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PURPOSE: The saphenous nerve is a predominantly sensory nerve. It is the longest nerve of the body which supplies the skin of the medial side of the leg and foot as far as the ball of the great toe. We present here an unusual motor branch of the saphenous nerve to the sartorius muscle. METHOD: Institutional guidelines for use of human cadaver were followed. Routine dissection of the lower limbs for undergraduate medical teaching was performed in a 67 years old female cadaver employing standard methods. Relevant gross features of the variations were photographed. H&E staining of relevant structure was done and photomicrographed. RESULTS: The unusual motor branch to Sartorius was observed in the right thigh. The branch was given off in the lower third of the thigh after the saphenous nerve exited the adductor canal. The branch was distinctly seen entering the substance of the sartorius. The structure was confirmed to be a peripheral nerve by histological examination. The saphenous nerve then descended between the sartorius and gracilis tendons, pierced the fascia lata and became cutaneous. CONCLUSION: The motor branch to the sartorius muscle is a very rare branch whose knowledge is important for clinicians as it can get damaged during arthroscopy and other knee surgery or during adductor canal block.

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Evaluating reciprocal inhibition of the thigh muscles is important to investigate the neural circuits of locomotor behaviors. However, measurements of reciprocal inhibition of thigh muscles using spinal reflex, such as H-reflex, have never been systematically established owing to methodological limitations. The present study aimed to clarify the existence of reciprocal inhibition in the thigh muscles using transcutaneous spinal cord stimulation (tSCS). Twenty able-bodied male individuals were enrolled. We evoked spinal reflex from the biceps femoris muscle (BF) by tSCS on the lumber posterior root. We examined whether the tSCS-evoked BF reflex was reciprocally inhibited by the following conditionings: (1) single-pulse electrical stimulation on the femoral nerve innervating the rectus femoris muscle (RF) at various inter-stimulus intervals in the resting condition; (2) voluntary contraction of the RF; and (3) vibration stimulus on the RF. The BF reflex was significantly inhibited when the conditioning electrical stimulation was delivered at 10 and 20 ms prior to tSCS, during voluntary contraction of the RF, and during vibration on the RF. These data suggested a piece of evidence of the existence of reciprocal inhibition from the RF to the BF muscle in humans and highlighted the utility of methods for evaluating reciprocal inhibition of the thigh muscles using tSCS.

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Targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) are used to prevent or treat neuromas in amputees. TMR for above-the-knee amputation (AKA) is most commonly performed through a posterior incision rather than the stump wound because recipient motor nerves are primarily located in the proximal third of the thigh. When preventative TMR is performed with concurrent AKA, a posterior approach requires intraoperative repositioning and an additional incision. The purpose of this study was to evaluate feasibility of TMR and operative times for nerve management performed through the wound compared to a posterior approach in AKA patients to guide surgical decision-making. Patients who underwent AKA with TMR between 2018-2023 were reviewed. Patients were divided into two groups: TMR performed through the wound (Group I) and TMR performed through a posterior approach (Group II). If a nerve was unable to undergo coaptation for TMR due to the lack of suitable donor motor nerves, RPNI was performed. Eighteen patients underwent AKA with nerve management were included from Group I (8 patients) and Group II (10 patients). TMR coaptations performed on distinct nerves was 1.5 ± 0.5 in Group I compared to 2.6 ± 0.5 in Group II (p = 0.001). Operative time for Group I was 200.7 ± 33.4 min compared to 326.5 ± 37.1 min in Group II (p = 0.001). TMR performed through the wound following AKA requires less operative time than a posterior approach. However, since recipient motor nerves are not consistently found near the stump, RPNI may be required with TMR whereas the posterior approach allows for more TMR coaptations.

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Reconstruction of composite abdominal wall defects is challenging. An anterolateral thigh (ALT) flap has established itself in the algorithm for abdominal wall reconstruction. Augmenting innervated vastus lateralis (iVL) muscle to ALT has added advantages. We describe previously unreported advantage of ALT with iVL.A woman in her 30s, suffering from Mullerian adenocarcinoma with metastasis to the right anterior abdominal wall and right inguinal lymph node, was taken for wide local excision and reconstruction. After excision, there was a 15×12 cm defect of the anterior abdominal wall. We reconstructed the defect with prosthetic mesh and pedicled composite ALT and iVL. There was venous congestion in the ALT flap and it could not be salvaged. We debrided the ALT flap and applied split skin graft over iVL. The grafted and donor sites healed well. The patient was able to do moderate strenuous activities. The presence of iVL allowed us to get away with minor procedure and averted the need for another flap.

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Meralgia paresthetica (MP) is a disorder of lateral femoral cutaneous nerve mononeuropathy caused by entrapment or compression of the nerve. It is characterized by numbing, tingling, and burning pain in the lateral aspect of the thigh. The current treatments for MP include conventional medical management, peripheral nerve blocks, and surgical interventions. Some patients who suffer from MP can experience intractable pain and medical management of MP is often inadequate to provide satisfactory pain control. Although regional anesthesia provides excellent pain relief, the analgesic effects of peripheral nerve block are short-lived. Emerging evidence suggests that cryoneurolysis has a low-risk safety profile and can provide prolonged pain relief of superficial nerves when administered appropriately. We present a successful case of a patient with intractable neuropathic pain resulting from MP treated with cryoneurolysis therapy. The patient demonstrated immediate pain relief by 100% after the procedure followed by 80% and 60% pain reduction at 1-month and 3-months follow-up, respectively. Cryoneurolysis may be an alternative modality for patients who fail at conventional medical treatments of neuropathic pain.

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ABSTRACT: The location of the lateral femoral cutaneous nerve (LFCN) makes it susceptible to injury with trauma, external compression, and iatrogenic injury. The objectives of this study were to report the single-institution efficacy of LFCN visualization on ultrasound (US), define the clinical characteristics of patients with LFCN palsy, and describe sonographic appearances of LFCN abnormalities by pictorial review. A retrospective chart review of LFCN cases evaluated using US at a single institution was performed, documenting rate of visibility on US, mode of nerve injury, and US imaging findings. Nerve visibility rates on US were correlated with magnetic resonance imaging (MRI) when both modalities were used. Imaging findings were confirmed with clinical/surgical history and follow-up. Retrospective review found that 170 patients underwent US for LFCN evaluation in the last 10 years. Injury was associated with surgical intervention in 56% of cases, and perineural scarring was the most common pathology described using US. Lateral femoral cutaneous nerve was visible on US in 97% of cases; MRI visualized LFCN in 60%. Chart review showed US as an effective tool in evaluating LFCN pathology, with a higher visualization rate than MRI. Through pictorial review, the array of LFCN pathology sonographically detectable is demonstrated.

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STUDY OBJECTIVE: A saphenous nerve block is an important tool for analgesia after foot and ankle surgery. The conventional midthigh approach to saphenous nerve block in the femoral triangle may impede ambulation by impairing quadriceps motor function. PRIMARY OBJECTIVE: Developing a selective saphenous nerve block targeting the nerve distal to its emergence from the adductor canal in the subsartorial compartment. DESIGN: This study consists of A) a dissection study and B) Data from a clinical case series. SETTING: A) Medical University of Innsbruck, Austria (dissection of 15 cadaver sides) and. B) Aarhus University Hospital, Denmark (5 patients). INTERVENTIONS: A) Five mL of methylene blue was injected into the subsartorial compartment distal to the intersection of the saphenous nerve and the tendon of the adductor magnus guided by ultrasound. B) Five patients undergoing major hindfoot and ankle surgery had a subsartorial compartment block with 10 mL of local anesthetic in addition to a popliteal sciatic nerve block. MEASUREMENT: A) The frequencies of staining the saphenous and medial vastus nerves. B) Assessment of postoperative pain by NRS score (0-10) and success rate of saphenous nerve block by presence of cutaneous anesthesia in the anteromedial lower leg, and motor impairment by ability to ambulate. MAIN RESULTS: A) The saphenous nerve was stained in 15/15 cadaver sides. A terminal branch of the medial vastus nerve was stained in 2/15 cadaver sides. B) All patients were fully able to ambulate without support. No patients had any post-surgical pain from the anteromedial aspect of the ankle and foot (NRS score 0). The success rate of saphenous nerve block was 100%. CONCLUSION: The saphenous nerve can be targeted in the subsartorial compartment distal to the intersection of the nerve and the tendon of the adductor magnus. The subsartorial compartment block provided efficient analgesia without quadriceps motor impairment.

