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| IMAGE QUIZ ARCHIVE | ||||||
| Image Quiz | ||
| Sciatica Following a Fall1 continued |
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| Answer: Piriformis syndrome secondary to myositis ossificans of the piriformis muscle. | ||
| Discussion | ||
| Piriformis syndrome is usually a diagnosis of exclusion once the more common causes of sciatica have been ruled out2. Yoeman3 is credited as being the first author to have described entrapment of the sciatic nerve by the piriformis muscle. Freiberg and Vinke4,5 further defined the condition and described what is known as the Freiberg sign (pain caused by passive internal rotation of the extended thigh). Beaton and Anson6 described four anatomical variations in the relationship between the piriformis muscle and the sciatic nerve and implicated these variations as a cause of compression and inflammation of the sciatic nerve. | ||
| The diagnosis often can be made on the basis of a careful clinical evaluation2,7-10. Physical findings that suggest compression of the sciatic nerve by the piriformis muscle include tenderness over the sciatic notch, isolated atrophy of the gluteus maximus, dysesthesia of the posterior aspect of the thigh, and tenderness of the rectal wall with or without a sausage-shaped mass that is felt laterally during a rectal examination11. Additional findings that are indicative of such compression include the Freiberg sign4,5 (pain with forced internal rotation of the extended thigh) and the sign of Pace and Nagle8 (pain with resistance to abduction and external rotation of the thigh). The innervations of the gluteus medius, gluteus minimus, and tensor fasciae latae often are spared as the superior gluteal nerve branches proximal to the piriformis muscle. The tibial division of the sciatic nerve is involved less often than is the peroneal division because the former is located more medially in the sciatic notch7,12,13. Hypoesthesia in the distribution of the posterior cutaneous nerve of the thigh may be present7. A positive Lasègue sign has also been reported to be a clinical feature of piriformis syndrome2,7,9,11,14. In our experience, most patients who have piriformis syndrome secondary to trauma involving the buttock will have a positive Lasègue sign. Back pain is uncommon, nonspecific, and not related to piriformis syndrome. | ||
| Plain radiographs are usually normal. However, computerized axial tomography and magnetic resonance imaging have been reported to show hypertrophy of the piriformis muscle in some instances11,13,15. In our experience, eight patients who ultimately had an operation for the treatment of piriformis syndrome had asymmetry (hypertrophy or atrophy) of the piriformis muscles on computerized axial tomography scans. | ||
| References | ||
| 1. Beauchesne RP, Schutzer SF. Myositis ossificans of the piriformis muscle: An unusual cause of piriformis syndrome. A case report. J Bone Joint Surg Am. 1997;79:906-10. 2. Vandertop WP, Bosma WJ. The piriformis syndrome. A case report. J Bone Joint Surg Am. 1991;73:1095-7. 3. Yoeman W. The relation of arthritis of the sacro-iliac joint to sciatica, with an analysis of 100 cases. Lancet. 1928;2:1119-22. 4. Freiberg AH. Sciatica pain and its relief by operations on muscle and fascia. Arch Surg. 1937;34:337-50. 5. Freiberg AH, Vinke TH. Sciatica and the sacro-iliac joint. J Bone Joint Surg. 1934;16:126-36. 6. Beaton LE, Anson BJ. The sciatic nerve and the piriformis muscle: their interrelation a possible cause of coccygodynia. J Bone Joint Surg. 1938;20:686-8. 7. Hughes SS, Goldstein MN, Hicks DG, Pellegrini VD Jr. Extrapelvic compression of the sciatic nerve. An unusual cause of pain about the hip: report of five cases. J Bone Joint Surg Am. 1992;74:1553-9. 8. Pace JB, Nagle D. Piriform syndrome. West J Med. 1976;124:435-9. 9. Solheim LF, Siewers P, Paus B. The piriformis muscle syndrome. Sciatic nerve entrapment treated with section of the piriformis muscle. Acta Orthop Scand. 1981;52:73-5. 10. Steiner C, Staubs C, Ganon M, Buhlinger C. Piriformis syndrome: pathogenesis, diagnosis, and treatment. J Am Osteopath Assoc. 1987;87:318-23. 11. Jankiewicz JJ, Hennrikus WL, Houkom JA. The appearance of the piriformis muscle syndrome in computed tomography and magnetic resonance imaging. A case report and review of the literature. Clin Orthop. 1991;262:205-9. 12. Hallin RP. Sciatic pain and the piriformis muscle. Postgrad Med. 1983;74:69-72. 13. Palliyath S, Buday J. Sciatic nerve compression: diagnostic value of electromyography and computerized tomography. Electromyogr Clin Neurophysiol. 1989;29:9-11. 14. Robinson DR. Pyriformis syndrome in relation to sciatic pain. Am J Surg. 1947;73:355-8. 15. Chen WS, Wan YL. Sciatica caused by piriformis muscle syndrome: report of two cases. J Formos Med Assoc. 1992;91:647-50. |
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