Piriformis syndrome
Template:Cs1 config Template:Use dmy dates Template:Infobox medical condition (new)
Piriformis syndrome is a condition which is believed to result from nerve compression at the sciatic nerve by the piriformis muscle.<ref name=Cas2015>Template:Cite journal</ref><ref name=Mil2012>Template:Cite journal</ref> It is a specific case of deep gluteal syndrome.<ref>Template:Cite journal</ref>
The largest and most bulky nerve in the human body is the sciatic nerve. Starting at its origin it is 2 cm wide and 0.5 cm thick. The sciatic nerve forms the roots of L4-S3 segments of the lumbosacral plexus. The nerve will pass inferiorly to the piriformis muscle, in the direction of the lower limb where it divides into common tibial and fibular nerves.<ref>Template:Cite journal</ref> Symptoms may include pain and numbness in the buttocks and down the leg.<ref name="Cas2015" /><ref name="Mer2014Pro" /> Often symptoms are worsened with sitting or running.<ref name="Mer2014Pro">Template:Cite web</ref>
Causes may include trauma to the gluteal muscle, spasms of the piriformis muscle, anatomical variation, or an overuse injury.<ref name=Cas2015/> Few cases in athletics, however, have been described.<ref name=Cas2015/> Diagnosis is difficult as there is no definitive test.<ref name=Mil2012/><ref name=Hop2017>Template:Cite journal</ref> A number of physical exam maneuvers can be supportive.<ref name=Mer2014Pro/> Medical imaging is typically normal.<ref name=Cas2015/> Other conditions that may present similarly include a herniated disc.<ref name=Mer2014Pro/>
Treatment may include avoiding activities that cause symptoms, stretching, physiotherapy, and medication such as NSAIDs.<ref name=Mer2014Pro/><ref name=Mil2012/> Steroid or botulinum toxin injections may be used in those who do not improve.<ref name=Cas2015/> Surgery is not typically recommended.<ref name=Mer2014Pro/> The frequency of the condition is unknown, with different groups arguing it is more or less common.<ref name=Hop2017/><ref name=Cas2015/>
Anatomy
Template:See alsoTemplate:See alsoThe piriformis is a flat, pear-shaped muscle. The thicker side of the piriformis is medial (closer to the center of the body). The function of the piriformis is as an external thigh rotator. When the hip is extended, such as standing, the piriformis rotates the thigh outwards. When the hip is flexed, such as sitting, the piriformis abducts the hip (spreading the legs). The piriformis originates at the anterior surface of the sacrum, passes through the greater sciatic foramen, and inserts at the greater trochanter.<ref>Template:Cite book</ref>
The sciatic nerve is the largest peripheral nerve in the body and innervates significant portions of the skin and muscles of the thigh, leg, and foot. The sciatic nerve originates from spinal nerves L4-S3. It forms in the pelvis from nerves of the sacral plexus, and exits the greater sciatic foramen just underneath the piriformis. A number of anatomic variations exist in the branching pattern of sciatic nerve around the piriformis, such as passing over, through, or under the piriformis, as well as early branching into the tibial nerve and common peroneal nerve before passing the piriformis.<ref>Template:Cite book</ref>
Signs and symptoms
Patients with piriformis syndrome may have some of the following symptoms:
- sciatica, or pain felt in the leg along the distribution of the sciatic nerve<ref name=":9" /><ref name=":10" /><ref name="Hopayian-2010" /><ref name="Hop2017" /><ref name="Mer2014Pro" />
- external tenderness near the greater sciatic notch<ref name="Hopayian-2010" /><ref name="Hop2017" />
- buttock pain<ref name="Hopayian-2010" /><ref name="Hop2017" />
- pain on any maneuver that increases piriformis muscle tension<ref name="Hopayian-2010" /><ref name="Hop2017" />
- pain aggravated on sitting<ref name="Hopayian-2010" /><ref name="Hop2017" />
- limitation of the straight leg raise<ref name="Hop2017" />
There are also some reports of gluteal atrophy on the same side as the symptoms for chronic cases, but this is less commonly seen.<ref name=":9" /><ref>Template:Cite journal</ref>
Etiology
Causes of piriformis syndrome include the following
- Trauma to the hip or buttock area such as a fall is the most common precipitating factor.<ref name="pmid17385355">Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name=":9" />
- Athletes and weightlifters overtraining or acquiring a repetitive strain injury, causing piriformis irritation or hypertrophy<ref name=":10">Chang A, Ly N, Varacallo M. Piriformis Injection. [Updated 2023 Aug 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448193/</ref><ref>Template:Cite journal</ref>
- Sitting for prolonged periods (office workers, taxi drivers, bicycle riders)
- Anatomic variations which might cause piriformis syndrome have been reported (e.g. sciatic nerve branching, bipartite piriformis muscle); however, comprehensive anatomic data on the piriformis morphology is lacking.<ref>Template:Cite journal</ref> In other words, patients with piriformis syndrome sometimes have anatomic variations suggesting a cause, but it's not known if these anatomic variations actually occur more frequently in patients with piriformis syndrome.
