Piriformis muscle

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The piriformis (from the Latin piriformis , meaning 'pear shaped') is a muscle in the gluteal region of the lower limb. This is one of the six muscles in the lateral rotator group.

It was first named by Adriaan van den Spiegel, a professor from the University of Padua in the 16th century.

Video Piriformis muscle

Structure

Piriformis muscle is derived from the front (front) of the sacrum, part of the spine in the gluteal region, and from the superior margin of the larger sciatic notch (as well as the sacroiliac joint capsule and the sacrotuberous ligament). Exit the pelvis through a larger sciatic foramen to fit into the major trochanter of the femur. The tendon often joins the superior tendon gemellus, the inferior gemellus, and the obturator internal muscle prior to insertion.

The piriformis is a flat, pyramid-shaped muscle, lying almost parallel to the posterior margin of the gluteus medius.

It lies partly inside the pelvis against the posterior wall, and partly at the back of the hip joint.

It appears from the front of the sacrum by three fleshy stripes, attached to the bony portion between the first, second, third, and fourth sacral foramen, and to the curvature that leads from the foramina: some fibers also arise from the greater foramen skiat margin, and from the anterior surface sacrotuberous ligament.

The muscle exits the pelvis through the larger sciatic foramen, the top of which fills, and is inserted by the round tendon to the upper limit of the large trochanters behind, but often partially mixed with, the common tendon of the internal obturator and superior and inferior gemellus muscles.

Variations

In 17% of people, piriformis muscle is punctured by part or all of the sciatic nerve. Some variations occur, but the most common type of anomaly (81% anomaly) is the Beaton B type which when the peroneal nerve commonly penetrates the piriformis muscle.

It can be incorporated with the gluteus medius, sending fibers to the minimus gluteus, or receiving fibers from the superior gemellus.

It may have one or two sacred attachments; or may be inserted into the hip joint capsule.

Maps Piriformis muscle

Function

Piriformis muscle is part of the hip's lateral rotator, along with quadratus femoris, inferior gemellus, superior gemellus, externus obturator, and internal obturator. The lateral piriformis rotates the femur with hip extension and abducts the femur with hip flexion. Abduction of the flexed thigh is important in walking action because it shifts the weight to the opposite side of the raised foot, which prevents falls. The lateral rotator action can be understood by crossing the legs to rest the ankle on the knee of the other foot. This causes the thigh bones to spin and aim the knee toward the lateral. The lateral rotator also opposes the medial rotation by the gluteus medius and gluteus minimus. When the hip is bent to 90 degrees, the piriformis abducts the femur in the hip and reverses the main function, internally rotating the hip when the hip flexs at 90 degrees or more. (Netter's Clinical Anatomy, 2010)

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Clinical interests

Piriformis syndrome occurs when the piriformis irritates the sciatic nerve, which comes into the gluteal area beneath the muscle, causing pain in the buttocks and pain along the sciatic nerve. This referred pain is known as sciatica . Seventeen percent of the population has sciatic nerves that flow through the piriformis muscle. This population subgroup tends to develop into sciatica. Sciatica can be explained by pain, tingling, or numbness deep in the buttocks and along the sciatic nerve. Sitting, stretching, climbing stairs, and doing squats usually increase pain. Diagnosing syndrome is usually based on symptoms and on physical examination. More testing, including MRI, X-rays, and nerve conduction tests can be done to rule out other possible illnesses. If diagnosed with piriformis syndrome, the first treatment involves progressive stretching exercises, massage therapy (including neuromuscular therapy) and physical care. Corticosteroids can be injected into the piriformis muscle if pain persists. The findings suggest the possibility that Botulinum toxin type B may be of potential benefit in the treatment of pain associated with piriformis syndrome. Treatment is more invasive, but sometimes necessary involves surgical exploration; However, the side effects of surgery can be much worse than alternative treatments such as physical therapy. Surgery should always be the last resort.

Landmarks

The piriformis is a very important landmark in the gluteal region. As it travels through the larger sciatic foramen, it effectively divides it into its inferior and superior parts.

This determines the names of vessels and nerves in this region - nerves and veins that appear higher than piriformis are superior gluteal nerve and superior gluteal vessels. Inferiorly, it's the same, and the sciatic nerve also moves inferiorly to the piriformis.

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Additional images

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References

This article combines text in the public domain of page 476 of the 20th edition of Gray's Anatomy (1918)

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External links

• "Piriformis" University of Washington
• Photo anatomy: 13: st-0408 in SUNY Downstate Medical Center - "Gluteal Area: Muscle"
• Photo anatomy: 43: 15-0101 in SUNY Downstate Medical Center - "Female Pelvis: Posterolateral Plate Wall"

Source of the article : Wikipedia