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Basics ⬇

Author(s): DouglasComeau, DO, CAQSM, FAAFP and Angelene M.Elliott, DO

Description

  • Sciatic nerve irritation as it courses underneath or through the piriformis muscle causing buttock pain with or without radiation into the leg
  • The piriformis muscle acts as an external rotator in hip extension and an abductor in hip flexion.
  • Piriformis muscle spasm or hypertrophy can occur in certain motions, such as running downhill or repetitive motions.
  • Direct irritation of the sciatic nerve may be caused by inflammatory agents released from an injured piriformis muscle.
  • Synonym(s): piriformis syndrome; sciatica; sciatic neuritis; “hip pocket neuropathy”; “wallet neuritis”; “pelvic outlet syndrome”; “deep gluteal syndrome”; “pseudosciatica”

Epidemiology

Incidence

  • 6/100 cases of sciatica; 2.4 million cases per year (1)
  • Mean age 38 yr old
  • Predominant gender: female > male (6:1 in some trials)
  • The incidence of piriformis syndrome is skewed secondary by the lack of evidence-based guidelines. The ratio is likely higher.

Etiology and Pathophysiology

  • The piriformis muscle originates at the S2–S3 vertebrae, sacrotuberous ligament, and upper margin of the greater sciatic foramen.
  • The piriformis muscle then passes through the greater sciatic notch, inserting on the greater trochanter.
  • It is innervated by L5, S1, and S2.
  • In hip extension, the piriformis serves as an external rotator.
  • In hip flexion, it serves as a hip abductor.

Risk-Factors

  • In roughly 20% of the population, the sciatic nerve passes through the piriformis muscle, which may irritate the nerve and cause pain.
  • Leg-length discrepancy may predispose a patient to development of symptoms.
  • A Morton foot can predispose a patient from the change in ambulation.

General Prevention

  • Maintaining an appropriate lumbar core stabilization can decrease the recurrence of symptoms.
  • A core stabilization program includes the anterior pelvis, posterior back, and buttocks.

Commonly Associated Conditions

Diagnosis ⬆ ⬇

History

  • Trauma to the gluteal region is seen in <50% of patients.
  • Sitting on hard surfaces exacerbates pain.
  • Location of referred pain; not likely piriformis syndrome if below the knee
  • Complaint of pain with movements that cause external hip rotation
  • Women may complain of dyspareunia.

Physical Exam

  • Cramping or aching pain in the buttock ± pain radiating into the hamstrings
  • Sensation of “tight hamstrings”
  • Point tenderness to deep palpation over any part of the piriformis muscle
  • Pain increased with sitting
  • Full range of motion and 5/5 strength in active and passive forward flexion and extension
  • Negative stork test
  • Negative straight-leg raise and negative flexion, abduction, and external rotation
  • Buttock pain ± radiation to hamstrings produced by combination of hip flexion, adduction, and internal rotation; this maneuver stretches the piriformis muscle.
  • Pace sign: weakness in resisted abduction and external rotation
  • Tenderness to palpation over the piriformis muscle
  • Sciatic notch tenderness
  • Usually normal neurologic examination
  • Pelvic and/or digital rectal examination elicits pain ipsilaterally proximal to the ischial tuberosity.
  • A proposed clinical scoring system using history and exam may be helpful with sensitivity of 96.4% and specificity of 100% (2).

Differential Diagnosis

  • Lumbar facet arthropathy
  • Lumbar spondylolysis and spondylolisthesis
  • Lumbosacral radiculopathy
  • Myofascial pain
  • Achilles tendinitis
  • Cord tumor
  • Spinal stenosis
  • Aneurysm of the inferior or superior gluteal artery
  • Fibrotic band around the sciatic nerve
  • Hematoma
  • Gluteal abscess
  • Pelvic tumor
  • Endometriosis and other pelvic diseases
  • Bursitis: obturator internus, trochanteric or ischial

Diagnostic Tests & Interpretation

Initial Tests (lab, imaging)

  • No laboratory tests are recommended in the workup.
  • Diagnostic imaging is rarely helpful in confirming the diagnosis.
  • Clinical history and physical examination are keys to diagnosing piriformis syndrome.
  • Further diagnostic tests may be needed to rule out other potential diagnoses.
  • Magnetic resonance imaging (MRI) and computed tomography (CT) scanning can be used if history and physical examination are not conclusive; two case reports supporting the use of magnetic resonance neurography to confirm diagnosis and verify effect of treatment (3)
  • Atrophy or fibrous tissue replacement of the piriformis muscle on MRI or CT scan supports the diagnosis.
  • Musculoskeletal ultrasound (US) demonstrating hypertrophy of the muscle is a newer radiologic technique that may be used in difficult cases.

Diagnostic Procedures/Other

Electromyography (EMG) findings of peronei and/or tibial H reflex prolongation in the adducted, internally rotated, flexed hip strongly anecdotally support the diagnosis in some studies; however, EMG is typically normal and not a recommended diagnostic tool.

