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.

Evaluation of the Interrater Reliability of Sonographic Measurements of Muscle Thickness of 38 Piriformis Muscles in 19 Patients with Piriformis Syndrome.

BACKGROUND The piriformis muscle is a flat superficial muscle of the deep gluteal muscles that externally rotates the hip. Ultrasound is widely used to identify the piriformis muscle, especially for guidance of the needle during injections; however, its diagnostic use has recently gained popularity. The operator-dependent nature of ultrasound requires demonstration of reliability between operators. This study aimed to evaluate interrater reliability of sonographic measurements of muscle thickness of 38 piriformis muscles in 19 patients with piriformis syndrome. MATERIAL AND METHODS An ultrasound transducer was placed transversely on the sacral spinous process and moved caudo-laterally until the piriformis muscle was visualized under the gluteus maximus while patients were lying in prone position. The thickness of piriformis muscle was measured with a 2 to 5-MHz broadband curvilinear transducer in 3 regions (thickest regions of muscle over the ilium, near the greater trochanter, and near the sacrum). The interrater reliability of measurements of 2 examiners who were blinded to each other's measurements was assessed by intraclass correlation coefficient. RESULTS In total, 114 samples from 38 piriformis muscles of 19 patients with a diagnosis of piriformis syndrome were evaluated by 2 raters in this study. The median (interquartile range) patient age was 41 (15) years. Intraclass correlation coefficient value for overall thickness measurements of piriformis muscle was 0.836. Intraclass correlation coefficient values for 3 different regions were over the ilium, near the greater trochanter, and near the sacrum were 0.777, 0.883, and 0.811, respectively. CONCLUSIONS Ultrasound measurement of piriformis muscle thickness has good interrater reliability.

Effective Stretching Positions of the Piriformis Muscle Evaluated Using Shear Wave Elastography.

CONTEXT: Piriformis syndrome is often associated with muscle spasms and shortening of the piriformis muscle (PM). Physical therapy, including static stretching of the PM, is one of the treatments for this syndrome. However, the effective stretching position of the PM is unclear in vivo. This study aimed to determine the effective stretching positions of the PM using ultrasonic shear wave elastography. DESIGN: Observational study. METHODS: Twenty-one healthy young men (22.7 [2.4] y) participated in this study. The shear elastic modulus of the PM was measured at 12 stretching positions using shear wave elastography. Three of the 12 positions were tested with maximum internal rotation at 0°, 20°, or 40° hip adduction in 90° hip flexion. Nine of the 12 positions were tested with maximum external rotation at positions combined with 3 hip-flexion angles (70°, 90°, and 110°) and 3 hip-adduction angles (0°, 20°, and 40°). RESULTS: The shear elastic modulus of the PM was significantly higher in the order of 40°, 20°, and 0° of adduction and higher in external rotation than in internal rotation. The shear elastic modulus of the PM was significantly greater in combined 110° hip flexion and 40° adduction with maximum external rotation than in all other positions. CONCLUSION: This study revealed that the position in which the PM was most stretched was maximum external rotation with 110° hip flexion and 40° hip adduction.

Could dry needling change the kinematics of gait in individuals with piriformis muscle syndromes? Secondary analysis of a randomized controlled trial.

INTRODUCTION: Piriformis muscle syndrome (PMS) is a condition that can lead to symptoms including gluteal pain, local tenderness, and limitation of hip joint motion in daily activities, and it may have a major impact on some daily functions such as gait. We proposed that dry needling (DN) can improve the gait of individuals with PMS. METHODS: Thirty-two individuals with PMS were assigned equally and randomly to the treatment group or the wait-list control group. Subjects in the treatment group received three sessions of DN of the piriformis muscle. All participants in both groups were educated to correct their lifestyles. The outcome measures were the gait-related parameters (walking speed, peak hip flexion, peak hip extension, time to peak internal and external hip rotation, and knee sagittal range of motion), which were evaluated at baseline and after treatment. To compare different outcomes, analysis of covariance (ANCOVA) was used, with baseline as the covariance and groups as a factor. RESULT: After DN sessions, peak hip extension during gait showed a statistically significant difference [adjusted MD 1.9 (3.7-0.08), p < 0.05, d = 0.56 (0.1-1.28)] in favor of the DN group. Peak hip flexion, on the other hand, exhibited a marginal statistically significant difference [adjusted MD -3.2 (-6.51 to 0.01), p = 0.053, d = 0.44 (1.16 to -0.02)] compared to the control group. CONCLUSION: The findings suggest that participants in DN showed significantly greater peak extension angle of the hip during walking in individuals with PMS than in the control group.

