Piriformis Syndrome

United States statistics

The female-to-male incidence ratio of piriformis syndrome is 6:1. In one study at a regional hospital, 45 of 750 patients with LBP were found to have piriformis syndrome. Another author estimated that the incidence of piriformis syndrome in patients with sciatica is 6%. The overall incidence of piriformis syndrome has been estimated at 2.4 million per year. Most cases occur in middle-aged patients.[1]

The function of the piriformis muscle is to externally rotate and abduct the thigh. The sacral plexus is closely associated with the anterior surface of the piriformis muscle. The lumbosacral trunk and the ventral rami of the first 3 sacral nerves form the sacral plexus. The sciatic nerve passes inferior to the piriformis muscle.

The sciatic nerve exits the pelvis via 4 routes: (1) The nerve passes anteriorly to the piriformis between the rims of the greater sciatic foramen. (2) The peroneal portion of the sciatic nerve passes through the piriformis; the tibial portion passes anterior to the piriformis muscle. (3) The peroneal branch of the sciatic nerve loops above and posterior to the piriformis muscle, whereas the tibial branch passes anterior to the piriformis muscle. (4) The undivided sciatic nerve penetrates the piriformis muscle.

Dysfunction of the piriformis muscle can cause signs and symptoms of pain in the sciatic nerve distribution, that is, in the gluteal area, posterior thigh, posterior leg, and lateral aspect of the foot.[2]

Gait mechanics help in demonstrating the physiologic features of piriformis hypertrophy. When a person takes a step forward, the extremity moves from external rotation to internal rotation, and the piriformis muscle lengthens. This stretching is followed by reflex contraction. A second contraction in the initially stretched piriformis muscle occurs when the opposite foot swings forward. This gait pattern leads to hypertrophy, and the dual contraction is further exacerbated by the stretching of the piriformis muscle on the side of a shortened leg.

More commonly, piriformis syndrome is secondary to inflammation due to gluteal trauma or spasm. The effect of this inflammatory process on the sciatic nerve is chemical rather than mechanical. Several theories suggest that the following are key factors in the muscle hyperfunction or spasm that leads to an interstitial myofibrositis: extravasation of blood; release of serotonin from platelets; and prostaglandin E, serotonin, bradykinin, and histamine release.

Although no general consensus about the etiology and pathophysiology of piriformis syndrome exists, many physicians and physical therapists attribute this syndrome to a specific mechanism involving the sciatic nerve. For example, Benson and Schutzer attributed the syndrome to blunt trauma to the buttocks that results in hematoma formation and subsequent scarring between the sciatic nerve and the short external rotators.[3] Entrapment of the sciatic nerve at the sciatic trunk (where it leaves the pelvis and crosses the greater sciatic notch) is an infrequent cause. This entrapment can also occur as a result of an enlarged hypertrophic piriformis, an inflamed piriformis muscle, tumors, cysts, and pseudoaneurysms.

Trauma to the buttocks or gluteal region is the most common cause of piriformis syndrome.

Skiers, truck drivers, tennis players, and long-distance bikers are at high risk.

In Morton foot, the prominent head of the second metatarsal causes foot instability and a reactive contraction of the external rotators of the hip during gait.

Spinal stenosis can lead to bilateral piriformis tenderness.

Anatomic variations of the divisions of the sciatic nerve above, below, and through the belly of the piriformis muscle may be causative factors.[4]

Most patients with piriformis syndrome progress well after a local trigger-point injection. Recurrences are uncommon after 6 weeks of therapy. After surgery, patients treated with piriformis release return to their activities in an average of 2-3 months.

Patients with piriformis syndrome should modify their activity habits. For example, patients are recommended to adhere to the following: avoid prolonged sitting, perform the suggested stretching exercises 2 or 3 times a day and before participating in a sports activity, and avoid direct trauma to the gluteal region.

Patient education should be an ongoing process throughout the course of rehabilitation. Physical therapists and occupational therapists are valuable members of the team for teaching the patient strategies used to recover from this syndrome and also to prevent recurrences. Patients should be informed of the importance of their routine compliance with an individualized home exercise program.

Patients with piriformis syndrome have the following symptomatic history:

• Chronic pain in the buttocks

  • This pain may radiate to the lower leg and worsens with walking or squatting.

  • This pain may imitate LBP.

• Pain with bowel movements

• Pain in the labia majora in women; pain in the scrotum in men

• Dyspareunia in women

• Pain when getting up from bed

• Pain exacerbated by hip adduction and internal rotation

• Intolerance to sitting

Piriformis syndrome is a diagnosis of exclusion.

