Surgical anatomy of the sciatic nerve: A meta-analysis

Morphologic and morphometric bilateral analysis and sexual dimorphism in sciatic nerves of adult cadaveric specimens in Uganda

BACKGROUND

The Sciatic nerve (SN) exhibits distinct sex and side-related differences, which have significant implications for clinical practice. The study investigated the sex and side-related morphologic and morphometric variations of the nerve using cadavers.

METHODS

This is a cross-sectional cadaveric study involving 62 Ugandan cadavers. Continuous variables were reported using descriptive statistics and discrete variables were reported as percentages. Ordinary two-way ANOVA was used to compare the dimensions and proportion of the patterns of the SN.

RESULTS

The study identified six categories of exit patterns of the SN, type A ("Below and undivided") occurred in a majority of cases (62.9%). A penta-furcate branching pattern dominated the whole population. Bifurcate termination pattern was found in most SNs (90.3% and 87.1% for right and left limbs respectively) while the rest have the trifurcate termination pattern, with no side or sex-related variations. The average dimensions of SN were within normal ranges, and showed no side-related differences but with a sex difference (significantly higher in males than females), mean length of the SN in centimetres (length A: Males, right limbs = 30.58 ± 9.00; left limbs = 31.30 ± 6.20; Females, right = 26.07 ± 6.58; left = 26.30 ± 5.56). The difference in the length "A" for the males left limb and females right limb was statistically significant with a p-value of 0.0195.

CONCLUSIONS

Most of the examined SNs showed normal anatomical characteristics with rare cases of sex-related dimorphism in the termination level and morphometry (length and diameter) of the nerve. The observed sexual dimorphisms in sciatic nerves are of clinical and surgical interest; hence, suggesting the need for further investigations in different populations, especially using advanced techniques such as ultrasonography anatomic techniques.

Understanding Deep Endometriosis: From Molecular to Neuropsychiatry Dimension

Endometriosis is a widely spread disease that affects about 8% of the world's female population. This condition may be described as a spread of endometrial tissue apart from the uterine cavity, but this process's pathomechanism is still unsure. Apart from classic endometriosis symptoms, which are pelvic pain, infertility, and bleeding problems, there are neuropsychiatric comorbidities that are usually difficult to diagnose. In our review, we attempted to summarize some of them. Conditions like migraine, anxiety, and depression occur more often in women with endometriosis and have a significant impact on life quality and pain perception. Interestingly, 77% of endometriosis patients with depression also have anxiety. Neuroimaging gives an image of the so-called endometriosis brain, which means alternations in pain processing and cognition, self-regulation, and reward. Genetic factors, including mutations in KRAS, PTEN, and ARID1A, influence cellular proliferation, differentiation, and chromatin remodeling, potentially exacerbating lesion severity and complicating treatment. In this review, we focused on the aspects of sciatic and obturator nerve endometriosis, the emotional well-being of endometriosis-affected patients, and the potential influence of endometriosis on dementia, also focusing on prolonged diagnosis. Addressing endometriosis requires a multidisciplinary approach, encompassing molecular insights, innovative therapies, and attention to its psychological and systemic effects.

Step-by-step demonstration of "sciatic-nerve-preserved beyond-LEER" in a Thiel-embalmed cadaver: a novel salvage surgery for recurrent gynecologic malignancies

OBJECTIVE

Complete resection is the curative treatment choice for recurrent gynecological malignancies. Laterally extended endopelvic resection (LEER) is an effective surgical salvage therapy for lateral recurrence. However, when a recurrent tumor occupies the ischial spine and sacrum, LEER is not indicated, and surgical salvage therapy is abandoned. Theoretically, complete resection of such a tumor is possible by additional pelvic bone resection along with the standard LEER. Nevertheless, owing to the anatomical complexities of the beyond-LEER procedure, 2 major issues should be solved: sciatic nerve injury and tumor disruption during pelvic bone amputation. To overcome these technical challenges, we applied a multidirectional beyond-LEER approach, a novel salvage surgical procedure, with an aim of demonstrating its technical feasibility.

