Background: Piriformis syndrome has remained a controversial diagnosis since its initial description in 1928. Piriformis syndrome 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 discogenic sciatica (pseudosciatica).
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). This muscle passes through the greater sciatic notch and 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 piriformis muscle itself becomes a hip abductor. This muscle is innervated by branches from L5, S1, and S2. A lower lumbar radiculopathy also may cause secondary irritation of the piriformis muscle, which may complicate the diagnosis and hinder patient progress.
Many developmental variations of the relationship between the sciatic nerve in the pelvis and piriformis muscle have been observed. In approximately 20% of the population, the muscle belly is split with one 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; the tibial division rarely splits the muscle belly.
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.
Etiology can be subdivided into a few categories as follows:
Other causes can include the following:
This syndrome remains controversial because, in most cases, the diagnosis is clinical, and no confirmatory tests exist to support the clinical findings.
Mortality/Morbidity: Piriformis syndrome is not life-threatening, but it can have significant associated morbidity. The total cost of low back pain (LBP) and sciatica is significant, exceeding $16 billion in both direct and indirect costs.
Sex: Some reports suggest a 6:1 female-to-male predominance.
History: Piriformis syndrome often is not recognized as a cause of LBP and associated sciatica. This clinical syndrome is due to a compression of the sciatic nerve by the piriformis muscle. This condition is identical in clinical presentation to LBP with associated L5, S1 radiculopathy due to discogenic 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 both the trochanteric bursitis and the piriformis syndrome are treated inadequately, both conditions remain resistant to medical management.
Physical: Examination findings may include the following:
Causes: Approximately 50% of patients with piriformis syndrome have a history of trauma, with either a direct buttock contusion or 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 this problem, lest it be overlooked.
Functional biomechanical deficits may include the following:
Functional adaptations to these deficits include the following:
Once the diagnosis has been made, these underlying perpetuating biomechanical factors must be corrected.
Consider the use of ultrasound and other heat modalities prior to physical therapy sessions. Prior to performing piriformis stretches, the hip joint capsule should be mobilized anteriorly and posteriorly to allow for more effective stretching. Soft tissue therapies of 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 orthostatic position with the involved hip flexed and passively adducted/internally rotated.
Medical Issues/Complications: No consensus exists on overall treatment of piriformis syndrome due to lack of objective clinical trials. Conservative treatment (eg, stretching, manual techniques, injections, activity modifications, modalities like heat or ultrasound, natural healing) is successful in most cases.
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. Then the piriformis muscle is injected using a 3.5-inch (8.9-cm) spinal needle. Care must be taken to avoid direct injection of the sciatic nerve.
Surgical Intervention: Surgical management is the treatment of last resort. Surgery for this condition involves resection of the muscle itself or the muscle tendon near its insertion at the superior aspect of the greater trochanter of the femur (as described by Mizuguchi). These surgical procedures are described as effective, and they do not cause any associated superimposed postoperative disability.
Other Treatment (injection, manipulation, etc.):
Further Inpatient Care:
Further Outpatient Care: