■ letters to the editor

Piriformis Syndrome

To the Editor: unresolved chronic irritation, such as a myofascial , may In the article on piriformis syndrome by Foster, which eventually lead to adhesions and entrapment. appeared in the August 2002 issue of Orthopedics (25[8]:821- The sciatic nerve may be impinged or entrapped by an 825), a distinction of piriformis syndrome in primary and anatomical variant of the as postulated by secondary is presented and analyzed. Pecina8 and in several case reports.2,9-11 These anatomic According to the author, intrinsic piriformis muscle variations may increase the sciatic nerve susceptibility to problems constitute primary piriformis syndrome, such as the injury, thus we believe these cases should be classified as injury after a fall as described by Robinson,1 pyomyositis,2 or secondary piriformis syndrome because intrinsic piriformis pyositis ossificans3 of the muscle. Furthermore, Foster defines muscle pathology is not present. Some authors consider these secondary piriformis syndrome “as piriformis irritation variants an incidental finding11,12 in patients with primary secondary to the ” as described by Yeoman4 or piriformis syndrome. Pace and Nagle,5 or by a mass effect, as described in numerous McCrory and Bell13 proposed the term “deep gluteal case reports.6 syndrome,” as they found it difficult to attribute all pain elements We believe, however, that the reference by Yeoman4 should exclusively to the sciatic nerve and not to the posterior cutaneous cease or be reserved as a historic reference to , as he nerve of the thigh or the gluteal nerves. They also considered that considered sciatica to be the result of a periarthritis involving any other hip rotator could compress the neural structures.13 the anterior sacroiliac ligament, piriformis muscle, and Extending their suggestion, we believe “pelvic outlet adjacent branches of the sciatic nerve. syndrome” includes all cases of extraspinal nerve compression In the article by Pace and Nagle,5 the pathophysiologic and lower extremity pain, augmenting or replacing the term mechanism proposed is a focal irritability of the piriformis “secondary piriformis syndrome.” Compressive structures such muscle, usually caused by trauma, resulting in a so-called as aneurysms or arterial malformations,14-18 benign or malignant trigger-point syndrome. Thus, these cases should be classified tumors,19,20 endometriosis,21,22 inflamed structures,23-25 sciatic as primary piriformis syndrome, as the piriformis muscle is the hernias,26 adhesions after total hip replacement,27 or malunited structure of the symptoms’ origin. fractures28,29 may be sited anywhere before, at, or after the In addition, we do not recognize any relation between sciatic notch. The specific signs of piriformis muscle irritability, sacroiliac joint syndrome and piriformis syndrome. Bernard and such as pain in flexion, adduction, and internal rotation or Kirkaldy-Willis7 reported an incidence of 20.55% and 0.33%, positive Pace test may be present. This classification would respectively. Stressing the need to recognize coexisting lesions, increase physician’s vigilance to obtain a detailed history and they found only 13 cases of muscle syndrome (not specific perform a complete physical examination, to use the available piriformis syndrome) associated with 336 cases of sacroiliac imaging and electrodiagnostic studies, and avoid unnecessary joint syndrome. Finally, piriformis syndrome treated effectively spinal operations in cases of obscured lower leg pain syndromes. by injecting the sacroiliac joint has not been reported. E.C. Papadopoulos Aside from Foster’s classification, which is based on the D.S. Korres presence (primary) or absence (secondary) of intrinsic G. Papachristou piriformis muscle lesion, Chen2 classified piriformis syndrome N. Efstathopoulos based on the pain mechanism. He states two mechanisms Athens, Greece explain buttock pain and sciatica: 1) myofascial pain syndrome as described by Pace and Nagle,5 and 2) sciatic nerve REFERENCES entrapment as described by Robinson.1 In buttock pain, thus 1. Robinson DR. Pyriformis syndrome in relation to sciatic pain. Am J piriformis muscle trauma (primary piriformis syndrome), two Surg. 1947; 73:355-358. factors determine the energy absorbed: the magnitude of injury 2. Chen WS. Bipartite piriformis muscle: an unusual cause of sciatic nerve entrapment. Pain. 1994; 58:269-272. and the habitus of the patient. Low-energy absorption may 3. Beauchesne RP, Schutzer SF. Myositis ossificans of the piriformis mus- cause a myofascial piriformis syndrome, in contrast to a high- cle: an unusual cause of piriformis syndrome. A case report. J Bone energy absorption that causes hematoma formation and Joint Surg Am. 1997; 79:906-910. scarring and thus nerve entrapment. On the other hand, an (continued on page 799)