METHODS

We created a simulation model of a laterally recurrent tumor that occupied the right ischial spine and sacrum in a Thiel-embalmed cadaver.

RESULTS

Multidirectional approaches, including laparoscopic, perineal, and dorsal phases, were safely applied. We laparoscopically marked the L4-L5-S1 complex and S2 nerve with different colored tapes, and by pulling them out into a dorsal surgical field, the sciatic nerve was safely preserved. The dissection lines of the multidirectional approaches were aligned using tapes as landmarks, and complete tumor clearance without tumor disruption was accomplished. By following the cadaveric training, the first laparoscopic-assisted beyond-LEER procedure was successfully performed in a patient with recurrent ovarian cancer.

CONCLUSION

Using a Thiel-embalmed cadaver, we demonstrated the technical feasibility of a sciatic nerve-preserved beyond-LEER procedure, which was successfully performed in a patient with recurrent ovarian cancer.

F, López C. L, Fuentes-Rocabado N, Chaurasia B. Giant sciatic nerve schwannoma: a rare case report and literature review

Introduction and importance

Schwannomas are benign tumors that arise from Schwann cells commonly located in peripheral nerves. Depending on the size and location of sciatic nerve Schwannoma clinical manifestations can either varies from symptoms simulating radiculopathies such as positive Lasegue sign on the affected side, gait weakness and paresthesia or just present with pain and an associated palpable mass.

Case presentation

The authors present a case of a 34-year-old female patient suffering from pain, gait weakness, and a palpable mass since many months. The palpable mass was present in the posterior region of the left lower limb. Imaging studies reveal an extensive lesion measuring 35 cm×8 cm that extends from the gluteal region to the left popliteal fossa.

Clinical discussion

The finding of a palpable mass during physical examination guided us towards the diagnostic suspicion and thus necessitating the direct imaging studies. When approaching such type of patients, a history of neurofibromatosis must be ruled out due to its frequent association. Surgical resection should focus on the preservation of neurovascular structures, which offers improvement of the symptoms and the quality of life of patients.

Conclusion

Giant sciatic nerve schwannoma if excised completely can lead to relieve of symptoms. Although recurrences are uncommon follow-up for years is necessary.

An anomalous pseudoganglion associated with high division of sciatic nerve

Sciatic nerve (SN) is the thickest and longest nerve of the body. Deviations from the normal anatomical origin and level of bifurcation of SN have been frequently reported. In the present case, we are presenting a unique scenario of origin of terminal branches of the SN-tibial nerve (TN) and common peroneal nerve (CPN) in the pelvic region itself from divisions arising directly from the lumbosacral plexus. This variation was associated with origin of posterior femoral cutaneous nerve from the superior division of CPN with anomalous communicating branches between pudendal nerve and TN. The unique characteristics of the present case are the presence of 'pseudoganglion' found on the inferior division of TN. The present case stands out as the first of its kind to mention such pseudoganglion. Knowledge of some unusual findings like presence of pseudoganglion and intercommunications between nerves have clinical implications in anesthesiology, neurology, sports medicine, and surgery.

Innervation patterns of hamstring muscles, including morphological descriptions and clinical implication

PURPOSE

The hamstrings muscles are innervated by sciatic nerve branches. However, previous studies assessing which and how many branches innervate each muscle have yielded discrepant results. This study investigated the innervation patterns of hamstrings.

MATERIALS AND METHODS

Thirty-five cadaver limbs were investigated. The average age of subjects was 78.6 ± 17.2 years, with 48.6% male and 51.4% female, while 57.1% were right limbs and 42.9% left. The sciatic nerve, hamstrings and associated structures were dissected. The number of nerve branches for each muscle and the level where they penetrated the muscle were recorded.

