Lateral femoral cutaneous neuralgia: an anatomical insight

Targeted dorsal root entry zone stimulation alleviates pain due to meralgia paresthetica

Objective.Meralgia paresthetica (MP) is a mononeuropathy of the exclusively sensory lateral femoral cutaneous nerve (LFCN) that is difficult to treat with conservative treatments. Afferents from the LFCN enter the spinal cord through the dorsal root entry zones (DREZs) innervating L2 and L3 spinal segments. We previously showed that epidural electrical stimulation of the spinal cord can be configured to steer electrical currents laterally in order to target afferents within individual DREZs. Therefore, we hypothesized that this neuromodulation strategy is suitable to target the L2 and L3 DREZs that convey afferents from the painful territory, and thus alleviates MP related pain.Approach.A patient in her mid-30s presented with a four year history of dysesthesia and burning pain in the anterolateral aspect of the left thigh due to MP that was refractory to medical treatments. We combined neuroimaging and intraoperative neuromonitoring to guide the surgical placement of a paddle lead over the left DREZs innervating L2 and L3 spinal segments.Main results.Optimized electrode configurations targeting the left L2 and L3 DREZs mediated immediate and sustained alleviation of pain. The patient ceased all other medical management, reported improved quality of life, and resumed recreational physical activities.Significance.We introduced a new treatment option to alleviate pain due to MP, and demonstrated how neuromodulation strategies targeting specific DREZs is effective to reduce pain confined to specific regions of the body while avoiding disconfort.

Efficacy of neural prolotherapy in treatment of meralgia paresthetica: a case series

Background

Meralgia paresthetica is an entrapment neuropathy. Neuropathic pain was reported to be improved by using neural prolotherapy. Aim of the research was to assess and evaluate the short-term efficacy of neural prolotherapy on relieving pain, paresthesia and improving function and quality of life of patients with meralgia paresthetica. The study included 19 lower limbs with idiopathic meralgia paresthetica obtained from 15 patients. Subcutaneous perineural injection of dextrose (5%) in sterile water was given once. All patients were evaluated for outcome measures twice, at baseline visit and at follow-up visit four weeks after the injection which included: patient assessment of overall symptoms of meralgia paresthetica, patient assessment of meralgia paresthetica pain, patient assessment of meralgia paresthetica paresthesia and patient assessment of meralgia paresthetica effect on function and quality of life using visual analogue scale.

Results

There was a statistically significant improvement in the visual analogue scale of patient assessment of overall meralgia paresthetica symptoms, patient assessment of meralgia paresthetica pain, patient assessment of meralgia paresthetica paresthesia and patient assessment of meralgia paresthetica effect on function and quality of life when the findings at the postinjection visit were compared to the preinjection assessment among all patients. All the patients tolerated the injection procedure-induced pain. All the patients experienced immediate postinjection relieve of the meralgia paresthetica pain. At the postinjection assessment visit, all patients were satisfied with the procedure. There were 12 lower limbs (63.2%) from 10 patients (66.6%) that showed improvement and recovery. Two patients of them had bilateral meralgia paresthetica. There was no patient withdrawal, and no patients were lost to follow-up. There was one lower limb (5.3%) from one patient (6.7%) who had bruises at the injection sites that resolved within few days after the procedure.

Conclusions

Neural prolotherapy is easy, safe, tolerable, effective and successful in treatment of meralgia paresthetica. It is effective in relieving pain, paresthesia and improving function and quality of life of patients with meralgia paresthetica. Neural prolotherapy injection should be included in the conservative treatment armamentarium of meralgia paresthetica.

Trial registration : NCT04499911. Registered 5 August 2020—retrospectively registered.

Ultrasound of the Lateral Femoral Cutaneous Nerve: A Review of the Literature and Pictorial Essay

We review the ultrasound (US) findings in patients who present with meralgia paresthetica (MP). The anatomy of the lateral femoral cutaneous nerve at the level where the nerve exits the pelvis and potential entrapment sites that can lead to MP are discussed. A wide range of pathological cases are presented to help in recognizing the US patterns of MP. Finally, our experience with US-guided treatment is discussed.

Anatomical Analysis of the Lateral Femoral Cutaneous Nerve and Its Passage beneath the Inguinal Ligament

BACKGROUND

Meralgia paraesthetica is a mononeuropathy of the lateral femoral cutaneous nerve. According to the literature, the nerve travels beneath the inguinal ligament 1.3 to 5.1 cm medial to the anterior superior iliac spine. Compression at this site may cause pain and paresthesia. The aim of this study was to provide more accurate measurements to improve the diagnostic and surgical management of meralgia paraesthetica.

METHODS

The lateral femoral cutaneous nerve was dissected bilaterally in 50 Thiel-embalmed human cadavers. Measurements were performed with a standard caliper at the superior and inferior margins of the inguinal ligament. The distance from the inner lamina of the anterior superior iliac spine to the medial margin of the lateral femoral cutaneous nerve was measured. Data were collected and statistical analysis was performed with R.

RESULTS

Ninety-three lateral femoral cutaneous nerves of 50 cadavers were dissected. In 6 percent of cadavers, the lateral femoral cutaneous nerve could not be found. The mean distance from the inner lamina of the anterior superior iliac spine to the lateral femoral cutaneous nerve's medial border was 2.1 ± 1.3 cm (range, 0.2 to 6.4 cm; 95 percent CI, 1.8 to 2.4 cm) at the superior margin of the inguinal ligament and 1.9 ± 1.4 cm (range, 0.2 to 3.0 cm; 95 percent CI, 1.6 to 2.2 cm) at the inferior border of the inguinal ligament.

CONCLUSION

This anatomical study shows that the majority of the lateral femoral cutaneous nerve passes beneath the inguinal ligament in a very narrow area of 0.6 cm.

