Meralgia paresthetica

Meralgia paresthetica is a common but probably underrecognized syndrome caused by dysfunction of the lateral femoral cutaneous nerve. The diagnosis is based on the patient's description of sensory disturbance, often painful, on the anterolateral aspect of the thigh, with normal strength and reflexes. Sensory nerve conduction studies and somatosensory evoked potentials may be used to support the diagnosis, but both have technical limitations, with low specificity and sensitivity. Risk factors for meralgia paresthetica include obesity, tight clothing, and diabetes mellitus. Some cases are complications of hip or lumbar spine surgery. Most cases are self-limited, but a small proportion of patients remain with refractory and disabling symptoms. Treatment options include medications for neuropathic pain, neurolysis, neurectomy, and radioablation, but controlled trials to compare efficacy are lacking.

Clinical study of modified INFIX combined with sacroiliac joint screws for pelvic instable injuries

OBJECTIVE

The INFIX technique is becoming one of the most commonly performed surgical procedures for anterior pelvic ring instability injuries. The purpose of this article is to compare the clinical outcomes of modified anterior subcutaneous internal fixation (M-INFIX) with conventional anterior subcutaneous internal fixation (C-INFIX) for anterior pelvic ring instability injuries.

PATIENTS AND METHODS

A retrospective analysis of 36 cases of unstable pelvic injuries treated operatively at our institution, 20 of which were treated with C-INFIX and 16 with M-INFIX. Data collected included age, gender, ISS score, fracture typing, operative time, operative bleeding, postoperative complications, fracture healing time, Matta score, Majeed score, and follow-up time. Statistical sub-folding of each variable between the two groups was performed.

RESULTS

There was no statistical difference between the C-INFIX and M-INFIX groups in terms of age, gender, ISS (Injury Severity Score), follow-up time, fracture typing, fracture healing time, and Majeed score (P > 0.05). the M-INFIX had a significantly lower incidence of postoperative complications than the C-INFIX group, especially in the incidence of Lateral femoral cutaneous nerve (LFCN) injury (P < 0.05). In contrast, the M-INFIX group had statistically higher operative time, intraoperative bleeding, and Matta score than the C-INFIX group (P < 0.05).

CONCLUSION

This study was based on a modified application of the surgical experience with C-INFIX and showed better clinical outcomes in terms of complication rates and quality of repositioning than the conventional surgical approach. These findings indicate that further analytical studies of this study would be valuable.

Ultrasonographic identification of lateral femoral cutaneous nerve anatomical variation in persistent meralgia paresthetica: A case report

BACKGROUND

Meralgia paresthetica (MP) is an entrapment mononeuropathy of the lateral femoral cutaneous nerve (LFCN). Although structural abnormalities in nerve tissues can be confirmed using ultrasonography, this is not routinely performed.

CASE SUMMARY

Herein, we present the case of a 52-year-old woman who developed MP after laparoscopic gynecological surgery. The patient was referred to our clinic from an obstetrics and gynecology clinic with symptoms of numbness and a tingling sensation in the left anterolateral thigh, which developed after surgery performed 5 mo earlier. Tests were performed to assess the disease status and determine the underlying causes. Ultrasonographic examination revealed an anatomical variation, where the left LFCN was entrapped within the inguinal ligament. This case suggests that performing ultrasonographic examination before and after surgery in the lithotomy position could help prevent MP.

CONCLUSION

This case demonstrates the value of ultrasonography in detecting anatomical variation and diagnosing persistent MP. Ultrasonography should be considered an adjunct to electromyography for optimal MP management. Further, this case would help other clinicians determine patient prognosis and decide on targeted treatment strategies.

Cadaveric Study of Variations in the Course of Lateral Femoral Cutaneous Nerve: Insight to Prevent Injury

Objective

A recent spurt in incidence of meralgia paresthetica to 0.1-81% due to minimally invasive anterior approach to hip joint has resulted in reinterest in anatomy of lateral femoral cutaneous nerve (LFCN). Familiarity with variations in the course of LFCN will reduce the morbidity associated with orthopedic procedures around the anterior superior iliac spine (ASIS) and inguinal ligament (IL).

Methods

Twenty five adult human formalin embalmed cadavers were dissected. Course and relations of nerve to ASIS, IL and sartorius muscle was noted, distance of nerve from ASIS at IL was measured and statistically analyzed.

Results

Mean distance of LFCN from ASIS at IL was 1.73±1.15 cm. Differences between two sides and sexes was statistically not significant (p=0.51 and p=0.96 respectively). Inferomedial to ASIS, 94% of LFCNs crossed IL with 92% of them present within 4 cm medial to ASIS. Majority of LFCNs (90%) exited pelvis and entered thigh posterior to IL. Out of these nerves 48% were single trunks on entry into thigh, then bifurcated into anterior and posterior branches. Remaining LFCNs bifurcated proximal to IL or at level of IL. Trifurcations were seen in 6% while a rare case of pentafication was observed. In 66% main trunk/branches were present in intermuscular cleft between sartorius muscle and tensor fascia lata.

Conclusions

Care should be exercised by surgeons while dissecting around IL as more than half of nerves are liable to be injured during operative procedures. This would help in better anticipation of problem, acceptance and reducing litigation.

