Pain, 47 (1991) 345-352
345
© 1991 Elsevier Science Publishers B.V. All rights reserved 0304-3959/91/$03.50
PAIN 01926
Piriformis syndrome: a rational approach to management
1
Pamela M. Barton Department of Physical Medicine and Rehabilitation, Unit~ersityof Western Ontario, London, Ont. N6C 5Jl (Canada) (Received 20 March 1991, revision received 17 May 1991, accepted 3 June 1991)
Summary Although rarely recognized, the piriformis syndrome appears to be a common cause of buttock and leg pain as a result of injury to the piriformis muscle. Four cases representing a broad spectrum of presentations are described here. The major findings include buttock tenderness extending from the sacrum to the greater trochanter and piriformis tenderness on rectal or pelvic examination. Symptoms are aggravated by prolonged hip flexion, adduction, and internal rotation, in the absence of low back or hip findings. Minor findings may include leg length discrepancy, weak hip abductors, and pain on resisted hip abduction in the sitting position. Myofascial involvement of related muscles and lumbar facet syndromes may occur concurrently. The diagnosis is primarily clinical as no investigations have proved definitive. The role of MRI of the piriformis muscle is assessed and other investigative tools are discussed. A rational management schema is demonstrated: (1) underlying biomechanical factors and associated conditions should be corrected; (2) the patient is instructed in a home program of prolonged piriformis muscle stretching which may be augmented in physical therapy by preceding ultrasound or Fluori-Methane ® (dichlorodifluoromethane and trichloromonofluoromethane spray); (3) a trial of up to three steroid injections is attempted; and (4) if all these measures fail, consideration should be given to surgical sciatic nerve exploration and piriformis release. Key words: Piriformis syndrome; Low back pain; Pyriformis; Myofascial pain; Piriformis muscle; Sciatic nerve
Introduction
Piriformis syndrome is a little-known entity in which injury to the piriformis muscle results in buttock pain often associated with leg pain. It was first described by Yeomen [34] in 1928. The principal symptom of buttock pain, with or without leg pain, is aggravated by sitting or activity of the lower extremities. Other findings typically include buttock tenderness extending from the sacrum to the greater trochanter, piriformis muscle tenderness on rectal or pelvic examination, and aggra-
i An abstract of this work was presented as a poster at the American Academy of Physical Medicine and Rehabilitation in Seattle, WA, on 2 November, 1988.
Correspondence to: Dr. P.M. Barton, Dept. of Physical Medicine and Rehabilitation, Parkwood Hospital, 801 Commissioners Road East, London, Ontario, Canada, N6C 5J1. Tel.: (519) 685-4044. Fax: (519) 685-4052.
vation of symptoms by prolonged hip flexion, adduction and internal rotation, in the absence of low back or hip findings. Leg length discrepancy, weak hip abductors, and pain on resisted hip abduction in the sitting position may also be present. It has been suggested that pressure on the sciatic nerve by the piriformis muscle may contribute to the syndrome. The relevant anatomy has been explored in detail [1,2,6,10,19]. Myofaiciai involvement of related muscles and lumbar facet syndromes may be concurrent conditions. Fig. 1 shows the relationship of the piriformis muscle to the sciatic nerve and the iliopsoas muscle. The diagnosis of piriformis syndrome is primarily clinical as no definitive investigations have been reported. In general, bone scans and electrodiagnostic studies do not appear helpful, although there have been isolated reports of their utility [14,28]. Both conservative [3,7,11-13,17,18,21~24,25,27,2933] and surgical [4,8,9,16,20,22,26] management have been advocated and these approaches have been described extensively in individual reports. To date no
346
,rmis
Psoa:
Fig. 1. Anatomical relationships of the piriformis muscle: anterior (left) and posterior (right).
one seems to have described a comprehensive approach to the treatment of this condition. In the present report I describe four case studies of piriformis syndrome in which a systematic management program resulted in good therapeutic outcome. In two of these cases magnetic resonance imaging (MRI) proved useful. These case studies range from mild to severe examples of piriformis syndrome and outline an orderly progression of management from conservative to surgical.
Case 1
A 31-year-old woman developed pain in the right buttock while shovelling snow. One week later, the morning after bowling, she had severe pain in the back and right buttock. Two months later she also had pain radiating to the anterior thigh and groin, and occasionally into her posterior thigh and calf. She could sit for 2 h provided she shifted position frequently. She could walk for 30 min and had no difficulty standing or lying, preferably with her knees flexed. Previous management had included non-steroidal anti-inflammatory drugs, chiropractic manipulation and physical therapy. Her past medical history was unremarkable.
She was tender in the right buttock and in the right piriformis muscle on vaginal examination. Her discomfort was increased by right hip flexion, adduction and internal rotation with pain radiating to the anterior thigh. The lengths of her legs, the strength of her hip abductors and hip abduction against resistance in the sitting position were normal. Neurological examination, bowstring signs and gait were normal. She experienced slight discomfort on forward lumbar flexion and straight leg raising was equivocal on the right. Radiographs of the lumbosacral spine were unremarkable. As her physical examination and investigation were consistent with shortening of the piriformis muscle, she was instructed in prolonged stretching exercises of the right piriformis to be done every 2 h during waking hours. These exercises are illustrated in Fig. 2. Within 1 week she had significant relief of her right buttock symptoms and had no further complaints of back pain. She probably had mild involvement of her right iliopsoas muscle as well. This was determined in retrospect on the basis of her concurrent low back and groin pain and her preference for lying supine with her knees flexed. On hip flexion, adduction and internal rotation she also experienced groin rather than buttock pain. She did not require specific intervention for the iliop-
347
Fig. 2. Stretching exercises - prolonged stretching of right piriformis muscle by flexion, adduction and internal rotation of right hip in standing (right) and supine (left) positions. Patients are instructed to begin holding the stretch for 5 sec and gradually increase to a 60 sec stretch.
soas muscle as it was likely stretched by the internal rotation of the piriformis stretch.