The anatomical features of the lateral femoral cutaneous nerve with total hip arthroplasty: a comparative study of direct anterior and anterolateral supine approaches

BACKGROUND

Lateral femoral cutaneous nerve (LFCN) injury after total hip arthroplasty causes patient dissatisfaction. This cadaveric study aimed to assess the risk for LFCN injury after the direct anterior approach (DAA) and anterolateral supine approach (ALS) with a focus on the anatomical variations of the LFCN.

METHODS

Thirty-seven hemipelves from 20 formalin-preserved cadavers (10 males and 10 females) were dissected to identify the LFCN, evaluate variations, and measure the distance from the LFCN to each approach. The LFCN was classified as classical, late, multi trunk, or primary femoral.

RESULTS

There were no significant variations in the LFCN between the sexes. The distance from the LFCN to DAA incision (10 [0-17.8] mm) was significantly less than that from the LFCN to ALS incision (27 [0-40] mm); moreover, 64.9% of DAA incisions crossed the LFCN. The classical type LFCN was closest to the DAA incision. The DAA incision most frequently crossed the LFCN at the proximal third, and the frequency of intersection of the LFCN and DAA incisions decreased by 25% by a 10-mm shortening of the DAA proximal incision. In contrast, 27% of ALS incisions crossed the LFCN. Multi trunk type LFCN was closest to the ALS incision. There were no significant differences between each approach and LFCN variations, and the frequency of intersection of the LFCN and ALS incisions decreased by 20% by a 10-mm shortening of the ALS proximal incision.

CONCLUSIONS

The intersection rates between the LFCN and the DAA and between the LFCN and the ALS were approximately 65 and 30%, respectively. Approximately 20-25% of these injuries may be avoidable by a 10-mm shortening of the proximal incision.

Sonographic features of the lateral femoral cutaneous nerve in meralgia paresthetica

Background

The diagnosis of meralgia paresthetica (MP) is usually based on clinical symptoms and physical examination. Therefore, the present study aimed to investigate the lateral femoral cutaneous nerve (LFCN) sonographic features in MP patients.

Methods

A total of 86 clinically suspected MP patients and 40 asymptomatic volunteers were prospectively recruited in the study. The sonographic features of the LFCN were observed by 18 MHz high-frequency ultrasound. At the level of the anterior superior iliac spine, the cross-sectional area of the LFCN was measured.

Results

Of the 86 clinically suspected MP patients, 82 (95.3%) had sonographic findings positive for MP. There were 54, 63, and 44 cases of abrupt caliber change, indistinct perineurium, and abnormal intraneural vascularity. The average value of the cross-sectional area of the LFCN at the level of the anterior superior iliac spine was 4.47±2.64 mm², and the cut-off value was 2.65 mm².

Conclusions

The sonographic diagnosis of MP may be achieved based on the following signs: nerve abrupt caliber change, indistinct perineurium of the nerve, intraneural vascularity, or increased cross-sectional area.

Preoperative Ultrasound in Patients with Meralgia Paresthetica to Detect Anatomical Variations in the Course of the Lateral Femoral Cutaneous Nerve

OBJECTIVE

Sometimes during surgery for meralgia paresthetica, it can be difficult to find the lateral femoral cutaneous nerve (LFCN). The aims of this study were to study the prevalence of different anatomical variations in patients, compare preoperative ultrasound (US) data with intraoperative findings, and investigate the effect of type of anatomical variation on duration of surgery and success rate of localizing the LFCN.

METHODS

Fifty-four consecutive patients with idiopathic meralgia paresthetica who underwent either a neurolysis or neurectomy procedure were included. All patients preoperatively underwent US of the LFCN. Anatomical variations were categorized into type A, B, C, D, and E using the classification of Aszmann and Dellon. The cross-sectional area of the LFCN at the inguinal ligament and the distance of the LFCN to the anterior superior iliac spine were noted. Correlations with intraoperative findings were investigated, as well as the effect on duration of surgery and success rate of finding the LFCN. Clinical outcome was assessed using the Likert scale.

RESULTS

The most frequent anatomical variant was type B (79%), followed by type C (9%), D (5%), and E (7%). No type A was encountered. Correlation between preoperative US and intraoperative findings was 100%. During surgery, the LFCN could be identified in all cases. Duration of surgery did not significantly vary for the different anatomical variants.

CONCLUSIONS

Preoperative US is reliable in detecting anatomical variations of LFCN. This information can be very helpful in identifying the LFCN more frequently and easily during surgery, especially in more medial variants.

Effect of Fascia Penetration in Lateral Femoral Cutaneous Nerve Conduction

Objective

To evaluate the effect of fascia penetration and develop a new technique for lateral femoral cutaneous nerve (LFCN) conduction studies based on the fascia penetration point (PP) identified using ultrasound.

Methods

The fascia PP of the LFCN was localized in 20 healthy subjects, and sensory nerve action potentials (SNAPs) were obtained at four different stimulation points—2 cm proximal to the PP (2PPP), PP, 2 cm distal to the PP (2DPP), and 4 cm distal to the PP (4DPP). We compared the stimulation technique based on the fascia penetration point (STBFP) with the conventional technique.

Results

The SNAP amplitude of the LFCN was significantly higher when stimulation was performed at the PP and 2DPP than at other stimulation points. Using the STBFP, SNAP responses were elicited in 38 of 40 legs, whereas they were elicited in 32 of 40 legs using the conventional technique (p=0.041). STBFP had a comparable SNAP amplitude and slightly delayed negative peak latency compared to the conventional technique. In terms of the time required, the time spent on STBFP showed a more consistent distribution than the time spent on the conventional technique (two-sample Kolmogorov–Smirnov test, p<0.05).

Conclusion

SNAP of the LFCN significantly changed near the fascia PP, and stimulation at PP and at 2DPP provided high amplitudes. STBFP can help increase the response rate and ensure stable and consistent procedure time of the LFCN conduction study.