• At physical examination, the most important factor that differentiates sciatic pain from piriformis syndrome is the absence of neurologic deficit in piriformis syndrome.

• Herniation or disc compression results in intraneural derangement of the nerve root structure, whereas piriformis syndrome causes a qualitative epineural irritation.

• In piriformis syndrome, the only true-positive sign is tenderness over the gluteal region.[5]

  • The pain can be reproduced with maximum elongation of the piriformis muscle in flexion, adduction, and internal rotation of the hip.

  • Weakness can be observed with resisted external rotation and abduction of the hip.

• Several authors describe the use of the following signs in diagnosing piriformis syndrome:

  • Lasegue sign: Pain is present in the vicinity of the greater sciatic notch during extension of the knee with the hip flexed to 90 º, tenderness to palpation of the greater sciatic notch is noted.

  • Pace sign: Pain and weakness are present on resisted abduction-external rotation of the thigh.

  • Freiberg sign: Pain occurs with passive internal rotation of the extended thigh when the patient is supine.

• Robinson, who first described the syndrome, stated that piriformis syndrome had 6 cardinal features:

  • Positive Lasegue sign

  • Sausage-shaped mass over the piriformis muscle

  • Gluteal atrophy in chronic cases

  • Trauma to the region

  • Pain in the sacroiliac joint region, gluteal muscles, or greater sciatic notch

  • Pain exacerbated by lifting and relieved by traction on the affected extremity

• Beatty reproduced the pain of piriformis syndrome in the following way[6] :

  • The patient lies with the painful side up and the involved leg flexed.

  • The knee of the affected side rests on the table. Pain in the buttocks is reproduced when the patient lifts the leg and knee slightly above the table.

• Other authors conclude that pain can be reproduced in the lateral pelvic wall by means of rectal or pelvic examination.

Imaging studies include the following:

• Computed tomography (CT) scanning

  • CT scans may demonstrate a large mass anterior to the piriformis muscle.

  • More importantly, CT scans can be used to identify spinal stenosis or arthritic changes.

• Magnetic resonance imaging (MRI)

  • MRI findings can rule out other causes of back pain, such as a herniated disc, spinal tumor, or abscess.

  • The piriformis muscle also can appear enlarged on T1- or T2-weighted images.

• Electromyography (EMG)

  • EMG can also be performed to determine neurologic or muscular changes.

  • In piriformis syndrome, EMG findings in the gluteus minimus, gluteus medius, and tensor fasciae latae muscles are normal.

  • In piriformis syndrome, abnormal patterns are found in the gluteus maximus and piriformis muscles.

  • In the case of a herniated disc, all muscles that are posteriorly and anteriorly innervated should be affected.

  • With a herniated disc, a significant delay in the Hoffman reflex, or H-reflex (motor nerve fiber response after activation of afferent sensory spindle fibers), in the affected limbs is often present during EMG.[7]

Diagnostic injection of the piriformis syndrome trigger point is performed as follows:

• Localize the pain at the sciatic notch, transvaginally or transrectally.

• Draw 5-7 mL of 2.5% lidocaine or bupivacaine into a 10-mL syringe with a 27-gauge needle.

• Prepare a sterile field and apply Betadine over the trigger-point area.

• Inject the anesthetic after aspirating to confirm that the needle is not in a vascular bundle.

• Remove the needle, and apply pressure to the area to ensure hemostasis.

• Allow the patient to ambulate and to abduct and externally rotate the affected leg.

• If the pain subsides, the likely cause of the pain is piriformis syndrome.

• This procedure is both therapeutic and diagnostic.

Rehabilitation Program

Physical Therapy

After a diagnosis of piriformis syndrome has been made, the patient should be instructed to rest from offending activities and initiate physical therapy treatment. Physical therapy modalities are often beneficial forms of treatment when used in conjunction with stretching and manual therapy.

The use of moist heat and/or ultrasound is often recommended before stretching of the piriformis muscle. The piriformis muscle is stretched with flexion, adduction, and internal rotation of the hip adductors and the knee while the patient lies supine. This stretching is performed by bringing the foot of the affected side across and over the knee of the other leg. To enhance the stretch of the piriformis muscle, the physical therapist may perform a muscle-energy technique. This is completed by having the patient abduct the limb against light resistance provided by the therapist for 5-7 seconds, and then it is repeated 5-7 times.

Soft-tissue massage to the gluteal and lumbosacral regions may help to decrease tightness of the affected musculature and reduce irritation of the sciatic nerve. Some physical therapists may be trained in performing myofascial release techniques for the piriformis muscle as well. In addition to stretching the piriformis, the patient should also be instructed to stretch the iliopsoas, tensor fascia latae, hamstrings, and gluteal muscles.