Case 2 A 40-year-old male social worker developed back pain after each of three bouts of strenuous activity (racquet ball and dancing). H e required 3 days of bed rest and 1 week off work following the third episode of pain. T h r e e months later he presented with low back ache radiating into the thighs bilaterally. H e had no difficulty lying, standing or sitting, although he did report having pain after prolonged driving or the day
after extensive walking. He had slight discomfort on forward flexion, extension and left lateral rotation of the low back. T h e r e was tenderness in the right buttock from the sacrum to the greater trochanter. X-rays of the lumbosacral spine were normal. He was placed on 375 mg naproxen p.o., b.i.d. One month later, he reported that he had attempted to use some weight lifting equipment but his symptoms had increased. The naproxen was not helpful. At this time his pain was more localized to the right buttock. He was tender in the right buttock from the sacrum to the greater trochanter and tender in the right piriformis on rectal examination. He had slight buttock discomfort on right hip flexion, adduction and internal
348 the right buttock. He cancelled an appointment 2 months later as he had no further pain.
Case 3
4 Fig. 3. Piriformis injection sites: (a) medial and (b) lateral. Patient lies on unaffected side. Needle is placed perpendicular to skin at point of maximal tenderness.
rotation. Leg lengths were equal, right hip abductor strength was normal and there was no discomfort on resisted hip abduction while sitting. Low back range of motion and neurological examination were normal. One week later he received an injection of betamethasone sodium phosphate and 12 mg betamethasone acetate (Celestone ® Soluspan, Schering) and 8 ml of 0.5% lidocaine HCI into the medial right piriformis muscle. The location of the injection is illustrated in Fig. 3a. Two weeks later, he reported that the day after the injection, his right buttock pain had resolved and he had been dancing and playing soccer on several occasions without difficulty. His examination was unremarkable other than slight tenderness on palpation of
A 32-year-old male physician and marathon runner presented with an 8 month history of increasing pain in the left low back and left buttock with occasional radiation of pain posteriorly to the left knee. All running activities aggravated the pain. short fast runs being the most difficult, although he was still able to run five miles in 40 rain three times weekly. The low back pain was aggravated by lumbar extension as well as by prolonged sitting and standing. The ache in the left buttock, which did not consistently occur with the low back pain, was especially aggravated by the latter part of his golf swing which required internal rotation of the left hip. Previous treatment with non-steroidal anti-inflammatory drugs, discontinuance of running and chiropractic manipulations had been unsuccessful. Lumbar movement revealed pain on combined extension and left side bending. He was tender to the left of the L5 spinous process, in the left buttock from the sacrum to the greater trochanter and in the left piriformis muscle on rectal examination. Left buttock pain was noted on flexion, adduction and internal rotation of the left hip as well as on resisted hip abduction while sitting. There was a mild left Trendelenburg sign but his legs were equal in length. Neurological examination of his legs was normal. X-rays of the lumbosacral spine showed minor degenerative changes. M R I of the pelvis which is shown in Fig. 4 was normal. One week after a left L5 facet injection, he reported resolution of all the back pain and demonstrated normal and pain-free range of motion of the lumbar spine.
Fig. 4. MRI of pelvic muscles. Case 3 (left) normal piriformis (short solid arrows) and iliopsoas (long arrows) muscles bilaterally. Case 4 (right) normal piriformis muscles (white arrows) bilaterally and normal left iliopsoas muscle (black arrows). Note severe atrophy of right iliopsoas muscle.
349 As only the left buttock pain remained, he was given an injection of 8 ml of 0.5% lidocaine HCI and 80 mg of methylprednisolone acetate (Depo-medrol ®, Upjohn) into the medial left piriformis muscle with complete resolution of the remaining positive findings on re-examination 10 min later. He was placed on a home program of prolonged stretching of the left piriformis muscle with a concurrent physical therapy program of ultrasound to the left buttock followed by piriformis stretching. Shortly thereafter he reported that his pain had totally resolved and that he had resumed his normal activities. Two months after the piriformis injection, he noticed increasing left buttock discomfort, less severe than previously, and possibly due to discontinuing his stretching program and to building a deck at home. He continued running five miles three times weekly. He was tender in the left buttock as well as in the left piriformis muscle on rectal examination. A medial left piriformis injection was repeated with total resolution of his physical findings. He was placed on a nonsteroidal anti-inflammatory drug and reinstructed in prolonged stretching of the left piriformis muscle. Two months after the second injection he resumed normal activities and continued pain free.
Case 4
A 39-year-old dental assistant developed pain in the right buttock and hip gradually over 15 years with no specific inciting event. She presented with right buttock pain radiating to the right greater trochanter, aggravated by any form of physical activity and alleviated by right leg traction. All walking was painful and was limited to 20 min. When fatigued, she limped on her right leg. Standing was painful after sitting for any length of time. Right groin exploration had been performed twice, 10 and 5 years previously. Sitting on hard surfaces had caused slight discomfort since fracturing her coccyx 20 years previously. Five months of physical therapy had been unsuccessful in alleviating her pain. She was tender in the right buttock from the sacrum to the greater trochanter and in the right piriforrnis muscle on rectal examination. She had severe pain in the right buttock on right hip flexion, adduction and internal rotation as well as on resisted hip abduction while sitting. The right leg was 1 cm longer than the left. She experienced a pain in her right buttock which felt like electrical shocks when the right hip was internally rotated past neutral. Right straight leg raising caused pain at 60 °. Right iliopsoas stretching caused discomfort. There was a well healed longitudinal incision in the right groin. Lumbar spine range of motion and lower extremity neurological examination were normal. X-rays of the pelvis and right hip as well as a
Fig. 5. Surgicalrelease of right piriformismuscle.Posteriorapproach to hip. Forcepsunder piriformistendon.Solidarrowindicatesgreater trochanter.