Decompression and Neurolysis of the Lateral Femoral Cutaneous Nerve in the Surgical Treatment of Meralgia Paresthetica and the Results

Meralgia paresthetica (MP), also known as Bernhardt–Roth syndrome, is a peripheral neuropathy of the primary sensory lateral femoral cutaneous nerve (LFCN). Its diagnosis is challenging, because it can mimic other clinical conditions particularly associated with upper lumbar spine or pelvis. Patients present with pain and paresthesia over the anterolateral thigh. Diagnosis is usually based on clinical examination and is supported by sensory nerve conduction (SNC) studies. The initial treatment is always conservative. In limited number of patients who are refractory to conservative managements, surgical treatment via decompression/neurolysis or neurectomy is concerned. There is still no consensus on which surgical technique is the best and the first choice. We retrospectively analyzed the surgical outcomes of 12 nonobese patients who underwent decompression/neurolysis between the years 2013 and 2018. Bilateral SNC studies were performed in all cases which supported the diagnosis. We applied conservative treatments for 3 months in addition to the treatments previously applied in other centers. Surgery was recommended for the patients who were refractory to these treatments. Preoperative and postoperative pain levels during follow-up visits were evaluated with visual analogue scale (VAS). A retrospective analysis was performed on preoperative and postoperative 6th month VAS scores. The mean preoperative VAS value was 8.75 ± 0.62 and the postoperative VAS value at the sixth month was 1.17 ± 0.72. A significant reduction in the pain was shown (p < 0.05). Our surgical results showed that decompression/neurolysis of the LFCN should be concerned as the primary surgical approach to avoid negative outcomes of resection surgeries.

Fine architecture of the fascial planes around the lateral femoral cutaneous nerve at its pelvic exit: an epoxy sheet plastination and confocal microscopy study

OBJECTIVE

Meralgia paresthetica is commonly caused by mechanical entrapment of the lateral femoral cutaneous nerve (LFCN). The entrapment often occurs at the site where the nerve exits the pelvis. Its optimal surgical management remains to be established, partly because the fine architecture of the fascial planes around the LFCN has not been elucidated. The aim of this study was to define the fascial configuration around the LFCN at its pelvic exit.

METHODS

Thirty-six cadavers (18 female, 18 male; age range 38-97 years) were used for dissection (57 sides of 30 cadavers) and sheet plastination and confocal microscopy (2 transverse and 4 sagittal sets of slices from 6 cadavers). Thirty-four healthy volunteers (19 female, 15 male; age range 20-62 years) were examined with ultrasonography.

RESULTS

The LFCN exited the pelvis via a tendinous canal within the internal oblique-iliac fascia septum and then ran in an adipose compartment between the sartorius and iliolata ligaments inferior to the anterior superior iliac spine (ASIS). The iliolata ligaments newly defined and termed in this study were 2-3 curtain strip-like structures which attached to the ASIS superiorly, were interwoven with the fascia lata inferomedially, and continued laterally as skin ligaments anchoring to the skin. Between the sartorius and tensor fasciae latae, the LFCN ran in a longitudinal ligamental canal bordered by the iliolata ligaments.

CONCLUSIONS

This study demonstrated that 1) the pelvic exit of the LFCN is within the internal oblique aponeurosis and 2) the iliolata ligaments form the part of the fascia lata over the LFCN and upper sartorius. These results indicate that the internal oblique-iliac fascia septum and iliolata ligaments may make the LFCN susceptible to mechanical entrapment near the ASIS. To surgically decompress the LFCN, it may be necessary to incise the oblique aponeurosis and iliac fascia medial to the LFCN tendinous canal and to free the iliolata ligaments from the ASIS.

ALDI (Anterior Lateral Decubitus Intermuscular) approach to the hip: Comprehensive description of the surgical technique with operative video

The direct anterior approach to the hip is judged to be difficult and even after many solutions, such as special operating tables, have been proposed to perform it, in some reports the complication rate remains high. The complications reported are nerve lesions, dislocation, muscles damages, intraoperative fractures. We describe a modification of the anterior approach, undertaken keeping the patient in lateral decubitus, in order to gain a better range of leg movement and a significant reduction of the force applied to the retractors, the technique was named ALDI (anterior lateral decubitus intermuscular) approach. The surgeon starts behind the patient as in all the other traditional approaches, to maintain unchanged the acetabular view and the dexterity in cup implantation. For the femoral preparation, he moves in front of the patient to have a better visualization. In a series of 150 patients, with a mean operative time of 51.38minutes (range, 40-112), we had no intraoperative fractures, one (0.6%) lateral femoral cutaneous nerve temporary neurapraxia, one (0.8%) posttraumatic dislocation four years after the operation and, no revisions for aseptic loosening or infection. At the 5 years follow-up, the mean Oxford Hip score was 45.2 (range, 38-48; SD 2.6), the mean Harris Hip Score was 96,7 (range, 76-100; SD 2.8), and the mean UCLA score was 7 (range, 5-10; SD 1.4). The possibility to always obtain the optimal position of the surgical window with reduced tension on the muscles, and the unchanged initial surgeon position, could make the ALDI approach the ideal technique for the surgeons that decide to perform an anterior approach.

Reducing Lateral Femoral Cutaneous Nerve Palsy in Obese Patients in the Beach Chair Position: Effect of a Standardized Positioning and Padding Protocol

INTRODUCTION

To report on the effectiveness of a standardized patient positioning and padding protocol in reducing lateral femoral cutaneous nerve (LFCN) palsy in obese patients who have undergone shoulder surgery in the beach chair position.