RESULTS

The sciatic nerve was connected by a fibrous band to the long head of the biceps femoris. This muscle was innervated by either one or two branches, which penetrated the muscle into its superior or middle third. The short head of the biceps femoris was innervated by a single nerve that usually penetrated its middle third, but sometimes inferiorly or, less commonly, superiorly. The semitendinosus was always innervated by two branches, the superior branch penetrating its upper third, the inferior mostly the middle third. The semimembranosus usually was innervated by a single nerve branch that penetrated the muscle at its middle or lower third. Four specimens revealed common nerves that innervated than one muscle.

CONCLUSIONS

We have characterized hamstring innervation patterns, knowledge that is relevant to neurolysis, surgery of the thigh, and other procedures. Moreover, a mechanical connection between the sciatic nerve and biceps femoris long head was identified that could explain certain neuralgias.

Sciatic Nerve and Its Anatomical Variations: In-Depth Understanding Acquired During Dissection Classes

Knowledge of anatomical variability is extremely important in order to better understand the etiology of pain, if present, or to avoid iatrogenic consequences. Sometimes the anatomical "anomalies" have the same anamnesis but different causes. For example, sciatic neuralgia may be caused by a herniated disc or it may have a different origin. The sciatic nerve (SN), also known as the ischial nerve, is the widest in the human body. This huge peripheral nerve originates from the roots of the lumbosacral plexus (L4-S3) and passes through the great sciatic foramen, under the piriformis muscle (PM). However, there is much variability in the pattern of SNs about the muscle, which has been known since the first half of the 20th century. In the present study, we describe six different case reports of anatomical variations of the SN and its interplay with the PM. The observations were made during dissection classes at the ICLO Teaching and Research Centre (Verona, Italy), on both male and female cadavers aged between 58 and 84 years. The SN was reported as a single and divided nerve into the tibial nerve (TN) and the common peroneal nerve (CPN), passing alone above, below, or between the PM. However, the two parts of the SN may also interact with the PM in different ways, adding to the anatomical variability. A thorough knowledge of the anatomical variations in any part of the human body is extremely important. The various techniques used, from imaging to autopsy or surgery, are also useful in the SN pathway. Thus, the anatomical features and the understanding of each variation are useful for a correct approach that can lead to an effective and correct treatment with a favorable outcome.

The Anatomic Position of the Sciatic Nerve During Percutaneous Retrograde Posterior Column Fixation Is Determined by Hip Position

OBJECTIVES

There are multiple established patient positions for placement of a percutaneous retrograde posterior column screw for fixation of acetabulum fractures. The sciatic nerve is at risk of injury during this procedure because it lies adjacent to the start point at the ischial tuberosity. The purpose of this study was to define how the position of the sciatic nerve, relative to the ischial tuberosity, changes regarding the patient's hip position.

METHODS

In a cohort of 11 healthy volunteers, ultrasound was used to measure the absolute distance between the ischial tuberosity and the sciatic nerve. Measurements were made with the hip and knee flexed to 90 degrees to simulate supine and lateral positioning and with the hip extended to simulate prone positioning. In both positions, the hip was kept in neutral abduction and neutral rotation.

RESULTS

The distance from the lateral border of the ischial tuberosity to the medial border of the sciatic nerve was greater in all subjects in the hip-flexed position versus the extended position. The mean distance was 17 mm (range, 14-27 mm) in the hip-extended position and 39 mm (range, 26-56 mm) in the hip-flexed position ( P < 0.001).

CONCLUSIONS

The sciatic nerve demonstrates marked excursion away from the ischial tuberosity when the hip is flexed compared with when it is extended. The safest patient position for percutaneous placement of a retrograde posterior column screw is lateral or supine with the hip flexed to 90 degrees.

