|Year : 2013 | Volume
| Issue : 2 | Page : 94-99
Prevalence of piriformis syndrome among the cases of low back/buttock pain with sciatica: A prospective study
Usham Shyamkesho Singh1, Raj Kumar Meena1, Ch Arun Kumar Singh1, A K Joy Singh2, A Mahendra Singh1, Roel Langshong1
1 Department of Orthopedics, Regional Institute of Medical Sciences, Imphal, Manipur, India
2 Department of Physical Medicine and Rehabilitation, Regional Institute of Medical Sciences, Imphal, Manipur, India
|Date of Web Publication||19-Nov-2013|
Usham Shyamkesho Singh
Department of Orthopaedics, Regional Institute of Medical Sciences, Imphal, Manipur
Source of Support: None, Conflict of Interest: None
Aim: The aim of this study was to find out the prevalence and causes of piriformis syndrome in patients with complain of low back pain/buttock pain with sciatica attending Regional Institute of Medical Sciences (RIMS), Imphal. Materials and Methods: All the patients in the study group attending Orthopedic and Physical Medicine and Rehabilitation Out-patient Department in RIMS, Imphal were examined. Those with increased symptoms on sitting, localized significant tenderness on palpation of the muscle, presence of one or more of the following tests: Freiberg, pace, beatty, and FAIR (Flexion , Adduction and Internal Rotation) maneuvers with negative X-ray, ultrasound, computed tomography and magnetic resonance imaging findings were subjected to piriformis muscle injection of lidocaine (2%) 2 ml and methyl prednisolone 2 ml (40 mg) for confirmation of diagnosis. Result: Out of 2910 patients, 182 cases (M: 28, F: 154) in the age range of 19-75 years with a mean age of 43 years were clinically diagnosed as piriformis syndrome. Prevalence of piriformis syndrome was 6.25%. Conclusion: Piriformis syndrome is one of the differential diagnoses of low back/buttock pain with Sciatica. Individuals of all activity levels can be affected. Females are more affected than males. Causes are overuse, prolonged sitting, trauma, and vigorous massage. Diagnosis is by exclusion of other causes. Simple injection with local anesthetic and steroid in the piriformis muscle is both therapeutic and confirmatory of diagnosis. Early diagnosis and treatment with injection of piriformis muscle can prevent further complications and risks of surgery, which is also not 100% curative. With proper care, piriformis injection can be carried out without any complication. Long-term study is needed to evaluate the recurrence after injection treatment.
Keywords: Piriformis syndrome, Prevalence, Sciatica
|How to cite this article:|
Singh US, Meena RK, Singh CK, Singh AJ, Singh A M, Langshong R. Prevalence of piriformis syndrome among the cases of low back/buttock pain with sciatica: A prospective study. J Med Soc 2013;27:94-9
|How to cite this URL:|
Singh US, Meena RK, Singh CK, Singh AJ, Singh A M, Langshong R. Prevalence of piriformis syndrome among the cases of low back/buttock pain with sciatica: A prospective study. J Med Soc [serial online] 2013 [cited 2020 May 24];27:94-9. Available from: http://www.jmedsoc.org/text.asp?2013/27/2/94/121573
| Introduction|| |
Piriformis syndrome is one of a number of conditions that may produce low back/buttock pain with sciatica. Low back/buttock pain with pain radiating down the back of the leg should suggest piriformis syndrome as part of the differential diagnosis. This is especially true if a female patient has a complaint of dyspareunia. A description of the pain's location by a patient is often imprecise, the pain variously being considered a pain in the hip, tailbone, buttock or groin, and often down the back of the leg as sciatica.
Freiberg proposed the following characteristic features of sciatic pain caused by compression from the piriformis: (1) Positive Lasegue sign (pain around the greater sciatic notch on hip flexion with the knee extended and foot dorsiflexed, (2) tenderness at the sciatic notch, and (3) relief of symptoms with traction. He also described alleviation of sciatica by myofascial procedures that included the release of the piriformis. 
