Ultrasound appears to be a reliable technique for the diagnosis of piriformis syndrome

Use of Diagnostic Musculoskeletal Ultrasound in the Evaluation of Piriformis Syndrome: A Review for Rehabilitation Providers

Piriformis Syndrome (PS) is a neuromuscular condition caused by the entrapment of the sciatic nerve at the level of the piriformis muscle (PM) and can cause significant discomfort and disability. PS is often misdiagnosed due to its overlapping symptoms with other lumbar and sciatic issues and as such, diagnosing PS remains challenging despite recent invasive and non-invasive diagnostic methods. Diagnostic musculoskeletal ultrasound (MSK US) offers a non-invasive, cost-effective alternative for the identification and evaluation of PS, providing dynamic, real-time imaging of the PM and adjacent structures. This article reviews the applications, advantages, and procedural insights of MSK US in the diagnosis of PS, emphasizing its relevance in rehabilitation settings. We discuss the technical aspects of ultrasound use, interpretation of findings, and integration into clinical practice, aiming to enhance the diagnostic accuracy and therapeutic outcomes for patients with suspected PS.

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.

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 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.

EURO-MUSCULUS/USPRM Dynamic Ultrasound Protocols for (Adult) Hip

ABSTRACT

In this dynamic scanning protocol, ultrasound assessment of the adult hip is described using different maneuvers for various conditions. Real-time patient examination and ultrasound scanning videos are coupled for convenience as well as for better insight. The text covers the common conditions around the hip where especially dynamic ultrasound scanning provides valuable information in addition to static imaging. The protocol is prepared by an international consensus of several experts in the field of musculoskeletal ultrasound.

Human skeletal muscle size with ultrasound imaging: a comprehensive review

Skeletal muscle size is an important factor in assessing adaptation to exercise training and detraining, athletic performance, age-associated atrophy and mobility decline, clinical conditions associated with cachexia, and overall skeletal muscle health. Magnetic resonance (MR) imaging and computed tomography (CT) are widely accepted as the gold standard methods for skeletal muscle size quantification. However, it is not always feasible to use these methods (e.g., field studies, bedside studies, large cohort studies). Ultrasound has been available for skeletal muscle examination for more than 50 years and the development, utility, and validity of ultrasound imaging are underappreciated. It is now possible to use ultrasound in situations where MR and CT imaging are not suitable. This review provides a comprehensive summary of ultrasound imaging and human skeletal muscle size assessment. Since the first study in 1968, more than 600 articles have used ultrasound to examine the cross-sectional area and/or volume of 107 different skeletal muscles in more than 27,500 subjects of various ages, health status, and fitness conditions. Data from these studies, supported by decades of technological developments, collectively show that ultrasonography is a valid tool for skeletal muscle size quantification. Considering the wide-ranging connections between human health and function and skeletal muscle mass, the utility of ultrasound imaging will allow it to be employed in research investigations and clinical practice in ways not previously appreciated or considered.

Endoscopic Sciatic Neurolysis for Deep Gluteal Syndrome: A Systematic Review

Deep gluteal syndrome (DGS) is an underdiagnosed condition caused by an extra-spinal entrapment of the sciatic nerve in the deep gluteal space. Symptomatic patients who fail conservative treatment require surgical decompression of the nerve either by an open or endoscopic approach. In recent times, there has been an increasing trend towards minimally invasive surgery performed with endoscopic techniques. This systematic review aimed to assess the effectiveness of endoscopic sciatic nerve decompression in the management of DGS. A comprehensive search of the PubMed, Web of Science, Cumulated Index to Nursing and Allied Health Literature (CINAHL), and SPORTDiscus databases were performed on January 3, 2022. All English-language clinical studies on DGS treated with endoscopic surgical decompression were included. The initial search criteria identified 145 articles, of which four studies were available for the final review. There was one level III evidence, while the remaining three were level IV, comprising 144 patients with a mean age of 46 years. The Coleman methodology score (CMS) was utilized to assess the quality of the studies and the mean score was 62 (range, 52 to 71). The presence of fibrovascular bands and bursal tissue was the most common cause of DGS, followed by musculotendinous structures. The average follow-up of the included studies was 26.3 months (range, 12 to 32 months). Less favorable outcomes were seen in patients with major traumatic sciatic neuropathies after fractures or open reconstructive hip surgeries. Conversion to formal open surgery was recorded in one case of DGS caused by sciatic nerve schwannoma due to poor endoscopic access. One patient developed postoperative recurrent sciatic nerve entrapment due to a foreign body reaction requiring an open decompression. Overall, the available studies reported a high degree of clinical success with a low rate of complications, albeit no high-quality studies could be identified.