In addition to the specific stretching exercises, the patient can perform the following at home: (1) Before arising from bed, roll side to side and flex and extend the knees while lying on each side. This exercise can be repeated for a total of 5 minutes. (2) Rotate side to side while standing with the arms relaxed for 1 minute every few hours. (3) Take a warm bath with the full body (to the shoulders) immersed; the buoyancy effect is effective. (4) Lie flat on the back and pedal the legs as if riding a bicycle by raising the hips with the hands. (5) Perform knee bends, with as many as 6 repetitions every few hours. A countertop can be used for hand support.

Cold packs and, occasionally, electrical stimulation are applied after exercise or manual therapy. Cold modalities help to decrease pain and inflammation that may have been further triggered by stretching or massage. Remember to stress to patients the importance of light and gradual stretching techniques for the piriformis muscle to avoid overstretching and possible further irritation to the sciatic nerve.

Occupational Therapy

Professions that involve prolonged sitting can worsen symptoms of piriformis syndrome, and patients should avoid sitting for long periods. Patients should be instructed to stand and walk every 20 minutes. Patients should make frequent stops when driving to stand and stretch.

Surgical Intervention

Release of the piriformis tendon and sciatic neurolysis can lead to promising results. Benson and Schutzer performed such a procedure in 14 patients (15 cases) with an average symptom duration of 38 months (minimum, 2 y).[3] All patients had piriformis syndrome secondary to trauma. Benson and Schutzer reported that 11 patients had excellent outcomes, and 4 had good results.[3] Similarly, Frieberg reported favorable results in 10 of 12 patients in whom conservative treatment failed.

Most intraoperative findings include adhesions around the piriformis muscle and anatomic variations of the divisions of the sciatic nerve above, below, and through the belly of the piriformis muscle.

Consultations

Physical therapists are helpful in instructing the patient about the various maneuvers for stretching and pain relief.

Referral to an orthopedic surgeon is indicated when the diagnosis is not clear or when conservative therapy fails and a surgical evaluation is needed.

Referral to a neurologist and/or neurosurgeon is indicated for EMG studies and for an evaluation of associated disc herniation and spinal stenosis.

An osteopathic physician can perform manipulation techniques, along with primary conservative medical intervention.[8]

A gynecologist can also assist in differentiating causes of dyspareunia and pelvic pain in women with suspected piriformis syndrome. A gynecologist can assist in identifying trigger points for local injections in female patients via the vaginal route.

Other Treatment

Treatment options to alleviate the pain in the region of the piriformis include the use of local anesthetics, nonsteroidal anti-inflammatory medications (NSAIDs), transrectal massage, ultrasound treatment (~2 W/cm2 for 5-10 min), and manual manipulation. Benson and Schutzer noted a success rate of approximately 85% after conservative treatment with manual therapy and local injections.[3]

• The most widely recognized treatment is local injection. Local anesthetics (eg, lidocaine, bupivacaine) can be injected in trigger points. The painful piriformis muscle can be identified by palpating the buttocks or by palpating transrectally in males and transvaginally in females. A spinal needle or 25-gauge, 1.5-inch needle is directly aimed at the examining finger. The location is usually through the sciatic notch and inferior to the bony margin; the most common trigger point is 1 inch lateral and caudal to the midpoint of the lateral border of the sacrum. An intramuscular (IM) dose of 50-100 mg can be injected. Studies have established that ultrasound, MRI, and CT-guided piriformis injections can confirm the correct placement of the local anesthetic within the muscle.[9, 10, 11]  A double-blind, randomized study that considered the clinical efficacy of local piriformis muscle injections found that local anesthetic (LA) injections were clinically effective. The authors also reported that the addition of corticosteroid (CS) to LA did not give an additional benefit.[12]

• Manual manipulation can also be applied (see Physical Therapy above). A common method, mobilization of the spine, is often used by osteopathic physicians (those with a DO degree).[8] The patient is placed in a lateral recumbent position on the unaffected side. The physician faces the patient and rotates the patient’s upper body away by laterally pulling on the lower arm. Then the physician places his or her cephalad hand most superiorly on the paravertebral muscles.The patient’s top leg is brought over the edge of the table. The physician places her caudal hand over the patient's hip in the line of the lowered leg. Force is applied in the direction of the lowered leg but perpendicular to the muscle fibers. When tension is reduced, a thrust (high-velocity low-amplitude [HVLA]) technique can be applied.