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Aims: Lateral femoral cutaneous nerve (LFCN) injury is a potential complication after the direct anterior approach for total hip arthroplasty (DAA-THA). The aim of this study was to determine how the location of the fasciotomy in DAA-THA affects LFCN injury. Methods: In this trial, 134 patients were randomized into a lateral fasciotomy (n = 67) or a conventional fasciotomy (n = 67) group. This study was a dual-centre, double-blind, prospective randomized controlled two-arm trial with parallel group design and a 1:1 allocation ratio. The primary endpoint was the presence of LFCN injury, which was determined by the presence of numbness, decreased sensation, tingling, jolt-like sensation, or pain over the lateral aspect of the thigh, excluding the surgical scar, using a patient-based questionnaire. The secondary endpoints were patient-reported outcome measures (PROMs) using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ), and the Forgotten Joint Score-12 (FJS-12). Assessments were obtained three months after surgery. Results: The incidence of LFCN injury tended to be lower in the lateral fasciotomy group (p = 0.089). In the lateral fasciotomy group, there were no significant differences in the mean PROM scores between patients with and without LFCN injury (FJS-12: 54.42 (SD 15.77) vs 65.06 (SD 26.14); p = 0.074; JHEQ: 55.21 (SD 12.10) vs 59.72 (SD 16.50); p = 0.288; WOMAC: 82.45 (SD 6.84) vs 84.40 (SD 17.91); p = 0.728). In the conventional fasciotomy group, there were significant differences in FJS-12 and JHEQ between patients with and without LFCN injury (FJS-12: 43.21 (SD 23.08) vs 67.28 (SD 20.47); p < 0.001; JHEQ: 49.52 (SD 13.97) vs 59.59 (SD 15.18); p = 0.012); however, there was no significant difference in WOMAC (76.63 (SD 16.81) vs 84.16 (SD 15.94); p = 0.107). Conclusion: The incidence of LFCN injury at three months after THA was comparable between the lateral and conventional fasciotomy groups. Further studies are needed to assess the long-term effects of these approaches.

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BACKGROUND: Pain and sensory disturbance in the distribution of the lateral femoral cutaneous nerve in the ventrolateral portion of the thigh is called meralgia paresthetica (MP). The incidence of MP has risen along with the increasing prevalence of obesity and diabetes mellitus and was recently estimated at 32 new cases per 100 000 persons per year. In this review, we provide an overview of current standards and developments in the diagnosis and treatment of MP. METHODS: This review is based on publications retrieved by a selective literature search, with special attention to meta-analyses, systematic reviews, randomized and controlled trials (RCTs), and prospective observational studies. RESULTS: The diagnosis is mainly based on typical symptoms combined with a positive response to an infiltration procedure. In atypical cases, electrophysiological testing, neurosonography, and magnetic resonance imaging can be helpful in establishing the diagnosis. The literature search did not reveal any studies of high quality. Four prospective observational studies with small case numbers and partly inconsistent results are available. In a meta-analysis of 149 cases, pain relief was described after infiltration in 85% of cases and after surgery in 80%, with 1-38 months of follow-up. In another meta-analysis of 670 cases, there was pain relief after infiltration in 22% of cases, after surgical decompression in 63%, and after neurectomy in 85%. Hardly any data are available on more recent treatment options, such as radiofrequency therapy, spinal cord stimulation, or peripheral nerve stimulation. CONCLUSION: The state of the evidence is limited in both quantity and quality, corresponding to evidence level 2a for surgical and non-surgical methods. Advances in imaging and neurophysiological testing have made the diagnosis easier to establish. When intervention is needed, good success rates have been achieved with surgery (decompression, neurectomy), and variable success rates with infiltration.

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INTRODUCTION: Obturator nerve entrapment or idiopathic obturator neuralgia is an unfamiliar pathology for many physicians which can lead to diagnostic errancy. This study aims to identify the potential compression areas of the obturator nerve to improve therapeutic management. MATERIAL AND METHODS: 18 anatomical dissections of lower limbs from 9 anatomical cadavers were performed. Endopelvic and exopelvic surgical approaches were utilized to study the anatomical variations of the nerve and to identify areas of entrapment. RESULTS: On 7 limbs, the posterior branch of the obturator nerve passed through the external obturator muscle. A fascia between the adductor brevis and longus muscles was present in 9 of the 18 limbs. The anterior branch of the obturator nerve was highly adherent to the fascia in 6 cases. In 3 limbs, the medial femoral circumflex artery was in close connection with the posterior branch of the nerve. CONCLUSION: Idiopathic obturator neuropathy remains a difficult diagnosis. Our cadaveric study did not allow us to formally identify one or more potential anatomical entrapment zones. However, it allowed the identification of zones at risk. A clinical study with staged analgesic blocks would be necessary to identify an anatomical area of compression and would allow targeted surgical neurolysis.