bone scan were normal. MRI of the pelvis and lumbar spine which is shown in Fig. 4 revealed atrophy of the right iliopsoas muscle with a normal lumbar spine and normal piriformis muscles. A 1 cm heel lift was placed on the left shoe. A 1 month trial of physiotherapy twice weekly consisting of ultrasound to the right buttock followed by specific piriformis stretching, in parallel with a home stretching program of the piriformis, produced 20 ° of right hip internal rotation, but no other changes. Two sequential medial right piriformis injections with 8 ml of 0.5% lidocaine HCI and 80 mg of methylprednisolone acetate (Depo-medrol ®, Upjohn) were unsuccessful and the patient was referred for surgery. Surgical exploration through a posterolateral approach revealed the right sciatic nerve to exit normally from under the piriformis muscle which was released by resecting 1 cm of the tendon near its insertion at the piriformis fossa. The greater trochanteric bursa was noted to be normal. One month after surgery, her buttock pain had resolved. She had reduced range of right hip flexion, adduction and internal rotation but this manoeuver did not elicit any form of buttock pain. However, she was experiencing constant right groin and slight low back pain which her previous severe buttock pain may have masked. Stretching exercises were deferred. Four months after surgery, reassessment reproduced her right groin and low back pain on stretching the right iliopsoas muscle in the supine and standing positions, and the right iliopsoas muscle was tender to abdominal palpation. Right hip flexion, adduction and internal rotation caused no buttock discomfort, but reproduced her right groin discomfort. (Due to its attachment to the lesser trochanter, the iliopsoas muscle is also stretched in this manoeuvre. It was not previously painful because internal rotation was re-
350 stricted prior to the piriformis release.) She was placed on prolonged stretching exercises for her right piriformis and right iliopsoas muscles. Seven months after the piriforrnis release, she was pain free, except for slight discomfort in the right groin after extreme activity such as excessive swimming or walking. Right hip flexion against resistance was painful. Twelve months after the piriformis release she reported difficulty without pain when putting pantyhose on her right leg. On examination, flexion of the right hip was painful and reduced in strength to 2/5. Movement of the right hip was pain free but reduced: flexion: right 110 °, left 135 °; extension: right - 3 0 °, left normal; abduction: right 15 °, left 30 °; adduction: right 15 °, left 45°; internal rotation: right 15 °, left 35 °; external rotation: right 25 °, left 65 °. (Strength and range of motion had previously been very difficult to assess due to pain.) She was placed on a program to increase the range of motion and strength of the right hip. Fourteen months after surgery the strength and range of motion respectively of the right hip were: flexion 2/5, 100 °; extension 2/5, - 3 0 °; abduction 5/5, 15 °; adduction 2/5, 15 °; internal rotation 3/5, 20 °; external rotation 3/5, 30 °. Hip strength testing was non-painful for the first time. Twenty-seven months after surgery she reported that she did not experience pain and had no restrictions of her activity. Her right hip strength and range of motion respectively were: flexion 4 + / 5 , 110 ° ; extension 5/5, - 3 5 ° ; abduction 5/5, 20°; adduction 4 + / 5 , 15°; internal rotation 4/5, 30 °; external rotation 4 + / 5 , 15 °. All testing was non-painful.
Discussion
The piriformis syndrome is probably more common than has been recognized to date. This syndrome may well show up in the practice of any physician (including physiatrists, orthopaedic surgeons, family practitioners, occupational physicians, neurologists, rheumatologists, anaesthetists and neurosurgeons) who routinely see cases of low back pain. It must be suspected and then specifically sought on physical examination. It is noteworthy that three of the four cases presented, as well as several others, were referred within 2 years by a single family practitioner. Due to the location of the piriformis muscle deep in the pelvic floor, a patient may also present to her gynaecologist with dyspareunia or to a gastroenterologist with rectal pain exacerbated by bowel movements. It may also be a complication of pelvic, hip or other surgery due to rough handling during anaesthesia, extreme or unusual positioning of the hips or prolonged
weight bearing on the buttocks during the surgical procedure [3], Historically, the diagnosis has been purely clinical with no known definitive investigation. This has severely compromised the credibility of this entity as a valid diagnosis [5]. However, recent reports suggest that bone scans [14] may show increased uptake of radioactivity in the affected piriformis muscles, and electrodiagnostic studies [28] may reveal denervation in a diagnostic distribution with supporting changes in H reflexes, F waves and somatosensory evoked potentials. MR1 and CT scans may demonstrate atrophy or fibrous tissue replacement of the piriformis muscle in long-standing cases. To my knowledge, cases 3 and 4 are the first reported MRI scans of the piriformis muscles in this syndrome. Higher resolution MRI may visualize local areas of scarring or oedema within the piriformis muscle and offers some hope for objectively documenting severe cases. The four cases described here were chosen for their clarity in demonstrating the salient features of this condition. The piriformis muscle functions as an external rotator of the hip in standing and an abductor of the hip in sitting. Although the piriformis syndrome may have isolated involvement of the piriformis muscle only, it commonly occurs as part of a constellation of soft tissue injuries as a result of rotation a n d / o r flexion of the torso and hip. These injuries can simultaneously affect the lumbar facet joints (case 3) or iliopsoas muscles [23] (cases 1 and 4) but may also injure other muscles including quadratus lumborum, gluteus medius and minimus, tensor fascia lata, lumbar paraspinals, hamstrings, etc., and structures such as the iliolumbar ligament. The pain of these other injured structures may be masked by the piriformis injury, as in case 4, or may themselves mask it, due to the direct and referred pain patterns which overlap. This makes it necessary to tease out the physical signs by specifically examining key structures and muscle groups for trigger points as well as reproducing symptoms with provocative stretching and resisted movement. Appropriate treatment for these other structures must be provided. The piriformis syndrome may present with neurological deficit on occasion [3]. Complete neurological examination and suitable radiologic and electrodiagnostic investigation must be completed to rule out other causes of pain. An appropriate management sequence begins with correcting abnormal biomechanics, e.g., a leg length discrepancy is corrected with a heel lift or weak hip abductors are strengthened. Associated conditions are treated, e.g., facet joint syndrome by facet injection or iliopsoas shortening by appropriate stretching. Treatment progresses to prolonged stretching of the piriformis muscle for up to sixty seconds with hip flexion, adduction and internal rotation in the standing or supine positions as a home program. If possible a