Delay in diagnosing piriformis syndrome may lead to pathologic conditions of the sciatic nerve, chronic somatic dysfunction, and compensatory changes resulting in pain, paresthesia, hyperesthesia, and muscle weakness. The challenge for physicians is to recognize symptoms and signs that are unique to piriformis syndrome, enabling appropriate treatment in a timely manner. 
The piriformis syndrome has been implicated as a potential source of pain and dysfunction, not only in the general population, but in athletes as well.
Because of its relative rarity, a high index of suspicion is necessary to make the diagnosis. 
There are two types of piriformis syndrome-primary and secondary:
Primary piriformis syndrome has an anatomic cause, such as a split piriformis muscle, split sciatic nerve or an anomalous sciatic nerve path.
Secondary piriformis syndrome occurs as a result of a precipitating cause, including macrotrauma, microtrauma, ischemic mass effect, and local ischemia. Among patients with piriformis syndrome, fewer than 15% of cases have primary causes. Piriformis syndrome is most often caused by macrotrauma to the buttocks, leading to hematoma formation, inflammation of soft-tissue, muscle spasm, with resulting nerve compression and subsequent scarring between the sciatic nerve and the short external rotators. Microtrauma may result from overuse of the piriformis muscle, such as in long-distance walking or running or by direct compression. The piriformis muscle is under strain during the entire gait cycle and it is postulated that it may be more prone to hypertrophy than other muscles in the region. Gait abnormalities may accentuate this, especially if they result in increased internal rotation or adduction such as with a leg length discrepancy.
It is postulated that the nerve is more susceptible to compression by the muscle because of the anomalous anatomic relationships of the sciatic nerve with the piriformis. However, understanding and inspecting for these anomalies is important during surgery for this condition. If a portion of the nerve passes through a bifid muscle belly, then simply releasing the tendon would allow the muscle to retract, further entrapping the nerve and worsening the condition. Thus, at surgery, it is imperative to explore the relationship of the sciatic nerve and the muscle at the level of the sciatic notch to assure complete decompression.
Patients who have blunt trauma to the buttock and then have signs and symptoms that are suggestive of lumbar nerve-root compression may have posttraumatic piriformis syndrome.  The sciatic nerve can be compressed between the piriformis muscle and the roof of the sciatic notch due to myositis ossificans of the piriformis muscle.  Post-radiotherapy fatty atrophy of the piriformis muscle is another cause of piriformis syndrome.  Sciatica can be caused by pyomyositis of the piriformis muscle, which causes swelling of the muscle pushing the sciatic nerve anteriorly and trapping the nerve between the piriformis muscle and gemellus superior muscle.  Recurrent piriformis syndrome may result from entrapment of the sciatic nerve due to extensive fibrous tissue formation in surgically treated piriformis syndrome cases. 
Piriformis syndrome is usually a diagnosis of exclusion once the more common causes of sciatica have been ruled out. The diagnosis can often be made on the basis of a careful clinical evaluation. 
There is a history of a recent trauma or changes in training regime or life-style. In general, individuals with piriformis syndrome will report deep pain that is localized to the posterior aspect of the hip and is accentuated with sitting standing or activity. This discomfort often lessens when the patient is lying down. 
Physical findings include tenderness over the sciatic notch, isolated atrophy of the gluteus maximus in chronic cases, 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 examination.  Contracted piriformis muscle may produce a sausage shaped mass in the buttock and ipsilateral external rotation of the hip putting the ipsilateral foot in externally rotated position - a feature referred to as a positive piriformis sign. 
Straight-leg raise findings are variable. A positive straight leg raise recreating radicular pain is more likely to be indicative of lumbar nerve root irritation. Typically, straight-leg raise may produce localized posterior hip discomfort, but this is often non-specific for a variety of conditions. 
Signs specific to piriformis syndrome that have been reported include external rotation of the hip, tenderness of the piriformis muscle found on external palpation over the greater sciatic notch or on internal palpation per vagina or rectum. Tests, which reproduce sciatica by augmenting PM tension, are:
Passive stretch tests:
- Freiberg test: Passive internal rotation of the hip in extension reproduces pain.