Piriformis syndrome

Piriformis syndrome is a condition that is proposed to result from compression of the sciatic nerve, either in whole or in part, in the deep gluteal space by the piriformis muscle. The prevalence of piriformis syndrome depends upon the diagnostic criteria being used and the population studied but is estimated by some to be 5%-6% in all cases of low back, buttock, and leg pain and up to 17% of patients with chronic low back pain. While the sciatic nerve may pierce the piriformis muscle in about 16% of healthy individuals, this frequency is no different in those with the syndrome; thus, the relationship to this anatomic finding is unclear. The most common symptoms are buttock pain, external tenderness over the greater sciatic notch, and aggravation of the pain through sitting. Many clinical signs are reported for piriformis syndrome, but the sensitivity and specificity are unclear, in part because of the lack of a uniformly accepted case definition. In the majority of cases in the literature, it appears that the diagnosis is more ascribed to a myofascial condition rather than a focal neuropathy. Electrodiagnostic studies can be useful to exclude other causes of symptoms, but there is no well-accepted test to confirm the presence of piriformis syndrome. Ultrasound imaging may show thickening of the piriformis muscle, but further research is required to confirm that this is correlated with the clinical diagnosis. Magnetic resonance imaging and neurography may hold promise in the future, but there are not yet sufficient data to support adopting these methods as a standard diagnostic tool. The initial treatment of piriformis syndrome is typically conservative management with the general rehabilitation principles similar to other soft tissue musculoskeletal conditions. Local anesthetic, botulinum toxin, and/or corticosteroid injections have been reported by some to be beneficial for diagnostic or treatment purposes. Surgical interventions have also been used with variable success.

Preoperative Femoral Nerve Block and Postoperative Sciatic Nerve Block at the Subgluteal Space After Total Knee Arthroplasty: A Retrospective Cohort Study

Background A preoperative sciatic nerve block (SNB) before total knee arthroplasty (TKA) frequently causes postoperative drop foot; however, this can also occur as an unintended result of surgical invasion. This study assessed the benefits of a postoperative SNB at the subgluteal space for patients who underwent TKA. Methodology This was a single-center, retrospective cohort study. Patients who underwent TKA under general anesthesia between May 2018 and June 2019 at the Teikyo University School of Medicine were screened for inclusion. They received either a preoperative femoral nerve block alone (control group; n = 87) or a preoperative femoral nerve block and postoperative SNB at the subgluteal space (post-SNB group; n = 40). The primary outcome was the pain-related Numerical Rating Scale (NRS) scores. The secondary outcomes were postoperative nausea and vomiting (PONV), intravenous patient-controlled analgesia (iv-PCA) suspension, and postoperative complications. Results No significant differences were observed in the characteristics, NRS scores, time to first drug use for pain, and iv-PCA suspension between groups. However, the incidence of PONV was significantly lower in the post-SNB group (p = 0.03). Logistic regression analysis revealed that droperidol doses of iv-PCA and the presence of postoperative SNB were independently associated with PONV occurrence [A1] {(p = 0.008, 95% confidence intervals (CI) [0.46, 0.89] and (p = 0.02, 95% CI [0.25, 0.88])}. Conclusions A postoperative SNB at the subgluteal space following TKA does not improve postoperative pain control; however, it may have contributed to reduced PONV.

Clinical Anatomy and Medical Malpractice-A Narrative Review with Methodological Implications

Anatomical issues are intrinsically included in medico-legal methodology, however, higher awareness would be needed about the relevance of anatomy in addressing medico-legal questions in clinical/surgical contexts. Forensic Clinical Anatomy has been defined as "the practical application of Clinical Anatomy to the ascertainment and evaluation of medico-legal problems". The so-called individual anatomy (normal anatomy, anatomical variations, or anatomical modifications due to development, aging, para-physiological conditions, diseases, or surgery) may acquire specific relevance in medico-legal ascertainment and evaluation of cases of supposed medical malpractice. Here, we reviewed the literature on the relationships between anatomy, clinics/surgery, and legal medicine. Some methodological considerations were also proposed concerning the following issues: (1) relevant aspects of individual anatomy may arise from the application of methods of ascertainment, and they may be furtherly ascertained through specific anatomical methodology; (2) data about individual anatomy may help in the objective application of the criteria of evaluation (physio-pathological pathway, identification-evaluation of errors, causal value, damage estimation) and in final judgment about medical responsibility/liability. Awareness of the relevance of individual anatomy (risk of iatrogenic lesions, need for preoperative diagnostic procedures) should be one of the principles guiding the clinician; medico-legal analyses can also take advantage of its contribution in terms of ascertainment/evaluation.

Visualizing Anatomic Variants of the Sciatic Nerve Using Diagnostic Ultrasound During Piriformis Muscle Injection: An Example of 4 Cases

Objective

The aim of this article is to present examples of patients in whom piriformis muscle (PM) and sciatic nerve (SN) variations were detected by a diagnostic ultrasound (US)-guided examination and were successfully diagnosed and treated for piriformis syndrome (PS) by US-guided injections.

Clinical Features

This series includes 4 cases. In case 1, a 30-year-old woman with a 7 numeric rating scale (NRS) score for pain (on a 0-10 scale) was evaluated for complaints of left gluteal pain radiating to the thigh for 5 years and right gluteal pain for 2 years. Case 2 involves a 32-year-old man with a 7 NRS score presenting with left gluteal pain radiating to his leg for 1 year. The third case presents a 37-year-old man who had pain (6 NRS score), numbness, and discomfort radiating from the right hip to the leg that lasted for 7 years. Finally, in case 4, a 23-year-old male patient was examined with deep gluteal paresthesia and discomfort on the left side for 1 year.

Intervention and Outcome

Diagnostic US evaluation of the gluteal region for each patient revealed anatomical variations of the SN. In 3 of the cases, corresponding contralateral US images demonstrated similar anatomic variations. Diagnosis of PS in each patient was made by US-guided injection. After the injection of 4 cm³ of lidocaine 2% into the PM, the patients' complaints resolved almost fully.

Conclusion

The anatomical variations of the SN and PM might be a facilitating factor for myofascial pain syndrome in PS. These cases demonstrate that SN variations could be visualized with the help of diagnostic US.

Common peroneal nerve palsy after primary total hip arthroplasty

PURPOSE

The study wants to evaluate the incidence, the clinical evolution, and treatment of common peroneal nerve (CPN) palsy after primary total hip arthroplasty.

METHODS

Our clinical prospective study was made between January 2016 and December 2020. The study group comprised 1240 total hip replacements over a period of five years. Six cases were diagnosed with CPN palsy (0.48%). Five were women and one man, aged from 52 to 71 years old. The common peroneal nerve lesion was diagnosed clinically and by electromyography.

RESULTS

The follow-up period was at least 24 months post-operatively. In all six cases, there was a complete common peroneal nerve palsy, documented by electromyography. The poorest results were obtained in the older patients and those who had the highest body mass index, which at two years post-operatively achieved only a partial sensory rehabilitation, with complete motor deficit. All patients can walk unassisted, without support, with one case having complete rehabilitation achieved 18 months postoperatively and three with partial rehabilitation.

CONCLUSION

CPN palsy after primary THA is a very serious complication with poor functional outcome. There is no consensus regarding the treatment. The age and the intensity of the rehabilitation program are the only significant factors for the medical rehabilitation after this debilitating post-operative complication.

Nerve Entrapments in the Pelvis and Hip

Clinical symptoms of pelvic entrapment neuropathies are widely variable and frequently nonspecific, thus rendering it difficult to localize and diagnose. Magnetic resonance imaging (MRI), and in particular MR neurography, has become increasingly important in the work-up of entrapment neuropathies involving the pelvic and hip nerves of the lumbosacral plexus. The major sensory and motor peripheral nerves of the pelvis and hip include the sciatic nerve, superior and inferior gluteal nerves, femoral nerve, lateral femoral cutaneous nerve, obturator nerve, and pudendal nerve. Familiarity with the anatomy and imaging appearance of normal and pathologic nerves in combination with clinical presentation is crucial in the diagnosis of entrapment neuropathies.

Nerve Injuries Following Total Hip Arthroplasty: The Influence of Surgical Approach

Nerve injuries following total hip arthroplasty are rare but devastating complications. The most important modifiable risk factor remains the choice of hip approach and surgical technique applied. The risk of nerve injuries is related to technical complexity of the procedure and anatomic variability of the nerves. Surgeons should remain cognizant of inherent risk factors, variations in the course and branching patterns of different nerves, and technical considerations of the surgical approach to mitigate risks. This article reviews the literature on postsurgical nerve injuries following total hip arthroplasty and characterizes the influence of surgical approach on the risk of this complication.