Diagnosis and treatment of meralgia paresthetica between 2005 and 2018: a national cohort study

The prevalence of meralgia paresthetica (MP), which is caused by compression of the lateral femoral cutaneous nerve (LFCN), has been increasing over recent decades. Since guidelines and large-scale studies are lacking, there are substantial regional differences in diagnostics and management in MP care. Our study aims to report on current diagnostic and therapeutic strategies as well as time trends in clinical MP management in Germany. Patients hospitalized in Germany between January 1, 2005, and December 31, 2018, with MP as their primary diagnosis were identified using the International Classification of Disease (ICD-10) code G57.1 and standardized operations and procedures codes (OPS). A total of 5828 patients with MP were included. The rate of imaging studies increased from 44% in 2005 to 79% in 2018 (p < 0.001) and that of non-imaging diagnostic studies from 70 to 93% (p < 0.001). Among non-imaging diagnostics, the rates of evoked potentials and neurography increased from 20%/16% in 2005 to 36%/23% in 2018 (p < 0.001, respectively). Rates of surgical procedures for MP decreased from 53 to 37% (p < 0.001), while rates of non-surgical procedures increased from 23 to 30% (p < 0.001). The most frequent surgical interventions were decompressive procedures at a mean annual rate of 29% (± 5) throughout the study period, compared to a mean annual rate of 5% (± 2) for nerve transection procedures. Between 2005 and 2018, in-hospital MP care in Germany underwent significant changes. The rates of imaging, evoked potentials, neurography, and non-surgical management increased. The decompression of the LFCN was substantially more frequent than that of the LFCN transection, yet both types of intervention showed a substantial decrease in in-hospital prevalence over time.

Spinal cord stimulation to treat meralgia paresthetica. Is it feasible? A case report

Meralgia paresthetica is a neurological disorder caused by a neuropathy of the lateral femoral cutaneous nerve. Its aetiology can be spontaneous or iatrogenic. It is characterized by pain, paresthesia, and numbness in the anterolateral aspect of the thigh. Diagnosis is based on clinical examination, although image and neurophysiological tests can be useful as well. Despite conservative measures use to be effective in most of patients, refractory cases can benefit from alternative treatments. Available surgical procedures are: nerve decompression (neurolysis) or section (neurectomy) and radiofrequency ablation. We present a case of refractory meralgia paresthetica where spinal cord stimulation was used as a possible effective technique in pain relief and to avoid the neurectomy of the lateral femoral cutaneous nerve.

[Meralgia paraesthetica as complication of patient positioning : A not fully controllable risk]

Als Meralgia paraesthetica (MP) bezeichnet man eine zu den neurologischen Engpasssyndromen zählende Schädigung des aus dem Plexus lumbalis entspringenden sensiblen N. cutaneus femoris lateralis. Symptome sind temporäre oder bleibende Parästhesien und Schmerzen an der Vorder- und Außenseite des Oberschenkels. Die MP kann idiopathisch auftreten, sich genuin als z. B. „seat belt syndrome“ oder „Jeans-Syndrom“ verwirklichen, sie kann aber auch Folge eines operativen Eingriffs oder einer chirurgischen bzw. intensivmedizinischen Lagerung sein. Im Fokus stehen hierbei in der Literatur die Steinschnitt-, die Bauch- und die „Beach-chair“-Lagerung.

Analysiert wurden 21 Beschwerden über eine postoperativ erstmals aufgetretene MP, die bei der Gutachterkommission für ärztliche Behandlungsfehler bei der Ärztekammer Nordrhein im Verlauf der letzten 10 Jahre eingereicht wurden. Unter diesen konnten 6 Fälle als Lagerungsschaden nach Steinschnittlagerung identifiziert werden; in 3 Fällen trat eine MP nach Rückenlagerung auf; die Ätiologie konnte nicht sicher geklärt werden. In 12 Fällen wurde die MP als direkte Operationskomplikation erkannt.

Pathophysiologie, Inzidenz und Verlauf sowie juristische Implikationen der lagerungsbedingten MP werden beschrieben. Als hauptsächlicher Pathomechanismus wird eine Druckschädigung des Nervs an seiner Kreuzungsstelle mit dem Leistenband diskutiert. Wenngleich alle hier vorgestellten Fälle nach der Steinschnittlagerung auftraten, scheint sich die Komplikation nach Literaturdaten auch bei anderen Lagerungsarten, am häufigsten möglicherweise bei Bauchlagerungen, zu verwirklichen. Dies erklärt auch die zunehmenden Fallberichte einer MP nach Bauchlagerung bei COVID-19-Patient*innen. Eine sichere Vermeidung der lagerungsbedingten Komplikation erscheint aufgrund der anatomischen Variabilität des Nervenverlaufs und der unklaren Pathomechanismen nicht möglich.

Lateral versus conventional fasciotomy for prevention of lateral femoral cutaneous nerve injury in total hip arthroplasty with direct anterior approach: a study protocol for a dual-center, double-blind, randomized controlled trial

BACKGROUND

An incision for total hip arthroplasty (THA) via the direct anterior approach (DAA) is generally made outside of the space between the sartorius and tensor fasciae latae muscles to prevent lateral femoral cutaneous nerve (LFCN) injury. Anatomical studies have revealed that the LFCN courses between the sartorius and tensor fasciae latae muscles. When the LFCN branches radially while distributing in the transverse direction from the sartorius muscle to the tensor fasciae latae muscle, it is called the fan type. Studies suggest that damage to the fan type LFCN is unavoidable during conventional fasciotomy. We previously demonstrated that injury to non-fan variation LFCN occurred in 28.6% of patients who underwent THA by fasciotomy performed 2 cm away from the intermuscular space. This suggests that the conventional approach also poses a risk of LFCN injury to non-fan variation LFCN. LFCN injury is rarely reported in the anterolateral approach, which involves incision of fascia further away than the DAA. The purpose of this study is to investigate how the position of fasciotomy in DAA affects the risk of LFCN injury.

