Meralgia Paresthetica: Chẩn đoán và điều trị ppt

In 1885, Hager was the first to postulate that compression of the lateral femoral cutaneous nerve LFCN was the cause of the pain.. Abstract Meralgia paresthetica is a symptom complex tha

The symptom complex of pain,

numbness, tingling, and

paresthe-sias in the anterolateral thigh not

associated with a surgical procedure

was first described by Bernhardt in

1878 In 1885, Hager was the first to

postulate that compression of the

lateral femoral cutaneous nerve

(LFCN) was the cause of the pain

In 1895, Roth reported on five

pa-tients with similar presentations

and initially coined the term

“meral-gia paresthetica” from the Greek

words meros (“thigh”) and algos

(“pain”) Perhaps the most famous case is that of Sigmund Freud, who described symptoms in himself as well as in one of his sons.1

Anatomic Considerations

Familiarity with the underlying neuroanatomy of the affected region

is key to understanding the patho-logic changes that occur in meralgia

paresthetica In particular, the ori-gin of the LFCN and its relation to the other structures about the ilium are characteristics that must be con-sidered

The LFCN is an entirely sensory nerve that is usually derived from one of several different combina-tions of the lumbar nerve roots, including L1 and L2, L2 and L3, and L3 alone.2 Piersol reported that the LFCN can also be partially or entirely derived from adjacent peripheral nerves, such as the genitofemoral and femoral nerves.3 Keegan and Holyoke4reported LFCN variation

in 30% of 50 cadaveric dissections The nerve emerges from the lat-eral aspect of the psoas muscle It runs beneath the iliac fascia as it crosses the anterior surface of the ili-acus muscle and travels along this retroperitoneal route across the ilium toward the anterior superior

Dr Grossman is Orthopedic Sports Medicine Fellow, Kerlan-Jobe Orthopedic Clinic, Los Angeles, Calif Dr Ducey is in private prac-tice in Bellville, NJ Dr Nadler is Attending Physician, Department of Physical Medicine and Rehabilitation, New Jersey Medical School, Newark Dr Levy is in private practice in Summit, NJ.

Reprint requests: Dr Grossman, Kerlan-Jobe Orthopedic Institute, Suite 125, 6801 Park Terrace, Los Angeles, CA 90045.

Copyright 2001 by the American Academy of Orthopaedic Surgeons.

Abstract

Meralgia paresthetica is a symptom complex that includes numbness,

paresthe-sias, and pain in the anterolateral thigh, which may result from either an

entrapment neuropathy or a neuroma of the lateral femoral cutaneous nerve

(LFCN) The condition can be differentiated from other neurologic disorders by

the typical exacerbating factors and the characteristic distribution of symptoms.

The disease process can be either spontaneous or iatrogenic The spontaneous

form is usually mechanical in origin The LFCN is subject to compression

throughout its entire course Injuries most commonly occur as the nerve exits

the pelvis The regional anatomy of the LFCN is highly varied and may account

for its susceptibility to local trauma Relief of pain and paresthesias after

injec-tion of a local anesthetic agent is helpful in establishing the diagnosis If no

improvement is found, proximal LFCN irritation should be sought Idiopathic

meralgia paresthetica usually improves with nonoperative modalities, such as

removal of compressive agents, nonsteroidal anti-inflammatory drugs, and, if

necessary, local corticosteroid injections If intractable pain persists despite

such measures, surgery can be considered, although whether neurolysis or

tran-section is the procedure of choice is still controversial Iatrogenic meralgia

paresthetica has been found to occur after a number of orthopaedic procedures,

such as anterior iliac-crest bone-graft harvesting and anterior pelvic procedures.

Prone positioning for spine surgery has also been implicated Variations in the

anatomy of the LFCN about the anterior superior iliac spine may place the

nerve at higher risk for damage Although nonoperative management usually

results in satisfactory results, efforts should be made to avoid injury at the time

of surgery.