Anatomical Relationships of the Sciatic Nerve and Pudendal Nerve to the Ischial Spine as They Exit the Greater Sciatic Foramen.

OBJECTIVE: Deep gluteal syndrome is a clinical condition in which discomfort may arise due to the pathoanatomy of the subgluteal space. We conducted an anatomical exploration to categorize the relationship of the piriformis muscle, sciatic nerve (SN), and pudendal nerve (PN) to the ischial spine (IS) and sacrospinous ligament. METHODS: We analyzed 22 cadavers. The piriformis muscle, SN, and PN were exposed through either a transgluteal approach or a gluteal flap. The relationship of the neural structures to the IS, sacrospinous ligament, and ischial bone as they exit the greater sciatic foramen was observed, and the exit zones were classified as zone A, medial to the IS (entirely on sacrospinous ligament); zone B, on the IS; and zone C, lateral to the IS (entirely on ischial bone). RESULTS: The SN was observed either in zone B or zone C in all specimens. The PN was found to be in either zone A or zone B in 97.6% of specimens. The most common combinations were SN in zone B and PN in zone A (type I), and SN in zone C and PN in zone B (type II). CONCLUSIONS: The results from this study show clear anatomical differences in the SN-PN relationship, which may play a role in pain seen in deep gluteal syndrome. Moreover, classification of the SN-IS and PN-IS relationships described in this article will help describe different pathologies affecting the deep gluteal area.

An atypical inferior gluteal artery passing through the piriformis muscle.

PURPOSE: In this article, we report a case of an atypical inferior gluteal artery that passed through the piriformis muscle when it emerged from the pelvic cavity in an elderly Japanese female cadaver. We speculate that this atypical artery could be entrapped and compressed by the piriformis muscle and may therefore be associated with piriformis syndrome; however, the anatomical characteristics of such an atypical artery have not been previously reported. To assess this potential association, the atypical inferior gluteal artery was anatomically examined. METHODS: The cadaver examined in this report was a 97-year-old Japanese female who was donated to The Nippon Dental University for use in medical education and research. The atypical inferior gluteal artery and surrounding structures in half of the pelvis were examined macroscopically. RESULTS: The atypical inferior gluteal artery arose from the common arterial trunk, formed by itself and the superior gluteal artery, passed through the superior proximal part of the piriformis muscle, and left the pelvic cavity. It supplies branches to the lower half of the gluteus maximus and proximal part of the long head of the biceps femoris muscle. The piriformis muscle originates from the 2nd to 4th sacral vertebrae and attaches to the greater trochanter via a single short tendon. CONCLUSION: According to our findings, when the atypical inferior gluteal artery is entrapped and compressed, ischemic signs and symptoms may emerge in the lower buttocks and proximal posterior thigh. These results provide a new perspective for the diagnosis and treatment of piriformis syndrome.

Unrepaired Trochanteric Bursae as a Risk Factor for Deep Gluteal Syndrome After Total Hip Arthroplasty: A Prospective Randomized Controlled Trial.