METHODS

We will conduct a prospective, randomized, controlled study. All patients will be divided into a fan variation and a non-fan variation group using ultrasonography before surgery. Patients with non-fan variation LFCN will receive conventional fasciotomy and lateral fasciotomy in the order specified in the allocation table created in advance by our clinical trial center. The primary endpoint will be the presence of LFCN injury during an outpatient visit using a patient-based questionnaire. The secondary endpoints will be assessed based on patient-reported outcomes at 3 months after surgery in an outpatient setting using the Western Ontario and McMaster Universities Osteoarthritis Index, the Japanese Orthopaedic Association Hip-disease Evaluation Questionnaire, and the Forgotten-Joint Score-12.

DISCUSSION

We hypothesize that the incidence of LFCN injury due to DAA-THA is reduced by making the incision further away from where it is typically made in conventional fasciotomy. If our hypothesis is confirmed, it will reduce the disadvantages of DAA and improve patient satisfaction.

TRIAL REGISTRATION

UMIN Clinical Trials Registry, UMIN000035945 . Registered on 20 February, 2019.

Variability in rod to bone distance needed in pelvic subcutaneous internal fixation to avoid nerve compression: A tridimensional population-based study

INTRODUCTION

Pelvic internal fixation has become a popular method for treatment of unstable pelvic ring injuries. Although successful, one complication is femoral nerve palsy from compression of the connecting rod. In light of this complication, this study was designed to evaluate sagittal inclinations of the rod and the feasibility of using a rod with a constant curvature.

HYPOTHESIS

It is hypothesized that that there is a connection between the sagittal inclination of the rod and the rod to bone distance, as well as single rod can be contoured with a constant curvature to be used in the majority of all patients.

METHODS

Three dimensional models of pelvis CTs from a single level 1 trauma center were created and imported into a program where software superimposed a pre-contoured rod in the sagittal planes upon the pelvic slices. The sagittal inclination was deemed acceptable is no interference occurred between the area of compression risk and the rod. For each pelvis and considered sagittal rod inclination, the rod radius of curvature (ROC), minimal rod to bone distance (RTB) and transverse inclinations (φ_L and φ_R) were measured at which the pedicle screws should be inserted to follow the direction of the smallest RTB.

RESULTS

The sagittal inclinations feasible for all subjects were between 15° to 30°. In this sagittal range, the average RTB varied in values ranging from 4.0±0.9mm to 25.4±11.4mm (p<0.01). Only 46% of subjects allowed a rod with constant curvature.

DISCUSSION AND CONCLUSION

Our study found that a rod to bone distance of 15mm was not safe for all models. As well, many subject models did not allow placement of pre-contoured rod. Patient specific templating of pelvic subcutaneous internal fixation is strictly needed to limit complications.

LEVEL OF EVIDENCE

VII; Basic Science.

Meralgia Paresthetica

PURPOSE OF REVIEW

This review article summaries the epidemiology, etiology, clinical presentations, and latest treatment modalities of meralgia paresthetica, including the latest data about peripheral and spinal cord stimulation therapy. Meralgia paresthetica (MP) causes burning, stinging, or numbness in the anterolateral part of the thigh, usually due to compression of the lateral femoral cutaneous nerve (LFCN).

RECENT FINDINGS

There are emerging data regarding the benefit of interventional pain procedures, including steroid injection and radiofrequency ablation, and other interventions including spinal cord and peripheral nerve stimulation reserved for refractory cases. The strength of evidence for treatment choices in meralgia paraesthetica is weak. Some observational studies are comparing local injection of corticosteroid versus surgical interventions. However, more extensive studies are needed regarding the long-term benefit of peripheral and spinal cord stimulation therapy.

Surgical anatomy of the lateral femoral cutaneous nerve for meralgia paraesthetica: A simple technical guide for surgeons and trainees alike

Meralgia paraesthetica is an entrapment neuropathy of the lateral femoral cutaneous nerve, usually due to compression at the inguinal ligament as the nerve passes from the pelvis into the thigh. Surgical decompression of the lateral femoral cutaneous nerve is a simple and effective treatment option, but the surgical anatomy of the area is not always familiar to neurosurgeons and neurosurgical trainees alike. This paper is a simple review of the relevant surgical anatomy and the surgical steps of lateral femoral cutaneous nerve decompression, with the aim of providing the busy surgeon and trainee a quick and easy reference guide to the procedure.

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.

Preoperative ultrasound to map the three-dimensional anatomical distribution of the lateral femoral cutaneous nerve in direct anterior approach for total hip arthroplasty

Background

The postoperative complaints of hypoesthesia or a burning sensation due to lateral femoral cutaneous nerve (LFCN) injury in patients are not yet solved. The present study aimed to identify the three-dimensional (3D) distribution of LFCN using preoperative ultrasound and evaluate the rate of injury in direct anterior approach for total hip arthroplasty.

