Piriformis Muscle: Blood Supply and Innervation

The piriformis muscle is supplied by major blood vessels and nerves of the pelvic region. The arteries, veins, and nerves that supply the piriformis typically course together and pass through a large bony opening called the greater sciatic foramen, which also houses the piriformis muscle near its origin.¹Collinge CA, Ziran NM, Coons DA. Relationship between the superior gluteal vessels and nerve at the greater sciatic notch. Orthopedics. 2015;38(10). https://pubmed.ncbi.nlm.nih.gov/26488790/ 

The piriformis muscle’s position within the greater sciatic foramen divides it into two passages—suprapiriform foramen, which is above the piriformis, and infrapiriform foramen, which is below the piriformis. Both these foramina contain numerous blood vessels and nerves supplying the pelvis and legs. 

Blood Supply of the Piriformis Muscle

The predominant vascular supply of the piriformis muscle and buttock comes from the inferior gluteal artery, but the superior gluteal artery and lateral sacral artery are also contributors.²Pan J, Vasudevan J. Chapter 24 – Piriformis Syndrome: A review of the Evidence and Proposed New Criteria for Diagnosis. In: Freedman MK, Gehret JA, Young GW, Kamen LB, eds. Challenging Neuropathic Pain Syndromes. Elsevier; 2018:205-215. http://doi.org/10.1016/B978-0-323-48566-1.00024-3

• Inferior gluteal artery: the primary arterial supply of the piriformis muscle, buttock, and thigh. Specifically, the piriformis is supplied by a branch of the inferior gluteal artery, which diverges from the main arterial trunk below the level of the piriformis muscle.³Grose AW, Gardner MJ, Sussmann PS, Helfet DL, Lorich DG. The surgical anatomy of the blood supply to the femoral head: description of the anastomosis between the medial femoral circumflex and inferior gluteal arteries at the hip. The Journal of Bone and Joint Surgery British volume. 2008;90-B(10):1298-1303. http://doi.org/10.1302/0301-620X.90B10.20983

• Superior gluteal artery: the largest artery of the pelvis, which supplies the skin and muscles in the buttock region.
• Lateral sacral artery: comprises the superior and inferior branches of the sacral arteries. The superior branch supplies the skin and lower back muscles, while the inferior branch supplies the piriformis muscle and lower pelvis muscles.

Traumatic injuries of the superior and inferior gluteal arteries are rare but can occur following blunt trauma to the buttock during a fall, motor vehicle accidents, or pelvic fractures. Injuries to the gluteal arteries can range from being asymptomatic to presenting as painful or pulsating swelling of the buttock and can be accompanied by bruising of the sciatic nerve or symptoms of sciatic nerve compression.⁴Babu A, Gupta A, Sharma P, Ranjan P, Kumar A. Blunt traumatic superior gluteal artery pseudoaneurysm presenting as gluteal hematoma without bony injury: A rare case report. Chin J Traumatol. 2016.19(4):244-246. http://doi.org/10.1016/j.cjtee.2015.11.018^,5Zhang Q, Liu H, Smith WR, Pan J, Chen W, Zhang Y. Blunt injury to the inferior gluteal artery: case report of a rare “near miss” event. Patient Saf Surg. 2008.2(27) http://doi.org/10.1186/1754-9493-2-27

Nerve Supply of the Piriformis Muscle

The piriformis muscle is innervated by two or three nerves in the pelvic region. The primary nerves include the ventral rami of the lower spinal nerves of the sacral plexus S1 and S2 and the superior gluteal nerve.⁶Iwanaga J, Eid S, Simonds E, Schumacher M, Loukas M, Tubbs RS. The majority of piriformis muscles are innervated by the superior gluteal nerve. Clin Anat. 2019 Mar;32(2):282-286. https://pubmed.ncbi.nlm.nih.gov/30408241/ 

In some cases, the piriformis muscle is also supplied by the L5 spinal nerve, but this is less common.

• Ventral rami of S1 and S2: lower spinal nerves of the sacral plexus, which are made up of both motor and sensory fibers supplying parts of the thigh and lower limbs, in addition to the piriformis muscle.
• Superior gluteal nerve: major motor nerve branch of the sacral plexus, which arises from divisions of L4, L5, and S1 spinal nerves. The superior gluteal nerve innervates the piriformis and the other gluteal muscles including the gluteus medius, gluteus minimus, and the tensor fasciae latae.

Based on the severity, an injury to these nerves (such as during a surgical procedure) can cause permanent dysfunction of the pelvic muscles, resulting in limping, weakness while moving the thigh, or other gait problems.¹Collinge CA, Ziran NM, Coons DA. Relationship between the superior gluteal vessels and nerve at the greater sciatic notch. Orthopedics. 2015;38(10). https://pubmed.ncbi.nlm.nih.gov/26488790/ 

Relation of the piriformis muscle with nearby nerves

The greater sciatic foramen, which contains the piriformis muscle, also serves as a passage for 6 main nerves—the sciatic nerve, inferior pudendal nerve, inferior gluteal nerve, posterior femoral cutaneous nerves, and the nerves to obturator internus and quadratus femoris muscles.⁷Chaitow L, DeLany J. The pelvis. In: Clinical Application of Neuromuscular Techniques, Volume 2. Elsevier; 2011:299-389. http://doi.org/10.1016/B978-0-443-06815-7.00011-5 Identifying these nerves during swelling or trauma can be a critical aspect in determining the differential diagnosis of piriformis syndrome.

The most significant nerve near the piriformis muscle is the sciatic nerve. As the largest and longest nerve in the human body, it supplies most areas of the thigh, leg, and feet. The sciatic nerve’s proximity to the piriformis muscle makes it susceptible to impairment or impingement if the piriformis muscle becomes injured or inflamed.

Entrapment of nerves in the deep gluteal space is sometimes referred to as Deep Gluteal Syndrome, which usually involves the sciatic nerve.⁸Kizaki K, Uchida S, Shanmugaraj A, et al. Deep gluteal syndrome is defined as a non-discogenic sciatic nerve disorder with entrapment in the deep gluteal space: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2020;28(10):3354-3364. http://doi.org/10.1007/s00167-020-05966-x This type of nerve entrapment can occur due to muscle spasms, swelling of tissues in the pelvis, or other anatomic causes. 

For any concerning symptoms in the lower back, pelvis, or legs, it is advisable to consult a physician for a diagnosis and treatment plan that addresses the underlying cause of the symptoms.