BACKGROUND: The trochanteric bursae are often left unrepaired after total hip arthroplasty (THA) and they retract posteriorly over the muscle belly of the piriformis. Deep gluteal syndrome (DGS) is a multifactorial condition presenting as buttock pain and is attributed to nondiscogenic sciatic nerve irritation or impingement causes. The purpose of this study was to investigate the relationship between bursal repair and incidence of DGS in patients undergoing THA. METHODS: This prospective randomized trial included patients treated with a THA between January and December 2022 for a diagnosis of primary osteoarthritis. Patients were randomized into 2 groups: group 1 underwent a routine bursal repair, while group 2 did not, leaving the bursae unrepaired. Follow-up was performed on the 15th, 30th, and 90th day postoperatively with clinical scores, physical examinations, and laboratory tests. In this cohort of 104 patients, mean age was 55 years (range, 26 to 88). Demographic variables as well as range of motion and overall clinical results showed no significant difference between the groups. RESULTS: DGS rates were significantly more common in the patients who had an unrepaired bursa (group 2) both on the 30th and 90th postoperative days, while comparison of lateral trochanteric pain on palpation showed similar results between the groups. CONCLUSIONS: DGS is common in individuals who have unrepaired trochanteric bursal tissue following a THA. Despite its higher frequency, these symptoms did not have a substantial impact on the overall clinical scores, which remained consistent across the study groups.

A Case-Control Study of 40 Patients with Piriformis Muscle Syndrome to Evaluate Diagnostic Findings Using Two-Dimensional Ultrasound and Shear Wave Elastography.

BACKGROUND Piriformis muscle syndrome (PMS) is a neuropathy caused by compression of the sciatic nerve by the piriformis muscle. This case-control study included 40 patients with PMS and aimed to evaluate the diagnostic findings using two-dimensional ultrasound and shear wave elastography (SWE), as non-invasive and cost-effective diagnostic methods. MATERIAL AND METHODS In order to evaluate the value of two-dimensional ultrasound diagnosis, a new imaging technique called shear wave elastography (SWE) was used in the screening of PMS, with a total of 40 PMS patients and 40 healthy individuals participating in our study. We analyzed the correlation and area under the curve (AUC) of changes in thickness (mm) and Young's modulus (kpa) of the bilateral piriformis muscle (PM). RESULTS We found that PM thickness and Young's modulus on the lesion sides were significantly higher in PMS patients than in controls (P<0.05). Also, we determined that there was a positive correlation between PM thickness and Young's modulus (r=0.454, P<0.05). Using two-dimensional ultrasonic diagnosis and the SWE technique, a specificity of 95.8% and sensitivity of 78.8% were demonstrated in the clinical diagnosis of PM. CONCLUSIONS Two-dimensional ultrasound with SWE technology has demonstrated its superior sensitivity and specificity in diagnosing PMS in the clinic.

An Extremely Rare Case of a Sciatic Nerve Variant.

The sciatic nerve (SN) is the nerve of the posterior compartment of the thigh and typically traverses beneath the piriformis muscle (PM) before continuing along a vertical course deep to the gluteus maximus and biceps femoris. However, cadaveric studies have often revealed significant variations in the structural features of the SN in relation to the piriformis. Knowledge of such variations is not only useful for clinicians treating pathophysiologies such as piriformis syndrome and sciatica but is also essential for surgeons carrying out procedures involving the hip and sacroiliac joints to avoid iatrogenic injury to the SN. During routine cadaveric dissection, one such anatomical variant was identified with the SN passing over the superior border of the piriformis muscle. To our knowledge, such a variant is exceedingly rare.

Left Gluteal Maximus Neuroma Causing Long-Standing Gluteal Pain.