Methods

A total of 59 patients (28 males and 31 females, age 69.0 ± 4.6 years, BMI 24.7 ± 3.0 kg/m²) were randomly allocated to the ultrasound group and 58 patients (28 males and 30 females, age 68.5 ± 4.5 years, BMI 24.8 ± 2.8 kg/m²) were in the control group. Surgeons received the data of 3D distribution of LFCN only in the ultrasound group before surgery with respect to the direction, the depth on the skin, and the length to tensor fasciae latae (TFL). The anatomical characteristics of LFCN in the surgical region were summarized. At 1 and 3 months of post surgery, the rate of LFCN injury and abnormal sensitive area was evaluated in both groups.

Results

There was a significant consistency in gender, age and BMI of these two groups (P > 0.05). Based on the data from the ultrasound group, over 90% of patients had one or two branches of LFCN. LFCN always courses in the fascia layer, the depth ranged from 6.8 ± 2.6 (3.0–12.0) mm to 11.1 ± 3.4 (4.0–17.0) mm and depended on the thickness of the subcutaneous fat, and length was 3.3 ± 4.6 (− 5.0–10.0) mm at proximal part and − 2.7 ± 4.7 (− 10.0–8.0) at distal end to the medial edge of TFL. Both the rate of LFCN injury and abnormal sensory area in the ultrasound group was significantly lower than those in the control group (3.4% vs. 25.9%, P = 0.001, at 1 month; 3.4% vs. 22.4%, P = 0.005, at 3 months).

Conclusions

LFCN mostly courses along the medial border of TFL in the fascia layer. The 3D distribution of LFCN using preoperative ultrasound mapping could help the surgeons to evaluate the risk of injury preoperatively and decrease the rate of injury during the operation. However, some branch injuries, especially for the fan type LFCN, could not be avoided.

Risk factors of meralgia paresthetica after prone position surgery: Possible influence of operating position, laminectomy level, and preoperative thoracic kyphosis

Obesity and a prolonged surgical duration are reported risk factors for meralgia paresthetica (MP) after prone position surgery; however, this fails to explain why MP seldom occurs after prone position craniotomy. We reviewed the incidence of MP after spinal surgery and craniotomy in the prone position and investigated whether unidentified factors are involved in the mechanism of postoperative MP. Between January 2014 and March 2020, we performed 556 prone position surgeries. We excluded patients aged ≤16 years and those who were comatose or who required redo-surgery, and reviewed 446 eligible patients (124 who underwent craniotomies and 322 who underwent posterior spinal surgeries). Postoperative MP occurred in 46 (10.3%) patients with a higher incidence after spinal surgery than after craniotomy (13.7% vs. 1.6%, p < 0.001). Among the 322 patients who received posterior spinal surgery, thoracic and lumbar laminectomies were associated with a higher incidence of MP than cervical laminectomy. Analyses limited to those patients who received thoracic and lumbar laminectomies revealed that the preoperative thoracic kyphosis (TK) angle was significantly greater in patients with MP than in those without MP (average TK angle, 38.9° vs. 23.1°; p < 0.001), and that the preoperative lumbar lordosis angle did not significantly differ between the two groups. Apart from the known predisposing factors, we found that thoracolumbar-sacral laminectomy in patients with a greater TK angle is also a risk factor for MP after prone position surgery.

Treatment of meralgia paresthetica (Lateral Femoral Cutaneous Neuropathy): A meta-analysis of ultrasound-guided injection versus surgery

PURPOSE

To compare ultrasound (US)-guided injections and surgery for the treatment of meralgia paresthetica (lateral femoral cutaneous neuropathy).

METHODS

Two reviewers, independently, up to 10 October 2020 retrieved Studies that assessed the outcome of US-guided injections and surgery for the treatment of meralgia paresthetica from major medical libraries. Predefined inclusion and exclusion criteria were adopted.

RESULTS

399 studies were initially found, and the meta-analysis was conducted on 10 studies for a total of 149 patients. US-guided injections were done in three studies, surgery in seven studies. N = 38 % (57/149) of patients were treated with US-guided injection and 62 % (92/149) were treated with surgery. After US-guided injections, 85 % (49/57) of patients were treated successfully, whereas 80 % (74/92) were treated with surgery successfully from the clinical point of view. Differences were not statistically significant even with a slight heterogeneity of studies and outcome pooled on random-effect model. No comparative cohort study or RCT was conducted.

CONCLUSION

This meta-analysis showed that there was no statistically significant difference in treatment of meralgia paresthetica with ultrasound-guided injection or surgery. A RCT to compare a standardized US-guided approach versus surgery is essential to compare these techniques properly.

Incidence and clinical outcome of lateral femoral cutaneous nerve injury after periacetabular osteotomy

AIMS

Injury to the lateral femoral cutaneous nerve (LFCN) is one of the known complications after periacetabular osteotomy (PAO) performed using the anterior approach, reported to occur in between 1.5% and 65% of cases. In this study, we performed a prospective study on the incidence of LFCN injury as well as its clinical outcomes based on the Harris Hip Score (HHS), Short-Form 36 Health Survey (SF-36), and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ).

