Re: piriformis syndrome

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http://emedicine.medscape.com/article/94554-treatment

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Piriformis Syndrome

Milton J Klein, DO, MBA, Consulting Physiatrist, Sewickley Valley Hospital, Allegheny General Hospital, Harmarville Rehabilitation Center, Ohio Valley General Hospital, and Aliquippa Community Hospital
Contributor Information and Disclosures

Updated: Nov 6, 2008

Background

Piriformis syndrome has been a controversial diagnosis since its initial description in 1928.¹ The condition usually is caused by a neuritis of the proximal sciatic nerve. The piriformis muscle can either irritate or compress the proximal sciatic nerve due to spasm and/or contracture, and this problem can mimic a diskogenic sciatica. Piriformis syndrome is also referred to as pseudosciatica, wallet sciatica, and hip socket neuropathy.

Related eMedicine topics:
Chronic Pelvic Pain
Piriformis Syndrome [Sports Medicine]

Pathophysiology

The piriformis muscle is flat, pyramid-shaped, and oblique. This muscle originates to the anterior of the S2-S4 vertebrae, the sacrotuberous ligament, and the upper margin of the greater sciatic foramen (see Image 1). Passing through the greater sciatic notch, the muscle inserts on the superior surface of the greater trochanter of the femur. With the hip extended, the piriformis muscle is the primary external rotator; however, with the hip flexed, the muscle becomes a hip abductor. The piriformis muscle is innervated by branches from L5, S1, and S2.

A lower lumbar radiculopathy may cause secondary irritation of the piriformis muscle, which may complicate diagnosis and hinder patient progress.

Many developmental variations of the relationship between the sciatic nerve in the pelvis and piriformis muscle have been observed.² In approximately 20% of the population, the muscle belly is split with 1 or more parts of the sciatica nerve dividing the muscle belly itself. In 10% of the population, the tibial/peroneal divisions are not enclosed in a common sheath. Usually, the peroneal portion splits the piriformis muscle belly, although in rare cases, the tibial division does so.

Involvement of the superior gluteal nerve usually is not seen in cases of piriformis syndrome. This nerve leaves the sciatic nerve trunk and passes through the canal above the piriformis muscle.

Blunt injury may cause hematoma formation and subsequent scarring between the sciatic nerve and short external rotators. Nerve injury can occur with prolonged pressure on the nerve or vasa nervorum.

The etiology of piriformis syndrome can be divided into the following categories:

• Hyperlordosis
• Muscle anomalies with hypertrophy
• Fibrosis (due to trauma)
• Partial or total nerve anatomical abnormalities

Other causes can include the following:

• Pseudoaneurysms of the inferior gluteal artery adjacent to the piriformis syndrome
• Bilateral piriformis syndrome due to prolonged sitting during an extended neurosurgical procedure
• Cerebral palsy
• Total hip arthroplasty
• Myositis ossificans
• Vigorous physical activity

Piriformis syndrome remains controversial because, in most cases, the diagnosis is clinical, and no confirm‎atory tests exist to support the clinical findings.

Papadopoulos and colleagues proposed the following classifications for piriformis syndrome³:

• Primary piriformis syndrome - This designation would apply to piriformis syndrome resulting from intrinsic pathology of the piriformis muscle itself, such as myofascial pain, anatomic variations, and myositis ossificans.
• Secondary piriformis syndrome (pelvic outlet syndrome) - This classification would encompass all other etiologies of piriformis syndrome, with the exclusion of lumbar spinal pathology.

Frequency

United States

Given the lack of agreement on exactly how to diagnose piriformis syndrome, estimates of the frequency of sciatica caused by piriformis syndrome vary from rare to approximately 6% of sciatica cases seen in a general family practice. Approximately 90% of adults have had at least 1 episode of disabling low back pain (LBP) in their lifetime.

Mortality/Morbidity

Piriformis syndrome is not life-threatening, but it can have significant associated morbidity. The total cost of low back pain and sciatica is significant, exceeding $16 billion in direct and indirect costs.

Sex

Some reports suggest a 6:1 female-to-male ratio for piriformis syndrome.