- FAIR test: Maintaining the hip in flexion, adduction, and internal rotation reproduces pain.
Resisted muscle contraction tests:
- Pace test: Reproduction of pain when the clinician provides resistance to hip abduction by holding the sitting patient's knee.
- Beatty test: Reproduction of pain when the patient holds the flexed hip in abduction against gravity whilst lying on the unaffected side. 
Injection of local anesthetic along with a small dose of steroid into the precise focal point of hyperirritability deep in the belly of the muscle gives immediate relief from pain, which is both diagnostic and therapeutic. ,
Differential diagnosis includes herniated lumbar disc, intervertebral discitis, intraspinal lesions, lumbar canal stenosis, pelvic masses, diabetic neuropathy, primary sacral dysfunction, sacroiliitis, and trochanteric bursitis. ,
Plain radiographs, including an anteroposterior pelvis and lateral of the affected hip are routinely performed. There are no specific radiographic features associated with piriformis syndrome, but this is important to rule out other radiographically identifiable causes.
Investigation of the lumbar spine will often include radiographs and magnetic resonance imaging (MRI) to assess for lumbar nerve root pathology. For recalcitrant cases when surgery is contemplated, MRI of the pelvis is prudent to rule out a mass effect within the sciatic notch or intrapelvic lesion. 
Non-operative treatment measures are physiotherapy, administration of analgesics, administration of non-steroidal anti-inflammatory agents, transrectal massage, transvaginal application of ultrasonic waves, and injection of local anesthetics and corticosteroids.  The essential therapy is the injection of local anesthetic into the precise focal point of hyperirritability deep in the belly of the muscle. One may, and usually does, add a small dose of corticoid. Empirically, results are slightly more lasting and permanent with the addition of corticoid.
Operative treatment consists of sectioning of the piriformis muscle at its tendinous attachments, release of fibrous bands or compressing vessels, and external neurolysis. The functional loss after sectioning of the piriformis muscle is slight since there are there are other short external rotators of the hip. 
| Materials and Methods|| |
The aim of our study was to find out the prevalence of piriformis syndrome in patients with complain of low back pain/buttock pain with sciatica attending Regional Institute of Medical Sciences (RIMS), Imphal.
It was a cross-sectional study conducted at Department of Orthopedics and Department of Physical Medicine and Rehabilitation (PMR), RIMS, Imphal from August 2010 to July 2012. Study population consisted of patients suffering from low back/buttock pain with radiation to lower limbs, aged 15 years and above. Patients with a history of leg injuries, loss of follow-up were excluded from the study. Analysis of the result was carried out using the statistical methods. Injection of local anesthetic combined with steroid into the piriformis muscle was also used as diagnostic and therapeutic procedure.
| Results and Observation|| |
A total of 2910 patients with the complaint of low back/buttock pain with sciatica attended outpatient department (OPD) of Orthopedics and PMR Department, RIMS, Imphal between September 2010 and August 2012. Age range was 15-81 years. A total of 182 cases were clinically diagnosed as piriformis syndrome.
Prevalence of piriformis syndrome was 6.25%. There was no patient developing recurrence of piriformis syndrome during the study period.
| Discussion|| |
In this study, the total number of piriformis syndrome confirmed with diagnostic injection was 182 out of 2910 OPD cases, which is 6.25% of all cases with low back/buttock pain with sciatica. This finding is within the range of 5-36% as mentioned by Pace and Nagle,  Boyajian-O'Neill et al.  and Keskula and Tamburello.  Jawish et al.  mentioned that, although the incidence of this affection remains controversial, it was increasing progressively with the improvement of investigations.
The females were found to be more affected. In this study, the male to female ratio was found to be 1:6.4 as shown in [Table 1], which is again close to 1:6 as given by Benson and Schutzer. 
Most frequently affected age group was found to be the fourth and fifth decades constituting 31.32 and 33.52% of all cases respectively, which is again similar as stated by Boyajian-O'Neill et al. 
Individuals of all occupations and activity levels were found to be affected, which is again similar with the report as mentioned by Boyajian-O'Neill et al. 