- A heavily scrutinized anatomic variation involves sciatic nerve branching around the piriformis using the 6-category classification first described by Beaton and Anson. In this classification, the normal anatomy (type A) seen in about 80% of people is where the sciatic nerve passes under the piriformis muscle at the greater sciatic notch. However, the incidence of atypical anatomic variations (types B-F) has not been found to differ significantly between piriformis syndrome patients and cadavers, leading to doubt about the importance of this anatomic variation in the development of piriformis syndrome.<ref>Template:Cite journal</ref>
Pathophysiology
Template:See also Under certain conditions, the piriformis muscle is believed to compress the sciatic nerve, also known as sciatic nerve entrapment, causing sciatica.<ref name="Mil2012" /> The pathophysiology of piriformis syndrome is not completely understood.<ref name=":7" /> There are several mechanisms by which the piriformis muscle is thought to be capable of compressing the sciatic nerve, and these mechanisms are not mutually exclusive.
Piriformis muscle spasm may compress the sciatic nerve.<ref name=":1" /> As the piriformis muscle spasms, it shortens and becomes harder, applying greater pressure on the sciatic nerve against the ischium at the inferior greater sciatic foramen. The empirical evidence supporting this is that patients can often see immediate and permanent relief from local anesthetic and the effectiveness of Botox injections as a muscle relaxer.<ref name=":1" /><ref name=":18" />
Piriformis muscle hypertrophy may cause crowding around the greater sciatic foramen.<ref>Template:Cite journal</ref><ref name="PopeBloem2014">Template:Cite book</ref> Both the piriformis and sciatic nerve pass through the greater sciatic foramen and the deep gluteal space. An enlarged (hypertrophic) piriformis muscle may place pressure on nearby structures. The empirical evidence supporting this is that ipsilateral (same-side) piriformis hypertrophy is a common image finding in piriformis syndrome,<ref name=":13">Template:Cite journal</ref> and that botox injections reduce symptoms (by paralyzing a muscle for months the muscle shrinks).
A single injury, or many smaller injuries, may predispose the piriformis muscle to fibrosis, making the tissue tougher and tighter, applying greater pressure on the sciatic nerve against the ischium at the greater sciatic foramen.<ref>Template:Cite journal</ref> Or the formation of scar tissue from a hematoma might restrict normal movement of the sciatic nerve as it passes by the piriformis muscle.<ref name="Cas2015" />
The piriformis may be capable of dynamically compressing the sciatic nerve with certain hip movements.<ref>Template:Cite journal</ref> The empirical evidence supporting this is the presence of electrophysiology testing abnormalities (delayed H reflex) of the sciatic nerve during the FAIR test,<ref>Template:Cite journal</ref> as well as the improvement of these electrophysiology results after successful treatment.<ref>Template:Cite journal</ref>
Diagnosis
Piriformis syndrome does not yet have a validated set of diagnostic criteria;<ref name="Hop2017" /><ref name=":0" /><ref name=":10" /> however, the diagnosis is primarily clinical, involving a physical examination and an evaluation of patient history.<ref name="Kirschner-2009">Template:Cite journal</ref> Imaging can assist in excluding other conditions with similar symptoms, such as lumbar disc herniation and spinal stenosis.<ref name=":0" /> Diagnostic injections of anesthetic into the piriformis may be used to confirm the diagnosis.<ref name=":0" /> Often piriformis syndrome is a diagnosis of exclusion.<ref name=":0" />