Clinical

History

Piriformis syndrome often is not recognized as a cause of low back pain (LBP) and associated sciatica. This clinical syndrome is due to a compression of the sciatic nerve by the piriformis muscle; it is identical in clinical presentation to LBP with associated L5, S1 radiculopathy due to diskogenic and/or lower lumbar facet arthropathy with foraminal narrowing. Not uncommonly, patients demonstrate both of these clinical entities simultaneously. This diagnostic dilemma highlights the need for patients with LBP and associated radicular pain to undergo a complete history and physical examination, including a digital rectal examination.

Many cases of refractory trochanteric bursitis are observed to have an underlying occult piriformis syndrome due to the insertion of the piriformis muscle on the greater trochanter of the hip. If a patient's trochanteric bursitis and piriformis syndrome are treated inadequately, both conditions remain resistant to medical management.

Physical

Examination findings may include the following:

• Piriformis muscle spasm often is detected by careful, deep palpation.
• A digital rectal examination may reveal a tenderness on the lateral pelvic wall that reproduces symptoms.
• The reproduction of sciatica-type pain with weakness results from resisted abduction/external rotation (Pace test).
• The Freiberg test is another diagnostic sign that elicits pain upon forced internal rotation of the extended thigh.
• The Beatty maneuver reproduces buttock pain by selectively contracting the piriformis muscle.⁴ The patient lies on the uninvolved side and abducts the involved thigh upward; this activates the ipsilateral piriformis muscle, which is a hip external rotator and, when the hip is flexed, an abductor.
• A painful point may be present at the lateral margin of the sacrum.
• Shortening of the involved lower extremity may be seen.
• The patient may have difficulty sitting due to an intolerance of weight bearing on the buttock.
• The patient may have the tendency to demonstrate a splayed foot on the involved side when in the supine position.
• Piriformis syndrome alone is rarely the cause of a focal neuromuscular impairment; either a sciatic mononeuropathy or an L5-S1 radiculopathy can mimic both of these conditions, obscuring diagnosis of piriformis syndrome.
• A Morton foot may predispose the patient to developing piriformis syndrome. The prominent second metatarsal head destabilizes the foot during the push-off phase of the gait cycle, causing foot pronation and internal rotation of the lower limb. As a compensatory mechanism, the piriformis muscle (external hip rotator) reactively contracts repetitively during each push-off phase of the gait cycle , leading to piriformis syndrome.

Causes

Approximately 50% of patients with piriformis syndrome have a history of trauma, with either a direct buttock contusion or a hip/lower back torsional injury. The remaining 50% of cases are of spontaneous onset, so the treating physician must have a high index of suspicion for the problem, lest it be overlooked.

Differential Diagnoses

Achilles Tendon Injuries and Tendonitis
Lumbar Facet Arthropathy
Lumbar Spondylolysis and Spondylolisthesis
Lumbosacral Radiculopathy
Myofascial Pain
Trochanteric Bursitis

Other Problems to Be Considered

Degenerative lumbar disk disease 
Buttock pain
Ischial tuberosity bursitis
Sciatica

Workup

Laboratory Studies

• Laboratory studies generally are not indicated in the diagnosis of piriformis syndrome.

Imaging Studies

• Diagnostic imaging of the lumbar spine is mandatory to exclude associated diskogenic and/or osteoarthritic contributing pathology.
• Reports in the literature on the piriformis muscle describe imaging by nuclear diagnostic studies and magnetic resonance imaging (MRI) of the pelvis,⁵ but these tests are neither practical nor reliable approaches to the diagnosis of piriformis syndrome. The history and clinical diagnostic examination provide the greatest and most specific diagnostic yield for the disorder.
• Magnetic resonance neurography is a newer, sensitive imaging technique that increases nerve conspicuity by suppressing the signal from adjacent soft tissue, including fat, bone, and muscle.⁶ The nerve itself contains minimal fat, and its signal is unsuppressed. According to Filler and colleagues, MR neurography demonstrated piriformis muscle asymmetry and sciatic nerve hyperintensity at the sciatic notch with 93% specificity.⁷ The investigators also found that the technique had a sensitivity of 64% with regard to distinguishing patients with piriformis syndrome from persons who, despite having similar symptoms, did not have the condition (p<0.01).
• Diagnostic ultrasonographic imaging of the piriformis muscle for the assessment of muscle morphology has demonstrated a significant correlation of piriformis muscle morphology abnormality, especially in patients with lumbosacral/buttock pain and pain ascending stairs, referred pain to the posterior thigh on the symptomatic side, and reproduction of pain with needling of the piriformis muscle.