351
physical therapist may precede the stretch with ultrasound or Fluori-Methane ®. If these measures fail, piriformis corticosteroid injections should be attempted up to three times. They may be done either medially with a spinal needle as described by Pace and Nagle [18], Wyant [33] and Kirkaldy-Willis [15] (lateral to the sacrum and medial to the sciatic nerve), with the index finger of the non-dominant hand monitoring the rectum or vagina during injection, or with a 1.5 inch regular or 3 inch spinal needle (depending upon the extent of patient obesity) laterally into the region of the piriformis tendon in the posterior greater trochanteric fossa. In the latter case, the injection may include radiographic dye and be done under fluoroscopic control. If the dye outlines the characteristic shape of the piriformis muscle, the injection location is correct (R.W. Grainger, personal communication). Sarapin ® (High Chemical Co.), an aqueous distillate of Sarracenia purpurea, the purple pitcher plant, which blocks C-fibre pain transmission without affecting motor or sensory function, has also been incorporated into these injections [3]. The medial and lateral injection sites are shown in Fig. 3. Surgical release of the piriformis muscle with exploration of the sciatic nerve is the definitive procedure in recalcitrant cases but may require supplementary exercises subsequently.
Conclusion The primary symptom of piriformis syndrome is buttock pain with or without posterior thigh pain, which is aggravated by sitting or activity. Associated low back pain suggests involvement of other structures such as facet joints or iliopsoas muscles. In an isolated piriformis syndrome the major findings include buttock tenderness from the sacrum to the greater trochanter, piriformis tenderness on rectal or vaginal examination and reproduction of buttock pain on prolonged hip flexion, adduction and internal rotation. Minor findings include leg length discrepancy, weak hip abductors (there may be a positive Trendelenburg sign) and painful hip abduction against resistance while sitting. External rotation of the hip on lying supine has also been noted. High resolution MRI of the pelvic muscles may offer some hope for objective documentation in severe cases.
Acknowledgements I would like to thank R.W. Grainger for doing a piriformis release on case 4 and for sharing his experience with this syndrome; R.L. Nicholson for doing many MRI scans of patients with possible piriformis syndromes; G. Wyant for making me aware of the
surgical release of the piriformis muscle; R. McKenzie for teaching me the standing piriformis stretch; H. Merskey, N. Bellamy and K. Hayes for detailed manuscript review; G. Gillis for referral of cases 1, 2 and 3; and R. Weichelt for excellent assistance with manuscript preparation.
References 1 Beaton, L.E. and Anson, B.J., The relation of the sciatic nerve and of its subdivisions to the piriformis muscle, Anat. Rec., 70 (1937) 1-5. 2 Beaton, L.E. and Anson, B.J., The sciatic nerve and the piriformis muscle: their interrelation a possible cause of coccydynia, J. Bone Joint Surg., 20 (1938) 686-688. 3 Brown, J.A., Braun, M.A. and Namey, T.C., Pyriformis syndrome in a 10-year-old boy as a complication of operation with the patient in the sitting position, Neurosurgery, 23 (1988) 117-119. 4 Cameron, H.U. and Noftal, F., The piriformis syndrome, Can. J. Surg., 31 (1988) 210. 5 Chung, T.S. and Diffily, J., Piriformis syndrome: myth or fact?, Arch. Phys. Med. Rehabil., 68 (1987) 641. 6 Clemente, C.D., Anatomy: A Regional Atlas of the Human Body, 2nd edn., Urban and Schwarzenberg, Baltimore, MD, 1981. 7 Edwards, F.O., Pyriformis Syndrome, Academy of Applied Osteopathy Yearbook, Colorado Springs, CO, 1962, pp. 39-41. 8 Freiberg, A.H., Sciatic pain and its relief by operations on muscle and fascia, Arch. Surg., 34 (1937) 337-350. 9 Freiberg, A.H., The fascial elements in associated low-back and sciatic pain, J. Bone Joint Surg., 23 (1941) 478-480. 10 Freiberg, A.H. and Vinke, T.H., Sciatica and the sacroiliac joint, J. Bone Joint Surg., 16 (1934) 126-136. 11 Goddard, M., Sciatic nerve dysfunction and reflex sympathetic dystrophy as a consequence of the piriformis syndrome, Arch. Phys. Med. Rehabil., 70 (1989) A93. 12 Grant, J.H., Leg length inequality in piriformis syndrome, J. Am. Osteopath. Assoc., 87 (1987) 456. 13 Hallin, R.P., Sciatic pain and the piriformis muscle, Postgrad. Med., 74 (1983) 69-72. 14 Karl, Jr., R.D., Yedinak, M.A., Hartshorne, M.F. et al., Scintigraphic appearance of the piriformis muscle syndrome, Clin. Nuc. Med., 10 (1985) 361-363. 15 Kirkaldy-Willis, W.H., Managing Low Back Pain, 2nd edn., Churchill Livingstone, New York, 1988, pp. 342-343. 16 Mizuguchi, T., Division of the pyriformis muscle for the treatment of sciatica, Arch. Surg., 111 (1976) 719-722. 17 Pace, J.B., Commonly overlooked pain syndromes responsive to simple therapy, Postgrad. Med., 58 (1975) 107-113. 18 Pace, J.B. and Nagle, D., Piriformis syndrome, West J. Med., 124 (1976) 435-439. 19 Pecina, M., Contribution to the etiological explanation of the piriformis syndrome, Acta. Anat. (Basel), 105 (1979) 181-187. 20 Rask, M.R., Superior gluteal nerve entrapment syndrome, Muscle Nerve, 3 (1980) 304-307. 21 Retzloff, E.W., Berry, A.H., Haight, A.S. et al., The piriformis muscle syndrome, J. Am. Osteopath. Assoc., 73 (1974) 799-805. 22 Robinson, D.R., Pyriformis syndrome in relation to sciatic pain, Am. J. Surg., 73 (1947) 355-358. 23 Simons, D.G. and Travell, J.G., Myofascial origins of- low back pain. 2. Torso muscles, Postgrad. Med., 73 (1983) 89-98. 24 Simons, D.G. and Travell, J.G., Myofascial origins of low back pain. 3. Pelvic and lower extremity muscles, Postgrad. Med., 73 (1983) 99-108.