Effect of hip external rotator muscle contraction on pelvic floor muscle function and the piriformis

INTRODUCTION AND HYPOTHESIS

There is a lack of in-depth understanding of the muscles surrounding the pelvic floor muscle (PFM). The study aimed to investigate the functional relationship between PFM and hip external rotator muscles by observing the piriformis muscle thickness and displacement of the bladder base under different contraction conditions of the hip external rotator and/or PFM. We hypothesized that PFM function would be the strongest when the hip external rotator and PFM contracted simultaneously and that during PFM contraction, the piriformis muscle would act as an auxiliary muscle and show coactivation.

METHODS

The participants included 13 healthy adult women (mean age 23.8 ± 2.8 years). The three contraction conditions were PFM contraction, hip external rotator contraction, and simultaneous contraction of the hip external rotator and PFM. During the tasks, the piriformis muscle thickness and bladder base displacement were measured using ultrasonography and compared among the contraction conditions using one-way analysis of variance.

RESULTS

Significant differences were noted in bladder base displacement among the three contraction conditions (P < 0.01), with PFM contraction having the highest value. The piriformis muscle thickness showed the greatest increase in simultaneous contraction.

CONCLUSIONS

In our study, we showed PFM contraction positively influences piriformis contraction, while PFM function operationalized by bladder base displacement was highest during PFM contraction alone.

Ultrasound-Guided Measurement of Piriformis Muscle Thickness to Diagnose Piriformis Syndrome

Background: Piriformis syndrome (PS) is a neuromuscular condition caused by the entrapment of the sciatic nerve at the level of the piriformis muscle (PM). Diagnosing PS remains challenging despite recent invasive and non-invasive diagnostic methods. Response to invasive nerve block is still one of the most reliable diagnostic modalities because there is no gold standard test for PS. As early diagnosis may prevent delayed diagnosis that results in chronic somatic dysfunction and muscle weakness, a screening test with high sensitivity could guide clinicians in performing the next appropriate step in diagnosing PS.

Aim: The purpose of this study is to determine the sensitivity, specificity, and best cut-off point of ultrasound-guided PM thickness in PS.

Method: This case-control study was conducted in a general hospital in Tangerang during a 3-month period. We recruited 58 patients clinically diagnosed with PS and 58 healthy patients (without a history of hip and buttock pain) during their visits to the outpatient clinic. All patients underwent ultrasound assessment to measure bilateral PM thickness. Sex, age, body mass index, history of micro-/macro-trauma, and prolonged sitting duration were recorded. Statistical analyses were performed using the Statistical Package for the Social Sciences version 25.

Result: The PS and control groups predominantly comprised female subjects, with mean ages of 51.79 ± 14.10 and 50.09 ± 13.26 years on PS and healthy subjects, respectively. The mean ultrasound-guided PM thickness was higher in PS subjects compared to healthy subjects with mean thicknesses of 1.16 ± 0.13 and 0.85 ± 0.11 cm, respectively (p < 0.05). The area under the receiver operating characteristic curve of the PM was 0.970 (95% confidence interval 0.943–0.998, p < 0.05). The best cut-off point defined by Youden's J index was 0.9950 cm for all PS subjects.

Conclusion: We propose 0.9950 cm as the cut-off point for diagnosing PS by ultrasound, which has the sensitivity and specificity of 94.8 and 87.9%, respectively.

Ultrasonography Findings in the Proximal Sciatic Nerve and Deep Gluteal Muscles in 29 Dogs With Suspected Sciatic Neuritis

The present study aimed to describe the ultrasonography technique and analyze the ultrasonographic findings of the proximal sciatic nerve and deep gluteal muscles in dogs with suspected sciatic neuritis. The records of 29 dogs that underwent musculoskeletal ultrasound of the sciatic nerve and deep gluteal muscles were retrospectively evaluated. Both right and left sides were evaluated. Abnormal findings were unilateral in 28/29 (97%) of the dogs. The muscles examined included the piriformis muscle, gemelli muscles, internal obturator muscle, and medial gluteal muscle. Data included signalment, purpose of the dog, orthopedic examination findings, lameness examination findings, other diagnostic imaging findings, and ultrasonography findings. Irregular margins of the sciatic nerve were recorded in 76% of the dogs. The diameter of the sciatic nerve on the affected limb was significantly larger than the nerve on the contralateral, unaffected side (p < 0.00001). The mean ± standard deviation (SD) of the sciatic nerve inner diameter between the unaffected and affected limbs was 15 ± 14.66%. The mean ± SD in sciatic nerve outer diameter was 12 ± 7.71%. Abnormal ultrasonographic findings in at least one of the examined muscles were found in 28/29 (97%) of the dogs and included changes in echogenicity in 28/29 (97%) of the dogs, loss of detail in muscle fiber pattern in 5/29 (17%) of the dogs, and impingement between the sciatic nerve and piriformis muscle in 6/29 (21%) of the dogs. The most common underlying diagnosis was lumbosacral stenosis in 9/29 (31%) of the dogs. The most common sport was agility for 21/29 (71%) of the dogs. Repetitive jumping may predispose to both lumbosacral disease, through dynamic compression, and changes within the piriformis muscle, due to overuse of the muscle leading to irritation to sciatic nerve. Ultrasonography is considered a safe and non-invasive diagnostic method to evaluate the sciatic nerve and deep gluteal muscles of dogs, and provides additional guidance for diagnostics and rehabilitation planning. This is the first study documenting ultrasonography findings in a case series of the sciatic nerve and deep gluteal muscles and their pathology in dogs.