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Meralgia paresthetica is often idiopathic, but sometimes symptoms may be caused by traumatic injury to the lateral femoral cutaneous nerve (LFCN) or compression of this nerve by a mass lesion. In this article the literature is reviewed on unusual causes for meralgia paresthetica, including different types of traumatic injury and compression of the LFCN by mass lesions. In addition, the experience from our center with the surgical treatment of unusual causes of meralgia paresthetica is presented. A PubMed search was performed on unusual causes for meralgia paresthetica. Specific attention was paid to factors that may have predisposed to LFCN injury and clues that may have pointed at a mass lesion. Moreover, our own database on all surgically treated cases of meralgia paresthetica between April 2014 and September 2022 was reviewed to identify unusual causes for meralgia paresthetica. A total of 66 articles was identified that reported results on unusual causes for meralgia paresthetica: 37 on traumatic injuries of the LFCN and 29 on compression of the LFCN by mass lesions. Most frequent cause of traumatic injury in the literature was iatrogenic, including different procedures around the anterior superior iliac spine, intra-abdominal procedures and positioning for surgery. In our own surgical database of 187 cases, there were 14 cases of traumatic LFCN injury and 4 cases in which symptoms were related to a mass lesion. It is important to consider traumatic causes or compression by a mass lesion in patients that present with meralgia paresthetica.

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BACKGROUND: Our goal was to revisit the innervation of the adductor muscles of the thigh and add new evidence to currently existing knowledge. METHODS: Ten thighs from five fresh frozen cadavers were dissected. Obturator nerve innervation to the pectineus, obturator externus, adductor brevis, adductor magnus, adductor longus, and gracilis was documented. RESULTS: The adductor longus and gracilis were innervated by the anterior branch in 100%, and the adductor magnus was innervated by the posterior branch in 100%. The adductor brevis was supplied by both the anterior and posterior branches in 90%. The obturator externus was innervated by the posterior branch in 60% and a direct branch from the main trunk in 10%. No innervation of the obturator externus by the obturator nerve was found in 30%. CONCLUSIONS: The obturator externus and adductor brevis need to be explored further to clarify their innervation.

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BACKGROUND: Perineural catheters placed parallel to the nerve course are reported to have lower migration rates than those placed perpendicular to it. However, catheter migration rates for a continuous adductor canal block (ACB) remain unknown. This study compared postoperative migration rates of proximal ACB catheters placed parallel and perpendicular to the saphenous nerve. METHODS: Seventy participants scheduled for unilateral primary total knee arthroplasty were randomly assigned for parallel or perpendicular placement of the ACB catheter. The primary outcome was the migration rate of the ACB catheter on postoperative day (POD) 2. Catheter migration was defined as being unable to confirm saline administration via the catheter around the saphenous nerve at the mid-thigh level under ultrasound guidance. Secondary outcomes included active and passive range of motion (ROM) of the knee on postoperative rehabilitation. RESULTS: Sixty-seven participants were included in the final analyses. The catheter migrated significantly less often in the parallel group (5 of 34 (14.7%)) than in the perpendicular group (24 of 33 (72.7%)) (p<0.001). The mean (SD) active and passive knee flexion ROM (degrees) improved significantly in the parallel than in the perpendicular group (POD 1: active, 88.4 (13.2) vs 80.0 (12.4), p=0.011; passive, 95.6 (12.8) vs 85.7 (13.6), p=0.004; POD 2: active, 88.7 (13.4) vs 82.2 (11.5), p=0.036; passive, 97.2 (12.8) vs 91.0 (12.0), p=0.045). CONCLUSION: Parallel placement of the ACB catheter provided a lower postoperative catheter migration rate than perpendicular placement of the ACB catheter along with corresponding improvements in ROM and secondary analgesic outcomes. TRIAL REGISTRATION NUMBER: UMIN000045374.

