■ letters to the editor Piriformis Syndrome To the Editor: unresolved chronic irritation, such as a myofascial injury, may In the article on piriformis syndrome by Foster, which eventually lead to adhesions and sciatic nerve 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 piriformis muscle 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 sacroiliac joint” 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 sciatica, 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 arthritis 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 back pain. 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. 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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. 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