planes) to identify the nerve. At the crossing point of the ligament and nerve, the ligament is incised followed by nerve decompression.

Quadriceps stretching helps alleviate the symptoms of meralgia paraesthetica

Rehabilitation

In parallel to conservative treatment to control inflammation and neuropathic pain, the patient undergoes physiotherapy to improve the symptoms as follows:

Rest

Ice/heat treatment

Massage

Stretching (quadriceps)

Strengthening exercise of the hip

Activity modifying regime

Return to sport plan

Weight loss program

Acupuncture

Avoiding tight belt, jeans and heavy weight helps preventing meragia paraesthetica

Prevention

The approach for preventing lateral femoral cutaneous entrapment can only be partially achieved by modifying some life style activities. These include:

Maintenance of muscular strength and flexibility in the abdomen, hip, pelvis and buttocks

Avoid premature return to sport

Reduce sport intensity

Include stretches and warm-ups before sport

Reduce periods of standing, walking and intense physical activities

Prevent weight gain

Avoid wearing tight clothes and belts

Monitor onset and progress of neuropathies in chronic diseases (diabetes)