J Am Acad Orthop Surg 2001;9:336-344

Mark G Grossman, MD, Stephen A Ducey, MD, Scott S Nadler, DO, and Andrew S Levy, MD

iliac spine (ASIS) Distally, it enters

the anterior region of the thigh by

passing under, through, or above

the inguinal ligament It is in this

re-gion that the nerve most commonly

becomes trapped or injured during

surgery (Fig 1)

Most commonly, the LFCN passes

1 cm medial to the ASIS at the level

of the inguinal ligament, although

there is considerable anatomic

varia-tion.5,6 It is important to understand

the regional anatomy and have a

working knowledge of the most

common variations that can

precipi-tate entrapment and increase

sus-ceptibility to injury during surgery

Aszmann et al7delineated the

fre-quency of five variant locations of

the LFCN in 52 cadavers (Fig 2) In

type A, the nerve overlies the iliac

crest (which occurred in 4% of the

cadavers in that study) In type B, it

is ensheathed by the inguinal

liga-ment (27%) In type C, the LFCN is

ensheathed by the tendinous origin

of the sartorius (23%) In type D, it

is deep to the inguinal ligament and medial to the sartorius (26%) In type

E, it is positioned medially on top of the iliopsoas (20%) Of note, 34 (65%)

of the cadavers had symmetrical dis-tribution of nerves

Other authors have noted multi-ple branches of the LFCN crossing the inguinal ligament The intersec-tion with the inguinal ligament can

be up to 2 cm lateral to, adjacent to,

or as much as 6 cm medial to the ASIS.6 Murata et al8 characterized the degree of risk of injury to por-tions of the LFCN in relation to bone-graft harvesting from the ante-rior iliac crest In their anatomic study, 9.9% of the dissected nerves lay in peril on top of or near the iliac crest The LFCN lies at a marked angle to the inguinal ligament This angle can become more acute with extension of the hip; therefore, ex-treme positions should be avoided intraoperatively

Distal to the inguinal ligament, the LFCN splits into anterior and posterior divisions Each penetrates the fascia lata several centimeters below the ASIS The anterior branch innervates the area from the anterior thigh to the knee The posterior branch supplies the lateral thigh up

to the level of the greater trochanter

Epidemiology

Although spontaneous meralgia paresthetica occurs in all age groups,9

it is most frequently noted in middle-aged individuals It may be more prevalent in children than has been reported in the literature.10 The spontaneous condition is generally regarded as uncommon Ecker and Woltman11showed an incidence of 3 cases in 10,000 general clinic patients

Jones12 reported the diagnosis in 6.7% to 35% of patients referred for leg discomfort There is no consen-sus in the literature about whether there is a sex predominance

Etiology

The etiology of this mononeuropa-thy is highly variable The disease process may be categorized as either spontaneous or iatrogenic The spon-taneous form occurs in the absence

of any prior surgical procedure that may have injured the LFCN at some point along its pathway, and can be further categorized as either idio-pathic or metabolic The iatrogenic form is a well-known complication

of many common orthopaedic proce-dures Both mechanical and meta-bolic factors may be involved

Mechanical Factors

The LFCN is subject to injury at several sites along its course Irri-tation most often occurs at or near the site where the LFCN pierces or crosses the inguinal ligament The nerve is superficial at this point and lies at an acute angle in hip exten-sion Stookey13noted that standing aggravates symptoms and sitting helps to relieve them Predisposing anatomic variations, such as types

A, B, and C in the classification of Aszmann et al,7increase the likeli-hood of compression

External causes, such as the wearing of seat belts,11girdles,11

and tight trousers,14 can result in direct pressure on the LFCN Obe-sity, pregnancy, and other condi-tions associated with increased ab-dominal pressure may predispose

to entrapment.6 Pelvic disease, such

as an intra-abdominal tumor, has reportedly presented as meralgia paresthetica.15 The nerve may also become trapped in a retroperitoneal location or at the point where it pene-trates the fascia lata In rare in-stances, a bone tumor in the iliac crest near the ASIS can present as meralgia paresthetica.16

Metabolic Factors

Metabolic disorders such as dia-betes mellitus, alcoholism, and lead poisoning can cause an isolated

Figure 1 The anatomic course of the

LFCN (Adapted with permission from

Mirovsky Y, Neuwirth M: Injuries to the

lateral femoral cutaneous nerve during

spine surgery Spine 2000;25:1266-1269.)