ABSTRACT: Diagnosing buttock pain is a challenge due to complex anatomy and multiple causes. Potential pathologies range from common and benign to rare and life-threatening. Common causes for buttock pain include referred pain from the lumbar spine and sacroiliac joint, hamstring origin tendinopathy, myofascial pain, ischiogluteal bursitis, gluteal pathology, and piriformis syndrome. Rarer causes include malignancy, bone infection, vascular anomalies, and spondyloarthropathies. Other conditions may be present concurrently in the lumbar and gluteal area, which can cloud the clinical picture. Correct diagnosis and early treatment may improve quality of life by providing a targetable reason for their distress, improving pain, and allowing the patient to get back to their activities of daily living. When treating a patient with buttock pain, it is essential to reevaluate the diagnosis when symptoms fail to improve despite appropriate intervention.Here, we discuss a case of a peripheral nerve sheath tumor found in the left gluteus medius muscle of a patient that caused persistent, debilitating buttock pain. After years of treatment for piriformis syndrome and possible spinous causes, the patient was ultimately diagnosed with a peripheral nerve sheath tumor through magnetic resonance imaging with contrast. Peripheral nerve sheath tumors are a diverse group of mostly benign tumors that can occur sporadically or associated with certain disease processes. These tumors usually present with pain, a soft tissue mass, or focal neurological deficits. Upon removal of the tumor, her gluteal pain completely resolved.

Deep Gluteal Pain Syndrome: Endoscopic Technique and Medium-Term Functional Outcomes.

BACKGROUND: Sciatic nerve entrapment is an entity that generates disabling pain, mainly when the patient is sitting on the involved side. According to some studies, the presence of fibrovascular bands has been described as the main cause of this pathology, and the sciatic nerve's decompression by endoscopic release has been described as an effective treatment generally associated with a piriformis tenotomy. The aim of this study was to present the medium-term functional results of endoscopic release of the sciatic nerve without resection of the piriformis tendon. METHODS: This prospective, observational study included 57 patients who underwent an endoscopic operation for sciatic nerve entrapment between January 2014 and January 2019. In all cases, a detailed medical history was obtained and a physical examination and a functional evaluation were performed using the modified Harris hip score (mHHS), the 12-item International Hip Outcome Tool (iHOT-12), and the visual analog scale (VAS) for pain. All patients had pelvic radiographs and magnetic resonance imaging (MRI) scans of the hip on the involved side and underwent a prior evaluation by a spine surgeon. RESULTS: This study included 20 male and 37 female patients with a mean age of 43.6 years (range, 24 to 88 years) and a mean follow-up of 22.7 months. The median mHHS improved from 59 to 85 points. The median iHOT-12 improved from 60 to 85 points. The median VAS decreased from 7 to 2. Postoperative complications occurred in 12% of patients: 1 patient with extensive symptomatic hematoma, 3 patients with hypoesthesia, and 3 patients with dysesthesia. CONCLUSIONS: Endoscopic release of the sciatic nerve by resection of fibrovascular bands without piriformis tenotomy is a technique with good to excellent functional results comparable with those of techniques in the literature incorporating piriformis tenotomy. LEVEL OF EVIDENCE: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Comparing radial extracorporeal shockwave therapy and corticosteroid injection in the treatment of piriformis syndrome: A randomized clinical trial.

OBJECTIVE: This study was designed to compare the effects of shockwave therapy and corticosteroid injection in the treatment of piriformis syndrome. METHODS AND MATERIALS: In this randomized clinical trial, thirty-five patients with piriformis syndrome were randomly divided into two groups of 18 in the shockwave group and 17 in the corticosteroid group. The Shockwave group underwent three sessions of shockwave therapy per week (2000 pulses per session with 5Hz frequency and pressure equal to 4 Bar) and the corticosteroid group underwent an injection of 40 mg methylprednisolone with 1 mL of 1% lidocaine under ultrasound guidance. All patients were assessed by SF-36 questionnaire and visual analogue scale (VAS). The SF-36 questionnaire was used to evaluate the quality of life before and 4 weeks after the intervention. VAS scale was used to evaluate pain before the intervention, and 1, 4, 8, and 12 weeks after the intervention. RESULTS: The baseline characteristics of the two groups were not significantly different. At the end of the study, both groups had a significant improvement in pain and quality of life compared to before the intervention. However, according to the VAS, in the shockwave group improvement was seen in the first follow-up while not seen in the corticosteroid group (P-value <0.001 and P-value 1.00, respectively). According to the SF-36 questionnaire, the overall score in both groups had a significant improvement (P-value <0.05). CONCLUSIONS: It seems that shockwave therapy and corticosteroid injection are both effective in the treatment of piriformis syndrome. There was no significant difference between the two groups in the quarterly follow-up. Because shockwave therapy is a relatively non-invasive treatment with fewer side effects, it can be useful to improve pain and the quality of life of patients with piriformis syndrome.

