Introduction
Piriformis syndrome is one of the causes of sciatica. This syndrome occurs due to piriformis muscle pressure or stimulation on the sciatic nerve [2]. The clinical manifestations of piriformis syndrome are similar to intervertebral disc herniation, including pain in butt or hip without a specific reason, or neurological symptoms such as foot drop [4, 5]. Stretching the area that has muscle spasm can usually help improve or prevent its occurrence [3]. Considering the number of new cases of low back pain and sciatica (40 million cases per year), the incidence of piriformis syndrome is approximately 2.4 million people per year [9]. The present study aims to investigate the effect of core stability exercises on pain and inflammation in patients with piriformis syndrome.
Materials and Methods
This is a randomized clinical trial with a pre-test/post-test design. The study population consists of all patients with piriformis syndrome referred to medical centers in Arak, Iran. Using the G*Power software, and considering a test power of 0.84 and the effect size was 1.4, the sample size was determined 20. Participants were randomly divided into two groups of control (n=10) and exercise (n=10), after examination and clinical examinations by a specialist and performing the FAIR test to diagnose piriformis syndrome. Using the McGill pain questionnaire, the pain level of the subjects was examined, and their inflammation was evaluated by a specialist using MRI images. The exercise group performed core stability exercises for 6 weeks, while the control group continued their normal life during this period. T-test, Chi-square test, and McNemar’s test were used to examine the differences between groups. The significance level was set at 0.05.
Results
The mean pain score in the control group decreased from 95.2 to 90.7 after the exercise, which was not statistically significant (P=0.562). In the exercise group, the mean pain score decreased from 91.7 to 33.4, and this decrease was statistically significant (P=0.0); Therefore, at 95% confidence interval, we can say that core stability exercises had a significant effect on the pain of patients with piriformis syndrome (P<0.05; Table 1).


The number of patients with inflamed nerve in the control group decreased from 10 in the pre-test phase to 8 in the post-test phase, but this decrease was not statistically significant (P=0.5). In the exercise group, it was reduced from 10 to 2, and this decrease was statistically significant (P=0.008); Therefore, we can say that core stability exercises had a significant effect on the inflammation of patients with piriformis syndrome (P<0.05, Table 2).


Discussion
Due to the fact that the piriformis muscle is located near the sciatic nerve, its spasm causes pressure on the nerve, leading to sciatica pain and piriformis syndrome [20, 21]. The sciatic nerve may become inflamed due to the pressure caused by the abnormal piriformis muscle [1, 4]. Since the piriformis muscle is one of the muscles in the central region of the body [22], in this study, core stability stretching exercises were used which showed a significant effect on pain and inflammation in patients with piriformis syndrome. Therefore, it can be concluded that core stability exercises can reduce pain and inflammation in patients with piriformis syndrome. These exercises can be used in treatment of these patients.

Ethical Considerations
Compliance with ethical guidelines
All ethical principles were according to the guidelines of the ethics committee of Arak University of Medical Sciences (Ethical Code: IR.ARAKMU.REC.1400.157) and was registered by Iranian Registry of Clinical Trials (ID: IRCT20211003052662N1).

Funding
This study was extracted from the master thesis of the first author. It was not funded by any organizations.

Authors' contributions
Conceptualization, supervision, editing & review: Masoud Golpayegani; methodology: Rashid Doosti Irani and Fardin Faraji; data analysis: Rashid Doosti Irani.

Conflicts of interest
The authors declare no conflict of interest.

Acknowledgements
The authors would like to thank all patients participated in this research for their cooperation.