LFCN

Likely point of compression

neuropathy of the LFCN However,

the cause of metabolic neuropathy

has not been well defined

In diabetes, there are two current

theories One hypothesis involves

abnormalities in the metabolism of

pyruvate, sorbitol, and lipids

Spe-cifically, the slowing of nerve con-duction has been experimentally linked to activation of the polyol (sorbitol) pathway by glucose.17 Sec-ondary alterations in myo-inositol and phosphoinositide metabolism result in impairment of

sodium-potassium adenosine triphosphatase activity, which leads to nerve dys-function The second hypothesis is that in diabetes the nerve swells due

to decreased axoplasmic transport, rendering it more susceptible to compression.18 Optimization of blood glucose levels has not provided relief for affected patients

The treatment goal and therapeu-tic approach for metabolic meralgia paresthetica remain the same as those for the mechanical form of the disease Similar treatment is also employed for meralgia paresthetica associated with inflammatory disor-ders, such as lupus neuropathy.18

Evaluation

The clinical presentation of meralgia paresthetica includes pain, numb-ness, and/or dysesthesia in the region of the anterolateral thigh There is often a delay in diagnosis

in patients with these symptoms and even failure to recognize the entity It is important for the clini-cian to be familiar with the presen-tation and treatment of this condi-tion, because if undetected it may lead to significant patient distress and disability Figure 3 is an algo-rithm for the evaluation and treat-ment of meralgia paresthetica

History and Physical Examination

Patients typically describe numb-ness, tingling, pain, burning, and decreased sensitivity to pain, touch, and temperature in the distribution

of the LFCN Hypersensitivity to touch and dysesthesias may also be reported Palpating the area in question usually aggravates symp-toms Many patients have tender-ness over the lateral inguinal liga-ment at the point where the nerve crosses the ligament The condition

is often exacerbated by hip exten-sion during walking or getting into and out of an automobile An area

Figure 2 Five common variant locations of the LFCN as it exits the abdomen In type A,

the LFCN overlies the iliac crest (frequency in the study by Aszmann et al 7 of 52 cadavers,

4%) In type B, the nerve is ensheathed by the inguinal ligament (27%) In type C, it is

ensheathed by the tendinous origin of the sartorius (23%) In type D, the nerve is deep to

the inguinal ligament and medial to the sartorius (26%) In type E, it is positioned

medial-ly on top of the iliopsoas (20%) (Adapted with permission from Aszmann OC, Dellon ES,

Dellon AL: Anatomical course of the lateral femoral cutaneous nerve and its susceptibility

to compression and injury Plast Reconstr Surg 1997;100:600-604.)

Type A Type B Type C

Type D Type E

of hair loss may be present on the

thigh secondary to repetitive

rub-bing of the region by the patient

This massaging is a common

at-tempt to relieve symptoms and is an

important diagnostic clue

The clinical presentation is

usu-ally unilateral; however, 20% of

patients present with bilateral

com-plaints.11 Other neurologic,

gastro-intestinal, and urogenital symptoms

are not part of the process; their

presence should suggest that the leg

symptoms are due to a condition

other than meralgia paresthetica

The constellation of signs and

symptoms that has been described

usually enables the physician to

make a diagnosis based on the

histo-ry and physical examination

find-ings A Tinel’s sign is frequently

pres-ent 1 cm medial and inferior to the

ASIS, but is dependent on anatomic

variation The nerve may be

palpa-ble in thin patients, which may cause

irritation Rapid relief of symptoms

with a local anesthetic nerve block

can confirm the diagnosis

Electrodiagnostic Testing

When the history and physical

examination are nonconfirmatory,

electrodiagnostic testing may be

effective in establishing the

diagno-sis Two techniques for evaluating

nerve conduction can be used The

first method involves stimulating

the LFCN as it exits the pelvis near

the ASIS and recording potentials

distally The second technique

in-volves stimulating distally along the

course of the nerve and recording

proximally in the region of the ASIS

Measurements on the unaffected

side should always be recorded, as

these responses are typically of

small amplitude.19

Somatosensory evoked potentials

(SSEPs) can also be utilized with

segmental or dermatomal

tech-niques An abnormal latency or a

side-to-side decrement greater than

50% is considered abnormal.20,21

Wiezer et al22found that SSEPs

were useful in determining whether meralgia paresthetica was caused

by an injury in a region proximal to the ASIS However, on comparing the results of nerve conduction studies with the SSEP findings in 30 patients with clinical evidence of unilateral meralgia paresthetica, Seror23found that nerve conduction studies were more accurate