A three-headed piriformis muscle: an anatomical case study and narrative review of literature.

The piriformis muscle (PM) is found in the gluteal region, exiting the pelvis through the greater sciatic foramen and dividing it into the suprapiriform and infrapiriform foramina. The piriformis works as part of the hip external rotator muscle group, and is responsible for rotation of the femur upon hip extension and abduction of the femur during flexion of the hip joint. The aim of the present report is to describe a very rare case of the primary three-headed PM. To the best knowledge of the authors, the said variant has not yet been described in the existing literature. The 71-year-old male formalin-fixed cadaver was subjected to routine dissection. After careful removal of the connecting tissue, three separate, primary heads of the PM were identified. The lower head of the PM arose from the middle part of the sacral bone; 87.56 mm long and 9.73 mm wide. The medial head was attached to the internal part of the posterior inferior iliac spine; 121.6 mm long and 20.97 mm wide. The upper head was attached to the external part of the posterior inferior iliac spine; 78.89 mm long and 23.94 mm wide. All heads converged into a common tendon which inserted onto the greater trochanter. The clinical importance of this work comes down to the fact that the aberrant PM may be the reason behind the piriformis syndrome and its associated symptoms. Moreover, knowledge regarding the variant anatomy of the PM is of immense importance to, e.g. anaesthesiologists performing computed tomography- or ultrasound-guided sciatic nerve injection for local anaesthesia, radiologists interpreting imaging studies, and surgeons, especially during posterior approaches to the hip and pelvis.

A Sciatic Neuralgia Case of an Entrapment Neuropathy Mimicking Piriformis Syndrome Due to Soft Tissue Hemangioma.

BACKGROUND: Lumbosacral pain is commonly seen in daily clinical practice. In fact, entrapment of the part of the sciatic nerve after the sacral foramen causes some of these pains, which should not be overlooked. The sciatic nerve may be compressed during its course after the sacral foramen for a variety of reasons. We aimed in this article to review extra-spinal compressive sciatic neuropathy reasons and abnormal magnetic resonance imaging (MRI) by presenting a sciatic neuralgia case of an entrapment neuropathy mimicking piriformis syndrome due to soft tissue hemangioma. CASE PRESENTATION: A 30-year-old male patient was admitted with complaints of lumbosacral pain spreading to the leg that had been worsening over the previous 10 days. With the preliminary diagnosis of labral damage and piriformis syndrome, the patient was referred to the radiology clinic for a hip MRI. In the hip MR images, a mass lesion suggestive of heterogeneously enhanced soft tissue hemangioma after the injection of paramagnetic contrast material was observed in the proximal left thigh. The soft tissue hemangioma extends towards the obturator foramen and compresses the sciatic nerve proximal to the femur after the sciatic foramen. CONCLUSION: The diagnosis of lower extremity entrapment neuropathy is frequently misdiagnosed. In these cases, MRI becomes more important for accurate diagnosis. The radiologists' knowledge of the sciatic nerve in MRI, regional anatomy during the course of the sciatic nerve, and abnormal nerve imaging findings will aid in the diagnosis.

Errate: Effectiveness of Hydro-Dissection of the Piriformis Muscle Plus Low-Dose Local Anesthetic Injection for Piriformis Syndrome: A Report of 2 Cases.