METHODS

We retrospectively reviewed the medical records of 400 consecutive patients with a body mass index (BMI) of ≥30 kg/m who underwent either open or arthroscopic shoulder surgery in the beach chair position by a single surgeon. Before June 2013, all patients were placed in standard beach chair positioning with no extra padding. After June 2013, patients had foam padding placed over their thighs underneath a wide safety strap and underneath the abdominal pannus. Flexion at the waist was minimized, and reverse Trendelenburg was used to position the shoulder appropriately. Patient demographic and surgical data, including age, sex, weight, BMI, presence of diabetes, procedure duration, American Society of Anesthesiologists (ASA) grade, and anesthesia type (general, regional, regional/general) were recorded. Symptoms of LFCN palsy were specifically elicited postoperatively in a prospective fashion and identified clinically by focal pain, numbness, and/or tingling over the anterolateral thigh.

RESULTS

The median age was 58.0 years, and the study consisted of 142 male (36%) and 258 female (64%) subjects. Five cases (3.6%) of LFCN palsy occurred with conventional beach chair positioning, and a single case (0.4%) occurred with the standardized positioning and padding technique (P = 0.02). Median age, sex, presence of diabetes, median BMI, surgery type, and surgical time were not significantly different between the patients who did and did not develop LFCN palsy. All cases resolved completely within 6 months.

DISCUSSION

The occurrence of LFCN palsy following shoulder surgery in the beach chair position remains uncommon, even among obese patients. Use of a standardized positioning and padding protocol for obese patients in the beach chair position reduced the prevalence of LFCN palsy.

LEVEL OF EVIDENCE

Level III (prognostic).

Prevalence and Risk Factors for Lateral Femoral Cutaneous Nerve Palsy in the Beach Chair Position

PURPOSE

To report on the prevalence of lateral femoral cutaneous nerve (LFCN) palsy in patients who had undergone shoulder surgery in the beach chair position and to identify patient and surgical risk factors for its development.

METHODS

We retrospectively reviewed the medical records of 397 consecutive patients who underwent either open or arthroscopic shoulder surgery in the beach chair position by a single surgeon. Patient demographic and surgical data including age, gender, weight, body mass index (BMI), diabetes, procedure duration, and anesthesia type (general, regional, regional/general) were recorded. LFCN palsy symptoms were recorded prospectively at the initial postoperative visit and identified clinically by focal pain, numbness, and/or tingling over the anterolateral thigh.

RESULTS

The median patient age was 59.0 years and consisted of 158 males (40%) and 239 (60%) females. Five cases of LFCN palsy were identified for a prevalence of 1.3%. These patients had a higher median weight (108.9 kg vs 80.7 kg, P = .005) and BMI (39.6 vs 29.4, P = .005) than the patients who did not develop LFCN palsy. Median age, gender, diabetes, and surgical time were not significantly different between the groups. All cases resolved completely within 6 months.

CONCLUSIONS

LFCN palsy after shoulder surgery in the beach chair position in our study has a prevalence of 1.3%, making it an uncommon complication. Patients with elevated BMI should be counseled about its possible occurrence after shoulder surgery in the beach chair position.

LEVEL OF EVIDENCE

Level IV, prognostic.

The lateral femoral cutaneous nerve canal

OBJECTIVE

Meralgia paresthetica causes dysesthesias and burning in the anterolateral thigh. Surgical treatment includes nerve transection or decompression. Finding the nerve in surgery is very challenging. The author conducted a cadaveric study to better understand the variations in the anatomy of the lateral femoral cutaneous nerve (LFCN).

METHODS

Twenty embalmed cadavers were used for this study. The author studied the LFCN's relationship to different fascial planes, and the distance from the anterior superior iliac spine (ASIS).

RESULTS

A complete fascial canal was found to surround the nerve completely in all specimens. The canal starts at the inguinal ligament proximally and follows the nerve beyond its terminal branches. The nerve could be anywhere from 6.5 cm medial to the ASIS to 6 cm lateral to the ASIS. In the latter case, the nerve may lodge in a groove in the iliac crest. Other anatomical variations found were the LFCN arising from the femoral nerve, and a duplicated nerve. A thick nerve was found in 1 case in which it was riding over the ASIS.

CONCLUSIONS

The variability in the course of the LFCN can create difficulty in surgical exposure. The newly defined LFCN canal renders exposure even more challenging. This calls for high-resolution pre- or intraoperative imaging for better localization of the nerve.

Ultrasound-Guided Diagnosis and Injection of the Lateral Femoral Cutaneous Nerve with an Anatomical Variation

Meralgia paresthetica (MP) is an entrapment neuropathy of the lateral femoral cutaneous nerve (LFCN). There are many variations in the course of the LFCN. A 55-year-old woman presented with pain and tingling sensations on the anterolateral aspect of her left thigh. Physical examination revealed hypoesthesia of the proximal anterolateral thigh on the left side. During the electrodiagnostic study, sensory nerve action potential of the LFCN could not be obtained on both sides. Through those clinical and electrophysiological findings, we prediagnosed the case as MP and planned to perform diagnostic nerve block. For the injection to perform, ultrasonography was used. During the ultrasonographic evaluation, the left LFCN was visualized lateral to the anterior superior iliac spine (ASIS). Then ultrasound-guided nerve block with 2 cc lidocaine 2% for diagnostic purpose was performed in this region. Immediately after the injection, the patient's complaints relieved completely, and hence the patient was diagnosed as having MP with an LFCN anatomical variation. Two months later her complaints persisted, and ultrasound-guided LFCN injection with 2 mL of lidocaine 2% + 1 cc of betametazone was performed. One month after the second injection, her complaints were relieved markedly and she resumed her daily activities. In conclusion, the course of the LFCN is quite variable. We present a relatively rare anatomical variation of the LFCN, crossing lateral to the ASIS, diagnosed with ultrasonography. Ultrasonography can be performed to visualize the LFCN, especially a nerve with an anatomical variation.