Ultrasound-guided injections in pelvic entrapment neuropathies

Pelvic entrapment neuropathies represent a group of chronic pain syndromes that significantly impede the quality of life. Peripheral nerve entrapment occurs at specific anatomic locations. There are several causes of pelvic entrapment neuropathies, such as intrinsic nerve abnormality or inflammation with scarring of surrounding tissues, and surgical interventions in the abdomen, pelvis and the lower limbs. Entrapment neuropathies in the pelvic region are not widely recognized, and still tend to be underdiagnosed due to numerous differential diagnoses with overlapping symptoms. However, it is important that entrapment neuropathies are correctly diagnosed, as they can be successfully treated. The lateral femoral cutaneous nerve, ischiadic nerve, genitofemoral nerve, pudendal nerve, ilioinguinal nerve and obturator nerve are the nerves most frequently causing entrapment neuropathies in the pelvic region. Understanding the anatomy as well as nerve motor and sensory functions is essential in recognizing and locating nerve entrapment. The cornerstone of the diagnostic work-up is careful physical examination. Different imaging modalities play an important role in the diagnostic process. Ultrasound is a key modality in the diagnostic work-up of pelvic entraptment neuropathies, and its use has become increasingly widespread in therapeutic procedures. In the article, the authors describe the background of pelvic entrapment neuropathies with special focus on ultrasound-guided injections.

Imaging of peripheral nerve causes of chronic buttock pain and sciatica

Chronic buttock pain is a common and debilitating symptom, which severely impacts daily activities, sleep, and may affect athletic performance. Lumbar spine, posterior hip, or hamstring pathology are usually considered as the primary diagnoses; however, pelvic neural pathology may be a significant cause of chronic buttock pain, particularly if there are prolonged (>6 months) buttock and/or radicular symptoms. The subgluteal space is the site of most pelvic causes of neural-mediated buttock pain, primarily relating to entrapment neuropathy of the sciatic nerve (deep gluteal syndrome), although other nerves within the subgluteal space including the gluteal nerves, pudendal nerve, and posterior cutaneous nerve of thigh may also be involved. Additionally, cluneal nerve entrapment at the iliac crest may result in "pseudo-sciatica". Anatomical variants of the pelvic girdle muscles and functional factors, including muscle spasm and pelvic instability, may contribute to development of deep gluteal syndrome, along with neural senescence. Imaging findings primarily relate to the presence of sciatic neuritis and peri-sciatic pathology, including neural compression and peri-neural adhesions or fibrosis. This imaging review describes the causes, magnetic resonance imaging and ultrasound imaging findings and imaging-guided treatment of pelvic neural causes of chronic buttock pain and sciatica.

Surgical and Non-surgical Treatment Options for Piriformis Syndrome: A Literature Review

Context

Piriformis syndrome is a solely clinical diagnosis that often eludes the practitioner and goes underdiagnosed. PS is a pain syndrome and for those it affects, causes persistent pain and limits daily activity and work capacity. It is a form of deep gluteal syndrome that needs to be considered on the differential of low back pain as it comprises between 0.3% - 6% of all low back pain cases and is frequently underdiagnosed. Piriformis syndrome may be primary due anatomic anomalies or secondary, though the majority of cases are secondary to some insult. The objective of this manuscript is to provide a description of the epidemiology and presentation of piriformis as well as both non-operative and operative treatment options. We review all of the recent clinical evidence regarding the aforementioned therapies.

Evidence Acquisition

Literature searches were performed using the below MeSH Terms using Mendeley version 1.19.4. Search fields were varied until further searches revealed no new articles. All articles were screened by title and abstract. Decision was made to include an article based on its relevance and the list of final articles was approved three of the authors. This included reading the entirety of the article. Any question regarding the inclusion of an article was discussed by all authors until an agreement was reached.