AUGUST 2004 | Volume 27 • Number 8 797 ■ letters to the editor

(Letters to the Editor continued) 4. Yeoman W. The relation of of the sacroiliac joint to sciatica, Reply: with an analysis of 100 cases. Lancet. 1928; 2:1119-1122. The Yeoman reference is indeed historic, as it predated 5. Pace JB, Nagle D. Piriform syndrome. West J Med. 1976; 124:435-439. Mixtner and Barr’s recognition of disk herniation; however, I 6. Foster MR. Piriformis syndrome. Orthopedics. 2002; 25:821-825. consider sciatica as radiating pain below the knee, and I agree 7. Bernard TN Jr, Kirkaldy-Willis WH. Recognizing specific characteris- and re-emphasize the need to remain aware that sciatica is not tics of nonspecific low . Clin Orthop. 1987; 217:266-280. solely a result of intraspinal pathology. Regardless of the role 8. Pecina M. Contribution to the etiological explanation of the piriformis of the sacroiliac joint, overstated by Yeoman and in my opinion syndrome. Acta Anat (Basel). 1979; 105:181-187. not much better understood today, most hip replacement 9. Sayson SC, Ducey JP, Maybrey JB, Wesley RL, Vermilion D. Sciatic surgeons encounter patients who not only have deteriorated entrapment neuropathy associated with an anomalous piriformis mus- cle. Pain. 1994; 59:149-152. disks but also have, as he describes, a “periarthritis,” so leg 10. Ozaki S, Hamabe T, Muro T. Piriformis syndrome resulting from an pain is not an uncommon clinical diagnostic dilemma. anomalous relationship between the sciatic nerve and piriformis mus- Regardless of the interpretation of Pace and Nagle’s article, cle. Orthopedics. 1999; 22:771-772. they report a 6:1 female predisposition, with the most common 11. Benson ER, Schutzer SF. Posttraumatic piriformis syndrome: diagnosis complaint being dyspareunia. The focal irritability of the and results of operative treatment. J Bone Joint Surg Am. 1999; 81:941-949. piriformis muscle in the patients of Pace and Nagle would be 12. Levin SM. Piriformis syndrome. Orthopedics. 2000; 23:183-184. at the origin of the piriformis, which overlies the sacroiliac 13. McCrory P, Bell S. Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock. Sports Med. 1999; 27:261-274. joint, intrapelvic, and is consistent with the female 14. Geelen JA, de Graaff R, Biemans RG, Prevo RL, Koch PW. Sciatic predisposition and dyspareunia, for which intravaginal nerve compression by an aneurysm of the internal iliac artery. Clin injections have been done. Those injections also are in the Neurol Neurosurg. 1985; 87:219-222. vicinity of the sacroiliac joint. I do not consider an intrinsic 15. Merlo IM, Poloni TE, Alfonsi E, Messina AL, Ceroni M. Sciatic pain in problem of the piriformis muscle as a plausible cause of a young sportsman. Lancet. 1997; 349:846. dyspareunia; in fact, I consider birthing children and 16. Papadopoulos SM, McGillicuddy JE, Albers JW. Unusual cause of ‘pir- iformis muscle syndrome’. Arch Neurol. 1990; 47:1144-1146. subsequent sacroiliitis the only credible explanation for the 17. Hughes SS, Goldstein MN, Hicks DG, Pellegrini VD Jr. Extrapelvic female predisposition in Pace’s family practice population. In compression of the sciatic nerve. An unusual cause of pain about the this I depart from Papadopoulos et al, as I consider sacroiliitis hip: report of five cases. J Bone Joint Surg Am. 1992; 74:1553-1559. significantly correlated with piriformis syndrome. 18. Shinozaki T, Arita S, Watanabe H, Chigira M. Aneurysm of a persistent Further, I would suggest that trigger points are not sciatic artery. Arch Orthop Trauma Surg. 1998; 117:167-169. exclusively a problem intrinsic to muscle, and in my 19. Vanneste JA, Butzelaar RM, Dicke HW. Ischiadic nerve entrapment by an extra- and intrapelvic lipoma: a rare cause of sciatica. Neurology. experience, many are referred or secondary; many lumbar 1980; 30:532-534. “referred pain” syndromes or the muscles are normal. 20. Bickels J, Kahanovitz N, Rubert CK, et al. Extraspinal bone and soft- Perhaps a pelvic outlet syndrome would be appropriate for tissue tumors as a cause of sciatica. Clinical diagnosis and recommen- a compression neuropathy, essentially “peripheral” in terms of dations: analysis of 32 cases. Spine. 1999; 24:1611-1616. being distal to the spinal canal, but the symptoms are from the 21. Takata K, Takahashi K. Cyclic sciatica. A case report. Spine. 1994; 19:89-90. sciatic nerve, which the piriformis overlies, and in my 22. Torkelson SJ, Lee RA, Hildahl DB. Endometriosis of the sciatic nerve: experience, has been hour-glassed in every case I have a report of two cases and a review of the literature. Obstet Gynecol. explored. The other external rotators (obturator internus and 1988; 71:473-477. superior and inferior gemilli) are anterior to the sciatica nerve 23. Chen WS. Chronic sciatica caused by tuberculous sacroiliitis. A case and the piriformis muscle, hence, when they are detached from report. Spine. 1995; 20:1194-1196. the femur, and retracted posteriorly for a customary total hip 24. Birkbeck D, Watson JT. Obturator internus pyomyositis. A case report. Clin Orthop. 1995; 316:221-226. approach, they remove the sciatic nerve from the field and 25. Peh WC, Reinus WR. Piriformis bursitis causing sciatic neuropathy. harms way. The piriformis has a specific role in this form of Skeletal Radiol. 1995; 24:474-476. sciatic nerve irritation or compression by virtue of its 26. Servant CT. An unusual cause of sciatica. A case report. Spine. 1998; anatomical position. 23:2134-2136. Mark R. Foster, PhD, MD 27. Uchio Y, Nishikawa U, Ochi M, Shu N, Takata K. Bilateral piriformis Pittsburgh, Pa syndrome after total hip arthroplasty. Arch Orthop Trauma Surg. 1998; 117:177-179. 28. Spinner RJ, Atkinson JL, Wenger DE, Stuart MJ. Tardy sciatic nerve palsy following apophyseal avulsion fracture of the ischial tuberosity. Case report. J Neurosurg. 1998; 89:819-821. 29. Miller A, Stedman GH, Beisaw NE, Gross PT. Sciatica caused by an avulsion fracture of the ischial tuberosity. A case report. J Bone Joint Surg Am. 1987; 69:143-145.

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