Differential Diagnosis

Any patient with a motor deficit, reflex changes, or sensory deficits not specific to the LFCN should be completely evaluated Other causes

of anterolateral thigh pain must be considered A plain radiograph should be obtained to assess the pel-vic architecture as well as to elimi-nate pelvic tumors and osteoarthritis

Condition resolved

No further treatment

Condition unresolved

Condition resolved

Condition unresolved

No further treatment

Surgical exploration

Evaluate further for underlying condition (e.g., neuropathy, radiculopathy, proximal entrapment)

Initial treatment with NSAIDs, protection, avoidance of compression

Pharmacologic intervention Local steroid injection

History that suggests idiopathic meralgia paresthetica:

• Location of sensory alteration in anterolateral thigh

• Pain, numbness, dull ache, itching, tingling

• History of trauma to region

• History of diabetes, alcoholism, or lead poisoning

• No previous surgery that might have affected the LFCN

Diagnostic regimen:

• Diagnostic nerve block

• Electrodiagnostic testing

• Somatosensory evoked potentials

Physical examination findings that suggest idiopathic meralgia paresthetica:

• Sensory changes (hypesthesia, hyperesthesia, dysesthesia present over anterolateral thigh)

• Signs/symptoms exacerbated by hip extension

Figure 3 Algorithm for the evaluation and treatment of idiopathic meralgia paresthetica.

of the hip as potential etiologic

factors

Differentiation of inguinal

re-gional entrapment of the LFCN due

to upper lumbar nerve compression

or intra-abdominal compression is

more challenging In such cases,

local block would not be expected to

relieve the symptoms Any

con-comitant gastrointestinal or

urogen-ital symptoms should immediately

raise suspicion of a pelvic mass

Ultrasound, computed

tomogra-phy, or magnetic resonance imaging

can be used to assess the

retroperi-toneal region The entity most

com-monly confused with meralgia

paresthetica is lumbar disk disease

Meralgia paresthetica is purely

sen-sory in nature and does not follow

distinct dermatomal distributions,

in contrast to disk disease, in which

there may be motor or reflex

def-icits In the patient with meralgia

paresthetica, there should be no

sci-atic notch tenderness or a positive

response to the straight-leg-raising

test Symptoms are usually relieved

with hip flexion Both clinical

exam-ination and electromyography can

usually differentiate the entities

However, magnetic resonance

imag-ing may be necessary to establish the

diagnosis Somatosensory evoked

potentials have been used

success-fully by several authors to support a

diagnosis of meralgia paresthetica if

further clarification is needed.24

Nonoperative Management

Nonoperative treatment of patients

with focal compression of the LFCN

should be directed at correcting the

underlying disorder A history of

recent weight gain, tightness when

wearing trousers, or recent trauma

should be sought The patient should

be warned to avoid compression, and

application of protective padding

over the region should be considered

Nonsteroidal anti-inflammatory

drugs are the mainstay of treatment

to alleviate inflammation, which may cause intrinsic compression The use

of tricyclic antidepressants, anticon-vulsants, and antiarrhythmic agents may be initiated to treat the effects of neuropathic pain.25 Topical agents, such as capsaicin and lidocaine-prilocaine cream, can also be tried to decrease surface hypersensitivity.26

Meralgia paresthetica in pregnancy usually resolves after delivery.5

Local injection of xylocaine with a corticosteroid may be beneficial to decrease local inflammation This should be performed 1 cm medial to the ASIS or in the region of maximal tenderness Repeat injections may be required, as determined by the clini-cal course Loclini-cal infiltration resulted

in complete relief for 32 (74%) of 43 patients in one study with a

follow-up interval of 1 year.27 Edelson and Stevens,10however, found a lack of response to steroids in children

