Piriformis syndrome-sciatic pain research
Pathology Report – Piriformis Syndrome
By Roger Fontaine
remedial massage therapist
The term “piriformis syndrome” refers to a set of signs and symptoms which refer the origin or cause of the pain to the piriformis muscle sometimes mimicking sciatic nerve pain.
Nerves in the hip and buttocks region
Sciatic/sacral plexus (L4,L5,S1,S2,S3 nerve roots)
Nerve to piriformis (S1, S2 nerve root)
Piriformis nerve originates from the sacral plexus and innervates the piriformis muscle.
The nerve to the piriformis branches off from the sacral plexus from which originates the sciatic nerve.
The sciatic nerve comprises the combined tibial/common peroneal branches until it divides at the popliteal space.
The piriformis muscle originates from the anterior sacrum and inserts onto the top of the greater trochanter of the femur.
The symptoms of “Piriformis Syndrome” are sometimes confused with those of sciatica: pain radiating down the buttocks, posterior thigh, calf, and plantar or dorsal foot; weakness of the hamstrings or calf muscles.
Gluteus miminus can also mimic the symptoms of sciatica when the innervation becomes irritated because of hypertonicity.
Neurologists believe that few if any cases of ‘true’ piriformis syndrome exist.(see reference article at end of report)
Observed signs are difficulty squatting, standing from sitting, walking, running; lateral hip rotation,especially driving a car.
The sciatic nerve which innervates the posterior muscles and the piriformis nerve which innervates the piriformis are in such close proximity that the establishment of the actual cause of the pain is sometimes difficult to ascertain.
Sciatic nerve usually passed deep to and inferior to piriformis. It sometimes, though, passes through piriformis and becomes entrapped. The pain is manifest or becomes aggravated when the piriformis becomes hypertonic and/or hypertrophic. This muscle has a tendency to become hypertrophic because of its postural functions.
Distinguishing sciatic nerve origin versus localized piriformis nerve origin.
This is assessed by performing the straight leg test for sciatic condition by applying dorsiflexion to establish or eliminate herniated disc and sciatic pain in the tested leg. There may be other causes such as a subluxated vertebra causing nerve root impingement.
Because the nerve roots originate laterally between the intervetebral foramina, a herniated disc would only protrude to the left or right when performing the straight leg test. It would therefore only occlude the nerve on one side.
Pain radiating down both legs could be caused by a virus to the sciatic nerve. It is also possible to have pain down both legs with a degenerated disc condition. This is however beyond our ability to assess and should be referred to a physician for diagnosis.
The localized piriformis nerve origin would be restricted to the piriformis muscle but could also cause ‘sciatic’ pain if the sciatic nerve were entrapped.
TESTING AND ISOLATING THE PIRIFORMIS
However, we do know that the piriformis muscle has certain attachments. It has as its origin an attachment to the anterior sacrum between segments S2 and S4. It proceeds laterally around the great sciatic notch and attaches to the top of the greater trochanter of the femur.
Its concentric contraction results in assisting leg abduction and when the knee is flexed to 90 degrees, assists in lateral rotation of the femur, as a secondary action.
The eccentric contraction would be made during adduction and internal rotation. This is the position which one uses to introduce a passive stretch to the piriformis muscle. (See sketch lower)
A test to isolate the piriformis muscle as the cause of pain is to perform an active ROM test in abduction and lateral rotation, first of the non-affected leg and then with the affected leg. Should the pain be reproduced in these positions we could conclude that the piriformis is the main source of the pain.
A patient history may also detect other situations which reproduce the onset of pain, such as getting up from the seated position in the standing position, or from standing into sitting position. Also when going from a flexed lumbar position into an extended lumbar position.
Any anterior/posterior movement of the sacrum may exacerbate the piriformis pain. The conraction of the psoas major in hip flexion would increase the lumbo-sacral angle and place more pressure on the piriformis muscle.
A passive Range of motion test between the non-affected hip and affected hip should detect asymmetry and pain in the affected hip only.
CAUSES OF PIRIFORMIS PAIN
The cause of the pain is due to either an imbalance in the size and strength of the two piriformis muscles. A larger or hypertrophic piriformis on one side will cause a sacral torsion which will exacerbate any sciatic nerve entrapment which may be involved. Besides the possibility of the sciatic nerve being entrapped within the piriformis muscle it is possible for the sciatic nerve or piriformis nerve to be entrapped between the muscle and the greater sciatic notch.
Hertling and Kessler in their book “Management of Common Musculoskeletal Disorders” refer to the specific muscle groups fundamental to balancing the pelvis and lumbar spine. In this group they make reference to the importance of the piriformis to the sacrum and pelvic balance.