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BACKGROUND: The effectiveness of the muscle energy technique (MET) on postpartum meralgia paresthetica (MP) affecting the lateral femoral cutaneous nerve is unknown. OBJECTIVE: To investigate the effectiveness of the MET on postpartum MP affecting the lateral femoral cutaneous nerve. METHODS: In this randomized controlled trial, 30 patients with postpartum MP were randomly allocated to study and control groups. The study group received the MET with conventional therapeutic exercises and the control group received the conventional exercises alone for four weeks (thrice a week, for 30-40 minutes duration). Lateral femoral cutaneous nerve distal latency, pain intensity, response to the prone knee bend (PKB) test and pelvic compression test were assessed. RESULTS: Patients allocated to the MET group had improvements compared to the controls in pain intensity (MD: -1.66, 95%CI -2.39 to -0.94), distal latency (MD: -0.66, 95%CI -0.94 to -0.36), and knee range of motion in the PKB test (MD: 19.5∘, 95%CI 13 to 26.1) with high treatment effects, Cohen's d -ES = 1.71, 1.86 and 2.24 respectively. However, there was no between-group difference for the pelvic compression test (p= 0.41). CONCLUSION: The MET can reduce pain, distal latency, and increase the prone knee range of motion in women with MP affecting the lateral femoral cutaneous nerve.

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BACKGROUND: A precise anatomical understanding of the adductor canal (AC) and its neural components is essential for discerning the action mechanism of the AC block. We therefore aimed to clarify the detailed anatomy of the AC using micro-computed tomography (micro-CT), histological evaluation, and immunofluorescence (IF) assays. METHODS: Gross dissections of 39 thighs provided morphometric data relevant to injection landmarks. Serial sectional images of the AC were defined using micro-CT and ultrasonography. The fascial and neural structures of the AC proper were histologically evaluated using Masson's trichrome and Verhoeff-Van Gieson staining, and double IF staining using choline acetyltransferase (ChAT) and neurofilament 200 antibodies. RESULTS: The posteromedial branch insertion of the nerve to vastus medialis (NVM) into the lateral border of the AC proper was lower (14.5 ± 2.4 cm [mean ± SD] above the base of the patella) than the origin of the proximal AC. The AC consists of a thin subsartorial fascia in the proximal region and a thick aponeurosis-like vastoadductor membrane in the distal region. In the proximal AC, the posteromedial branch of the NVM (pmNVM) consistently contained both sensory and motor fibers, and more ChAT-positive fibers were observed than in the saphenous nerve (27.5 ± 11.2 / 104 vs. 4.2 ± 2.6 / 104 [counts/µm2], P < 0.001). CONCLUSIONS: Anatomical differences in fascial structures between the proximal and distal AC and a mixed neural component of the neighboring pmNVM have been visualized using micro-CT images, histological evaluation, and IF assays.

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Meralgia paraesthetica (MP) is the consequence of an entrapment or stretch injury of the lateral femoral cutaneous nerve at the crossing region with the inguinal ligament where the nerve exits the pelvis. It results in temporary or permanent sensory loss, paraesthesia and pain in the anterolateral region of the thigh. Idiopathic forms are known for example as seat belt syndrome or jeans syndrome. An MP can also occur as a complication of surgical or intensive care patient positioning. In focus are the lithotomy position, prone position and beach chair position.We analyzed 21 complaints about MP occurring for the first time postoperatively, which had been submitted to the expert committee for medical treatment errors at the North Rhine Medical Association over the past 10 years. Among these, six cases could be identified as positioning damage after a lithotomy position. In three cases MP occurred after supine positioning but the etiology could not be clarified with certainty. In 12 cases MP was recognized as a direct surgical complication.The pathophysiology, incidence and course as well as legal implications of position-related MP are discussed. Pressure damage to the nerve at its intersection with the inguinal ligament is assumed to be the main pathomechanism. Although all the cases presented here occurred after lithotomy positioning, the complication also appears to occur with other types of positioning according to the literature data, the most common being prone positioning. This also explains the increasingly published case reports of MP after prone positioning in COVID-19 patients for respiratory treatment. Safe avoidance of the positioning-related complication does not appear to be possible due to the anatomical variability of the course of the nerve and the unclear pathomechanisms.

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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.

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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.

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