Overall, nonoperative treatment has yielded excellent results How-ever, most clinical series have em-ployed numerous treatment methods;

therefore, the efficacy of individual modalities is unclear In a review of

29 patients, Ecker and Woltman11

reported that approximately two thirds showed improvement with nonoperative treatment at the 2-year follow-up evaluation How-ever, no details were offered regard-ing the condition of those for whom nonoperative therapy was a failure

Williams and Trzil6demonstrated relief of symptoms with nonopera-tive care in more than 91% of 277 patients with meralgia paresthetica

Bollinger28reported a 25% recovery rate in his series of 158 patients

Surgical Intervention

Nonoperative treatment alone will reduce the severity of most patients’

symptoms to an acceptable level

Only when the complaints become intractable and disabling should surgery become an option Surgical

procedures for meralgia paresthetica date back to 1885 Three basic sur-gical techniques have evolved for this disorder: neurolysis of only the constricting tissue, neurolysis and transposition of the LFCN, and tran-section with excision of a portion of the LFCN

Neurolysis

Macnicol and Thompson29 re-ported on 25 patients with refractory meralgia paresthetica Exploration and decompression of the LFCN 18 months after the onset of pain was successful in 11 (44%) of these pa-tients at an average follow-up inter-val of 5.5 years On the basis of their results, the authors recommended surgery for patients with symptoms with a duration of less than 1 year as well as clearly defined sensory loss Nahabedian and Dellon18noted complete relief of symptoms in 18

of 23 patients and partial relief in 4 others after surgical decompression

of the nerve Edelson and Stevens10

reported the results of treatment of

21 lesions in 13 children After oper-ative decompression, there was com-plete relief of pain from 14 lesions, occasional pain but no disability from 5 lesions, and persistent pain only with sports activities with 2 lesions

Neurolysis and Transposition

Keegan and Holyoke4described two cases in which LFCN release and medial transposition provided good results Aldrich and van den Heever30described a suprainguinal ligament approach for release and transposition In both studies, per-formance of this procedure was con-tingent on the nerve appearing as a single trunk at the ASIS No larger series in which this particular tech-nique was used have been reported

Transection

Williams and Trzil6reported the data on 24 patients with meralgia paresthetica that was unrelieved by

nonoperative measures Sectioning

of the LFCN successfully relieved

symptoms in 23 of the 24 patients

Although sectioning of the nerve

results in permanent anesthesia in

the anterolateral thigh, there were

no other serious sequelae

Transection Versus Neurolysis

In 1995, van Eerten et al31

com-pared the results of transection and

neurolysis in 21 patients after failure

of nonoperative treatment

Transec-tion was performed in 11 patients

and neurolysis in 10 patients The

average follow-up interval was 74

months Complete relief of

symp-toms occurred in 9 patients who

underwent transection, compared

with 3 patients in whom neurolysis

was used Therefore, the authors

recommended transection as the

procedure of choice

Ivins32 performed neurolysis in

four of eight operative cases of

me-ralgia paresthetica All four patients

had consistent immediate relief,

but the symptoms recurred 2 to 24

months later All four subsequently

underwent resection of the LFCN

and had no recurrence The other

four underwent initial transection

and had persistent relief at

long-term follow-up (3 to 6 years)

Whether the preferred surgical

management is neurolysis or

tran-section remains controversial

Pro-ponents of neurolysis assert that the

nerve should be decompressed

from just proximal to the pelvic

brim to as far distally as possible

They believe this will provide

ade-quate decompression and successful

surgery without the disadvantage of

creating permanent anterolateral

anesthesia Some surgeons have

reported unpleasant hyperesthesias

with resection, whereas others have

reported dysesthesias after

neu-rolysis but not after transection.31

Symptoms in an intact nerve may

be due to an LFCN neuroma, which

neurolysis cannot ameliorate

Re-section should, therefore, be

cura-tive, providing more predictable relief but at the expense of the sen-sory innervation

