Thepiriformis muscle(fromLatinpiriformis'pear-shaped') is a flat, pyramidally-shapedmusclein theglutealregion of thelower limbs.It is one of the six muscles in thelateral rotator group.
| Piriformis muscle | |
|---|---|
 Buttocks seen from behind (the piriformis and the rest of thelateral rotator groupare visible) | |
 Muscles of the gluteal and posterior femoral regions seen from the front | |
| Details | |
| Origin | Sacrum |
| Insertion | Greater trochanter |
| Artery | Inferior gluteal,lateral sacralandsuperior gluteal artery, |
| Nerve | Nerve to the piriformis(L5,S1,andS2) |
| Actions | External rotatorof thethigh |
| Identifiers | |
| Latin | musculus piriformis |
| TA98 | A04.7.02.011 |
| TA2 | 2604 |
| FMA | 19082 |
| Anatomical terms of muscle | |
The piriformis muscle has its origin upon the front surface of thesacrum,and inserts onto thegreater trochanterof thefemur.Depending upon the given position of the leg, it acts either as external (lateral) rotator of the thigh or as abductor of the thigh. It is innervated by thepiriformis nerve.
Structure
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The piriformis is a flat muscle, and is pyramidal in shape.[1]
Origin
editThe piriformis muscle originates from theanterior (front) surfaceof thesacrum[2][3]by three fleshy digitations attached to thesecond, third, and fourth sacral vertebra.[1]
It also arises from the superior margin of thegreater sciatic notch,[4]the gluteal surface of theilium(near theposterior inferior iliac spine), thesacroiliac jointcapsule, and (sometimes) thesacrotuberous ligament(more specifically, the superior part of the pelvic surface of this ligament).[3]
Insertion
editThe muscle inserts onto thegreater trochanterof thefemur[2](itstendonunite with the tendons of thesuperior gemellus,inferior gemellus,andobturator internusmuscles prior to insertion).[5]
Innervation
editThe piriformis muscle isinnervatedby thepiriformis nerve.[2]
Relations
editThe posterior aspect of the muscle lies against the sacrum. The anterior surface of the muscle is related to therectum(especially on the left side of the body), and thesacral plexus.[3]
The muscle lies almost parallel with the posterior margin of thegluteus medius.It is situated partly within thepelvisagainst its posterior wall, and partly at the back of thehip joint.[5]
It exits thepelvisthrough thegreater sciatic foramen[1]superior to the sacrospinous ligament.[3]
Variation
editIn around 80% of the population, thesciatic nervetravels below the piriformis muscle.[2][1]In 17% of people, the piriformis muscle is pierced by parts or all of the sciatic nerve.[2]Several variations occur, one of which is the rarely found Beaton's type-b where the sciatic nerve divides between and below the piriformis.[6]
It may be united with thegluteus medius,send fibers to thegluteus minimus,or receive fibers from thesuperior gemellus.
It may have one or two sacral attachments; or it may be inserted into the capsule of the hip joint.
Function
editThe piriformis muscle is part of thelateral rotators of the hip,along with thequadratus femoris,gemellus inferior,gemellus superior,obturator externus,andobturator internus.The piriformis laterally rotates the femur with hip extension and abducts the femur with hip flexion.[2]Abduction of the flexed thigh is important in the action of walking because it shifts the body weight to the opposite side of the foot being lifted, which prevents falling. The action of the lateral rotators can be understood by crossing the legs to rest an ankle on the knee of the other leg. This causes the femur to rotate and point the knee laterally. The lateral rotators also oppose medial rotation by thegluteus mediusandgluteus minimus.When the hip is flexed to 90 degrees, piriformis abducts the femur at the hip and reverses primary function, internally rotating the hip when the hip is flexed at 90 degrees or more.[7]
Clinical significance
editPiriformis syndrome
editPiriformis syndrome occurs when the piriformis irritates thesciatic nerve,which comes into the gluteal region beneath the muscle, causing pain in the buttocks and referred pain along the sciatic nerve.[8]This referred pain is known assciatica.Seventeen percent of the population has their sciatic nerve coursing through the piriformis muscle. This subgroup of the population is predisposed to developing sciatica. Sciatica can be described by pain, tingling, or numbness deep in the buttocks and along the sciatic nerve. Sitting down, stretching, climbing stairs, and performing squats usually increases pain. Diagnosing the syndrome is usually based on symptoms and on the physical exam. More testing, including MRIs, X-rays, and nerve conduction tests can be administered to exclude other possible diseases.[8]If diagnosed with piriformis syndrome, the first treatment involves progressive stretching exercises, massage therapy (including neuromuscular therapy) and physical treatment. Corticosteroids can be injected into the piriformis muscle if pain continues. Findings suggest the possibility thatBotulinum toxintype B may be of potential benefit in the treatment of pain attributed to piriformis syndrome.[9]A more invasive, but sometimes necessary treatment involves surgical exploration; however, the side effects of the surgery could be much worse than alternative treatments such as physical therapy. Surgery should always be a last resort.[8]
Landmark
editThe piriformis is a very important landmark in the gluteal region. As it travels through the greater sciatic foramen, it effectively divides it into an inferior and superior part.