METHODS

The study included 42 consecutive hips in 42 patients (three male and 39 female) who underwent PAO from May 2016 to July 2018. We prospectively evaluated the incidence of LFCN injury at ten days, three months, six months, and one year postoperatively. We also evaluated the clinical scores, including the HHS, SF-36, and JHEQ scores, at one year postoperatively.

RESULTS

LFCN injury was observed in 31 of 42 (74%) patients at ten days, of which 11 resolved completely by one year. Incidence decreased gradually, to 25 of 42 (60%) patients at three months, 24 of 42 patients (57%) at six months, and 20 of 42 (48%) patients at one year postoperatively. There was no significant difference in the HHS between patients with and without LFCN injury at one year postoperatively. Regarding the SF-36 and JHEQ, a significant difference in the mental score was recognized between patients with and without LFCN injury, but there were no significant differences in the other clinical scores.

CONCLUSION

The incidence of LFCN injury was 74% at ten days after PAO, and subsequently decreased to 48% at one year. LFCN injury did not influence the hip function as assessed by the HHS, but had a negative impact on mental health at one year. Cite this article: Bone Joint J 2021;103-B(4):659-664.

Sonographic evaluation of the lateral femoral cutaneous nerve in meralgia paresthetica

OBJECTIVE

Identify sonographic features of the lateral femoral cutaneous nerve (LFCN) in meralgia paresthetica (MP) and report therapeutic outcomes in sonographically confirmed cases.

MATERIALS AND METHODS

Retrospective review of 50 patients with clinically suspected MP and 20 controls. Ultrasounds were reviewed for characteristics of the LFCN and compared between groups. When available, MRIs were reviewed. In cases of sonographically pathologic LFCN, subsequent therapeutic interventions were recorded.

RESULTS

Thirty-five of the suspected MP cases (70%) had ultrasound findings suggestive of MP, 10 (20%) were negative, and in 5 (10%) the LFCN was not seen. Sonographic findings in positive cases included nerve enlargement in all cases (mean cross-sectional area 9 mm² (standard deviation (SD) ± 5.59) versus 4 mm² (SD ± 2.31) and 3 mm² (SD ± 2.31) in negative cases and normal controls, respectively; p < 0.01), nerve hypoechogenicity (30 of 35 cases, 86%), and focal lesion (7 of 35 cases, 20%). Sixteen ultrasounds positive for MP had MRIs with only 4 (25%) reporting a concordant LFCN abnormality (enlargement or T2 hyperintensity). Twenty-five of the 35 (71%) patients with positive sonographic findings for MP had a US-guided LFCN block (local anesthetic ± corticosteroid), with 24 of 25 (96%) patients reporting immediate symptomatic improvement. Eighteen of 35 (51%) underwent LFCN neurectomy or neurolysis, all of whom experienced symptomatic improvement.

CONCLUSION

Ultrasound is a useful modality for LFCN assessment in clinically suspected MP and is more sensitive for abnormalities than MRI. Nearly all patients who received perineural analgesia and/or neurectomy or neurolysis had symptomatic improvement.

Inguinal segmental nerve conduction of the lateral femoral cutaneous nerve in healthy controls and in patients with meralgia paresthetica

A common entrapment site of the lateral femoral cutaneous nerve (LFCN) is in the vicinity of the inguinal ligament. However the more distal segment of this nerve can also be affected. Electrophysiological evaluation of this nerve is difficult. Additionally, available methods have failed in the lesion localization of LFCN. In this study, we aimed to evaluate nerve conduction study in different segments of the LFCN. Nerve action potentials of the LFCN were recorded with distal surface electrodes from a relatively distant point (about 30 cm caudal to the spina iliaca anterior superior). An electrical stimulus was given both 10 cm distal to the SIAS and at the level of the SIAS. Inguinal segmental and distal sensory nerve conduction studies were performed on the LFCN. Thirty-eight healthy controls and 34 patients with meralgia paresthetica (MP) were analyzed by this method. All patients with MP showed electrophysiological abnormalities. Slowed sensory conduction on the inguinal channel (p:0.0001) and loss of response were the most frequent abnormalities (44.7% and 31.6%). In one patient, the only abnormality was slowed sensory conduction at the distal site. Our findings suggest that this technique can help in diagnosis and lesion localization in MP.

Laparoscopic-Assisted Intra-Abdominal Section of the Lateral Femoral Cutaneous Nerve for Meralgia Paresthetica Following Anterior Hip Arthroplasty

BACKGROUND

Meralgia paresthetica, a pain syndrome that is caused by injury to the lateral femoral cutaneous nerve, is a well-documented complication after anterior hip arthroplasty (THA). Traditional treatment of this peripheral nerve entrapment syndrome can be complicated in patients who have had THA via an anterior approach owing to the presence of scar in the postoperative bed.

CASE DESCRIPTION

In a 70-year-old man, we performed a novel laparoscopic-assisted intra-abdominal approach to treat meralgia paresthetica in the setting of previous anterior THA.

CONCLUSIONS

Minimally invasive intra-abdominal treatment of meralgia paresthetica following anterior THA results in durable pain relief. This approach is a helpful alternative to traditional techniques of decompression or section of the lateral femoral cutaneous nerve below the inguinal ligament.