“Lower extremity rotation is directly related to pelvic inclination and thus to the lumbosacral angle. External hip rotation facilitates posterior pelvic tilt and so may decrease the lumbosacral angle. One of the external rotators, the piriformis, primarily, a tonic muscle, is considered responsible for restricting SIJ motion or producing local pain and symptoms of the pirifomis syndrome. Imbalance in piriformis length and strenth appears to strongly influence movements of the sacrum between the innominates.”(P.704)
The authors are referring to the piriformis being responsible for restricting Sacro-iliac joint motion when hypertonic because it would place more resistance to SIJ motion.
Another comment found in Hertling /Kessler referring to the sacrum is this one:
“In studies of functional movements, motion of the sacrum has been found to peak in the act of rising from a supine to a standing or long-sitting position.” (P.702)(Hip flexion)
This would assist us in understanding why these functional motions of the pelvis would impact upon moving the sacrum and on exacerbating the piriformis-related pain.
Referred pain into hip and anterior groin region
The hip is innervated primarily from L-3 lumbar plexus, hip joint rotation usually felt along L-3 dermatome from the groin down the anterior thigh to knee. Hip pain would therefore radiate anteriorly and medially down to the knee. Pain in this area would be related to the femoral or obturator nerve and not be related to piriformis nerve or muscle.
Referred pain subcutaneously to the buttock and thigh
The”Lateral Femoral Cutaneous Nerve”- (L2-L3 lumbar plexus origin); innervates skin over lateral, anterior, and posterior aspects of thigh.
The “Perforating Cutaneous Nerve”- has (S1-S2) origin as piriformis, and innervates skin over inferior medial aspect of buttocks.
The “Posterior Femoral Cutaneous Nerve” has a (S1-S3) origin and innervates skin over the anal region, inferior lateral aspect of buttock, the superior posterior aspect of thigh, superior part of calf, scrotum and labia majora
ASSESSMENT OF PIRIFORMIS
Using hip assessment techniques for external rotation I would ascertain in active test that there was a restriction on the affected leg. I would ask the patient to perform the external rotation Range of Motion and then with the hip flexed to 90 degrees. I would then administer the passive test to detect any restriction on the affected leg.
The piriformis is an agonist for abduction and antagonist for adduction. I would therefore ask the patient to perform an active test for adduction. The intention of this is to detect any resistance from the piriformis during adduction. There should be some restriction in adduction on the affected hip with a hypertonic piriformis. Should there be symmetry one could eliminate the piriformis as hypertonic. Or can we?
However, shouldn’t a hypertonic piriformis produce a positive test for asymmetry in hip anterior adduction because of increased resistance to adduction on the affected hip?
If we find asymmetry in active adduction, can we deduce or conclude that the piriformis alone is hypertonic or can the other abductors also be hypertonic?
The gluteus medius and minimus are also involved as antagonists during adduction. It may be difficult to isolate the piriformis from the other gluteal abductors. The gluteus minimus is also known to mimic the symptoms of sciatic entrapment when that muscle is hypertonic, being innervated by the superior gluteal nerve.(ref:Hertling/Kessler, p.36)
The next step would be to have the patient abduct and laterally rotate with flexed hip to 90 degrees,to reproduce the pain:,whether sciatic or piriformis. If this test reproduces the pain I would conclude hypertonicity of the piriformis and palpate to confirm conclusion. If hypertonic, I would then treat for hypertonicity.
Should there be no detected asymmetry in abduction I would conclude that the agonists were of equal strength on both hips.
Treatment of hypertonic piriformis:
Place the patient in lateral recumbent position with hip flexed and knee off table. Allow sufficient stretch to proceed with treatment. Proceed with goading across fiber direction with palmar aspect of hand. This will stimulate the mechanoreceptors, desensitizing the nociceptors subcutaneously, allowing for deeper penetration through the gluteal maximus, to the piriformis muscle. It may be possible to palpate the muscle for hypertonicity. I would then apply some effleurage to warm the tissue and increase circulation and flushing. I then would apply some slow and deliberate local cross-fibering along the tendinous portion of the proximal end of the piriformis near the lateral sacrum and along the ischial spine.
Next I would apply local cross-fibering to the attachment to the greater trochanter. Applying ischemic compression at either or both ends may assist in obtaining some golgitendon organ override resulting in some gamma motor neuron and alphha motor neuron inhibition and muscle spindle adaptation and resultant elongation. Strain/counterstrain could also be used at this juncture with one thumb at the sacral musculo/tendinous junction and and the other thumb at the trochanteric musculo/tendinous junction.