Report of a Novel Bilateral Variation of Sciatic and Inferior Gluteal Nerve: A Case Study

Introduction:

The sciatic nerve is the thickest nerve of the sacral plexus which innervates many muscles and vast areas of the skin of the lower limb. It leaves the pelvis via the greater sciatic foramen, emerges into the gluteal region by passing under the piriformis muscle, and descends beneath the gluteus maximus to divide into its terminal branches; the tibial and common peroneal nerve at the superior angle of the popliteal fossa. In some cases, the sciatic nerve divides into the tibial and common peroneal nerves at a higher level and one of them or both passes through or over the piriformis muscle.

Case Presentation:

We find an interesting bilateral variation of sciatic nerve accompanying a very thick inferior gluteal nerve on the right side and unusual route and branching of tibial and common peroneal nerves on the left side.

Conclusion:

As in conditions like intramuscular injections, gluteal surgeries, and piriformis syndrome such variations may increase the risk of injury, it is important for the medical team to be aware of them. In this paper, by reporting many variations in a cadaver, we emphasize the importance of anatomical variations, especially for surgeons and nurses.

Acute piriformis syndrome mimicking cauda equina syndrome: illustrative case

BACKGROUND

This report depicts a rare case of acutely developed urinary retention as well as sensory and motor disturbances caused by formation of a large hematoma within the piriformis muscle, which caused compression of nerves within the suprapiriform and infrapiriform foramina, thus imitating cauda equina syndrome. Although cases of acute lumbosacral plexopathy have been described, this case is the first time both urinary retention and sensory and motor disturbances were present.

OBSERVATIONS

The most useful tools for diagnosis of acute piriformis syndrome are detailed patient history, magnetic resonance imaging (MRI) of the pelvic region, and electrophysiological testing performed by an experienced electrophysiologist. As a result of diligent rehabilitation, including physiotherapy and electrostimulation, the patient was able to successfully recover, regardless of acute compression of the sacral plexus that lasted 6 days.

LESSONS

Clinicians should actively ask about previous pelvic trauma when taking a patient history in similar cases, especially if the patient is receiving anticoagulation treatment. If MRI of the lumbar spine does not reveal any pathologies, MRI of the pelvic region should be performed. Acute surgical decompression is crucial for preserving neurological function. In similar cases, it is possible to differentiate between spinal cord, cauda equina, and pelvic lesions using electrophysiological studies.

Innervation of the Posterior Hip Capsule: A Cadaveric Study

OBJECTIVE

Recent studies of hip anatomy have turned to the posterior hip capsule to better understand the anatomic location of the posterior capsular sensory branches and identify nerves with potential for neural blockade. Current literature has shown the posterior hip capsule is primarily supplied by branches from the sciatic nerve, nerve to quadratus femoris, and superior gluteal nerve (1, 2). This cadaveric study investigated the gross anatomy of the posterior hip, while also identifying potential targets for hip analgesia, with emphasis on the superior gluteal nerve and nerve to quadratus femoris.

DESIGN

Cadaveric study.

SETTING

UT Health San Antonio Anatomy Lab.

METHODS

In total, 10 total cadavers (18 hips total), were posteriorly dissected identifying nerve to quadratus femoris, superior gluteal nerve, and sciatic nerve. Nerves were labeled with radio-opaque markers. Following the dissections, fluoroscopic images were obtained at sequential angles to identify neural anatomy and help expand anatomic knowledge for interventional pain procedures.

RESULTS

The posterior hip capsule was supplied by the sciatic nerve in 1/16 hips, the nerve to quadratus femoris in 15/18 hips, and the superior gluteal nerve in 6/18 hips.

