Diagnosis and Management of Piriformis Syndrome
SOURCE: J Am Osteopath Assoc. 2008 (Nov); 108 (11): 657-664 ~ FULL TEXT
Lori A. Boyajian-O’Neill, DO, Rance L. McClain, DO,
Michele K. Coleman, DO, Pamela P. Thomas, PhD
Department of Family Medicine, Kansas City University of Medicine,
Biosciences College of Osteopathic Medicine,
1750 Independence Ave, SEP 358,
Kansas City, MO 64106-145, USA.
Piriformis syndrome is a neuromuscular condition characterized by hip and buttock pain. This syndrome is often overlooked in clinical settings because its presentation may be similar to that of lumbar radiculopathy, primary sacral dysfunction, or innominate dysfunction. The ability to recognize piriformis syndrome requires an understanding of the structure and function of the piriformis muscle and its relationship to the sciatic nerve. The authors review the anatomic and clinical features of this condition, summarizing the osteopathic medical approach to diagnosis and management. A holistic approach to diagnosis requires a thorough neurologic history and physical assessment of the patient based on the pathologic characteristics of piriformis syndrome. The authors note that several nonpharmacologic therapies, including osteopathic manipulative treatment, can be used alone or in conjunction with pharmacotherapeutic options in the management of piriformis syndrome.
From the Full-Text Article:
Epidemiologic Considerations
Piriformis syndrome occurs most frequently during the fourth and fifth decades of life and affects individuals of all occupations and activity levels. [7-12] Reported incidence rates for piriformis syndrome among patients with low back pain vary widely, from 5% to 36%. [3, 4, 11] Piriformis syndrome is more common in women than men, possibly because of biomechanics associated with the wider quadriceps femoris muscle angle (ie, “Q angle”) in the os coxae (pelvis) of women. [3]
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Difficulties arise in accurately determining the true prevalence of piriformis syndrome because it is frequently confused with other conditions.
Anatomic Characteristics
The piriformis muscle acts as an external rotator, weak abductor, and weak flexor of the hip, providing postural stability during ambulation and standing. [4, 9, 13] The piriformis muscle originates at the anterior surface of the sacrum, usually at the levels of vertebrae S2 through S4, at or near the sacroiliac joint capsule. The muscle attaches to the superior medial aspect of the greater trochanter via a round tendon that, in many individuals, is merged with the tendons of the obturator internus and gemelli muscles (Figure 1). [1, 13, 14] The piriformis muscle is innervated by spinal nerves S1 and S2 — and occasionally also by L5.
The proper understanding of piriformis syndrome requires knowledge of variations in the relationships between the sciatic nerve and the piriformis muscle (Figure 2). In as much as 96% of the population, the sciatic nerve exits the greater sciatic foramen deep along the inferior surface of the piriformis muscle. [15-17] In as much as 22% of the population, the sciatic nerve pierces the piriformis muscle, splits the piriformis muscle, or both, predisposing these individuals to piriformis syndrome. The sciatic nerve may pass completely through the muscle belly, or the nerve may split — with one branch (usually the fibular portion) piercing the muscle and the other branch (usually the tibial portion) running inferiorly or superiorly along the muscle. [7, 13-16, 18, 19] Rarely, the sciatic nerve exits the greater sciatic foramen along the superior surface of the piriformis muscle. [15-17]
Some symptoms of piriformis syndrome occur as a result of local inflammation and congestion caused by the muscular compression of small nerves and vessels — including the pudendal nerve and blood vessels, which exit at the medial inferior border of the piriformis muscle. [13]
Etiologic Considerations
There are two types of piriformis syndrome — primary and secondary. Primary piriformis syndrome has an anatomic cause, such as a split piriformis muscle, split sciatic nerve, or an anomalous sciatic nerve path. [8, 9, 20] Secondary piriformis syndrome occurs as a result of a precipitating cause, including macrotrauma, microtrauma, ischemic mass effect, and local ischemia. [1, 6, 11, 21, 22] Among patients with piriformis syndrome, fewer than 15% of cases have primary causes. [4, 11]
yndrome in an attempt to avoid surgical intervention.
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