There was a history of overuse in 86 (47.25%). Boyajian-O'Neill et al. stated that microtrauma may result from overuse of the piriformis. They also postulated that as piriformis muscle is under strain during the entire gait cycle, it may be more prone to hypertrophy than other muscles in the region. This overuse may explain the cause of piriformis syndrome in 86 (47.25%) cases in this study.
There was a history of prolonged sitting in 69 (37.91%) in this study. Boyajian-O'Neill et al.  also stated that microtrauma may result from direct compression as in sitting on hard surfaces ("wallet neuritis"). This prolonged sitting may explain the cause of piriformis syndrome in 69 (37.91%) cases in this study.
There was a history of trauma in 8 (4.4%) in this study. Jawish et al.  found only one case out of 26 cases (3.85%) of piriformis syndrome giving a history of trauma due to a fall on to the buttock 3 months back before presentation. Said et al.  found only two patients (9%) out of their study group of 22 patients with piriformis syndrome giving a history of trauma to the ipsilateral buttock.
There was only history of vigorous massage by unqualified persons in 6 cases (3.3%). Massage was also found associated with 54, 47, and 6 cases of overuse, prolonged sitting and trauma respectively. No literature was found to give comment on massage, which we found quite frequently associated in this study.
In this study, we found that all the cases had buttock pain, which was increased on sitting [Table 2]. In a study group of 14 patients of posttraumatic piriformis syndrome Benson and Schutzer,  the most common presenting symptoms were pain in the buttock and intolerance to sitting on the involved side. Byrd  found buttock pain worse with sitting and with activity in his study of 15 cases of piriformis syndrom. Jawish et al.  found all their 26 cases of piriformis syndrome having intolerance to sitting on the involved side.
Right side was involved in 67.58% and left side in 32.42% [Table 2]. There was no bilateral involvement in this study.
Nearly, 72.17% of married ladies between the age group of 22 and 50 were found to have dyspareunia, which is a high figure. This finding matches those of Pace and Nagle.  They reported that most of the piriformis syndrome cases have dyspareunia. They however, did not give the range of dyspareunia and age group. In the case report of Jankiewicz et al.  pain was found increased with sexual intercourse.
There was no case having gluteal atrophy or leg muscle wasting in this study. Vandertop and Bosma  in their report of a case of piriformis syndrome found the left calf smaller than the right along with fasciculation of the muscle of the left calf, buttock, and hamstring muscles. Jawish et al.  found four patients having gluteal atrophy at the affected side and one patient having posterior leg atrophy out of their study group of 26 cases of piriformis syndrome. The time average from the beginning of pain to the treatment was 3.14 years (range: 1 month to 11 years) for the non-operative treatment group and 5.44 years (range, 2-19 years) for the operative treatment group. In this study, the time period from the onset of symptoms to the beginning of treatment was only 11-35 days with a mean of 23.2 days. The shorter duration of symptoms in this study may explain the absence of muscle wasting.
In this study, there were 94 cases showing positive piriformis sign, which was 51.64%. Boyajian-O'Neill et al.  explained this sign as ipsilateral external rotation of the affected lower extremity due to contraction of the piriformis muscle in a patient who is relaxed in the supine position. No literature was found to give the frequency of this positive piriformis sign.
There was tenderness over the greater sciatic notch in all the patients in this study. Jawish et al.  also found tenderness over the sciatic notch in all their 26 cases of piriformis syndrome. Benson and Schutzer  found tenderness to palpation of the greater sciatic notch as one of the most consistent findings on physical examination in their fourteen cases of posttraumatic piriformis syndrome.
Lasegue sign was present in all cases of piriformis syndrome in this study [Table 3]. Beauchesne and Schutzer  commented that, most patients who have piriformis syndrome secondary to trauma involving the buttock have a positive Lasegue sign. However, most cases in this study did not give a history of trauma.
Sausage shaped mass caused by spasm of the piriformis muscle, was found in only 5 cases (2.75%)as shown in [Table 3]. However, it was found in only 5.32% of cases with positive piriformis sign. This finding might be because of the different severity of the spasm and also because of the different builds of the patients making palpation of the deeply seated piriformis muscle difficult.