The initial step should be to per-form neurolysis with decompres-sion Resection is contemplated only after failure of neurolysis In certain situations, transection may

be the treatment of choice if neurol-ysis and/or transposition is not feasible Transection may be ap-propriate if the LFCN has been irreparably damaged by pressure,

if there are multiple branches of the LFCN exiting the pelvis, if the LFCN crosses the iliac crest, or if an adult patient has had symptoms for more than 1 year

Surgical Technique

As the entire nerve should be ex-plored, an adequate incision must

be made to allow for the anatomic variations that have been reported

With the patient under general anesthesia, a 3- to 5-cm oblique or S-shaped incision is made 2 cm distal

to the area of tenderness at the pre-sumed pelvic brim exit of the LFCN

Exposure is carried down to the level of the LFCN Once identified, the nerve is examined for pathologic changes (Fig 4) The nerve is then released toward the thigh and into the retroperitoneum, with excision

of all overlying and underlying fas-cia, including the compressive por-tion of the inguinal ligament

The nerve must be properly ex-posed for transection The nerve is then pulled distally and sectioned

so that the released proximal end falls back in the pelvis, thereby avoiding neuroma formation A nerve segment of at least 4 cm must

be resected, including any portion with obvious pathologic changes

Iatrogenic Meralgia Paresthetica

Meralgia paresthetica has been re-ported after several types of surgical

procedures in the region of the ASIS The surgical approaches may either directly injure the nerve or endanger the nerve with local scarring.33

These procedures include acetabular fracture surgery,34,35pelvic osteoto-mies,36 and bone-graft harvesting from the iliac crest.33,37-39 It has also been reported after several nonor-thopaedic interventions, such as bariatric surgery40 and laparoscopic hernia repair.41 Symptoms of antero-lateral dysesthesia after surgery in the region of the hip or pelvis should suggest the presence of meralgia paresthetica

Nonoperative modalities, in-cluding the use of nonsteroidal anti-inflammatory drugs, looser clothing, and steroid injections, are impor-tant initial measures Resolution of symptoms generally occurs within 3 months However, persistent symp-toms may necessitate surgical inter-vention

There has not yet been a well-controlled study comparing the use

of neurolysis and transection in the treatment of postsurgical meralgia paresthetica However, most authors

of larger series recommend transec-tion because of the potential for neu-roma formation

Figure 4 Exploration of the LFCN reveals

entrapment of the nerve White arrow indicates inguinal ligament; arrowhead, LFCN; black arrow, point of entrapment between two slips of inguinal ligament.

Bone-Graft Harvesting From

the Anterior Iliac Crest

Injury to the LFCN has been

re-ported in as many as 10% of cases in

series in which bone was harvested

from the anterior iliac crest.33,37-39

Kurz et al39described three

mecha-nisms for nerve injury in this setting:

neurotmesis as the nerve crosses the

anterior iliac crest, neurapraxia due

to retraction of the iliacus during

exposure of the ilium, and crush

injury to the outer table of the iliac

crest secondary to excessive

strip-ping One recommendation is to

keep incisions 2 cm lateral to the

ASIS.39 The LFCN is lateral to the

ASIS when it crosses the iliac crest in

as many as 10% of cases.5-8

When taking a graft from the

outer table of the iliac crest, it is

important to avoid penetration of

the inner table, so as to prevent

in-jury as the LFCN crosses the iliacus

muscle Careful retraction and

dis-section of the inner table will also

limit injury to the LFCN If the

LFCN is found to be injured, the

nerve should be severed and allowed

to retract into the pelvic region This

will decrease the incidence of

neu-roma formation Overall,

meticu-lous hemostasis and dissection will

minimize hematoma and scar

for-mation Use of a drain may be

ben-eficial in preventing postoperative

hematoma formation

Newer coring techniques for

bone-graft harvesting from the iliac

crest have also been implicated in

LFCN damage.42 Although there

are many potential advantages to

the coring technique for graft

har-vesting, one must understand that

with certain anatomic variants the

LFCN is still in danger

Recom-mendations to avoid injury include

making a 1-cm incision at least 5 cm

but no more than 8 cm posterior to

the ASIS Retractors should be

placed after careful blunt dissection

to the crest and should remain fixed

during coring to minimize the risk

of neurotmesis

Spine Procedures

Spine surgery carries the risk of LFCN injury during bone-graft har-vesting from the anterior iliac crest, prone positioning, and retroperito-neal approaches Mirovsky and Neuwirth43 found a 20% complica-tion rate in 105 patients who under-went a spine procedure Each subset