352 25 Sinaki, M., Merritt, J.L. and Stillwell, G.K., Tension myalgia ol' the pelvic floor, Mayo Clin. Proc., 52 (1977) 717-722. 26 Solheim, LF., Siewers, P. and Paus, B.. The piriformis muscle syndrome, Acta. Orthop. Scand., 52 (1981)73-75. 27 Steiner, C., Staubs, C., Ganon, M. et al., Piriformis syndrome: pathogenesis, diagnosis and treatment. J. Am. Osteopath. Assoc.. 87 (1987) 318-323. 28 Synek, V.M., The pyriformis syndrome: review and case presentation, Clin. Exp. Neurol., 23 (1987) 31-37. 29 Te Poorten, B.A., The piriformis muscle, J. Am. Osteopath. Assoc., 69 (1969) 150-160. 30 Thiele, G.H., Coccygodynia and pain in the superior gluteal region, JAMA, 109 (1937) 1271-1275.
31 Thiele, G.H.. Tonic spasm of the levator am, coccygcus and piriformis muscles, Trans. Am. Pract. Soc., 37 (1936) 145 155. 32 Travell, J. and Travell, W., Therapy of low back pain by manipulation and of referred pain in the lower extremity by procaine infiltration, Arch. Phys. Med. Rehabil., 27 (1t)46) 537-47. 33 Wyant, G.M., Chronic pain syndromes and their treatment. I11. The pirifl)rmis syndrome, Can. Anaesth. Soc. J.. 26 (lt~79) 305 308. 34 Yeoman, W., The relation of arthritis of the sacroiliac joint to sciatica, Lancet, ii (1928) 1119-1122.
345
© 1991 Elsevier Science Publishers B.V. All rights reserved 0304-3959/91/$03.50
PAIN 01926
Piriformis syndrome: a rational approach to management
1
Pamela M. Barton Department of Physical Medicine and Rehabilitation, Unit~ersityof Western Ontario, London, Ont. N6C 5Jl (Canada) (Received 20 March 1991, revision received 17 May 1991, accepted 3 June 1991)
Summary Although rarely recognized, the piriformis syndrome appears to be a common cause of buttock and leg pain as a result of injury to the piriformis muscle. Four cases representing a broad spectrum of presentations are described here. The major findings include buttock tenderness extending from the sacrum to the greater trochanter and piriformis tenderness on rectal or pelvic examination. Symptoms are aggravated by prolonged hip flexion, adduction, and internal rotation, in the absence of low back or hip findings. Minor findings may include leg length discrepancy, weak hip abductors, and pain on resisted hip abduction in the sitting position. Myofascial involvement of related muscles and lumbar facet syndromes may occur concurrently. The diagnosis is primarily clinical as no investigations have proved definitive. The role of MRI of the piriformis muscle is assessed and other investigative tools are discussed. A rational management schema is demonstrated: (1) underlying biomechanical factors and associated conditions should be corrected; (2) the patient is instructed in a home program of prolonged piriformis muscle stretching which may be augmented in physical therapy by preceding ultrasound or Fluori-Methane ® (dichlorodifluoromethane and trichloromonofluoromethane spray); (3) a trial of up to three steroid injections is attempted; and (4) if all these measures fail, consideration should be given to surgical sciatic nerve exploration and piriformis release. Key words: Piriformis syndrome; Low back pain; Pyriformis; Myofascial pain; Piriformis muscle; Sciatic nerve
Introduction
Piriformis syndrome is a little-known entity in which injury to the piriformis muscle results in buttock pain often associated with leg pain. It was first described by Yeomen [34] in 1928. The principal symptom of buttock pain, with or without leg pain, is aggravated by sitting or activity of the lower extremities. Other findings typically include buttock tenderness extending from the sacrum to the greater trochanter, piriformis muscle tenderness on rectal or pelvic examination, and aggra-
i An abstract of this work was presented as a poster at the American Academy of Physical Medicine and Rehabilitation in Seattle, WA, on 2 November, 1988.
Correspondence to: Dr. P.M. Barton, Dept. of Physical Medicine and Rehabilitation, Parkwood Hospital, 801 Commissioners Road East, London, Ontario, Canada, N6C 5J1. Tel.: (519) 685-4044. Fax: (519) 685-4052.
vation of symptoms by prolonged hip flexion, adduction and internal rotation, in the absence of low back or hip findings. Leg length discrepancy, weak hip abductors, and pain on resisted hip abduction in the sitting position may also be present. It has been suggested that pressure on the sciatic nerve by the piriformis muscle may contribute to the syndrome. The relevant anatomy has been explored in detail [1,2,6,10,19]. Myofaiciai involvement of related muscles and lumbar facet syndromes may be concurrent conditions. Fig. 1 shows the relationship of the piriformis muscle to the sciatic nerve and the iliopsoas muscle. The diagnosis of piriformis syndrome is primarily clinical as no definitive investigations have been reported. In general, bone scans and electrodiagnostic studies do not appear helpful, although there have been isolated reports of their utility [14,28]. Both conservative [3,7,11-13,17,18,21~24,25,27,2933] and surgical [4,8,9,16,20,22,26] management have been advocated and these approaches have been described extensively in individual reports. To date no
346
,rmis
Psoa:
Fig. 1. Anatomical relationships of the piriformis muscle: anterior (left) and posterior (right).
one seems to have described a comprehensive approach to the treatment of this condition. In the present report I describe four case studies of piriformis syndrome in which a systematic management program resulted in good therapeutic outcome. In two of these cases magnetic resonance imaging (MRI) proved useful. These case studies range from mild to severe examples of piriformis syndrome and outline an orderly progression of management from conservative to surgical.
Case 1
A 31-year-old woman developed pain in the right buttock while shovelling snow. One week later, the morning after bowling, she had severe pain in the back and right buttock. Two months later she also had pain radiating to the anterior thigh and groin, and occasionally into her posterior thigh and calf. She could sit for 2 h provided she shifted position frequently. She could walk for 30 min and had no difficulty standing or lying, preferably with her knees flexed. Previous management had included non-steroidal anti-inflammatory drugs, chiropractic manipulation and physical therapy. Her past medical history was unremarkable.
She was tender in the right buttock and in the right piriformis muscle on vaginal examination. Her discomfort was increased by right hip flexion, adduction and internal rotation with pain radiating to the anterior thigh. The lengths of her legs, the strength of her hip abductors and hip abduction against resistance in the sitting position were normal. Neurological examination, bowstring signs and gait were normal. She experienced slight discomfort on forward lumbar flexion and straight leg raising was equivocal on the right. Radiographs of the lumbosacral spine were unremarkable. As her physical examination and investigation were consistent with shortening of the piriformis muscle, she was instructed in prolonged stretching exercises of the right piriformis to be done every 2 h during waking hours. These exercises are illustrated in Fig. 2. Within 1 week she had significant relief of her right buttock symptoms and had no further complaints of back pain. She probably had mild involvement of her right iliopsoas muscle as well. This was determined in retrospect on the basis of her concurrent low back and groin pain and her preference for lying supine with her knees flexed. On hip flexion, adduction and internal rotation she also experienced groin rather than buttock pain. She did not require specific intervention for the iliop-
347
Fig. 2. Stretching exercises - prolonged stretching of right piriformis muscle by flexion, adduction and internal rotation of right hip in standing (right) and supine (left) positions. Patients are instructed to begin holding the stretch for 5 sec and gradually increase to a 60 sec stretch.
soas muscle as it was likely stretched by the internal rotation of the piriformis stretch.
Case 2 A 40-year-old male social worker developed back pain after each of three bouts of strenuous activity (racquet ball and dancing). H e required 3 days of bed rest and 1 week off work following the third episode of pain. T h r e e months later he presented with low back ache radiating into the thighs bilaterally. H e had no difficulty lying, standing or sitting, although he did report having pain after prolonged driving or the day
after extensive walking. He had slight discomfort on forward flexion, extension and left lateral rotation of the low back. T h e r e was tenderness in the right buttock from the sacrum to the greater trochanter. X-rays of the lumbosacral spine were normal. He was placed on 375 mg naproxen p.o., b.i.d. One month later, he reported that he had attempted to use some weight lifting equipment but his symptoms had increased. The naproxen was not helpful. At this time his pain was more localized to the right buttock. He was tender in the right buttock from the sacrum to the greater trochanter and tender in the right piriformis on rectal examination. He had slight buttock discomfort on right hip flexion, adduction and internal
348 the right buttock. He cancelled an appointment 2 months later as he had no further pain.
Case 3
4 Fig. 3. Piriformis injection sites: (a) medial and (b) lateral. Patient lies on unaffected side. Needle is placed perpendicular to skin at point of maximal tenderness.
rotation. Leg lengths were equal, right hip abductor strength was normal and there was no discomfort on resisted hip abduction while sitting. Low back range of motion and neurological examination were normal. One week later he received an injection of betamethasone sodium phosphate and 12 mg betamethasone acetate (Celestone ® Soluspan, Schering) and 8 ml of 0.5% lidocaine HCI into the medial right piriformis muscle. The location of the injection is illustrated in Fig. 3a. Two weeks later, he reported that the day after the injection, his right buttock pain had resolved and he had been dancing and playing soccer on several occasions without difficulty. His examination was unremarkable other than slight tenderness on palpation of
A 32-year-old male physician and marathon runner presented with an 8 month history of increasing pain in the left low back and left buttock with occasional radiation of pain posteriorly to the left knee. All running activities aggravated the pain. short fast runs being the most difficult, although he was still able to run five miles in 40 rain three times weekly. The low back pain was aggravated by lumbar extension as well as by prolonged sitting and standing. The ache in the left buttock, which did not consistently occur with the low back pain, was especially aggravated by the latter part of his golf swing which required internal rotation of the left hip. Previous treatment with non-steroidal anti-inflammatory drugs, discontinuance of running and chiropractic manipulations had been unsuccessful. Lumbar movement revealed pain on combined extension and left side bending. He was tender to the left of the L5 spinous process, in the left buttock from the sacrum to the greater trochanter and in the left piriformis muscle on rectal examination. Left buttock pain was noted on flexion, adduction and internal rotation of the left hip as well as on resisted hip abduction while sitting. There was a mild left Trendelenburg sign but his legs were equal in length. Neurological examination of his legs was normal. X-rays of the lumbosacral spine showed minor degenerative changes. M R I of the pelvis which is shown in Fig. 4 was normal. One week after a left L5 facet injection, he reported resolution of all the back pain and demonstrated normal and pain-free range of motion of the lumbar spine.
Fig. 4. MRI of pelvic muscles. Case 3 (left) normal piriformis (short solid arrows) and iliopsoas (long arrows) muscles bilaterally. Case 4 (right) normal piriformis muscles (white arrows) bilaterally and normal left iliopsoas muscle (black arrows). Note severe atrophy of right iliopsoas muscle.
349 As only the left buttock pain remained, he was given an injection of 8 ml of 0.5% lidocaine HCI and 80 mg of methylprednisolone acetate (Depo-medrol ®, Upjohn) into the medial left piriformis muscle with complete resolution of the remaining positive findings on re-examination 10 min later. He was placed on a home program of prolonged stretching of the left piriformis muscle with a concurrent physical therapy program of ultrasound to the left buttock followed by piriformis stretching. Shortly thereafter he reported that his pain had totally resolved and that he had resumed his normal activities. Two months after the piriformis injection, he noticed increasing left buttock discomfort, less severe than previously, and possibly due to discontinuing his stretching program and to building a deck at home. He continued running five miles three times weekly. He was tender in the left buttock as well as in the left piriformis muscle on rectal examination. A medial left piriformis injection was repeated with total resolution of his physical findings. He was placed on a nonsteroidal anti-inflammatory drug and reinstructed in prolonged stretching of the left piriformis muscle. Two months after the second injection he resumed normal activities and continued pain free.
Case 4
A 39-year-old dental assistant developed pain in the right buttock and hip gradually over 15 years with no specific inciting event. She presented with right buttock pain radiating to the right greater trochanter, aggravated by any form of physical activity and alleviated by right leg traction. All walking was painful and was limited to 20 min. When fatigued, she limped on her right leg. Standing was painful after sitting for any length of time. Right groin exploration had been performed twice, 10 and 5 years previously. Sitting on hard surfaces had caused slight discomfort since fracturing her coccyx 20 years previously. Five months of physical therapy had been unsuccessful in alleviating her pain. She was tender in the right buttock from the sacrum to the greater trochanter and in the right piriforrnis muscle on rectal examination. She had severe pain in the right buttock on right hip flexion, adduction and internal rotation as well as on resisted hip abduction while sitting. The right leg was 1 cm longer than the left. She experienced a pain in her right buttock which felt like electrical shocks when the right hip was internally rotated past neutral. Right straight leg raising caused pain at 60 °. Right iliopsoas stretching caused discomfort. There was a well healed longitudinal incision in the right groin. Lumbar spine range of motion and lower extremity neurological examination were normal. X-rays of the pelvis and right hip as well as a
Fig. 5. Surgicalrelease of right piriformismuscle.Posteriorapproach to hip. Forcepsunder piriformistendon.Solidarrowindicatesgreater trochanter.
bone scan were normal. MRI of the pelvis and lumbar spine which is shown in Fig. 4 revealed atrophy of the right iliopsoas muscle with a normal lumbar spine and normal piriformis muscles. A 1 cm heel lift was placed on the left shoe. A 1 month trial of physiotherapy twice weekly consisting of ultrasound to the right buttock followed by specific piriformis stretching, in parallel with a home stretching program of the piriformis, produced 20 ° of right hip internal rotation, but no other changes. Two sequential medial right piriformis injections with 8 ml of 0.5% lidocaine HCI and 80 mg of methylprednisolone acetate (Depo-medrol ®, Upjohn) were unsuccessful and the patient was referred for surgery. Surgical exploration through a posterolateral approach revealed the right sciatic nerve to exit normally from under the piriformis muscle which was released by resecting 1 cm of the tendon near its insertion at the piriformis fossa. The greater trochanteric bursa was noted to be normal. One month after surgery, her buttock pain had resolved. She had reduced range of right hip flexion, adduction and internal rotation but this manoeuver did not elicit any form of buttock pain. However, she was experiencing constant right groin and slight low back pain which her previous severe buttock pain may have masked. Stretching exercises were deferred. Four months after surgery, reassessment reproduced her right groin and low back pain on stretching the right iliopsoas muscle in the supine and standing positions, and the right iliopsoas muscle was tender to abdominal palpation. Right hip flexion, adduction and internal rotation caused no buttock discomfort, but reproduced her right groin discomfort. (Due to its attachment to the lesser trochanter, the iliopsoas muscle is also stretched in this manoeuvre. It was not previously painful because internal rotation was re-
350 stricted prior to the piriformis release.) She was placed on prolonged stretching exercises for her right piriformis and right iliopsoas muscles. Seven months after the piriforrnis release, she was pain free, except for slight discomfort in the right groin after extreme activity such as excessive swimming or walking. Right hip flexion against resistance was painful. Twelve months after the piriformis release she reported difficulty without pain when putting pantyhose on her right leg. On examination, flexion of the right hip was painful and reduced in strength to 2/5. Movement of the right hip was pain free but reduced: flexion: right 110 °, left 135 °; extension: right - 3 0 °, left normal; abduction: right 15 °, left 30 °; adduction: right 15 °, left 45°; internal rotation: right 15 °, left 35 °; external rotation: right 25 °, left 65 °. (Strength and range of motion had previously been very difficult to assess due to pain.) She was placed on a program to increase the range of motion and strength of the right hip. Fourteen months after surgery the strength and range of motion respectively of the right hip were: flexion 2/5, 100 °; extension 2/5, - 3 0 °; abduction 5/5, 15 °; adduction 2/5, 15 °; internal rotation 3/5, 20 °; external rotation 3/5, 30 °. Hip strength testing was non-painful for the first time. Twenty-seven months after surgery she reported that she did not experience pain and had no restrictions of her activity. Her right hip strength and range of motion respectively were: flexion 4 + / 5 , 110 ° ; extension 5/5, - 3 5 ° ; abduction 5/5, 20°; adduction 4 + / 5 , 15°; internal rotation 4/5, 30 °; external rotation 4 + / 5 , 15 °. All testing was non-painful.