• NSAIDs and opiates can also be administered to patients with piriformis syndrome. However, to the author’s knowledge, no study has been performed to assess the treatment of piriformis pain with intravenous (IV) or oral medications. Physician discretion is recommended in using medications such as those used to treat LBP.

• A study by Fishman et al found that incobotulinum toxin A chemodenervation may be useful for treating piriformis syndrome.[13]

• Botulinum toxin has been used to help alleviate the symptoms of piriformis syndrome. However, because the duration of pain relief may be short-lived, repeated injections are often necessary.[1] A meta-analysis that compared botulinum toxin injection with local anesthetic plus corticosteroid, local anesthetic, and corticosteroid injection therapy showed that injection of local anesthetics plus a corticosteroid provided the most effective pain relief.[14] The results of a systematic review suggested that botulinum toxin is a safe option for pain reduction in patients with piriformis syndrome; however, insufficient data exist to quantify pain relief, and the optimal dose of botulinum toxin is unclear.[15]

Rehabilitation Program

Physical Therapy

In the recovery phase, the patient may begin gradual strengthening activities for the piriformis and gluteal muscles. Therapeutic modalities may be continued through this phase to enhance the benefits of rehabilitation. As the patient becomes asymptomatic, he or she may initiate light sport-specific activities and functional training. Addressing posture and faulty pelvic mechanics is important when resuming activity. Some athletes may need to change their footwear or undergo an orthotic consultation to correct their pelvic alignment and avoid further stress on the piriformis muscle.

Other Treatment (Injection, manipulation, etc.)

See Other Treatment for the acute phase.

Rehabilitation Program

Physical Therapy

During the maintenance phase of rehabilitation, the patient should continue performing a home exercise program for increasing flexibility and strength. Athletes may gradually increase their training volume as tolerated. Runners should be cautious when resuming speed training and hill running, doing so in a gradual fashion with proper warm-up and cool-down periods. Compliance to a daily stretching program is crucial to avoid recurrence of this syndrome. Return to play is dependent on many factors (eg, severity of condition, how soon treatment was initiated, level of patient compliance to program).

Surgical Intervention

See Surgical Intervention for the acute phase.

Consultations

See Consultations for the acute phase.

Other Treatment

See Other Treatment for the acute phase.

Return to play

Athletes with piriformis syndrome may return to play when they demonstrate full pain-free range of motion and strength of the affected side and can perform their sport-specific activities without discomfort. Patients must adhere to the aforementioned stretching exercises and perform a liberal warm-up before the activity. The duration for return to play varies with each individual and the type of treatment rendered. The longer an athlete ignores the problem before seeking treatment, the longer his or her rehabilitation will take.

Prevention

Recurrence of pain in the piriformis muscle can be prevented by continuing the stretching exercises and by avoiding risk factors.

NSAIDs are mentioned not in this section because of the lack of any documented or studied effectiveness in piriformis syndrome. However, physicians may use any number of these agents, on the basis of their experience in managing LBP or neuropathies.

Naja et al investigated whether clonidine-bupivacaine nerve-stimulator guided injections are effective in achieving long-lasting pain relief in piriformis syndrome compared with bupivacaine guided injection.[16] Significantly lower pain scores and analgesic consumption were observed with bupivacaine-clonidine compared with bupivacaine-saline. Additionally, pain at 6 months was significantly greater in the bupivacaine-saline group (78%) compared with the bupivacaine-clonidine group (8%).[16]

Class Summary

The drugs of choice for local injection in painful piriformis syndrome include the anesthetic agents lidocaine and/or bupivacaine. Both are in the family of amide anesthetics. Use is based on the desired duration of action. Doses, as described below, are intramuscularly (IM) administered by identifying the trigger point. Be sure to aspirate first to avoid injecting the medication into a blood vessel.

Lidocaine HCL (Xylocaine, Dilocaine, Anestacon)

Amide anesthetic that stabilizes neuronal membrane by inhibiting ionic fluxes. Absorbed completely with parenteral administration. Metabolized by the liver. Unchanged metabolites are excreted by the kidneys. Half-life is typically 1.5-2 h. Lidocaine crosses blood-brain and placental barriers by passive diffusion. Indicated for regional and local anesthesia.

Bupivacaine Hydrochloride (Sensorcaine, Marcaine)

Amide anesthetic that blocks conduction of nerve impulses by inhibiting ionic fluxes. Absorbed completely with parenteral administration and metabolized by the liver. Unchanged metabolites are excreted by the kidneys. Half-life is typically 3-4 h and peak levels are achieved in 30-40 min. Bupivacaine crosses blood-brain and placental barriers by passive diffusion. Indicated for regional and local anesthesia.