CONCLUSIONS

The nerve to quadratus femoris reliably innervates the posterior hip joint. Both the sciatic nerve and superior gluteal nerve have small articular branches that may be involved in posterior hip innervation, but this is not seen commonly. The results of this study may elucidate novel therapeutic targets for treatment of chronic refractory hip pain (i.e., the nerve to quadratus femoris).

Bifurcation of the sciatic nerve: A descriptive study on a South African cadaver cohort

BACKGROUND

The sciatic nerve bifurcates into the tibial and common fibular nerves in six different regions: the pelvic region, gluteal region, proximal, middle, or distal third of the posterior thigh, or in the popliteal fossa. Inadequate knowledge of sciatic nerve anatomy could lead to failed nerve blocks, and damage during intramuscular injections. Limited studies have been done on African population groups and lack a quantifiable method to classify the levels of sciatic nerve bifurcation.

AIM

Thus, this descriptive cadaver study aimed to assess the bifurcation level of the sciatic nerve in a South African population group using a quantifiable method.

METHODS

Three hundred and thirty-eight formalin-fixed limbs from three universities were dissected between March and August 2018. Type A was classified if the sciatic nerve bifurcated within the pelvic region. A sciatic nerve bifurcation level index (SNBLI) was developed for this study to quantitatively classify the region of sciatic nerve bifurcation into types B to F.

RESULTS

Type F bifurcation was most common (79.6%), and types B and C were not observed. In 15 (0.04%) specimens, two separate nerves entered the gluteal region and converged to form the sciatic nerve distal to the piriformis, which could bifurcate either in the distal third of the posterior thigh or popliteal fossa.

CONCLUSION

This is the first study to provide information on the sciatic nerve bifurcation in a large South African cadaver cohort. Moreover, we created a quantifiable method that can be used to classify the sciatic nerve bifurcation level. This will be beneficial in ensuring accurate comparison between different population groups in future.

Deep gluteal syndrome as a cause of posterior hip pain and sciatica-like pain

Deep gluteal syndrome is an increasingly recognized disease entity, caused by compression of the sciatic or pudendal nerve due to non-discogenic pelvic lesions. It includes the piriformis syndrome, the gemelli-obturator internus syndrome, the ischiofemoral impingement syndrome, and the proximal hamstring syndrome. The concept of the deep gluteal syndrome extends our understanding of posterior hip pain due to nerve entrapment beyond the traditional model of the piriformis syndrome. Nevertheless, there has been terminological confusion and the deep gluteal syndrome has often been undiagnosed or mistaken for other conditions. Careful history-taking, a physical examination including provocation tests, an electrodiagnostic study, and imaging are necessary for an accurate diagnosis. After excluding spinal lesions, MRI scans of the pelvis are helpful in diagnosing deep gluteal syndrome and identifying pathological conditions entrapping the nerves. It can be conservatively treated with multidisciplinary treatment including rest, the avoidance of provoking activities, medication, injections, and physiotherapy. Endoscopic or open surgical decompression is recommended in patients with persistent or recurrent symptoms after conservative treatment or in those who may have masses compressing the sciatic nerve. Many physicians remain unfamiliar with this syndrome and there is a lack of relevant literature. This comprehensive review aims to provide the latest information about the epidemiology, aetiology, pathology, clinical features, diagnosis, and treatment. Cite this article: Bone Joint J 2020;102-B(5):556-567.

Composite Anatomical Variations between the Sciatic Nerve and the Piriformis Muscle: A Nepalese Cadaveric Study

Piriformis syndrome is a rare syndrome which is one of the main causes of nondiscogenic sciatica causing severe low back pain due to entrapment of sciatic nerve either by the hypertrophy or by inflammation of the piriformis muscle. We have carried out dissection in 20 Nepalese cadavers. Out of 40 dissected gluteal regions, 37 exhibited typical appearance of sciatic nerve, piriformis muscle, and their relations resembling type-a, whereas 3 gluteal regions showed composite structural variations resembling type-b and type-c based on Beaton and Anson's classification. Knowledge pertaining to such variations will be helpful during a surgical intervention in the gluteal region and in turn reduces the risk of injuring these nerves which are more susceptible to damage. Our study reports such variations in Nepalese population which will be helpful during evaluation of the pain induction in various test positions and also useful for analysis of the range of the neurological deficiency in sciatic nerve neuropathies. The present study also explains the basis of the unsuccessful attempt of the sciatic nerve block during popliteal block anaesthesia.