Other Tests

• The results of electrodiagnostic testing for piriformis syndrome usually are normal. Reports of positional H-reflex abnormalities can be found in the literature⁸; however, such findings have not been widely accepted or reproduced.

Rehabilitation Program

Physical Therapy

Because there is no definitive method to accurately diagnose piriformis syndrome, treatment regimens are controversial and have not been subjected to randomized, blind clinical trials. Despite this fact, numerous treatment strategies exist for patients with this condition.

Functional biomechanical deficits associated with piriformis syndrome may include the following:

• Tight piriformis muscle
• Tight hip external rotators and adductors
• Hip abductor weakness
• Lower lumbar spine dysfunction
• Sacroiliac joint hypomobility

Functional adaptations to these deficits include the following:

• Ambulation with the thigh in external rotation
• Functional limb length shortening
• Shortened stride length

Once the diagnosis has been made, these underlying, perpetuating biomechanical factors must be corrected.

Consider the use of ultrasonography and other heat modalities prior to physical therapy sessions. Before piriformis stretches are performed, the hip joint capsule should be mobilized anteriorly and posteriorly to allow for more effective stretching. Soft-tissue therapies for the piriformis muscle can be helpful, including longitudinal gliding with passive internal hip rotation, as well as transverse gliding and sustained longitudinal release with the patient lying on his/her side. Addressing sacroiliac joint and low back dysfunction also is important.

A home stretching program should be provided to the patient. These stretches are an essential component of the treatment program. During the acute phase of treatment, stretching every 2-3 hours (while awake) is a key to the success of nonoperative treatment. Prolonged stretching of the piriformis muscle is accomplished in either a supine or an orthostatic position with the involved hip flexed and passively adducted/internally rotated.

Medical Issues/Complications

Due to lack of objective clinical trials, no consensus exists on the overall treatment of piriformis syndrome. In most cases, conservative treatment (eg, stretching, manual techniques, injections, activity modifications, natural healing, modalities such as heat and ultrasonography) is successful.

Injection therapy can be incorporated if the situation is refractory to the aforementioned treatment program. For effective injection, the piriformis muscle must be localized manually by digital rectal examination. The piriformis muscle is then injected using a 3.5-inch (8.9-cm) spinal needle. Care must be taken to avoid direct injection of the sciatic nerve. Fluoroscopic or ultrasonographic imaging guidance can significantly enhance the effectiveness of the piriformis muscle injection, because this deep muscle cannot otherwise be directly visualized.^{9, 10}

Failure or partial failure of piriformis syndrome treatment may be secondary to an underlying obturator internus muscle injury, since this problem can be obscured by piriformis syndrome. The obturator internus muscle is inferior to the piriformis muscle and is also an external hip rotator. It originates at the medial surface of the pubis and passes through the lesser sciatic notch to insert on the greater trochanter. Physical examination demonstrates a trigger point that is more caudal than that in piriformis syndrome. Injection therapy would require direct visualization by fluoroscopy, due to the small size and location of this muscle.

Surgical Intervention

Surgical management is the treatment of last resort for piriformis syndrome. Surgery for this condition involves resection of the muscle itself or of the muscle tendon near its insertion at the superior aspect of the greater trochanter of the femur (as described by Mizuguchi).¹¹ These surgical procedures are described as effective, and they do not cause any associated superimposed postoperative disability.

Consultations

• Because of the enigmatic nature of piriformis syndrome, the initial consultation obtained from an orthopedic surgeon or a similar specialist usually is nonspecific. This disorder is considered to be a soft-tissue problem that presents as low back or buttock pain with sciatica.
• After all of the differential diagnoses have been excluded, consider piriformis syndrome. Due to the traumatic etiology of most cases, piriformis syndrome usually is associated with other, more proximal causes of low back pain, sciatica, and buttock pain (thereby further clouding the diagnosis).

