Piriformis Syndrome: Symptoms, Causes, Risk Factors, Healing Cycle & Treatment

What is Piriformis Muscle?

The piriformis muscle originates from the anterior part of the sacral vertebrae, greater sciatic foramen, and the sacrotuberous ligament. The flat, pyramidal-shaped muscle then crosses the greater sciatic notch and inserts on the greater trochanter of the hip joint. The piriformis muscle acts as an external rotator and adductor of the hip joint. It is innervated by the anterior rami of the L5, S1, and S2 spinal nerves. The sciatic nerve lies in close relation to the muscle and maybe irritated when the muscle undergoes pathological changes. [1]

What is Piriformis Syndrome?

Piriformis syndrome, also known as sciatic nerve entrapment syndrome, is a rare neuromuscular disorder that is characterized by the compression of the sciatic nerve by the piriformis muscle spasm. This leads to pain in the lower back and hip region. The sciatic nerve and piriformis muscle have various anatomic variations in different individuals. Irritation, inflammation, and other pathologies of the piriformis muscle cause the muscle to spasm and compress the nearby sciatic nerve, eliciting neuropathic pain. Probst et al. described six anatomic variations of the sciatic nerve concerning the piriformis muscle. 

1. In approximately 90% of people, the sciatic nerve courses below the muscle without branching. 
2. The sciatic nerve divides and passes through the center and below the piriformis muscle. 
3. The sciatic nerve divides and branches pass superior and inferior to the piriformis muscle.
4. The nerve passes through the center of the muscle without branching. 
5. The nerve courses superior to the muscle without giving off branches. 
6. The sciatic nerve divides and passes through the center and above the piriformis muscle. [2]  

Symptoms of Piriformis Syndrome

Approximately 2.4 million people suffer from lower back and the sciatic pain associated with piriformis syndrome, per annum. Patients suffering from piriformis syndrome present with these common signs and symptoms. [3]

1. Lower back and buttock pain
2. The lower back and buttock pain worsens upon sitting and standing for longer than 20 minutes 
3. Intense pain when sitting and/or squatting
4. External and internal tenderness over the greater sciatic notch of the hip bone 
5. The pain radiates to the leg of the same side
6. Paresthesia or numbness and prickling sensation of the hip and lower limb
7. Dyspareunia or pain during or after sexual intercourse arises with piriformis syndrome in female patients 
8. Pain while performing maneuvers to assess the function of the piriformis muscle

1. Heel Contralateral Knee (HCLK) Maneuver – the heel of the foot of the affected limb is placed over the opposite knee causing maximum external rotation and flexion of the hip joint.
2. Lasegue or Straight Leg Raise (SLR) Test

The patient lies in a supine position and the physician adducts and flexes the hip joint while keeping the knee extended. 

3. Freiberg Maneuver 

Forceful adduction of the hip joint while keeping the thigh extended, causing the piriformis muscle to stretch and elicit pain.

4. Flexion, Adduction, Internal Rotation (FAIR) Test

The patient lies on the side with the affected hip above. The physician performs the FAIR test by flexing, adducting, and internally rotating the leg of the patient to check for the irritation of the sciatic nerve in the piriformis syndrome. 

9. Diminished power, reflexes, and sensation of the hip and lower limb. 

Causes and Risk Factors of Piriformis Syndrome 

Follow are the etiological and predisposing factors that increase the chances of developing piriformis syndrome. [4]

1. Bipartite or split piriformis muscle, branching sciatic nerve, and/or atypical course of the sciatic nerve about the piriformis muscle 
2. Inflammation, scar tissue, and hypertrophy of the piriformis muscle due to excessive exercise that is usually seen in athletes 
3. Direct trauma to the hip or buttock area 
4. Direct tumor invasion that compresses the nerve
5. Prolonged sitting position (drivers, bicycle riders, and office employees)
6. Excessive climbing of stairs 

通常の治癒サイクル 

Before discussing the treatment of piriformis syndrome, it is imperative to discuss the normal healing cycle. The cycle comprises three stages, named inflammation, proliferation, and maturation.

1. Inflammation refers to the redness (vasodilation and increased blood flow), warmth (increased blood flow), swelling (accumulation of fluid), pain (inflammatory mediators irritate nerve endings), and loss of function. This process aims to gather the inflammatory and immune cells to eliminate the cause that elicited inflammation. Inflammation may be acute (short-term) or chronic (long-term). 
2. Proliferation refers to the laying down of collagen and proteoglycans by the proliferating fibroblasts, which lay a scaffold for the new tissue to form. This is accompanied by reepithelization and angiogenesis to support the healing tissue. This is the stage where muscle knots or trigger points, fascia restrictions, and scar tissue form. Fascia is comprised of two layers, superficial and deep fascia. Deep fascia is further divided into aponeurosis (covering multiple muscles), epimysium (covering single muscle), perimysium (covering bundle of muscle fibers), and endomysium (covering of a single muscle fiber). The fascia structures are further complicated by the presence of sublayers within each, which may adhere and cause fascia restriction that limits the range of motion and incites pain. 
3. Maturation occurs as the inflammation and proliferation are resolved, the inflammatory substances are cleared off, and the muscle regains its structure and function. Excess collagen formed during the previous stage is degraded. [5]

Current At-Home Treatments That Do Not Work

Following home remedies are commonly used to stop piriformis syndrome pain, however, these remedies are ineffective and do not contribute to stopping the vicious healing cycle. 