The surgical anatomy of the lateral femoral cutaneous nerve in the inguinal region: a meta-analysis

Purpose

Several variations in the anatomy and injury of the lateral femoral cutaneous nerve (LFCN) have been studied since 1885. The aim of our study was to analyze the available data on the LFCN and find a true prevalence to help in the planning and execution of surgical procedures in the area of the pelvis, namely inguinal hernia repair.

Methods

A search of the major medical databases was performed for LFCN anatomy. The anatomical data were collected and analyzed.

Results

Twenty-four studies (n = 1,720) were included. The most common pattern of the LFCN exiting the pelvis was medial to the Sartorius as a single branch. When it exited in this pattern, it did so on average 1.90 cm medial to the anterior superior iliac spine (ASIS).

Conclusions

The LFCN and its variations are important to consider especially during inguinal hernia repair, abdominoplasty, and iliac bone grafting. We suggest maintaining a distance of 3 cm or more from the ASIS when operating to prevent injury to the LFCN.

Electronic supplementary material

The online version of this article (doi:10.1007/s10029-016-1493-7) contains supplementary material, which is available to authorized users.

Anatomical Variations of the Lateral Femoral Cutaneous Nerve and Iatrogenic Injury After Autologous Bone Grafting From the Iliac Crest

OBJECTIVE

We describe 2 patients with surgical injury to the lateral femoral cutaneous nerve (LFCN) after bone harvesting from the iliac crest for autologous bone grafting.

DESIGN

A case-series of 2 patients and literature study of all anatomical variants of the LFCN in relation to the anterior superior iliac spine and inguinal ligament.

SETTING

A teaching hospital in The Hague, the Netherlands.

PATIENTS

Two patients with surgical injury to the LFCN after bone harvesting from the iliac crest for autologous bone grafting.

RESULTS

All 9 known anatomical variations of the LFCN in the literature are reviewed, and the importance of these anatomical variations for surgeons and anesthetists is stressed.

CONCLUSIONS

For every trauma, orthopedic, plastic, and cranio-maxillofacial surgeon and anesthesiologist it is important to know the anatomy of the LFCN and its known variations. To prevent injury of the LFCN during bone harvesting, the bone should be harvested 4-5 cm posterior to the anterior superior iliac spine and the incision should be parallel to the iliac crest.

LEVEL OF EVIDENCE

Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

Mimickers of lumbar radiculopathy

Orthopaedic surgeons frequently treat patients who report pain that radiates from the back into the lower extremity. Although the most common etiology is either a herniated disk or spinal stenosis, a myriad of pathologies can mimic the symptoms of radiculopathy, resulting in differences in the clinical presentation and the workup. Therefore, the clinician must be able to distinguish the signs and symptoms of lumbar radiculopathy from pathologies that may have a similar presentation. Being cognizant of these other possible conditions enables the physician to consider a breadth of alternative diagnoses when a patient presents with radiating lower extremity pain.

Meralgia paresthetica-like symptoms following epidural analgesia after total knee arthroplasty

Meralgia paresthetica (MP) is generally caused by entrapment of the lateral femoral cutaneous nerve (LFCN), and presents with pain and paresthesia in the anterolateral thigh. This paper describes a patient who had MP-like symptoms as a result of continuous epidural analgesia after total knee arthroplasty. The patient with pre-existing left foraminal stenosis at L3-L4 and disc herniations at L4-5 did not complain of paresthesia or pain during the combined spinal-epidural anesthetic procedure. However, during epidural analgesia on the second post-operative day, he complained of paresthesia and pain in the anterolateral thigh of the contralateral leg. Electromyography showed a neurogenic lesion at the level of L3. Although an ultrasound-guided diagnostic block of the LFCN was performed twice post-operatively, the patient's symptoms persisted. The symptoms gradually resolved 12 months after the surgery. In our case, we suggest that the continuous epidural infusate caused neural ischemia of the L3 nerve root by a compressive effect.

How can we optimize anterior iliac crest bone harvesting? An anatomical and radiological study

PURPOSE

Anterior iliac crest bone is a widely used donor site for bone harvesting. It provides an autologous bone graft consisting of cancellous bone that can be packed or cortical bone with greater structural support. Uses include spinal fusion and fracture non-union surgery. Although its use is common, dedicated anatomical and radiological studies analysing graft dimensions and optimal harvesting site in relation to local anatomical landmarks [anterior superior iliac spine (ASIS), anterior iliac tubercle (AIT) and lateral femoral cutaneous nerve (LFCN)] have not been described.

METHODS

Twenty-eight female hemipelvises were dissected for this study. The LFCN, ASIS and AIT were identified. Calliper measurements and CT scan analysis were undertaken to determine the optimum positions in obtaining a 5-mm-thickness tricortical graft whilst remaining safe for the LFCN.

RESULTS

According to our measurements, the optimal location for harvesting a 5-mm-thick tricortical graft with 35-mm height and 47-mm width is situated anterior to a line passing at the level of the thickest point of the AIT. This thickest point was situated at a mean 67 mm from the centre of the EIAS in our study.

CONCLUSION

This anatomical and radiographic study determined the anatomical iliac crest landmarks to avoid neurological injury when taking an optimal 5-mm-width tricortical bone graft.

Ultrasound-guided pain interventions - a review of techniques for peripheral nerves

Ultrasound has emerged to become a commonly used modality in the performance of chronic pain interventions. It allows direct visualization of tissue structure while allowing real time guidance of needle placement and medication administration. Ultrasound is a relatively affordable imaging tool and does not subject the practitioner or patient to radiation exposure. This review focuses on the anatomy and sonoanatomy of peripheral non-axial structures commonly involved in chronic pain conditions including the stellate ganglion, suprascapular, ilioinguinal, iliohypogastric, genitofemoral and lateral femoral cutaneous nerves. Additionally, the review discusses ultrasound guided intervention techniques applicable to these structures.

