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AUTHOR
INFORMATION |
Section
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Authored by Milton J Klein,
DO, Consulting Staff, Department of Physical Medicine and
Rehabilitation, Sewickley Valley Hospital and Ohio Valley General Hospital
Milton J Klein, DO, is a member of the following medical societies: American
Academy of Disability Evaluating Physicians, American
Academy of Osteopathy, American Academy
of Physical Medicine and Rehabilitation, American
Association of Electrodiagnostic Medicine, American
Medical Association, American
Osteopathic Association, and American
Osteopathic College of Rehabilitation Medicine
Edited by Rajesh R Yadav, MD, Assistant Professor,
Department of Physical Medicine and Rehabilitation, MD Anderson Cancer
Center, University of Texas at Houston; Francisco Talavera, PharmD,
PhD, Senior Pharmacy Editor, eMedicine; Michael T Andary,
MD, MS, Program Director, Associate Professor, Department of
Physical Medicine and Rehabilitation, Michigan State University College of
Osteopathic Medicine; Kelly L Allen, MD, Staff Physician,
Department of Rehabilitation Medicine, Thomas Jefferson University; and Consuelo
T Lorenzo, MD, Consulting Staff, Department of Physical Medicine
and Rehabilitation, Alegent Health Care, Immanuel Rehabilitation Center
eMedicine Journal, May 7 2001, Volume 2, Number 5
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INTRODUCTION |
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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 Picture 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:
- 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
This syndrome remains controversial because, in most cases, the
diagnosis is clinical, and no confirmatory tests exist to support the
clinical findings.
Frequency:
- In the US: Given the lack of agreement on exactly
how to diagnose this condition, estimates of 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 one episode of disabling 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 (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:
- Piriformis muscle spasm often is detected by careful deep palpation.
- Digital rectal examination may reveal tenderness on lateral pelvic
wall that reproduces symptoms.
- Reproduction of sciatica type pain with weakness is noted by
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. The patient lies on the uninvolved
side and abducts the involved thigh upward; this activates the
ipsilateral piriformis muscle, which is both a hip external rotator
and abductor with the hip flexed.
- 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 a 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. The piriformis muscle
(external hip rotator) reactively contracts repetitively during each
push-off phase of the gait cycle as a compensatory mechanism, leading
to piriformis syndrome.
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.
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DIFFERENTIALS |
Section
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Lumbar Degenerative
Disc Disease
Lumbar Facet
Arthropathy
Lumbar Spondylolysis
and Spondylolisthesis
Myofascial Pain
Trochanteric Bursitis
Other Problems to be Considered:
Lumbosacral radiculopathy
Buttock pain
Ischial tuberosity bursitis
Sciatica
Lab Studies:
- Laboratory studies generally are not indicated in diagnosing
piriformis syndrome.
Imaging Studies:
- Diagnostic imaging of the lumbar spine is mandatory to exclude
associated discogenic and/or osteoarthritic contributing pathology.
- Reports in the literature on piriformis muscle describe imaging by
nuclear diagnostic studies and MRI of the pelvis, but these tests are
neither practical nor reliable diagnostic approaches to this problem.
The history and clinical diagnostic examination provide the greatest
and most specific diagnostic yield for this problem.
Other Tests:
- Results of electrodiagnostic testing for piriformis syndrome usually
are normal. Reports of positional H-reflex abnormalities can be found
in the literature; however, such findings have not been widely
accepted or reproduced.
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TREATMENT |
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Rehabilitation Program:
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.
Consultations:
- Because of the enigmatic nature of piriformis syndrome, initial
consultation obtained from an orthopedic surgeon or 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 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 LBP, sciatica, and buttock pain (thereby further clouding
the diagnosis).
Other Treatment (injection, manipulation, etc.):
- The Spray N' Stretch myofascial treatment and ultrasound modality
preceding physical therapy sessions are useful.
- Manual muscle medicine, including facilitated positional release,
may be helpful.
- Injections with steroids, local anesthetics, and botulinum toxin
have been reported in the literature for this condition. No single
technique is universally accepted. Localization techniques include
manual localization of muscle with fluoroscopic 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.
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FOLLOW-UP |
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Further Inpatient Care:
- Inpatient care would be 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/Prevention:
- No method has been demonstrated to prevent piriformis syndrome. The
best prevention is to maintain biomechanical balance by restoration of
a more physiologic weight bearing distribution with a level
pelvis/sacral base and equal leg lengths, achieved by 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 bilateral piriformis
muscles.
Complications:
- The most significant complication is failure to recognize, diagnose,
and treat this disabling condition. If left untreated, a patient may
undergo unsuccessful back surgery for a disc 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 depends upon early recognition and treatment. As this
is a soft tissue syndrome, it has a tendency to be chronic, usually
due to late diagnosis and treatment and has a less favorable
prognosis.
Patient Education:
- For conservative measures to be effective, the patient must be
educated with an aggressive home-based stretching program to maintain
piriformis muscle flexibility. He or she must comply with the program
even beyond the point of discontinuation of formal medical treatment.
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MISCELLANEOUS |
Section
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Medical/Legal Pitfalls:
- The greatest medical/legal concern is either misdiagnosis or 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 LBP. 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 LBP/sciatica, piriformis
syndrome can be a significant cause of soft tissue pain and
disability. This problem requires a skillful, attentive physician to
conduct a thorough history/physical examination that provides an
accurate diagnosis. Once the clinical diagnosis has been made, a
specific treatment can be formulated to provide the best outcome with
a minimal degree of long-term disability.
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BIBLIOGRAPHY |
Section
10 of 10
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| NOTE:
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changing science and not all therapies are clearly established.
New research changes drug and treatment therapies daily. The
authors, editors, and publisher of this journal have used their
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accurate and is generally accepted within medical standards at the
time of publication. However, as medical science is constantly
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