Results

Medical management and physical therapy show some promise; however, when conservative treatment fails minimally invasive methods such as steroid injections, botulinum toxin injections, dry needling are all efficacious and there is substantial clinical evidence regarding these therapies. In those patients in which minimally invasive techniques do not result in an adequate relief of pain and return of function, endoscopic release can be considered. Endoscopic release is far superior to open release of the piriformis syndrome given the higher success and lower rate of complications.

Conclusions

Piriformis syndrome is an important differential diagnosis in the work up of lower back pain and should not be ruled out with proper examination and testing. Clinicians should consider medical management and conservative management in the initial treatment plan for piriformis syndrome. There are many options within the conservative management and the literature shows much promise regarding these. Physical therapy, steroid injections, botulinum toxin injections, and dry needling are all potentially effective therapies with few adverse effects. Surgical options remain as gold standard, but only when conservative management has failed and the symptoms are significant to affect daily living activities. Endoscopic decompression of the sciatic nerve with or without release of the piriformis muscle has a reported high likelihood of success and a low complication rate. Current literature supports the preference of the endoscopic approach over the open approach due to improved outcomes and decreased complications. Further research is to well define the metrics for the diagnosis of piriformis syndrome and may include a need to develop diagnostic criteria.

Clinico-radiological review of peripheral entrapment neuropathies - Part 2 Lower limb

PURPOSE

This review discusses the relevant anatomy, etiopathogenesis, current notions in clinical and imaging features as well as management outline of lower limb entrapment neuropathies.

METHODS

The review is based on critical analysis of the current literature as well as our experience in dealing with entrapment neuropathies of the lower limb.

RESULTS

The complex anatomical network of nerves supplying the lower extremities are prone to entrapment by a heterogenous group of etiologies. This leads to diverse clinical manifestations making them difficult to diagnose with traditional methods such as clinical examination and electrodiagnostic studies. Moreover, some of these may mimic other common conditions such as disc pain or fibromyalgia leading to delay in diagnosis and increasing morbidity. Addition of imaging improves the diagnostic accuracy and also help in correct treatment of these entities. Magnetic resonance imaging is very useful for deeply situated nerves in pelvis and thigh while ultrasound is well validated for superficial entrapment neuropathies.

CONCLUSION

The rapidly changing concepts in these conditions accompanied by the advances in imaging has made it essential for a clinical radiologist to be well-informed with the current best practices.

Lower extremity entrapment neuropathies

Entrapment neuropathies are frequently encountered by rheumatologists, not only because they are common but also because of their association with certain rheumatological and systemic disorders. Recognizing entrapment neuropathy early can help avoid progressive neurological deficits, as well as facilitate appropriate treatment measures, which can effectively minimize a patient's symptoms. Entrapment neuropathies may be distinguished from other musculoskeletal causes of lower extremity pain by identifying characteristic patterns of weakness and/or sensory loss, so a focused bedside neurological examination is key for diagnosis. In this chapter, we review the most common entrapment neuropathies that occur in the lower extremities, review the relevant neuroanatomy, outline a diagnostic approach to distinguish them from other mimics, and highlight appropriate management options.

Feasibility and Reliability of an Ultrasound Examination to Diagnose Piriformis Syndrome

OBJECTIVE

We explored the diagnostic performance of ultrasound examinations in the diagnosis of piriformis syndrome (PS).

METHODS

In our single-center retrospective study, 52 patients with a diagnosis of PS and 50 healthy volunteers were enrolled to undergo ultrasound examination of the piriformis and sciatic nerve. The thicknesses of the piriformis and the diameter of the sciatic nerve were measured to compare the differences between the patients with PS and healthy volunteers. The diagnostic performance of ultrasound examinations was assessed by constructing a receiver operating characteristic curve and calculating the area under the curve.

RESULTS

In patients with PS, the piriformis and sciatic nerve were enlarged on the abnormal side compared with the asymptomatic side, accompanied by a decreased echo intensity and an unclear perineurium. In addition, the piriformis thickness and sciatic nerve diameter of those with PS were significantly greater than were those of the healthy volunteers. The diagnostic performance of ultrasonography was significant. The area under the receiver operating characteristic curve for piriformis thickness and sciatic nerve diameter to discriminate between the abnormal and asymptomatic sides was 0.778 and 0.871, respectively.

CONCLUSION

Ultrasound examinations can assist in the clinical diagnosis of PS and have the potential to be an alternative method for the diagnosis of PS for most musculoskeletal clinicians.