A complete exam of low back, pelvis, buttocks, lower extremities may be necessary to rule out differential diagnoses.<ref name=":0" /> Sciatica secondary to conditions to be ruled out include spinal disc herniation, facet arthropathy, spinal stenosis, lumbar muscle strain, wallet neuritis<ref>Template:Cite journal</ref> (sitting on a thick wallet), endometriosis, pelvic tumors, gluteal varicosities, and inferior gluteal artery aneuyrism.<ref name="Kirschner-2009" /><ref name="Cas2015" /> Pathology in the sacroiliac joint region, Sacroiliac joint dysfunction and Sacroiliitis are other conditions that present with pain in the low back and hip regions, which may radiate down along the back of the thigh, rarely going down below knee.<ref name=":0" />
The clinical signs may involve unilateral or bilateral buttocks pain that fluctuates throughout the day, the absence of lower back pain, buttocks or sciatica pain when in the sitting position (especially for prolonged periods), sciatic pain with fluctuating periods without pain throughout the day, buttocks pain near the piriformis.<ref name=":12">Template:Cite journal</ref> The pain may be exacerbated with any activity that causes flexion of the hip such as stooping or lifting.<ref name=":9" />
In a physical exam the piriformis can be palpated externally though it is so deep that it may not be possible to assess tenderness. If the piriformis can be located it may feel cord-like.<ref name=":9" /> Internal palpation is also possible which allows better access to assess piriformis muscle tenderness.<ref name=":0" /> There are a number of maneuvers that can be done in an attempt to provoke sciatic nerve compression. These tests either stretch the piriformis or cause the piriformis to contract. The most common tests used are the Freiberg test, FAIR test (flexion, adduction, internal rotation), Beatty test, Pace test, seated piriformis stretch test, and straight leg raise (Lasegue sign).<ref name=":0" />
Diagnostic modalities such as EMG, x-rays, ultrasound, CT, MRI is mostly used to exclude other conditions.<ref name=":0" /><ref name="Kirschner-2009" /> For example, and MRI of the spine can rule out conditions like radiculopathy and spinal stenosis. MRI of the pelvis can rule out conditions like pelvic tumors.<ref name=":0" /> MRI and ultrasound can be used to observe side-to-side differences, a common finding where the symptomatic side often exhibits increased piriformis size measured as increased thickness and cross-sectional area.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name=":1" /> Specialized sequences and protocols of MRI can be used for sciatic nerve imaging, namely MRN (magnetic resonance neurography) and DTI (diffusion tensor imaging). MRN can assess changes in the path, thickness, and signal intensity of the sciatic nerve.<ref>Template:Cite journal</ref> DTI uses the anisotropic diffusion of water to assess structural and functional properties of nerves.<ref>Template:Cite journal</ref> Both MRN and DTI can localize nerve lesions, their extension, and their spatial distribution due to conditions such as entrapment.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> MRN and DTI have also been used to visualize sciatic nerve lesions to diagnose of piriformis syndrome.<ref name=":1" /><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> However, magnetic resonance neurography is considered "investigational/not medically necessary" by some insurance companies. Neurography can determine whether or not a patient has a split sciatic nerve or a split piriformis muscle – this may be important in getting a good result from injections or surgery.