The authors have discovered an error in their figures and have provided replacement figures which have been corrected. Specifically, the positions of "Lateral" and "Medial" were reversed, and the positions of "Ischium" and "Sacrum" were reversed. Additionally, the solid lines at the boundaries of each muscle and bone have been removed, and only the nerves have been marked with dotted lines, which is a common notation in ultrasound images. The authors would also like to add the following Acknowledgment: The authors are grateful to Tadashi Kobayashi and Yoshihiko Shiraishi for advising us on the accurate anatomy of ultrasound images. Reference: Mihiro Kaga, Takeshi Ueda. Effectiveness of Hydro-Dissection of the Piriformis Muscle Plus Low-Dose Local Anesthetic Injection for Piriformis Syndrome: A Report of 2 Cases. Am J Case Rep, 2022; 23: e935346. DOI: 10.12659/AJCR.935346.

Botulinum toxin injection strategy of intractable and relapsed piriformis syndrome: A case report.

RATIONALE: Piriformis syndrome (PS) is neuromuscular disorder caused by sciatic nerve compression by piriformis muscle and related to sciatic-type pain. When the conservative care fails, local injection or surgery can be also performed into piriformis. In recent years, botulinum toxin (BoNT) has also been considered as a new therapeutic option of piriformis syndrome. PATIENT CONCERNS: A man in his late 40s came to pain clinic for left low back pain. The symptom was aggravated with sitting position. DIAGNOSIS: Piriformis syndrome. INTERVENTIONS: The patient underwent BoNT injection with 100 IU with 2 mL into piriformis muscle for piriformis syndrome treatment, and his pain was relieved. However, it recurred 8 months later. BoNT injection was repeated with 100 IU with 5 mL. OUTCOMES: At the time of this writing, his pain was reduced for 2 years without any medication. LESSONS: We report a case of treating relapsed piriformis syndrome with BoNT injection of different dilution volume, suggesting that the higher the dilution volume, the more effective for therapeutic effect of BoNT.

Evaluation of Accuracy of Shear Wave Elastography and Superb Microvascular Imaging Methods in Diagnosis of Piriformis Syndrome: A Preliminary Study.

Piriformis syndrome is a neuromuscular disease resulting from sciatic nerve compression caused by an abnormal condition in the piriformis muscle. Superb microvascular imaging (SMI) is a new ultrasound imaging technique that visualizes low-velocity and small-diameter blood vessel flow. In our prospectively designed study, we aimed to evaluate the accuracy of diagnosis of piriformis syndrome with innovative methods such as shear wave elastography (SWE) and SMI. Thirty-two patients diagnosed with unilateral piriformis syndrome were accepted to the statistical stage. The side without symptoms was considered the "unaffected side." Bilateral piriformis muscles were examined by ultrasonography. Muscle thickness was determined on gray scale, stiffness on SWE and vascularity characteristics on power Doppler and SMI by two independent radiologists. Piriformis muscle stiffness on the non-pathological (unaffected) side was measured by SWE as 18.27 ± 7.301 kPa, and the mean stiffness on the pathological side was 29.70 ± 10.095 kPa. Pathological side muscle stiffness was significantly higher (p < 0.05). Using innovative methods such as SWE and SMI in addition to conventional ultrasonography as much as possible in our daily practice and research helps us in making the correct diagnosis in piriformis syndrome.

Novel anatomical findings with implications on the etiology of the piriformis syndrome.