1. Heat and ice provide temporary pain relief but do not break off the scar tissue 
2. Electric stimulation is a temporary method to alleviate pain but does not have long-term benefits 
3. Foam roller and massage do not provide sufficient mechanical stimulation to the deeper piriformis muscle 
4. Stretching of the inflamed muscle aggravates the symptoms of piriformis syndrome. Similar outcomes are observed when strengthening exercises are performed during the inflammation stage of the healing cycle. 

Effective Piriformis Syndrome Treatment 

To stop piriformis syndrome pain and inhibit the vicious healing cycle, treatment should be administered in such a way as to address both the inflammation and proliferation stages simultaneously. 

1. 炎症段階 
   1. Take adequate rest and avoid stretching to treat mild inflammation
   2. MagnaHeal 2 is used for treating moderate to severe inflammation. The healing device is made of neodymium and coated with anti-inflammatory substances. MagnaHeal 2 has a magnetic force-length of 3 inches that provides soothing effects to the deeper area including the piriformis muscle. [6]
   3. Anti-inflammatory is crucial to prevent and reduce internal inflammation. Ingredients of this diet include polyunsaturated and monounsaturated fatty acids (PUFA and MUFA), flavonoids, antioxidants, phytochemicals, ginger, turmeric, black pepper, green tea, and fruits. [7]
   4. It is important to restore deficiency of essential vitamins and minerals such as magnesium to promote healing. AskASTR is a consultation program where an individual can identify a nutrient deficiency in his or her body that impairs the healing cycle and hinder the progression to the maturation stage.      
2. 増殖段階 
   1. A1 Tool is used for releasing fascia restriction in the superficial and aponeurotic fascia 
   2. A3 Tool is used for releasing superficial trigger points and scar tissue.
   3. A5 Tool is used for releasing deeper trigger points, scar tissue, and fascia restrictions. In the case of fascia restriction, it is important to release all the fascia layers to restore the range of motion and lift pressure off the sciatic nerve. 
3. Refrain from putting wallet and other items in the back pocket while sitting to prevent excessive stress on the muscle and scar tissue formation. 
4. Attain core stability and strengthen the muscles of the trunk.
5. Maintain a proper posture while sitting, standing, and performing other activities.  

結論

Piriformis syndrome contributes significantly to lower back pain and sciatica. Inflammation, irritation, hypertrophy, tumor invasion, and anatomic anomaly of the piriformis muscle causing the muscle to undergo spasm as well as develop muscle knots. These events lead to nerve compression which elicits pain in the lower back and hip area, which also radiated to the ipsilateral leg. Pain associated with piriformis syndrome can be alleviated by several treatment modalities and lifestyle modifications. 

参考文献 

1. Hicks BL, Lam JC, Varacallo M. Piriformis Syndrome. [Updated 2021 Jul 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448172/ 
2. Probst D, Stout A, Hunt D. Piriformis Syndrome: A Narrative Review of the Anatomy, Diagnosis, and Treatment. PM R. 2019 Aug;11 Suppl 1:S54-S63. doi: 10.1002/pmrj.12189. Epub 2019 Jul 22. PMID: 31102324.
3. Hopayian K, Danielyan A. Four symptoms define the piriformis syndrome: an updated systematic review of its clinical features. Eur J Orthop Surg Traumatol. 2018 Feb;28(2):155-164. doi: 10.1007/s00590-017-2031-8. Epub 2017 Aug 23. PMID: 28836092. 
4. Chang A, Ly N, Varacallo M. Piriformis Injection. [Updated 2021 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448193/ 
5. Wallace HA, Basehore BM, Zito PM. Wound Healing Phases. [Updated 2021 Nov 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470443/ 
6. Zwolińska J, Gąsior M, Śnieżek E, Kwolek A. The use of magnetic fields in treatment of patients with rheumatoid arthritis. Review of the literature. Reumatologia. 2016;54(4):201-206. doi: 10.5114/reum.2016.62475. Epub 2016 Oct 5. PMID: 27826175; PMCID: PMC5090029.
7. Bustamante MF, Agustín-Perez M, Cedola F, Coras R, Narasimhan R, Golshan S, Guma M. Design of an anti-inflammatory diet (ITIS diet) for patients with rheumatoid arthritis. Contemp Clin Trials Commun. 2020 Jan 21;17:100524. doi: 10.1016/j.conctc.2020.100524. PMID: 32025586; PMCID: PMC6997513.