Other Treatment

• Prior to physical therapy sessions, the use of ultrasonography and the spray-'n-stretch myofascial treatment is helpful.
• Manual muscle medicine, including facilitated positional release, may be helpful.
• Injections with steroids, local anesthetics, and botulinum toxin type B (12,500 U) have been reported in the literature for the management of piriformis syndrome.^{12, 13, 14, 15} No single technique is universally accepted. Localization techniques include manual localization of the muscle or localization with fluoroscopic, ultrasonographic, and electromyographic guidance. The piriformis muscle, after localization with a digital rectal examination, can be injected with a 3.5-inch (8.9-cm) spinal needle. Care should be taken to avoid direct injection of the sciatic nerve.
• Medical acupuncture, including vigorous, direct needling of the piriformis muscle performed in conjunction with the use of traditional meridian acupuncture, can be employed to remove the blockage of so-called “chi.”¹⁶

Related eMedicine topic:
Botulinum Toxin in Pain Management

Medication

No specific medication management of piriformis syndrome is indicated. The use of muscle relaxant medication can be beneficial, but this remains a nonspecific treatment.

Further Inpatient Care

• Inpatient care is necessary only if surgical intervention is warranted. Surgery is the last-resort treatment for severe cases of piriformis syndrome.

Further Outpatient Care

• Piriformis syndrome usually is treated effectively with conservative measures. Please refer to the Treatment section for a discussion of treatment recommendations.

Deterrence

• No method of preventing piriformis syndrome has been demonstrated. The best means of prevention is to maintain biomechanical balance through the restoration of a more physiologic weight-bearing distribution; this necessitates a level pelvis/sacral base and equal leg lengths, which can be achieved by using heel-lift therapy if necessary. This treatment approach also prevents recurrences of piriformis syndrome, especially if the underlying etiology is a leg-length discrepancy. The patient also must engage in a general stretching program that includes the bilateral piriformis muscles.

Complications

• The most significant complication of piriformis syndrome is a failure to recognize, diagnose, and treat this disabling condition. If left untreated, a patient may undergo unsuccessful back surgery for a disk herniation; however, a coexisting occult piriformis syndrome can result in a failed back syndrome.
• Another complication is inadvertent direct injection of the sciatic nerve, which usually results in a nondisabling and temporary sciatic mononeuropathy.

Prognosis

• The prognosis of piriformis syndrome depends on early recognition and treatment. Because it is a soft-tissue syndrome, the condition has a tendency to become chronic, usually due to late diagnosis and treatment (which lead to a less favorable prognosis).

Patient Education

• For conservative measures to be effective, the patient must be taught, via an aggressive, home-based stretching program, to maintain piriformis muscle flexibility. He/she must comply with the program even beyond the point of discontinuation of formal medical treatment.

Miscellaneous

Medicolegal Pitfalls

• The greatest medical/legal concern is either misdiagnosis or a failure to diagnose piriformis syndrome. In most cases, the diagnosis is one of exclusion. Therefore, if piriformis syndrome is not in the differential diagnosis list, it may be overlooked. The patient becomes a chronic pain patient doomed to a lifetime of disability and chronic management with medication.
• Because the diagnosis usually is elusive, missing the diagnosis does not constitute malicious negligence and, therefore, rarely would be sufficient grounds alone for a medical malpractice lawsuit.
• Piriformis syndrome may be a secondary perpetuating factor underlying chronic, posttraumatic, intractable low back pain. Negligent misdiagnosis or delayed diagnosis of this condition has caused a significant degree of unnecessary disability and financial loss.

Special Concerns

• In female patients, piriformis syndrome may be a cause of dyspareunia, but again, this connection becomes impossible to prove. Diagnosis of piriformis syndrome requires a high index of suspicion by either the primary care physician or the obstetric/gynecologic specialist/surgeon. A bimanual, simultaneous vaginal-rectal examination of female patients to determine this soft-tissue diagnosis helps the physician to prescribe appropriate treatment.
• Although it is a misdiagnosed etiology of low back pain/sciatica, piriformis syndrome can be a significant cause of soft-tissue pain and disability. In order for the condition to be accurately diagnosed, a skillful, attentive physician must conduct a thorough history/physical examination. Once the clinical diagnosis has been made, a specific treatment can be formulated to provide the best outcome, one with a minimal degree of long-term disability.