Attention must be made not to irritate the sciatic nerve which would be situated more mid-muscle in the belly of the piriformis and initiate a myotatic stretch reflex or muscle spasm.
Therefore GCF(general cross-fibering) may be too invasive into the belly of the muscle and irritate the sciatic nerve causing reactive pain.
TREATMENT OF HYPOTONIC PIRIFORMIS
Should it be necessary to treat the counterpart of the hypertonic piriformis because of hypotonicity I would place the patient in a lateral recumbent position with the muscle in a passive stretch, hip flexed, and knee sligthly off the table. I then would palpate for hypotonicity,
I would then apply intrafusal muscular stimulation to the hypotonic areas two or three times monitoring the areas for increases in resting tone subsequent to the treatment. I could also use quick stimulatory local cross-fibering to the areas being cautious not to contact the sciatic nerve by applying too much pressure over the belly of the piriformis.
STRETCH AS HOME CARE
Self-stretching the piriformis is one necessary therapy for the patient to implement as part of regaining a fully functioning piriformis.
One source states that piriformis syndrome can be influenced by faulty pelvic and foot mechanics. The faulty foot mechanics can be alleviated with different footwear which is more supportive or by obtaining foot orthotics.
It may also be necessary to review work and leisure postures to modify any postural stances which may be leading to pelvic imbalances stressing the piriformis muscle and the sacrum.
Medical reference to piriforms
syndrome “few if any cases of true piriformis syndrome exist”
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Subject: Re: Piriformis syndrome
Forum: The Neurology and Neurosurgery Forum
Topic Area: Neuromuscular
Posted by CCF Neurology MD:NT on December 21, 1998 at 19:48:51:
In Reply to: Piriformis syndrome posted by devan on December 20, 1998 at 23:27:52:
Is there an easy way to diagnose piriformis syndrome? Will my primary care physician be able to diagnose it or do I need to see a specialist? How can it be treated? Is there a permanent cure? Are there physicians in the Philadelphia area who can be consulted? Thanks.
Piriformis syndrome is a controversial entity. Non-neurologists often diagnose this syndrome when there is a patient who has leg pain that is worsened by pressure in the buttock area, and relieved by blocks in that area. When critically reviewed, there are very few, if any cases of a convincing piriformis syndrome in which there is clear evidence of sciatic neuropathy because of compression by the piriform muscle. Most cases that are felt to have the syndrome have either non-neurological causes of leg pain, or else have a lumbosacral radiculopathy or sciatic neuropathy/sacral plexopathy from other cause.
Most neuromuscular experts do not really believe in the existence of the piriformis syndrome.
I would suggest a consultation with one of the neuromuscular experts at Univ Penn, Temple, or Johns Hopkins to correctly diagnose the problem.
Additional bibliography (taken from Hertling/Kessler)
Maxwell, TD: The Piriformis muscle and its relation to the long-legged syndrome. J. Can Chiro Assoc.51:10-24, 1978
Steiner C, Stawbs C, Garron , et al, Piriformis Syndrome: Pathogenesis, diagnosis and treatment. J. Amer. Osteopath. Assoc. 87 :P.318-23;1987
Caillet R., Low back pain Syndrome, 4thEd. Philadelphia FA Davis, 1988,p.252-270
Hallin RP; Sciatic Pain and the Piriformis Muscle, Post grad Med;74:69-72,1983
Mitchell F, Structural Pelvic Function, Carmel, Ca. Academy of Applied Osteopathy, 1965
Namey, TC, An HS: Emergency diagnosis and management of sciatica Differentiating the non-diskogenic causes, Emerg.Med.Rep.6:101-109.1985
Pace, JB, Nagle D, Piriformis Syndrome, West J. Med 124:p.435-39,1976
Pace, JB; Commonly overlooked pain syndromes responsive to single therapy, Post Grad Med 58:P107-113,1975
Simons DG, Travell JG, Myofascial origins of low back pain, torso muscles; Post Grad Med 73:P.81-92,1983
Stein, JM, Warfield CA; Two entrapment neuropathies, Hosp.Pract.100A-100P;1983
Travell JG, Simons DG, Piriformis and other short lateral rotators in Travell/Simons Myofascial Pain and Dysfunction: The Trigger point Manual, vol.2 Baltimore, Williams and Wilkins;10,992, P.186-312
Wellington College of Remedial massage Therapies-manual.21
gluteus miminus p.36,muscle; massage application
Piriformis, muscle p.37,
Treatment for hypertonicity -external rotators, piriformis ;p.139