This determines the name of the vessels and nerves in this region – the nerve and vessels that emerge superior to the piriformis are the superior gluteal nerve and superior gluteal vessels. Inferiorly, it is the same, and the sciatic nerve also travels inferiorly to the piriformis.[10]
History
editThe piriformis muscle was first named byAdriaan van den Spiegel,a professor from theUniversity of Paduain the 16th century.[11]
Additional images
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Muscles of the gluteal and posterior femoral regions -
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See also
editReferences
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This article incorporates text in thepublic domainfrompage 476of the 20th edition ofGray's Anatomy(1918)
- ^abcdKhan, Dost; Nelson, Ariana (2018-01-01), Benzon, Honorio T.; Raja, Srinivasa N.; Liu, Spencer S.; Fishman, Scott M. (eds.),"Chapter 67 - Piriformis Syndrome",Essentials of Pain Medicine (Fourth Edition),Elsevier, pp. 613–618.e1,doi:10.1016/b978-0-323-40196-8.00067-x,ISBN978-0-323-40196-8,retrieved2021-02-03
- ^abcdefPan, Jason; Vasudevan, John (2018-01-01), Freedman, Mitchell K.; Gehret, Jeffrey A.; Young, George W.; Kamen, Leonard B. (eds.),"Chapter 24 - Piriformis Syndrome: A Review of the Evidence and Proposed New Criteria for Diagnosis",Challenging Neuropathic Pain Syndromes,Elsevier, pp. 205–215,ISBN978-0-323-48566-1,retrieved2021-02-03
- ^abcdStandring, Susan (2021).Gray's Anatomy: The Anatomical Basis of Clinical Practice(42nd ed.). [New York]. p. 1244.ISBN978-0-7020-7707-4.OCLC1201341621.
{{cite book}}:CS1 maint: location missing publisher (link) - ^Hicks, Brandon; Lam, Jason; Varacallo, Matthew (August 4, 2023).Piriformis Syndrome.Treasure Island (FL): StatPearls Publishing.PMID28846222.
- ^abChang, Carol; Jeno, Susan H.; Varacallo, Matthew (November 13, 2023).Anatomy, Bony Pelvis and Lower Limb: Piriformis Muscle.Treasure Island (FL): StatPearls Publishing.PMID30137781.
- ^Jha AK, Baral P (2020)."Composite Anatomical Variations between the Sciatic Nerve and the Piriformis Muscle: A Nepalese Cadaveric Study".Case Rep Neurol Med.2020:7165818.doi:10.1155/2020/7165818.PMC7150691.PMID32292613.
- ^Hansen, John T. (2009).Netter's Clinical Anatomy(2nd ed.). Philadelphia: Saunders/Elsevier.ISBN978-1-4377-0272-9.OCLC316421154.
- ^abc"The piriformis syndrome".Retrieved2007-11-16.
- ^Lang AM (March 2004). "Botulinum toxin type B in piriformis syndrome".American Journal of Physical Medicine & Rehabilitation.83(3): 198–202.doi:10.1097/01.PHM.0000113404.35647.D8.PMID15043354.S2CID9738513.
- ^"Muscles of the Gluteal Region".TeachMeAnatomy.Retrieved2012-12-15.
- ^Smoll NR (January 2010). "Variations of the piriformis and sciatic nerve with clinical consequence: a review".Clinical Anatomy.23(1): 8–17.doi:10.1002/ca.20893.PMID19998490.S2CID23677435.
External links
edit- "Piriformis"University of Washington
- Anatomy photo:13:st-0408at the SUNY Downstate Medical Center - "Gluteal Region: Muscles"
- Anatomy photo:43:15-0101at the SUNY Downstate Medical Center - "The Female Pelvis: The Posterolateral Pelvic Wall"
