surgery was performed on 12 patients from among 239 patients who were diagnosed with ps using our inclusion / exclusion criteria ( table 1 ) . of these
surgery was indicated when pain ( buttock pain or mainly sciatica ) was not relieved by conservative measures , including education for habitual position or physical activity change , medication , physical therapy , local steroid injections on the piriformis muscle , or extracorporeal shock wave therapy ( eswt ) for at least 3 months .
twelve patients underwent surgery for ps and the average age of the patients ( 4 males and 8 females ) who underwent surgery was 61 years ( range , 45 to 71 years ) .
the average duration of the symptoms before surgery was 22.1 months ( range , 4 to 72 months ) , and the mean follow - up period was 22.7 months ( range , 12 to 43 months ) .
of the 12 patients who had piriformis muscle resection with / without neurolysis , 8 had underlying pathologies including spinal stenosis ; 5 had been managed by spinal block and 3 had undergone lumbar spinal surgery , but their symptoms had not been relieved .
three patients had a long - time , occupation - related , habitual sitting position , and 1 patient had a history of sacral fracture .
we evaluated buttock pain with / without sciatica using a visual analog scale ( vas ; 0 , no pain ; 10 , maximum pain ) and recorded the responses preoperatively , and at 3 days and 12 months postoperatively .
kruskal - wallis and mann - whitney u - tests were used for post hoc analysis to compare changes in vas for pain over time .
the gluteus maximus was divided in the direction of its fibers by blunt dissection , and the fascia lata was incised in continuity where it overlaid the trochanter ; we then removed the trochanteric bursa .
the piriformis muscle was inserted into the posterior aspect of the greater trochanter as tendinous nature and was located above the obturator internus tendon ( fig .
the sciatic nerve was explored and found to pass anteriorly to the piriformis muscle in all cases . additionally , we divided the tight piriformis tendon at the insertion site at its tendinous portion .
the proximal portion of the muscle was retracted when the leg was internally rotated after its division .
neurolysis around the sciatic nerve into the sciatic notch was performed in two cases of a severely adherent sciatic nerve .
severely dilated and engorged epineurial vessels were found in two cases with intractable sciatica ( fig .
after surgery , patient activity with the assistance of a cane was encouraged to relieve pain from the gluteal muscle repair . the diagnostic procedure involved a detailed physical examination , including a palpation test for tenderness over the origin ( sacroiliac joint ) or insertion of the short external rotators behind the trochanter ( fig .
the clinical examination also included several provocation tests for pain and weakness on resisted abduction and external rotation of the thigh in a sitting position ( pace test ) , pain on forced passive internal rotation of the extended thigh ( freiberg 's test ) , and buttock and leg pain during passive straight leg raising ( lasgue 's sign ) .
in addition to electromyography , various imaging studies  including ct , mri , and ultrasonography were performed , and a steroid injection into the piriformis muscle was carried out for diagnostic treatment . to exclude sciatica caused by spinal problems , repeated
patients who had greater than 50% relief of symptoms of sciatica after caudal block were excluded from having a diagnosis of ps .
asymmetry of the piriformis muscle on ct or mri was considered a positive finding of ps .
an electromyographic finding of radiculopathy was attributed to spinal root compression , not to ps ( fig .
the gluteus maximus was divided in the direction of its fibers by blunt dissection , and the fascia lata was incised in continuity where it overlaid the trochanter ; we then removed the trochanteric bursa .
the piriformis muscle was inserted into the posterior aspect of the greater trochanter as tendinous nature and was located above the obturator internus tendon ( fig .
the sciatic nerve was explored and found to pass anteriorly to the piriformis muscle in all cases . additionally , we divided the tight piriformis tendon at the insertion site at its tendinous portion .
the proximal portion of the muscle was retracted when the leg was internally rotated after its division .
neurolysis around the sciatic nerve into the sciatic notch was performed in two cases of a severely adherent sciatic nerve .
severely dilated and engorged epineurial vessels were found in two cases with intractable sciatica ( fig .
after surgery , patient activity with the assistance of a cane was encouraged to relieve pain from the gluteal muscle repair .
the diagnostic procedure involved a detailed physical examination , including a palpation test for tenderness over the origin ( sacroiliac joint ) or insertion of the short external rotators behind the trochanter ( fig .
the clinical examination also included several provocation tests for pain and weakness on resisted abduction and external rotation of the thigh in a sitting position ( pace test ) , pain on forced passive internal rotation of the extended thigh ( freiberg 's test ) , and buttock and leg pain during passive straight leg raising ( lasgue 's sign ) .
in addition to electromyography , various imaging studies  including ct , mri , and ultrasonography were performed , and a steroid injection into the piriformis muscle was carried out for diagnostic treatment . to exclude sciatica caused by spinal problems , repeated
patients who had greater than 50% relief of symptoms of sciatica after caudal block were excluded from having a diagnosis of ps .
asymmetry of the piriformis muscle on ct or mri was considered a positive finding of ps .
an electromyographic finding of radiculopathy was attributed to spinal root compression , not to ps ( fig .