References

1. Golpayegani M, Alvani E, Shahrjardi Sh, Omidi M. [The effect of selected corrective exercises on the Q angle of patients with sciatic nerve pain (Persian)]. Paper preset at: The 5th International Conference on Physical Education and Sports Sciences. 10 March 2018; Tehran, Iran. [Link]
2. Mohammadi S. [The effect of a selected movement program course on the deformity, composition and muscle spasm of children with spastic hemiplegia (Persian)]. [MSc. thesis]. Arak: Arak University; 2010. [Link]
3. Mahmoudigilani M. [Review of antispasmodic drugs (Persian)]. [PhD. thesis]. Tehran: University of Tehran; 1968. [Link]
4. Carare RO, Goodwin M. A unique variation of the sciatic nerve. Clin Anat. 2008; 21(8):800-1. [DOI:10.1002/ca.20696] [PMID]
5. Ebraheim N, Andrews K, Stirling B, Tanios M. Piriformis Syndrome or True Sciatica: Are They the Same or Different?. MOJ Orthop & Rheumatol. 2017; 9(3):11-12. [DOI:10.15406/mojor.2017.09.00357]
6. Chaitow L. Soft-tissue Manipulation: A Practitioner’s Guide to the Diagnosis and Treatment of Soft-tissue Dysfunction and Reflex Activity. United State: Healig Art Perees; 1987. [Link]
7. Steiner C, Staubs C, Ganon M, Buhlinger C. Piriformis syndrome: pathogenesis, diagnosis, and treatment. J Am Osteopathic Association. 1987; 87(4):318-23. [DOI:10.1515/jom-1987-870422]
8. Hughes S, Goldstein M, Hicks D, Pellegrini Jr V. Extrapelvic compression of the sciatic nerve. An unusual cause of pain about the hip: Report of five cases. J Bone Joint Surg. 1992; 74(10):1553-9. [DOI:10.2106/00004623-199274100-00017]
9. Chang A, Ly N, Varacallo M. Piriformis injection.Piriformis Injection. 2022 Sep 4. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2020. [PMID]
10. Beaton LE, Anson BJ. The sciatic nerve and the piriformis muscle: their interrelation a possible cause of coccygodynia. J Bone Joint Surg. 1938; 20(3):686-8. [Link]
11. Beatty RA. The piriformis muscle syndrome: a simple diagnostic maneuver. Neurosurgery. 1994; 34(3):512-4. [DOI:10.1227/00006123-199403000-00018] [PMID]
12. Pace JB, Nagle D. Piriform syndrome. West J Med. 1976; 124(6):435. [PMID] .[PMCID]
13. Cummings M. Piriformis Syndrome. Acupuncture in Med. 2000; 18(2):108-21. [DOI:10.1136%2Faim.18.2.108]
14. Samimi S. [Evaluation of the effectiveness of three treatment methods for patients with chronic sciatica (Persian)]. [MSc. thesis]. Kermanshah: Razi University; 2009. [Link]
15. Jamili P, Tajik P, Kashfi A, Iria P, Babazadeh M, Bahadori M. [Repair of damaged sciatic nerve using low helium-neon laser in an experimental model (Persian)]. J Laser Med. 2005; 4(3):9-15. [Link]
16. Daneshmandi H, Alizadeh M, Gharakhanlou R. Corrective Exercises: Fifteenth Edition, Tehran: Organization for the Study and Compilation of University Humanities (Samt), Research Institute for Humanities Research and Development, and Research Institute for Physical Education and Sports Sciences; 2017. [Link]
17. Fishman LM, Zybert PA. Electrophysiologic evidence of piriformis syndrome. Arch Phys Med Rehabil. 1992; 73(4):359-64.[DOI:10.1016/0003-9993(92)90010-t] [PMID]
18. Ebrahiminejad Gh, Ebrahiminejad A, Kohan S, Bahrampour A. [Using McGill Questionnaire to assess pain in patients before and after neurosurgery (non-traumatic brain injury) in Shahid Bahonar Hospital in Kerman (Persian)]. J Kerman Uni Med Sci. 2004; 11(2).119-125 [Link]
19. Haaga JR. CT and MRI of the whole body. Philadelphia, PA: Mosby/Elsevier; 2009. [Link]
20. Güvençer M, Iyem C, Akyer P, Tetik S, Naderi S. Variations in the high division of the sciatic nerve and relationship between the sciatic nerve and the piriformis. Turk Neurosurg. 2009; 19(2):139-44. [PMID]
21. Klein MJ. Piriformis syndrome. eMedicine Web site. Available at: [Link]
22. Akuthota V, Nadler SF. Core strengthening. Arch Phys Med Rehabil. 2004; 85:86-92. [DOI:10.1053/j.apmr.2003.12.005] [PMID]
23. Fishman LM, Dombi GW, Michaelsen C, Ringel S, Rozbruch J, Rosner B, et al. Piriformis syndrome: diagnosis, treatment, and outcome--a 10-year study. Arch Phys Med Rehabil. 2002; 83(3):295-301. [DOI:10.1053/apmr.2002.30622] [PMID]
24. Tonley JC, Yun SM, Kochevar RJ, Dye JA, Farrokhi S, Powers CM. Treatment of an individual with piriformis syndrome focusing on hip muscle strengthening and movement reeducation: A case report. J Orthop Sports Phys Ther. 2010; 40(2):103-11. [DOI:10.2519/jospt.2010.3108] [PMID]
25. Golpayegani M, Sayari M, Rafati H. [The effect of three methods of movement therapy, massage therapy and medication on reducing pain and treating sciatica (Persian)]. Paper preset at: Sixth National Conference on Sports Science and Physical Education of Iran. 5 july 2020; Tehran, Iran. [Link]
26. Chen YW, Chiu CC, Hsieh PL, Hung CH, Wang JJ. Treadmill training combined with insulin suppresses diabetic nerve pain and cytokines in rat sciatic nerve. Anesth Analg. 2015; 121(1):239-46. [DOI:10.1213/ane.0000000000000799] [PMID]