Anatomical causes of compression of the sciatic nerve in the pelvis. Piriform syndrome

OBJECTIVE

The piriformis syndrome is one of the etiologies of pelvic pain due to the sciatic nerve's entrapment by the piriformis muscle. Nowadays this syndrome might be difficult to be diagnosed. The aim of this study is to know the prevalence of anatomic variations in our population that may contribute to the appearance of piriformis syndrome. Furthermore, anthropometric measurements of the piriformis muscle and the sciatic nerve procedures are studied for a possible application in the gluteal region.

MATERIAL AND METHOD

The study was carried out in 59 pelvis of 32 cryopreserved bodies. The anatomical variations of piriformis and sciatic nerve founded were described following the Beaton and Anson's classification. Anthropometric measurements of both structures with reference to the greater trochanter of the femur were performed.

RESULTS

The sciatic nerve and the piriformis had an anatomical variation in a 28.13%. The most frequent variation found was tipus II (21.64%) and tipus III (6.49%).Insertion most frequently observed was an independent piriformis tendon inserted into the trochanteric fossa with 53.85%.

CONCLUSION

The anatomic variations' incidence in the population studied indicates that those have to be evaluated as a differential diagnosis of gluteal region pain due to the symptoms and signs resemblance with the vertebral disc pathology involving nerve root injury. In addition, anatomical knowledge of this region can be useful for the interpretation of imaging techniques, especially when ultrasound-guided injections are performed.

Case report: absence of the right piriformis muscle in a woman

We report a very rare case of a unilaterally absent piriformis muscle in a 60 year old woman. Accompanying variations comprised a common gluteal artery (instead of two distinct superior and inferior gluteal arteries), and an absent gemellus inferior muscle. The contralateral left side showed a normally developed piriformis muscle. In hominoids, the piriformis is constant, but is regularly missing in several other vertebrates. The piriformis muscle is an anatomical landmark for ultrasound investigations and ultrasound-guided interventions in the deep gluteal region such as a superior gluteal nerve block or even a sacral plexus block, also for any surgical approach such as total hip arthroplasty. A missing piriformis muscle therefore affects the orientation in the deep gluteal region and therefore the identification of the targeted structures.

Spinal dysraphism and dislocated hip: Beware of anomalous sciatic nerve through Ilium, a case report

RATIONALE

The sciatic nerve runs a predictable course combining L4-S3 nerve roots through the true pelvis and under the greater sciatic notch. There are reports of bony protuberances from the sacrum and ilium in cases of spinal dysraphism; however advanced imaging, treatment, or outcomes are not described. There are no cases with associated fibular hemimelia in the current literature.

PATIENT CONCERNS

This is a 4-year-old girl with tethered cord, acetabular dysplasia with hip subluxation, congenital short femur, anterior cruciate ligament (ACL) deficiency, and fibular hemimelia with her sciatic nerve coursing through the ilium.

DIAGNOSIS

Aberrant course of the sciatic nerve through the ilium in the setting of spinal dysraphism.

OUTCOMES

The hip subluxation was treated with a femoral varus derotation osteotomy and Salter osteotomy with transposition of the sciatic nerve into the greater sciatic notch resulting in a stable hip with no sciatic nerve symptoms at last follow-up.

LESSONS

The combination of spinal dysraphism with acetabular dysplasia should be a warning for anomalous sciatic nerveanatomy, possibly through the ilium. Preoperative imaging (MRI, CT scan) may be obtained and carefully reviewed for the course of the sciatic nerve prior to pelvic or femoral osteotomy. Decompressing the sciatic nerve from the aberrant foramen may be considered as part of the procedure.