Image-guided injections into the piriformis muscle can assist in the diagnosis.<ref name=":0" /> Injections usually involve delivering anesthetic to the piriformis muscle to paralyze it.<ref name=":1" /> In the event of a piriformis muscle spasm causing sciatic nerve compression, paralyzing the piriformis muscle will temporarily relieve the symptoms.<ref name=":1" /> If successful, there should be a complete or near-complete relief of pain for 4–6 hours.<ref name=":1" /><ref name=":11" /> Needle guidance can be done with fluoroscopy, ultrasound, CT, or MRI.<ref name="Kirschner-2009" /> Ultrasound is a popular choice due to its low cost, lack of radiation, and accessibility, but lacks the spatial resolution of CT/MRI.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> While there is no gold standard test to diagnose piriformis syndrome,<ref name="Cas2015" /> in deep gluteal syndrome, the generalization of extra-spinal sciatica in the deep gluteal space, diagnostic blocks are considered the gold standard for differentiating alternate sources of pain.<ref>Template:Cite journal</ref>
Prevention
The most common etiology of piriformis syndrome is that resulting from a specific previous injury due to trauma.<ref name="Boyajian-O'Neill, L. 2008">Template:Cite journal</ref> Large injuries include trauma to the buttocks while "micro traumas" result from small repeated bouts of stress on the piriformis muscle itself.<ref>Template:Cite journal</ref> To the extent that piriformis syndrome is the result of some type of trauma and not neuropathy, such secondary causes are considered preventable, especially those occurring in daily activities: according to this theory, periods of prolonged sitting, especially on hard surfaces, produce minor stress that can be relieved with bouts of standing. An individual's environment, including lifestyle factors and physical activity, determine susceptibility to trauma of any given type. Although empirical research findings on the subject have never been published, many believe that taking sensible precautions during high-impact sports and when working in physically demanding conditions may decrease the risk of experiencing piriformis syndrome, either by forestalling injury to the muscle itself or injury to the nerve root that causes it to spasm. In this vein, proper safety and padded equipment should be worn for protection during any type of regular, firm contact (e.g. American football). In the workplace, individuals are encouraged to make regular assessments of their surroundings and attempt to recognize those things in their routine that may produce micro or macro traumas. No research has substantiated the effectiveness of any such routine, however, and participation in one may do nothing but heighten an individual's sense of worry over physical minutiae while have no effect in reducing the likeliness of experiencing or re-experiencing piriformis syndrome.Template:Citation needed
Other suggestions from some researchers and physical therapists have included prevention strategies including warming up before physical activity, practising correct exercise form, stretching and doing strength training, though these are often suggested for helping treat or prevent any physical injury and are not piriformis-specific in their approach<ref>Template:Cite journal</ref> As with any type of exercise, it is thought that warmups will decrease the risk of injury during flexion or rotation of the hip. Stretching increases range of motion, while strengthening hip adductors and abductors theoretically allows the piriformis to tolerate trauma more readily.<ref name="Boyajian-O'Neill, L. 2008"/>
Treatment
The initial treatments are often focused on avoiding/relieving pain such as activity modification (e.g. avoidance of activities that cause pain), heat/ice, NSAIDs, analgesics, muscle relaxants, and medications for neuropathic pain.<ref name=":8" /><ref name=":0" /><ref name="Kirschner-2009" /><ref name="Cas2015" /> Physical therapy, especially piriformis stretching, is often done concomitantly while treating pain.<ref name="Cas2015" /><ref name=":0" /> For patients who have failed physical therapy, injections into the piriformis muscle using some combination of anesthetic/steroids/botox may be considered.<ref name=":0" /><ref name="Kirschner-2009" /><ref name="HayekShah2015">Template:Cite book</ref> In refractory cases, surgery may be indicated where the sciatic nerve is dissected or the piriformis muscle/tendon is cut.<ref name="Kirschner-2009" /><ref name=":7" />
Data on treatment outcomes is very limited.<ref name="Cas2015" /> In a study of 42 patients with clinically suspected piriformis syndrome with normal MRI/CT imaging findings, 41 saw complete resolution of symptoms within 36 days. Of those 41 patients, 19 had spontaneous resolution of symptoms (46%), 13 improved with NSAIDs only (32%), and 9 improved with NSAIDs and physical therapy (22%).<ref name=":13" /> In a study of 14 patients, all (100%) saw improvement with physical therapy and/or injections. Of these patients, 9 (64%) improved with physical therapy alone. The remaining 5 (36%) improved with injections (steroids or ozone). However, 6 months after the end of treatment, only 5/14 patients (36%) had complete resolution of pain.<ref name="J.L. Ruiz-Arranz">Template:Cite journal</ref> In a study of 250 patients, medication and physical therapy led to complete pain relief in 51% of patients. Of those who did not see improvement with physical therapy, botox injections led to greater than 50% pain relief in 77% of patients. Of those who also did not see improvement with injections, surgery led to greater than 50% pain relief in 79% of patients.<ref name=":12" /> Some caution should be applied in interpreting these results as therapy is usually not compared to an untreated control group (patients sometimes get better on their own without treatment), and the diagnosis of piriformis syndrome isn't validated (meaning different studies can select patients differently).<ref name=":8" />