Ultrasound of the lateral femoral cutaneous nerve in asymptomatic adults

Background

To define the sites where the lateral femoral cutaneous nerve (LFCN) is more easily visualized and to describe the anatomical variations of the LFCN.

Methods

A total of 240 LFCNs in 120 volunteers were evaluated with 18 MHz ultrasound; the intermuscular space between the tensor fasciae latae muscle and the sartorius was used as an initial sonographic landmark. The time taken to identify the nerve was recorded. The number of nerve branches at the level of the inguinal ligament (IL) and the relationship between the LFCN and the IL was assessed. The nerve cross-sectional area (CSA) of the LFCN and the distance between the LFCN and the anterior superior iliac spine was measured.

Results

Each nerve was identified using ultrasound in all participants. The mean time for identifying the nerve was 7s for unilateral LFCNs. The nerve passed under the IL in 198 cases, whereas in 44 cases, it passed through to the IL. The LFCN consisted of 1–4 branches just after its passage under or through the IL. The CSA of the LFCN was 1.04±0.44 mm², and the mean distance between the LFCN and the anterior superior iliac spine was 15.6 ± 4.2 mm.

Conclusions

It is easier to identify the LFCN if the intermuscular space between the tensor fasciae latae muscle and the sartorius is used as an initial sonographic landmark. The anatomical variation of the LFCN can be viewed with high-frequency ultrasound.

Relationships of the lateral femoral cutaneous nerve to bony landmarks

BACKGROUND

The lateral femoral cutaneous nerve (LFCN) can be at risk during, for example, the insertion of pins in the anterior superior iliac spine (ASIS) during external fixation of the pelvis, total hip arthroplasty through a direct anterior approach, open surgery for impingement in the hip through an anterior approach, and periacetabular osteotomy. During surgery, the surgeon usually assumes the location of the LFCN by using the ASIS as a landmark.

QUESTIONS/PURPOSES

We investigated (1) whether there is any relationship between the LFCN and the ASIS and (2) the anatomy of the LFCN at the lateral border of the psoas major.

METHODS

Using 25 formalin-fixed cadavers, we determined the location of the LFCN emergence point as above, same level with, or below the iliac crest (IC). We measured the distances between the LFCN emergence point and the crossing of the IC and psoas major, ASIS, and pubic tubercle. We measured the distances between the ASIS and pubic tubercle (AB) and the ASIS and the point where the LFCN crossed the inguinal ligament (AC) and then calculated AC/AB.

RESULTS

The LFCN was below the IC on 19 sides, at the same level on 13 sides, and above on 12 sides. The distances were -0.98 ± 5.57 cm to the IC, 12.39 ± 2.67 cm to the ASIS, and 17.76 ± 3.33 cm to the pubic tubercle. AB was 13.11 ± 1.08 cm, AC 2.95 ± 2.01 cm, and AC/AB 0.22 ± 0.16.

CONCLUSIONS/CLINICAL RELEVANCE

The LFCN may emerge from the lateral border of the psoas major above or below the IC. The AC/AB ratio can help surgeons to find the LFCN in patients with different body types.

Pulsed radiofrequency neuromodulation treatment on the lateral femoral cutaneous nerve for the treatment of meralgia paresthetica

We describe a rare case of pulsed radiofrequency treatment for pain relief associated with meralgia paresthetica. A 58-year-old female presented with pain in the left anterior lateral thigh. An imaging study revealed no acute lesions compared with a previous imaging study, and diagnosis of meralgia paresthetica was made. She received temporary pain relief with lateral femoral cutaneous nerve blocks twice. We performed pulsed radiofrequency treatment, and the pain declined to 25% of the maximal pain intensity. At 4 months after the procedure, the pain intensity did not aggravate without medication. Pulsed radiofrequency neuromodulation treatment on the lateral femoral cutaneous nerve may offer an effective, low risk treatment in patients with meralgia paresthetica who are refractory to conservative medical treatment.

Utility of ultrasound-guided surface electrode placement in lateral femoral cutaneous nerve conduction studies

INTRODUCTION

Meralgia paresthetica is a common clinical complaint for which some patients ultimately undergo surgical treatment. The lateral femoral cutaneous nerve (LFCN) has been difficult to reliably test electrophysiologically, likely due to anatomic variability and lack of responses in asymptomatic obese subjects.

METHODS

We compared a novel ultrasound-guided antidromic sensory nerve conduction study (NCS) with a technique described previously in a population of normal subjects, of whom 50% had body mass indices within the obese range (>27.5).

RESULTS

Responses were obtained in at least 92% of subjects using either technique, and 92% of normal subjects had <60% interside variability using the ultrasound-guided technique.

CONCLUSIONS

LFCN sensory nerve action potentials can be obtained in the vast majority of normal subjects, even in an obese population and can provide a useful sensory NCS for evaluation of mid-lumbar radiculopathy, plexopathy, or meralgia paresthetica.

The applied anatomy of anterior approach for minimally invasive hip joint surgery

The anterior approach for minimally invasive hip joint surgery is one of the common approaches utilized in hip joint surgery. Here, we report the results of dissections in 60 sides of human adult cadavers. We observed and measured the branches of the superficial circumflex iliac artery, the lateral femoral cutaneous nerves, the lateral circumflex femoral artery, and the superior gluteal nerves in the experiment via the anterior approach for minimally invasive hip joint surgery. The relationship between these structures and the anterior approach was studied. The present study provides important data demonstrating the location, path of dominant structures that might be encountered during the surgery and their relationships with the surgical incision. These data may allow surgeons performing the anterior approach for hip joint surgery to minimize the risk of neurovascular injury.