Sartorius muscle tear presenting as acute meralgia paresthetica

We present an unusual case of sartorius muscle tear presenting as acute meralgia paresthetica. A healthy 67-year old male was referred to our department with a one-week history of pain, numbness and bruising over his hip and anterolateral thigh. Extended ultrasound assessment revealed an intramuscular tear of sartorius, with acute hematoma surrounding the adjacent lateral femoral cutaneous nerve. Meralgia paresthetica from acute trauma is rare, with only three published cases relating to fractures of the anterior superior iliac spine. To our knowledge, this is the first case caused by muscular tear in the literature. The presence of features attributable to neuropraxia of the lateral femoral cutaneous nerve allowed for proper localization and diagnosis of the patient's injury.

Anatomic Variation in Patient with Lateral Femoral Cutaneous Nerve Entrapment Neuropathy

BACKGROUND

We report a surgical case of entrapment neuropathy of lateral femoral cutaneous nerve (LFCN) with anatomical variation.

CASE DESCRIPTION

This 53-year-old man had a 10-year history of paresthesia and pain in the right anterolateral thigh exacerbated by prolonged standing and walking. His symptoms improved completely but transiently by LFCN block. The diagnosis was LFCN entrapment. Because additional treatment with drugs and repeat LFCN block was ineffective, we performed surgical decompression under local anesthesia. A nerve stimulator located the LFCN 4.5 cm medial to the anterior superior iliac spine. It formed a sharp curve and was embedded in connective tissue. Proximal dissection showed it to run parallel to the femoral nerve at the level of the inguinal ligament. The inguinal ligament was partially released to complete dissection/release. Postoperatively, his symptoms improved and the numeric rating scale fell from 8 to 1.

CONCLUSION

We report a rare anatomical variation in the course of the LFCN.

An Unusual Case of Bilateral Meralgia Paresthetica Following Femoral Cannulations

Meralgia paresthetica (MP) is a sensory mononeuropathy of the lateral femoral cutaneous nerve (LFCN). MP has rarely been reported after a femoral intervention approach. We report a case of bilateral meralgia paresthetica following bilateral femoral cannulation. A 64-year-old male received cardiac catheterization and treatment via a bilateral femoral vein. After cardiac catheterization, the patient presented with paresthesia in the anterolateral aspect of the bilateral thigh. After performing nerve conduction studies and electromyography, he was diagnosed as MP. Although a bilateral LFCN lesion following a femoral approach is very rare, MP might require caution regarding potential variations in LFCN when performing the femoral approach.

The use of an anterior pelvic internal fixator to treat disruptions of the anterior pelvic ring: a report of technique, indications and complications

AIMS

The anterior pelvic internal fixator is increasingly used for the treatment of unstable, or displaced, injuries of the anterior pelvic ring. The evidence for its use, however, is limited. The aim of this paper is to describe the indications for its use, how it is applied and its complications.

PATIENTS AND METHODS

We reviewed the case notes and radiographs of 50 patients treated with an anterior pelvic internal fixator between April 2010 and December 2015 at a major trauma centre in the United Kingdom. The median follow-up time was 38 months (interquartile range 24 to 51).

RESULTS

Three patients were excluded from the analysis leaving 47 patients with complete follow-up data. Of the 47 patients, 46 achieved radiological union and one progressed to an asymptomatic nonunion. Of the remaining patients, 45 required supplementary posterior fixation with percutaneous iliosacral screws, 2 of which required sacral plating. The incidence of injury to the lateral femoral cutaneous nerve (LFCN) was 34%. The rate of infection was 2%. There were no other significant complications. Without this treatment, 44 patients (94%) would have needed unilateral or bilateral open reduction and plate fixation extending laterally to the hip joint.

CONCLUSION

The anterior pelvic internal fixator reduces the need for extensive open surgery and is a useful addition to the armamentarium for the treatment of anterior pelvic injuries. It is associated with injury to the LFCN in a third of patients. Cite this article: Bone Joint J 2017;99-B.1232-6.

Preoperative Ultrasound-Guided Wire Localization of the Lateral Femoral Cutaneous Nerve

BACKGROUND

Difficulty and sometimes inability to find the lateral femoral cutaneous nerve (LFCN) intraoperatively is well known. Variabilities in the course of the nerve are well documented in the literature. In a previous paper, we defined a tight fascial canal that completely surrounds the LFCN in the proximal thigh. These 2 factors sometimes render finding the nerve intraoperatively, to treat meralgia paresthetica, very challenging.

OBJECTIVE

To explore the use of preoperative ultrasound to minimize operative time and eliminate situations in which the nerve is not found.

METHODS

Since 2011, we have used preoperative ultrasound-guided wire localization (USWL) in 19 cases to facilitate finding the nerve intraoperatively. Data were collected prospectively with recording of the timing from skin incision to identifying the LFCN; this will be referred to as the skin-to-nerve time.

RESULTS

In 2 cases, the localization was incorrect. In the 17 cases in which the LFCN was correctly localized, the skin-to-nerve time ranged from 3 min to 19 min. The mean was 8.5 min, and the median was 8 min.

CONCLUSION

Preoperative USWL is a useful technique that minimizes the time needed to find the LFCN. For the less experienced surgeon, it is extremely valuable. For the experienced surgeon, it can identify anatomical abnormalities such as duplicate nerves, which may not be readily recognizable without ultrasound. Collaboration between the surgeon and the radiologist is very important, especially in the early cases.