Physical therapy
Physical therapy for piriformis syndrome follows general rehabilitation principles for musculoskeletal conditions.<ref name=":8">Template:Cite book</ref> The goals of physical therapy are to reduce piriformis muscle tightness, improve spine/hip/pelvis mobility, and restore normal biomechanics to the spine/hip/pelvis.<ref name=":0" /><ref name=":12" />
The rehabilitative protocol usually involves piriformis stretching, gluteal muscle massage (to massage the piriformis below it), lumbosacral stabilization (e.g. abdominal muscle exercises, spine stretching), hip strengthening/stretching, and the correction of biomechanical errors.<ref name=":0" /><ref name=":8" /><ref name=":12" /> Direct application of heat and ultrasound (which generates heat) and are often suggested before physical therapy.<ref name="Kirschner-2009" /><ref>Template:Cite journal</ref> Heat will enhance muscle elasticity and blood flow, which helps to increase the efficacy of stretching.<ref>Template:Cite journal</ref> Piriformis stretching is meant to reduce muscle tightness and lengthen the muscle which may relieve pressure on the sciatic nerve.<ref name=":0" /> Massage is meant to break up trigger points, increase blood circulation, and lengthen the muscle fibers.<ref name=":0" /> Strengthening abdominal muscles (part of core stabilization) is to improve spine stability and to avoid compensatory tension on the hip and buttocks.<ref>Template:Cite journal</ref> Stretching the spine and hip muscles is meant to increase flexibility and range of motion. The purpose of correcting poor biomechanics in the hip/pelvis/spine is that they move in coordination, so a biomechanical error may have cascading effects.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
In one study, the cure rate of physiotherapy for 250 piriformis syndrome patients was found to be approximately 50% after three months.<ref name=":12" /> However, this study did not use a control group for physiotherapy and so this may simply reflect the natural history of the syndrome. In other words, patients may often just get better on their own without any particular treatment. The exact benefits of physiotherapy for piriformis syndrome are unclear as well-designed, randomized trials are extremely limited.<ref name=":8" /> However, physiotherapy is safe and relatively inexpensive, so it is often recommended before more invasive and expensive treatments.
Local injections
Injections are part of multi-modal therapy and can be therapeutic.<ref name=":0" /><ref name="Cas2015" /> They may be used with conservative treatments like physical therapy or after the failure of conservative treatments. Injections deliver medication directly to the piriformis muscle through a needle. The needle is placed into the piriformis muscle with image guidance such as fluoroscopy, ultrasound, CT, or MRI.<ref name="Cas2015" /><ref name="Kirschner-2009" /> Ultrasound is a popular choice due to a balance of accuracy, accessibility, lack of radiation exposure, and affordability.<ref name=":0" /><ref name="Cas2015" />
The medications injected are local anesthetics (e.g. lidocaine, bupivacaine), corticosteroids, and Botulinum toxin (Botox, BTX), which may be used together or in combination.<ref name="Cas2015" /><ref name="Kirschner-2009" /> Local anesthetic will temporarily paralyze a muscle in the hope that it breaks the cycle of chronic muscle spasm.<ref name=":1" /> The duration is in hours and consequently doesn't lead to long lasting relief from the direct action of the anesthetic.<ref name=":11">Template:Cite journal</ref> Corticosteroids is used for its anti-inflammatory effects.<ref>Hodgens A, Sharman T. Corticosteroids. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554612/</ref> The duration is unclear but somewhere between 1 week and 3 months.<ref>Template:Cite journal
</ref> Botulinum Toxin will paralyze a muscle with a much longer duration than local anesthetics, up to 3 months.<ref name="Kirschner-2009" /> By paralyzing a muscle for so long the muscle will atrophy (shrink in size), reducing pressure on nearby structures such as the sciatic nerve.<ref name="Kirschner-2009" /> In addition to helping break the cycle of chronic muscle spasms, it reverses piriformis hypertrophy where the muscle is enlarged and presses on the sciatic nerve.<ref name="Kirschner-2009" /> Though the piriformis muscle becomes inactivated for months, the loss of piriformis muscle function does not cause any deficit in strength or gait as the surrounding muscles quickly take over its role.<ref name=":9">Template:Cite journal</ref>
Typically the combination of therapies is local anesthetics with corticosteroids (LA+CS), or Botulinum toxin (BTX). Both are more effective than placebo.<ref name=":18" /><ref name=":19">Template:Cite journal</ref> Comparing local anesthetic with corticosteroids against Botulinum toxin is difficult because existing studies tend to lack controls<ref name=":19" /> which means that the effect of the treatment under observation is confounded with the natural history of the disease (patients with piriformis syndrome often see their symptoms resolve even without treatment). When comparative studies exist, Botulinum toxin is found to be more effective and local anesthetic with corticosteroids.<ref name=":18" /><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Citation</ref>
Injections may be more or less curative (with no return to pain), or may have limited timespans of effectiveness.