In this study, all the active (pace and beatty) and passive resisted tests (FAIR, freiberg), were not present in all cases of piriformis syndrome. Those positive tests in the descending order of frequency were FAIR 93.41%, freiburg 84.07%, pace 55.49%, and beatty 51.10% [Table 4]. All the four tests were found to be positive in 15 cases 8.24%. Only three tests were found to be positive in 158 cases 86.81%. Only two tests were found to be positive in nine cases 4.95%. Most of the cases had all four tests positive. Different authors used different criteria for the diagnosis of piriformis syndrome. Fishman and Schaffer  included FAIR test as one of their criteria for diagnosing piriformis syndrome. Fishman and Schaffer  stated that at least one positive test along with a history of more pain sitting than standing; a history of overuse, trauma or unusual body habitus (obesity or cachexia); or finding of tenderness in the mid-buttock must lead to a diagnosis of piriformis syndrome.
In this study, X-ray, MRI and computed tomography (CT) scan were used only to exclude other causes of low back, buttock pain or sciatica. Kobbe et al.  in their study of two cases of piriformis syndrome found MRI not helpful, although one showed a slightly thickened piriformis muscle. Due to conflicting reports regarding its use for diagnosing piriformis syndrome, MRI of the hip area was not carried out routinely in their series. Benson and Schutzer.  found CT not helpful in confirming the diagnosis of posttraumatic piriformis syndrome.
There were three cases of sensory deficit (1.65%) in this study [Table 5]. Said et al.  found associated sensory loss in 11 patients (50%) out of their study group of 22 cases of piriformis syndrome whose symptoms were chronic with a mean of 70 months (range 12-192 months). Less number of patients with sensory deficit in this study as compared to their finding may be explained by less duration of symptoms, early detection, and prompt treatment of cases in this study.
There were no cases with diminished motor power on the affected side in this study [Table 5]. Jawish et al.  found one complete right drop foot out of their study of 26 cases of piriformis syndrome. Their time average from the beginning of pain to the treatment was 3.14 years (range: 1 month to 11 years) for the non-operative treatment group and 5.44 years (range, 2-19 years) for the operative treatment group. The shorter period of symptoms (11-35 days with a range of 23.2 days) in this study may explain the absence of diminished motor power.
There were two cases of diminished ankle jerk on the affected side in this study, which was 1.1% of the total cases [Table 5]. In a case report by Beauchesne and Schutzer,  they found achilles-tendon reflex absent on the affected side.
In this study, single injection could not relieve all the cases [Table 6] and [Table 7]. 151 cases were relieved with a single injection at an average time period of 23.2 days, with a range of 11-35 days. Second injection was given to the remaining 31 cases and it could relieve the symptoms in another 27 cases at an average time period of 30.13 days with a range of 19-49 days. Third injection could relieve the remaining 4 cases at an average time period of 39.75 days with a range of 35-48 days. The injection protocol as given by Barton  who attempted a trial of up to three steroid injections were followed in this study. There was no complication due to piriformis injection. All patients in this study group could get complete recovery with diagnostic injection. There was no recurrence of the symptoms till the end of this study.
| Conclusion|| |
Piriformis syndrome is one of the differential diagnoses of low back/buttock pain with sciatica, most of which being prolapsed intervertebral disc. Individuals of all activity levels can be affected. Females are more affected than males.
Causes are overuse, prolonged sitting, trauma, and vigorous massage. Massage is both an independent cause and an aggravating factor.
Diagnosis is by exclusion of other causes of pain in the buttock or low back or sciatica with appropriate history, clinical examination, and investigations. Simple injection with local anesthetic and steroid of the piriformis muscle is both therapeutic and confirmatory of diagnosis.
Early diagnosis and treatment with injection of piriformis muscle can prevent from further complication to risks of surgery, which is also not 100% curative. With proper care, piriformis injection can be carried out without any complication. Long-term study is needed to evaluate the recurrence after injection treatment.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]