Suprainguinal retroperitoneal approach for the successful surgical treatment of meralgia paresthetica

Object

Neurosurgical textbooks describe an infrainguinal approach as the standard or preferred option for the surgical treatment of meralgia paresthetica (MP), the most frequent entrapment neuropathy of the lower limb. However, inhomogeneous results led the authors to adopt a suprainguinal, retroperitoneal approach for decompression of the lateral femoral cutaneous nerve. In this paper the authors' aim was to study the outcome of patients harboring MP treated via this different surgical approach.

Methods

The outcome of 55 consecutive patients who underwent surgery for MP via the suprainguinal retroperitoneal approach during a 15-year period was ascertained through postal questionnaires (in 47 patients) and follow-up visits (in 8 patients). The male to female ratio was 1:0.67, and the mean patient age was 50 ± 12.9 years. The mean follow-up was 3.2 ± 3.3 years. Seven of the patients underwent bilateral surgery.

Results

Intraoperatively the lateral femoral cutaneous nerve was consistently found in close anatomical relationship to the anterior superior iliac spine, although some variations regarding the diameter, number of branches, and underlying pathological entity were observed. Eighty-seven percent of patients showed improvement (21 patients) or complete remission (27 patients) of painful dysesthesia in the anterolateral thigh, and 13% (7 patients) remained unchanged. In addition 82% had improvement (31 patients) or complete remission (14 patients) of hypesthesia, leaving 18% with unchanged (9 patients) or worsened (1 patient) hypesthesia. In the patient-evaluated group 66% (31 of 47) were completely satisfied with the outcome, 23% (11 of 47) were partially satisfied, and 11% (5 of 47) were not satisfied with the outcome. Two cases each of recurrence, seroma, wound infection, and 1 case of hematoma requiring revision were encountered as complications.

Conclusions

The suprainguinal retroperitoneal approach is a viable first-choice option for the surgical relief of MP.

Sonographic assessment of the lateral femoral cutaneous nerve

PURPOSE

To evaluate the ability of high-frequency sonography to evaluate the lateral femoral cutaneous nerve (LFCN).

METHODS

A cadaveric study was performed on 5 cadavers to outline the normal course of the LFCN. Next, 37 LFCNs in 21 volunteers were evaluated via sonography with a 5-13-MHz linear-array transducer.

RESULTS

The LFCN was easily identified in our dissections. It always entered the thigh under the inguinal ligament and coursed superficially to the sartorius muscle. In 2/10 (20%) cases, anatomical variants were observed. Sonography revealed the LFCN in 26/37 (70%) cases. The relationships of the nerve with the deep circumflex iliac artery, the anterior superior iliac spine, and the sartorius were visualized. Neuromas were observed bilaterally in 1 volunteer.

CONCLUSION

The LFCN can be seen in the groin with the aid of sonography.

Prone position-related meralgia paresthetica after lumbar spinal surgery : a case report and review of the literature

Lateral femoral cutaneous neuropathy occurring during spinal surgery is frequently related to iliac bone graft harvesting, but meralgia paresthetica (MP) can result from the patient being in the prone position. Prone position-related MP is not an uncommon complication after posterior spine surgery but there are only few reports in the literature on this subject. It is usually overlooked because of its mild symptoms and self-limiting course, or patients and physicians may misunderstand the persistence of lower extremity symptoms in the early postoperative period to be a reflection of poor surgical outcome. The authors report a case of prone position-related MP after posterior lumbar interbody fusion at the L3-4 and reviewed the literature with discussion on the incidence, pathogenesis, and possible risk factors related to this entity.

Anatomical study of the lateral femoral cutaneous nerve with special reference to minimally invasive anterior approach for total hip replacement

BACKGROUND

Lesion of the lateral femoral cutaneous nerve (LFCN) represents the main complication during minimally invasive anterior approach dissection to the hip joint. The aim of this anatomical study was to describe the different presentation features of the LFCN at the thigh and particularly to determine the potential location of damage during minimally invasive anterior approach for total hip replacement.

METHODS

The LFCN was dissected bilaterally at the thigh under the inguinal ligament in 17 formalin-preserved cadavers. Branching patterns of the nerve were recorded and distances from the LFCN to the anterior superior iliac spine (ASIS) and the anterior margin of the tensor fascia lata (TFL) were measured to clarify skin incision positioning during minimally invasive anterior approach for total hip replacement.

RESULTS

The LFCN divided proximal to the inguinal ligament in 13 cases and distal to it in 21 cases. In the distal group the mean distance from the ASIS to the nerve division was 34.5 mm (10-72 mm). The gluteal branch crossed the anterior margin of the TFL 44.5 mm (24-92 mm) distally to the ASIS. In 18 cases the femoral branch did not cross the TFL and was located in the intermuscular space between TFL and sartorius. In the remaining 16 cases, this branch crossed the anterior margin of the TFL 46 mm (27-92 mm) distally to the ASIS. During minimally invasive anterior approach along the anterior border of the TFL, the LFCN was found to be potentially at risk between 27 and 92 mm below the ASIS. We used those informations to describe a map of "danger zones" for the LFCN or its two main branches.

CONCLUSION

According to this study, numerous anatomical variations of the LFCN at the thigh should be considered when performing anterior approach to the hip joint. Different mechanisms of injury during surgery should be considered especially during minimally invasive total hip replacement, such as section of the gluteal or the femoral branch where it crosses the anterior margin of the TFL or stretching of the femoral branch due to retractors positioned into the intermuscular space between sartorius and TFL. According to the map of "danger zones" reported, the author policy consists of positioning the skin incision as lateral and distal to the ASIS as possible.

Distal lesion of the lateral femoral cutaneous nerve

We report three patients with a typical clinical picture of unilateral meralgia paresthetica in whom routine nerve conduction studies were normal. However, cortical somatosensory evoked potentials were absent after lateral femoral cutaneous nerve (LFCN) stimulation on the affected side. After stimulation of the LFCN in the anterosuperior iliac spine (ASIS) region and recording the responses distal to conventional sites (20 cm from the ASIS), sensory nerve action potentials (SNAPs) were absent in the symptomatic leg, but present in the normal leg. We suggest that thigh paresthesias may be caused by a distal LFCN lesion. Eliciting this requires recording SNAPs distal to conventional sites.