of spine procedures or approaches was examined separately Compres-sion was implicated as the cause of LFCN damage when a Hall-Relton frame was used for posterior spinal fusions All the bilateral injuries were found in this group Bone-graft harvesting from the anterior iliac crest was also implicated in the anterior cervical fusion group Two patients who did not recover func-tion after 1 year were in this group

It may be assumed that the nerve was transected during the surgical approach Retraction of the psoas during retroperitoneal dissection was also found to be a cause of LFCN neurapraxia, as the LFCN travels just lateral to the muscle in the pelvic region

Because of the small numbers of patients in the subgroups in that study, it was not possible to mea-sure the prevalence of LFCN injury

in each However, 89% of all injured nerves had recovered by 3 months

Avoiding excessive retraction about the LFCN and using adequate pad-ding during prone positioning may decrease the incidence of postopera-tive meralgia paresthetica It is im-portant that patients be informed about the potential occurrence of this complication

Use of Ilioinguinal and Iliofemoral Approaches

The ilioinguinal approach to the acetabulum risks injury to the LFCN

The nerve may be injured due to excessive retraction, postoperative scar or hematoma formation, or di-rect injury Hospodar et al35 per-formed cadaver dissections utilizing the ilioinguinal approach to

deter-mine its relationship to the LFCN

At some points, the nerve was as much as 40 mm away from the ASIS Therefore, if the LFCN is not found near the ASIS, careful medial dissec-tion may be necessary to locate the nerve

De Ridder et al34performed a two-part study: an anatomic study and a clinical correlation An ilioin-guinal approach was used on 200 cadavers The LFCN was found to

be normal in position in 149 (74%) and abnormal in 51 (26%) A clini-cal retrospective analysis found 82 patients with postoperative LFCN sensory changes after use of an ilioinguinal approach Eleven had persistent symptoms after 1 year, and 5 went on to require surgical in-tervention In a second group of 40 patients treated after the first group,

a perioperative protocol was insti-tuted to diminish the risk of meral-gia paresthetica The LFCN was identified and neurolysis was per-formed in 33 patients The remain-ing 7 patients underwent transection

of the nerve because of an intraoper-ative lesion No complaints were noted at 1 year The transection group had a decrease in the area of insensate distribution Overall, the incidence of decreased sensation in their series was 35%, and painful dysesthesias occurred in 5% of their patients

Recommendations regarding acetabular approaches include flexing the hip to minimize LFCN tension and trimming the anterior iliac crest before wound closure to avoid excessive retraction of the nerve Knowledge of the anatomic variations should lessen direct injury If intraoperative injury is discovered, transection may be necessary to avoid neuroma for-mation Most symptoms subside

by 3 to 6 months after surgery The patient should always be informed of the risk of potential LFCN injury when discussing these acetabular approaches

Meralgia paresthetica is a

mono-neuropathy of the LFCN The

con-dition may be categorized as either

spontaneous or iatrogenic The

spontaneous form may be further

categorized as either mechanical or

metabolic in origin A thorough clinical history and physical exami-nation will often be sufficient for accurate diagnosis of the disorder

Nonoperative treatment is usually successful However, a small num-ber of patients will need operative intervention Most iatrogenic cases

of meralgia paresthetica abate with time It is essential to clearly in-form patients about the risk of LFCN injury before surgery about the ASIS Meticulous intraopera-tive technique may decrease the incidence of the disorder after pelvic surgery

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Anatomical course of the lateral

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suscepti-bility to compression and injury Plast

Reconstr Surg 1997;100:600-604.

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