Surgery
Surgical intervention may be considered when conservative treatments fail.<ref name=":3" /> Surgery for piriformis syndrome involves resection of the piriformis tendon (or muscle) and a sciatic nerve decompression.<ref name=":0">Template:Cite journal</ref><ref name=":1">Template:Cite journal</ref> This surgery can be done with open surgery or endoscopically.<ref name=":2" /> While there is no difference seen in outcomes between open and endoscopic surgery, the endoscopic approach has a lower complication rate<ref name=":2">Template:Cite journal</ref> and is significantly less invasive (open surgery can involve a 10 cm incision<ref name=":3">Template:Cite journal</ref>).
Piriformis syndrome surgery is still in the preliminary stages and so there are no randomized, prospective trials or cross-sectional studies.<ref name="Hop2017" /> Existing evidence is largely retrospective studies and systematic reviews of those studies. Surgical outcomes are typically assessed by VAS scores (numerical pain scores) and various questionnaires (e.g. Oswestry Disability Index), potentially with a follow up of up to 2 years;<ref name=":3" /><ref name=":4">Template:Cite journal</ref><ref name=":1" /> however, no validated outcome measure exists.<ref name=":1" />
For surgery, results typically show that at least 80% of patients see improvement.<ref name=":1" /><ref name=":4" /><ref name=":3" /><ref name=":5">Template:Cite journal</ref><ref name=":12" /> When VAS scores (pain scores) are measured, patients typically have severe pain (>7.5) before surgery and at most mild pain (< 3.5) after surgery.<ref>Template:Cite journal</ref><ref name=":4" /><ref name=":3" /><ref name=":5" /> A systematic review of deep gluteal syndrome (of which piriformis syndrome is a major cause) found consistently positive results for surgeries in the included studies.<ref name=":2" />
Failure may in part be due to an incorrect diagnosis.<ref name="Emedicine308798">Template:EMedicine</ref><ref name=":5" /> Piriformis syndrome does not have well-validated diagnostic criteria and consequently some patients being treated for piriformis syndrome may have a different underlying condition with a similar symptom profile.<ref name=":0" />
Epidemiology
Piriformis syndrome (PS) data is often confused with other conditions<ref name="Boyajian-O'Neill, L. 2008"/> due to differences in definitions, survey methods and whether or not occupational groups or general population are surveyed.<ref name="Hopayian-2010">Template:Cite journal</ref> This causes a lack of group harmony about the diagnosis and treatment of PS, affecting its epidemiology.<ref name="Papadopoulos-2004">Template:Cite journal</ref> In a study, 0.33% of 1293 patients with low back pain cited an incident for PS.<ref name="Papadopoulos-2004"/> A separate study showed 6% of 750 patients with the same incidence.<ref name="Papadopoulos-2004"/> About 6–8% of low back pain occurrences were attributed to PS,<ref name="Fishman-2002">Template:Cite journal</ref><ref name="Kirschner-2009"/> though other reports concluded about 5–36%.<ref name="Boyajian-O'Neill, L. 2008"/> In a survey conducted on the general population, 12.2–27% included a lifetime occurrence of PS, while 2.2–19.5% showed an annual occurrence. However, further studies show that the proportion of the sciatica, in terms of PS, is about 0.1% in orthopaedic practice.<ref name="Hopayian-2010"/> This is more common in women with a ratio of 3 to 1<ref name="Papadopoulos-2004"/> and most likely due to the wider quadriceps femoris muscle angle in the os coxae.<ref name="Boyajian-O'Neill, L. 2008"/> Between the years of 1991 and 1994, self-selecting patients seeking piriformis syndrome treatment from a group of American physicians had the following distribution: 75% were in New York, Connecticut, New Jersey, Pennsylvania; 20% in other American urban centers; and 5% in North and South America, Europe, Asia, Africa and Australia.<ref name="Fishman-2002"/> The common ages of occurrence happen between thirty and forty, and are scarcely found in patients younger than twenty;<ref name="Papadopoulos-2004"/> this has been known to affect all lifestyles.<ref name="Boyajian-O'Neill, L. 2008"/>