A novel approach to the diagnosis and management of meralgia paresthetica

OBJECTIVE

To review the results of conservative and surgical treatment of meralgia paresthetica (MP), with particular reference to the use of a simple clinical test for diagnosing this condition and the outcome of primary nerve decompression surgery.

METHODS

Records of all patients with a diagnosis of MP were reviewed. Information was obtained about clinical presentation and risk factors, diagnostic evaluation, management, and outcome. Actuarial analysis was used to determine the intervention-free interval after surgical decompression.

RESULTS

Between 2000 and 2005, MP was diagnosed in 45 patients. There were 27 men and 18 women, and the average age at presentation and duration of symptoms were 47 and 1.9 years, respectively. The pelvic compression test had a sensitivity of 95% and a specificity of 93.3% for this condition. Twenty-five patients were managed conservatively and 20 required operative intervention, which was bilateral in two patients. The average follow-up period was 25 months, and the actuarial 2- and 5-year intervention-free rates were 91 and 78%, respectively, with no specific risk factors for revision surgery.

CONCLUSION

The pelvic compression test is a sensitive and specific test for MP, helping to distinguish it from lumbosacral radicular pain. Most patients with this condition can be managed successfully with conservative measures, and those requiring surgery can be treated effectively with nerve decompression.

Variability in conduction of the lateral femoral cutaneous nerve

The purpose of this study was to establish a reliable technique for assessing conduction in the lateral femoral cutaneous nerve (LFCN), bearing in mind its anatomical variation. Based on our anatomical study, normative values were obtained in 40 healthy nerves. The optimal stimulation site was located 1 cm or more media 16470526 l to the anterior superior iliac spine (ASIS) in 93% of cases and over the ASIS in 7%. Sensory nerve action potentials (SNAPs) were recorded simultaneously along an imaginary line between the ASIS and the lateral border of the patella and 2 cm medial to this line. Side-to-side variability in amplitude was 31% for the recording from the line and 30% for the medial recording. The variability significantly decreased to 16% when the higher value of each side was compared. Therefore, the measurement of higher amplitude recorded at two different sites may minimize interside variability and improve the diagnostic utility of the LFCN conduction study.

Postoperative meralgia paresthetica after posterior spine surgery: incidence, risk factors, and clinical outcomes

STUDY DESIGN

A prospective study on postoperative meralgia paresthetica after posterior thoracolumbar spine surgery on the Relton-Hall frame.

OBJECTIVES

To assess the incidence of postoperative lateral femoral cutaneous nerve (LFCN) neuralgia and to investigate its risk factors and clinical outcomes.

SUMMARY OF BACKGROUND DATA

Postoperative meralgia paresthetica is a common complication of posterior thoracolumbar spine surgery. The injury mechanism is external compression to the LFCN near the anterior superior iliac spine in the prone position.

METHODS

A total of 252 patients were examined for signs of meralgia paresthetica before and after surgery. Patients with a LFCN injury were followed regularly until sensory impairment resolved. Several possible contributing factors were assessed to evaluate the correlations.

RESULTS

Postoperative meralgia paresthetica was experienced by 60 patients (23.8%). Patients with an LFCN injury had a significantly greater body mass index (23.6 vs. 22.4 kg/m2) and a longer surgical time (3.7 vs. 3.2 hours). Overweight/obese patients had a significantly greater incidence (odds ratio, 1.83; 95% confidence interval, 1.02-3.29). Patients operated for degenerative spinal disorders also had a significantly higher incidence of LFCN injury (odds ratio, 2.81; 95% confidence interval, 1.53-5.13). Recovery took 10.5 days on average (range, 2 days to 2 months). Thirty-two patients (53%) recovered completely within the first week and every patient recovered within 2 months.

CONCLUSION

Postoperative meralgia paresthetica is a common but benign complication of posterior thoracolumbar spine surgery. Degenerative spinal disorders, overweight/obesity, and longer surgical time are factors related to a higher incidence of LFCN injury. The clinical outcome is always excellent, and complete recovery can be expected within 2 months.

Cutaneous silent periods of the vastus medialis evoked by the stimulation of lateral femoral cutaneous nerve

OBJECTIVE

Cutaneous silent period (CSP), which is a spinal reflex mediated by A-delta cutaneous afferents, is transient suppression of the electromyographic activity. In this study, our aim is to investigate CSPs of vastus medialis muscle (vm-CSP) evoked by the stimulation of the lateral femoral cutaneous nerve (LFCN) in healthy controls and in patients with meralgia paresthetica (MP).

METHODS

Twenty-one patients with MP (17 unilateral, 4 bilateral) and 27 healthy controls were included. Nerve conduction studies of LFCN and vm-CSP were analyzed in all subjects. A stimulus train consisting of five electrical shocks was applied to the skin at the anterolateral side of the thigh for recording of the vm-CSP.

RESULTS

Nerve conduction abnormalities of LFCN were observed in all patients with MP. Mean duration of vm-CSP was 69.7+/-9.2ms, and mean onset latency was 44.7+/-6.9 in healthy controls. Onset latency of vm-CSP was significantly prolonged and the duration of vm-CSP was significantly shortened in patients with MP. Vm-CSP abnormalities were observed in 20/25 extremities with MP.

CONCLUSIONS

Dysfunction of A-delta afferents may cause these findings in patients with MP. Additionally, spinal modulation of pain may also play a role in the explanation of our findings.

SIGNIFICANCE

The present study demonstrates the CSP alterations in the patients with entrapment neuropathy of a cutaneous nerve.