Discussion
The piriformis syndrome is probably more common than has been recognized to date. This syndrome may well show up in the practice of any physician (including physiatrists, orthopaedic surgeons, family practitioners, occupational physicians, neurologists, rheumatologists, anaesthetists and neurosurgeons) who routinely see cases of low back pain. It must be suspected and then specifically sought on physical examination. It is noteworthy that three of the four cases presented, as well as several others, were referred within 2 years by a single family practitioner. Due to the location of the piriformis muscle deep in the pelvic floor, a patient may also present to her gynaecologist with dyspareunia or to a gastroenterologist with rectal pain exacerbated by bowel movements. It may also be a complication of pelvic, hip or other surgery due to rough handling during anaesthesia, extreme or unusual positioning of the hips or prolonged
weight bearing on the buttocks during the surgical procedure [3], Historically, the diagnosis has been purely clinical with no known definitive investigation. This has severely compromised the credibility of this entity as a valid diagnosis [5]. However, recent reports suggest that bone scans [14] may show increased uptake of radioactivity in the affected piriformis muscles, and electrodiagnostic studies [28] may reveal denervation in a diagnostic distribution with supporting changes in H reflexes, F waves and somatosensory evoked potentials. MR1 and CT scans may demonstrate atrophy or fibrous tissue replacement of the piriformis muscle in long-standing cases. To my knowledge, cases 3 and 4 are the first reported MRI scans of the piriformis muscles in this syndrome. Higher resolution MRI may visualize local areas of scarring or oedema within the piriformis muscle and offers some hope for objectively documenting severe cases. The four cases described here were chosen for their clarity in demonstrating the salient features of this condition. The piriformis muscle functions as an external rotator of the hip in standing and an abductor of the hip in sitting. Although the piriformis syndrome may have isolated involvement of the piriformis muscle only, it commonly occurs as part of a constellation of soft tissue injuries as a result of rotation a n d / o r flexion of the torso and hip. These injuries can simultaneously affect the lumbar facet joints (case 3) or iliopsoas muscles [23] (cases 1 and 4) but may also injure other muscles including quadratus lumborum, gluteus medius and minimus, tensor fascia lata, lumbar paraspinals, hamstrings, etc., and structures such as the iliolumbar ligament. The pain of these other injured structures may be masked by the piriformis injury, as in case 4, or may themselves mask it, due to the direct and referred pain patterns which overlap. This makes it necessary to tease out the physical signs by specifically examining key structures and muscle groups for trigger points as well as reproducing symptoms with provocative stretching and resisted movement. Appropriate treatment for these other structures must be provided. The piriformis syndrome may present with neurological deficit on occasion [3]. Complete neurological examination and suitable radiologic and electrodiagnostic investigation must be completed to rule out other causes of pain. An appropriate management sequence begins with correcting abnormal biomechanics, e.g., a leg length discrepancy is corrected with a heel lift or weak hip abductors are strengthened. Associated conditions are treated, e.g., facet joint syndrome by facet injection or iliopsoas shortening by appropriate stretching. Treatment progresses to prolonged stretching of the piriformis muscle for up to sixty seconds with hip flexion, adduction and internal rotation in the standing or supine positions as a home program. If possible a
351
physical therapist may precede the stretch with ultrasound or Fluori-Methane ®. If these measures fail, piriformis corticosteroid injections should be attempted up to three times. They may be done either medially with a spinal needle as described by Pace and Nagle [18], Wyant [33] and Kirkaldy-Willis [15] (lateral to the sacrum and medial to the sciatic nerve), with the index finger of the non-dominant hand monitoring the rectum or vagina during injection, or with a 1.5 inch regular or 3 inch spinal needle (depending upon the extent of patient obesity) laterally into the region of the piriformis tendon in the posterior greater trochanteric fossa. In the latter case, the injection may include radiographic dye and be done under fluoroscopic control. If the dye outlines the characteristic shape of the piriformis muscle, the injection location is correct (R.W. Grainger, personal communication). Sarapin ® (High Chemical Co.), an aqueous distillate of Sarracenia purpurea, the purple pitcher plant, which blocks C-fibre pain transmission without affecting motor or sensory function, has also been incorporated into these injections [3]. The medial and lateral injection sites are shown in Fig. 3. Surgical release of the piriformis muscle with exploration of the sciatic nerve is the definitive procedure in recalcitrant cases but may require supplementary exercises subsequently.
Conclusion The primary symptom of piriformis syndrome is buttock pain with or without posterior thigh pain, which is aggravated by sitting or activity. Associated low back pain suggests involvement of other structures such as facet joints or iliopsoas muscles. In an isolated piriformis syndrome the major findings include buttock tenderness from the sacrum to the greater trochanter, piriformis tenderness on rectal or vaginal examination and reproduction of buttock pain on prolonged hip flexion, adduction and internal rotation. Minor findings include leg length discrepancy, weak hip abductors (there may be a positive Trendelenburg sign) and painful hip abduction against resistance while sitting. External rotation of the hip on lying supine has also been noted. High resolution MRI of the pelvic muscles may offer some hope for objective documentation in severe cases.
Acknowledgements I would like to thank R.W. Grainger for doing a piriformis release on case 4 and for sharing his experience with this syndrome; R.L. Nicholson for doing many MRI scans of patients with possible piriformis syndromes; G. Wyant for making me aware of the
surgical release of the piriformis muscle; R. McKenzie for teaching me the standing piriformis stretch; H. Merskey, N. Bellamy and K. Hayes for detailed manuscript review; G. Gillis for referral of cases 1, 2 and 3; and R. Weichelt for excellent assistance with manuscript preparation.
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