PURPOSE: The cause of the piriformis-related pelvic and extra-pelvic pain syndromes is still not well understood. Usually, the piriformis syndrome is seen as extra-pelvic sciatica caused by the entrapment of the sciatic nerve by the piriformis in its crossing through the greater sciatic foramen. However, the piriformis muscle may compress additional nerve structures in other regions and cause idiotypic pelvic pain, pelvic visceral pain, pudendal neuralgia, and pelvic organ dysfunction. There is still a lack of detailed description of the muscle origin, topography, and its possible relationships with the anterior branches of the sacral spinal nerves and with the sacral plexus. In this research, we aimed to characterize the topographic relationship of the piriformis with its surrounding anatomical structures, especially the anterior branches of the sacral spinal nerves and the sacral plexus in the pelvic cavity, as well as to estimate the possible role of anatomical piriformis variants in pelvic pain and extra-pelvic sciatica. METHODS: Human cadaveric material was used accordingly to the Swiss Academy of Medical Science Guidelines adapted in 2021 and the Federal Act on Research involving Human Beings (Human Research ACT, HRA, status as 26, May 2021). All body donors gave written consent for using their bodies for teaching and research. 14 males and 26 females were included in this study. The age range varied from 64 to 97 years (mean 84 ± 10.7 years, median 88). RESULTS: three variants of the sacral origin of the piriformis were found when referring to the relationship between the muscle and the anterior sacral foramen. Firstly, the medial muscle origin pattern and its complete covering of the anterior sacral foramen by the piriformis muscle is the most frequent anatomical variation (43% in males, 70% in females), probably with the most relevant clinical impact. This pattern may result in the compression of the anterior branches of the sacral spinal nerves when crossing the muscle. CONCLUSIONS: These new anatomical findings may provide a better understanding of the complex piriformis and pelvic pain syndromes due to compression of the sacral spinal nerves with their somatic or autonomous (parasympathetic) qualities when crossing the piriformis.

Efficacy of Botulinum Toxin, Local Anesthetics, and Corticosteroids in Patients With Piriformis Syndrome: A Systematic Review and Meta-analysis.

BACKGROUND: Piriformis syndrome (PS) is a painful condition caused by entrapment of the sciatic nerve within the piriformis muscle. PS is typically unilateral and mainly occurs related to entrapment of the sciatic nerve. Treatments include physiotherapy, analgesics, anti-inflammatory drugs, behavioral modifications, injection therapy with local anesthetics (LAs) and steroids, epidural injection, botulinum toxin (BT) injection, and surgery. OBJECTIVES: To investigate the efficacy of BT, LA, and corticosteroid (CS) injections in relieving pain in patients affected by PS. STUDY DESIGN: This systematic review and meta-analysis was conducted according to the "Cochrane Handbook for Systematic Reviews of Interventions" and the "Preferred Reporting Items for Systematic Reviews and Metaanalyses (PRISMA)" guidelines. METHODS: A systematic search was conducted through PubMed, Cochrane, Web of Science, and Scopus through April 2021 for studies investigating the efficacy of BT, LA, or CS injection in improving pain in patients with PS. After screening retrieved studies, data were extracted from included studies and pooled. Overall results were reported as standardized mean difference (SMD) and 95% confidence interval (CI). Analysis was performed using RevMan software version 5.4. RESULTS: Sixteen studies were included in this systematic review, and 12 of them were included in the quantitative synthesis. The pain scores decreased significantly after treatment with BT (SMD = -2.00; 95% CI [-2.84, -1.16], P < 0.001), LA and CS (SMD = -4.34; 95% CI [-5.77, 2.90], P < 0.001), LA (SMD = -3.73; 95% CI [-6.47, -0.99], P = 0.008), CS (SMD = -2.78; 95% CI [-3.56, -2.00], P < 0.001), and placebo injection (SMD = -0.04; 95% CI [-0.07, -0.01], P = 0.002). BT injection was less effective than LA and CS together (P = 0.006), more effective than placebo (P = 0.001), and similar to LA (P = 0.24) and CS (P = 0.18), when injected alone. LIMITATIONS: A wide variety of study designs were utilized to obtain the largest sample size available. Many of the included studies lack randomization, and some are retrospective in nature. These limitations may introduce bias into the analyzed data and affect the results. Many studies had a low sample size and are of moderate quality, limiting the generalizability of the results. Also, we could not conduct a direct meta-analysis due to the lack of sufficient double-arm studies comparing different types of injection therapies. CONCLUSIONS: In patients with PS, satisfactory pain improvement can be obtained by BT, LA plus CS, LA, or CS injection therapy. Injection of LA plus CS showed the best efficacy.