Treatment ⬆ ⬇

Emergency department (ED) treatment:

  • Low back pain is one of the top 10 causes of acute emergency visits.
  • Typically, a lumbar spine film will be taken and is negative.
  • The patient should be treated with nonsteroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants and sent for primary care and/or sports medicine follow-up.

Medication

First Line

  • NSAIDs for 10 to 4 days
  • Short course of analgesics and/or muscle relaxants may be beneficial (4)[C].
  • Ice
  • Acetaminophen

Additional Therapies

  • Relative rest for a short period but should begin piriformis stretch and physical therapy as soon as possible
  • Physical therapy incorporating stretching and strengthening of the piriformis muscle; also should incorporate correction of pelvic obliquities and leg-length discrepancies (4)[A]
  • Deep muscle massage with US
  • Long-term treatment:
    • Continued lumbar stabilization program
    • Continued piriformis stretching
  • Injections:
    • With no improvement after conservative therapy, consider local injection of anesthetic (1–2% lidocaine hydrochloride ± bupivacaine 4 to 6 mL) with or without steroids (mixed evidence for use of steroids) under fluoroscopic or US guidance into the tender area within the piriformis muscle.
    • Botulinum toxin has shown benefit in randomized, double blind, controlled trials (5)[A] and nonrandomized, controlled trials (6)[C]. The mechanism of action would be decreasing the piriformis spasm by injecting botulinum.
  • Surgery as indicated earlier for recalcitrant cases of piriformis syndrome

Surgery/Other Procedures

  • If conservative treatment fails, surgical release of the piriformis muscle around the sciatic nerve should be used as a last resort. In these cases, surgery has a favorable outcome in the majority of cases (7).
  • Patients with documented EMG nerve impairment have the best outcome after surgical release.

COMPLEMENTARY & ALTERNATIVE MEDICINE

  • Osteopathic manipulative treatment (OMT) may be used in conjunction with physical therapy.
  • Techniques include muscle energy technique and myofascial release to help with piriformis strengthening and stretching.

Admission, Inpatient, and Nursing Considerations

A patient typically is admitted only if preoperative for surgical correction.

Ongoing Care ⬆ ⬇

Follow-up Recommendations

Patient Monitoring

  • Initially, a patient should follow up with primary care or sports medicine 6 to 8 wk after starting physical therapy (8).
  • On follow-up, close interaction should be maintained to ensure compliance with the home exercise program (lumbar stabilization).

Patient Education

  • Patient education may include home exercise program handouts to ensure compliance.
  • Showing the patient a diagram of the piriformis and its closeness to the sciatic nerve may help in patient recognition.

Prognosis

  • Prognosis is predicated on compliance with home exercise program and core stability.
  • Although compliance with core stabilization cannot guarantee lifelong relief of symptoms, a stronger core can decrease the chance of recurrence.

Complications

  • Complications typically occur without early diagnosis and treatment.
  • Chronic low back pain may be debilitating and multifactorial.

References ⬆ ⬇

  1. Siddiq MA, Hossain MS, Uddin MM, et al. Piriformis syndrome: a case series of 31 Bangladeshi people with literature review. Eur J Orthop Surg Traumatol. 2017;27(2):193–203.
  2. Michel F, Decavel P, Toussirot E, et al. Piriformis muscle syndrome: diagnostic criteria and treatment of a monocentric series of 250 patients. Ann Phys Rehabil Med. 2013;56(5):371–383.
  3. Yang HE, Park JH, Kim S. Usefulness of magnetic resonance neurography for diagnosis of piriformis muscle syndrome and verification of the effect after botulinum toxin type A injection: two cases. Medicine (Baltimore). 2015;94(38):e1504.
  4. Rouzier P. Piriformis syndrome. The Sports Medicine Patient Advisor. Amherst, MA: McKesson; 2004.
  5. Fishman LM, Wilkins AN, Rosner B. Electrophysiologically identified piriformis syndrome is successfully treated with incobotulinum toxin A and physical therapy. Muscle Nerve. 2017;56(2):258–263.
  6. Kirschner JS, Foye PM, Cole JL. Piriformis syndrome, diagnosis and treatment. Muscle Nerve. 2009;40(1):10–18.
  7. Han SK, Kim YS, Kim TH, et al. Surgical treatment of piriformis syndrome. Clin Orthop Surg. 2017;9(2):136–144.
  8. Jankovic D, Peng P, van Zundert A. Brief review: piriformis syndrome: etiology, diagnosis, and management. Can J Anaesth. 2013;60(10):1003–1012.

Clinical Pearls ⬆

  • Prevention: a strong core stabilization program to increase strength and range of motion
  • Any activities that involve prolonged sitting (i.e., biking) should be avoided.
  • Return to play: weight-bearing as tolerated 5 to 10 days after surgery with gradual return to full activity; avoidance of prolonged sitting for 4 to 6 wk after surgery is recommended.