Evaluating the evidence: is neurolysis or neurectomy a better treatment for meralgia paresthetica?

BACKGROUND

Meralgia paresthetica is a mononeuropathy of the lateral femoral cutaneous nerve (LCFN). Surgical treatment involves transection or decompression of the LCFN. There is no clear consensus on the superiority of one technique over the other. We performed a systematic review of the literature to answer this question.

METHODS

Eligible studies included those that compared neurolysis versus neurectomy for the treatment of meralgia paresthetica after failure of conservative therapy. Our outcome of interest was resolution of symptoms. We performed a computerized search of MEDLINE (PubMed; all years) and of the Cochrane Central Register of Controlled Trials. Eligible studies had to include the words "meralgia paresthetica" and "surgery." All patients regardless of age were included, and there was no language restriction. We then reviewed the articles' titles and abstracts. All studies that compared neurolysis to neurectomy were included in the analysis.

RESULTS

Of the studies identified, none were randomized controlled trials. There were two German language articles that were translated by a third researcher. Each study was evaluated by two independent researchers who assigned a level of evidence according to American Association of Neurologist algorithm and also performed data extraction (neurolysis vs. neurectomy and resolution of pain symptoms). Each study was found to be level four evidence.

CONCLUSION

After reviewing the data, there was insufficient evidence to recommended one method of treatment over the other. This highlights the importance of keeping a national registry in order to compare outcomes between the two methods of treatment.

Small femoral offset is a risk factor for lateral femoral cutaneous nerve injury during total hip arthroplasty using a direct anterior approach

INTRODUCTION

Lateral femoral cutaneous nerve (LFCN) injury is a risk specific to the direct anterior approach (DAA) for total hip arthroplasty (THA). However, prevention strategies have not been established. This study aimed to identify the predisposing factors determining LFCN injury during THA via a DAA.

HYPOTHESIS

Patients with LFCN injury after THA via DAA would demonstrate predisposing factors.

MATERIAL AND METHODS

LFCN injury was identified using a patient questionnaire. Potential factors predisposing to LFCN injury were identified in four categories in patient records: patient factors (age, sex, BMI, diagnosis and range of hip motion), surgical factors (surgical time and surgeon's experience of the DAA), preoperative radiographic factors (neck-shaft angle, femoral offset, acetabular offset, total offset and length of muscle on computed tomography axial image) and radiographic changes (differences between each offset pre- and post-surgery). Multivariate analysis was performed to identify risk factors for LFCN injury during this surgery.

RESULTS

After application of inclusion and exclusion criteria, 102 hips (28 with LFCN injury; 74 without) in 102 patients (17 males, 85 females; mean age 66.0 years [range, 26-88 years]) were included. Univariate analysis of patients with and without LFCN injury revealed that small preoperative femoral offset and short preoperative long axis of the tensor fascia lata were statistically significant risk factors for LFCN injury (P=0.004, and P=0.01, respectively). Multivariate analysis showed that small preoperative femoral offset was the only independent risk factor for LFCN injury (odds ratio, 0.895; 95% Confidence Interval, 0.817-0.981; P=0.0018).

DISCUSSION

Smaller femoral offset was a significant risk factor for LFCN injury following THA via a DAA. Our recommendations are that careful attention should be paid to the skin-fascia incision and subcutaneous exposure, and that excessive retraction of the sartorius muscle and tensor fascia lata should be avoided, to reduce the risk of LFCN injury in patients with a small femoral offset.

LEVEL OF EVIDENCE

IV, retrospective historical cohort study.

"Anterior subcutaneous pelvic internal fixator (INFIX), Is it safe?" A cadaveric study

INTRODUCTION

Anterior pelvic internal fixator (INFIX) is used to treat unstable pelvic ring injuries. Nerve injury complications with this procedure have been reported.

OBJECTIVES

This anatomic study attempted to identify structures at risk after application of INFIX.

MATERIALS AND METHODS

INFIX was applied in fifteen fresh, frozen, anatomical specimens using polyaxial pedicular screws and subcutaneous rods. Surgical dissection was done to identify the structures at risk including the femoral nerve (FN), femoral artery (FA), femoral vein (FV) and the lateral femoral cutaneous nerve (LFCN) related to which are potentially affected by the implant.

RESULTS

All structures at risk were closer to the rod than to the pedicular screw. Measurements were made between the rod and the structures at risk. The LFCN was an average of 13.49±1.65mm (95% CI 12.871-14.103) from the lateral end of the rod. The FN was an average of 12.43±3.42mm (95% CI 11.151-13.709), the FA was an average of 12.80±3.67 (95% CI 11.430-14.173) and the FV was an average of 13.48±3.73 (95% CI 12.082-14.871) below the rod. No direct compression of the rod to the structure at risk was observed.

CONCLUSIONS

The femoral nerve is the structure most at risk of compression by the INFIX rod. Careful surgical technique is required in every step of this surgery. We suggest using polyaxial screws and recommend that during screw insertion the surgeon should leave some space between the screw and rectus fascia. The the rod should be trimmed as short as possible to reduce LFCN irritation.

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.

Meralgia paraesthetica: Ultrasound-guided injection at multiple levels with 12-month follow-up

OBJECTIVES

To evaluate the efficacy of ultrasound (US)-guided injections around the lateral femoral cutaneous nerve (LFCN) at different levels in meralgia paraesthetica (MP) patients.