Piriformis syndrome is often left undiagnosed and mistaken with other pains due to similar symptoms with back pain, quadriceps pain, lower leg pain, and buttock pain. These symptoms include tenderness, tingling and numbness initiating in low back and buttock area and then radiating down to the thigh and to the leg.<ref>Template:Cite journal</ref> A precise test for piriformis syndrome has not yet been developed and thus hard to diagnose this pain.<ref name="Chen, C.K.">Template:Cite journal</ref> The pain is often initiated by sitting and walking for a longer period.<ref>Template:Cite journal</ref> In 2012, one study found that 17.2% of low back pain patients met a clinical diagnosis for piriformis syndrome.<ref name= "Chen, C.K."/> Piriformis syndrome does not occur in children, and is mostly seen in women of age between thirty and forty. This is due to hormone changes throughout their life, especially during pregnancy, where muscles around the pelvis, including piriformis muscles, tense up to stabilize the area for birth.Template:Citation needed<ref name="Papadopoulos-2004"/> In 2011, out of 263 patients between the ages of 45 and 84 treated for piriformis syndrome, 53.3% were female.Template:Citation needed Females are two times more likely to develop piriformis syndrome than males. Moreover, females had longer stay in hospital during 2011 due to high prevalence of the pain in females. The average cost of treatment was $29,070 for hospitalizing average 4 days.<ref name="Hcupnet.ahrq.gov (2010, 2011)">Hcupnet.ahrq.gov (2010, 2011) Healthcare Cost and Utilization ProjectTemplate:Full citation needed</ref> Template:Clear
History
The history of piriformis syndrome is interrelated to advances in understanding causes of sciatica. In 1933, the proposal of disc herniation as a cause of sciatica shifted attention to the spine.<ref>Template:Cite journal</ref> Although the concept of piriformis syndrome was conceptualized as early as 1928,<ref name=":6">Template:Cite book</ref> the incompletely understood pathology and lack of clear diagnostic criteria made this syndrome highly controversial.<ref name=":7">Template:Cite journal</ref> Advancements in medical technology like anesthesia, antibiotics, electrophysiology, imaging, image-guided injections, and surgery have revived interest around piriformis syndrome.<ref name=":18">Template:Cite journal</ref><ref name=":1" /><ref>Template:Cite journal</ref> Recently, advances in endoscopic surgery led to discoveries suggesting a broader classification was necessary to describe all the causes of sciatic nerve entrapment in the deep gluteal space.<ref name=":14">Template:Cite journal</ref> This broader classification is now called deep gluteal syndrome, of which piriformis syndrome is one cause.<ref name=":14" /><ref name=":0" />
Today piriformis syndrome is in the same place herniated disk once were – there is a link between the pathophysiology and the symptoms (it is clear why the most studied treatments work), but piriformis syndrome does not have a clear set of diagnostic criteria and a known prevalence.<ref name="Hop2017" /> Controlled trials are unlikely to proceed without a sufficiently high prevalence and reliable diagnosis; however, the prevalence cannot be determined without a reliable method of diagnosis.<ref name="Hopayian-2010" />
See also
- Deep gluteal syndrome
- Sciatica
- Nerve compression syndrome
- Piriformis muscle
- Sciatic nerve
- Muscle spasm