METHODS

The study was approved by the university ethics committee and informed oral and written consent were obtained from all patients. Between June 2008 and August 2013, 20 patients with symptoms of MP, including nine men (mean age, 61.33 years) and 11 women (mean age 61.18 years), were treated with US-guided injection of steroids along the LFCN at three different levels in a mean of 2.25 sessions. A visual analogue scale (VAS) was used to measure symptoms before, immediately after and 12 months after treatment.

RESULTS

Complete resolution of symptoms was documented in 15/20 patients (mean VAS decreased from 82 to 0), and partial resolution in the remaining five (mean VAS decreased from 92 to 42), which was confirmed at 12-month follow-up. By using the different levels of injection approach overall significantly better symptom relief was obtained (p < 0.05).

CONCLUSION

The outcome of US-guided injection along the LFCN can be further improved by injections at different levels (p < 0.05), which was confirmed at 12-month long-term follow-up.

KEY POINTS

Meralgia paraesthetica is an entrapment neuropathy of the lateral femoral cutaneous nerve. Ultrasound proved effective in diagnosis and in guiding injection therapy. Injection at the anterior superior iliac spine has been used previously. Multiple injections along the nerve course were used in this study. Long-term follow-up (12 months) confirmed the results.

Ultrasound-guided lateral femoral cutaneous nerve conduction study

Objective

To verify the utility of the lateral femoral cutaneous nerve (LFCN) ultrasound-guided conduction technique compared to that of the conventional nerve conduction technique.

Methods

Fifty-eight legs of 29 healthy participants (18 males and 11 females; mean age, 42.7±14.9 years) were recruited. The conventional technique was performed bilaterally. The LFCN was localized by ultrasound. Cross-sectional area (CSA) of the LFCN and the distance between the anterior superior iliac spine (ASIS) and the LFCN was measured. The nerve conduction study was repeated with the corrected cathode location. Sensory nerve action potential (SNAP) amplitudes of the LFCN were recorded and compared between the ultrasound-guided and conventional techniques.

Results

Mean body mass index of the participants was 23.7±3.5 kg/m², CSA was 4.2±1.9 mm², and the distance between the ASIS and LFCN was 5.6±1.7 mm. The mean amplitude values were 6.07±0.52 µV and 6.66±0.54 µV using the conventional and ultrasound-guided techniques, respectively. The SNAP amplitude of the LFCN using the ultrasound-guided technique was significantly larger than that recorded using the conventional technique.

Conclusion

Correcting the stimulation position using the ultrasound-guided technique helped obtain increased SNAP amplitude.

Neural Anatomy of the Anterolateral Thigh Flap

The anterolateral thigh (ALT) flap is one of the commonly used sensate flaps for intra-oral, hand, and foot reconstruction. The objective of this study was to describe the anatomic location of the sensory nerves supplying the ALT flap in relation to the surface landmarks and with the vascular pedicles. The dissections were carried out in 28 embalmed specimens. An axial line from the anterior superior iliac spine to the superolateral border of the patella and two circles with radii of 5 and 10 cm centered on the midpoint of the former line were used for the surface landmarks. At the intersection point of the axial line and the 10-cm circle, the main lateral femoral cutaneous nerve (LFCN) and its anterior branch were located within 1 and 2.4 cm, respectively. At the intersection point of the axial line and the 5-cm circle, the anterior branch of the LFCN was located within 2.8 cm. The anterior branch of the LFCN can be detected within 3 cm from the central perforator pedicle in all specimens. The posterior branch of the LFCN, superior perforator nerve, and median perforator nerve were found in more variable locations. The findings from our study provide additional information for clinical use in the planning of sensate ALT flap harvest.

Neurolysis for meralgia paresthetica

Objective

Meralgia paresthetica (MP) is a syndrome of pain and/or dysesthesia in the anterolateral thigh that is caused by an entrapment of the lateral femoral cutaneous nerve (LFCN) at its pelvic exit. Despite early accounts of MP, there is still no consensus concerning the effectiveness of neurolysis or transaction treatments in the long-term relief for medically refractory patients with MP. We retrospectively analyzed available long-term results of LFCN neurolysis for medically refractory MP in an effort to clarify this issue.

Methods

During the last 7 years, 11 patients who had neurolysis for MP were enrolled in this study. Nerve entrapment was confirmed preoperatively by electrophysiological studies or a positive response to local anesthetic injection. Decompression of the LFCN was performed at the level of the iliac fascia, inguinal ligament, and fascia of the thigh distally. The outcome of surgery was assessed 8 weeks after the procedure followed at regular intervals if symptoms persisted.

Results

Twelve decompression procedures were performed in 11 patients over a 7-year period. The average duration of symptoms was 8.5 months (range, 4-15 months). The average follow-up period was 33 months (range, 12-60 months). Complete and partial symptom improvement were noted in nine (81.8%) and two (18.2%) cases, respectively. No recurrence was reported.

Conclusion

Neurolysis of the LFCN can provide adequate pain relief with minimal complications for medically refractory MP. To achieve a good outcome in neurolysis for MP, an accurate diagnosis with careful examination and repeated blocks of the LFCN, along with electrodiagnosis seems to be essential. Possible variation in the course of the LFCN and thorough decompression along the course of the LFCN should be kept in mind in planning decompression surgery for MP.

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.