for the diagnosis of ps , physical examinations , including several provocative tests , radiographic studies , such as plain x - ray , ct or mri , emg , or an injection were performed .
when a diagnosis of ps was suspected , various conservative treatments were initially performed in all patients and generally provided good results ( table 2 ) .
of the 239 patients , 12 patients who were refractory to conservative treatment underwent surgical treatment.table 3 summarizes the clinical features and the results of surgical treatment . on physical examination ,
tenderness in the gluteal area , particularly on the iliac side of the sacroiliac joint , was detected in 10 patients ( 83% ) .
pain provocative tests  such as the freiberg 's and pace tests  were positive in 7 patients ( 58% ) .
electrodiagnostic testing showed no specific findings ( delayed h - reflex at the flexion adduction internal rotation position ) suggesting ps as opposed to other pathologies , such as lumbosacral radiculopathy , sciatic nerve palsy , or posterior cutaneous neuropathy of the thigh .
asymmetry of the piriformis muscle or hyperintensity around the sciatic nerve on ct and mri was detected in only 5 patients ( 42% ) ( fig .
three patients had occupations that involved sitting for a long duration , such as sewing or driving .
of the 12 patients undergoing surgical resection of the piriformis muscle , neurolysis was performed in 2 patients due to a severely adherent or scarred sciatic nerve . engorged epineurial vessels around the sciatic nerve shrank spontaneously after resection of the piriformis muscle .
the average length of the skin incision was 9.5 cm , and the average amount of postoperative bleeding was 24.5 ml . there were no postoperative complications including hematoma , infection , delayed wound healing , scar formation , and myositis ossificans .
the average duration of hospitalization was 5.3 days ( range , 3 to 9 days ) . compared with preoperatively ( mean vas score , 9 )
, the vas scores significantly decreased both immediately after surgery ( mean vas score , 4 ) and at the 12-month follow - up ( mean vas score , 3.1 ) ( table 4 ) .
persistent buttock pain after surgery was present in 3 patients . among them , 1 patient had symptom relief after 12 months .
the diagnosis of ps is mostly elusive and remains controversial due to the lack of consistent objective diagnostic criteria .
the differential diagnoses should include herniation of the nucleus pulposus ( hnp ) , myofascial pain , sacroiliitis , trochanteric bursitis , or any other sciatic nerve - impinging conditions . in this study
, the diagnosis of ps could be established with the patient 's history , a careful physical examination , and a local injection of the piriformis muscle when no other etiological findings were identified on emg or imaging studies , including ct and mri ( fig .
because lumbosacral hnp or spinal stenosis commonly occurs at the l4 - 5 or l5-s1 intervertebral space , it is important to determine whether the pain originates from the root or peripheral nerve.10 ) in patients with ps , symptoms of neurological claudication are rare , while pain aggravation by a position change or prolonged sitting is frequently observed in them . specific sensory changes in dermatomes or muscle weakness can help to exclude ps . based on our cases , we suggest that the three cardinal symptoms of ps are buttock pain , radiating pain to the posterior thigh above the knee , and pain aggravated by position changes or prolonged sitting
. the piriformis muscle can be firm and hard to palpation from the greater sciatic notch to the posterior aspect of the greater trochanter .
in physical examination , tenderness of the piriformis muscle ( 83% ) is the most consistent finding .
although emg is often normal in patients with ps , continuous compression may result in abnormal spontaneous activity of the muscles innervated by the sciatic nerve , including a delay in the h - reflex with the affected leg in a flexed , adducted , and internally rotated position.11 ) in our study , electrodiagnostic testing was not helpful for the diagnosis of ps but useful in ruling out other causes with similar symptoms , such as lumbosacral radiculopathy .
diagnostic imaging modalities , including ct , mri , and mrn , have been used in many studies to diagnose ps.12131415 ) however , these studies are limited to cases showing atypical anatomy , including asymmetry of the piriformis muscle or hyperintensity of the sciatic nerve ; these conditions accounted for only 5 of the 12 surgical patients ( 42% ) in our study .
sayson et al.16 ) and barton17 ) found that preoperative mri failed to identify atypical anatomy that was found intraoperatively .
mrn is a relatively new technique that was developed specifically to enhance the imaging of nerves .
filler et al.1 ) used mrn to prospectively investigate 87 patients with sciatica - like pain in whom either standard testing had failed to yield a diagnosis or who had failed lumbar disc surgery ; 67% of this group was diagnosed with ps . however , tiel18 ) pointed out methodological and technical problems of mrn .
some reports have suggested diagnostic criteria for ps.1920 ) recently , michel et al.21 ) proposed to use a clinical scoring system : ps can be considered  probable  with a score of 8 or more out of 12 points .
however , it includes negative findings for spinal disease , such as no lower back pain , painless axial spinal palpation , negative lasgue 's maneuver , or absence of perineal irritation ( 4 points ) . a scoring system including negative findings for spinal problems can result in overdiagnosis of ps .
in addition , the scoring system involves obscure physical tests that provoke buttock pain or sciatica by stretching or resisted contraction , and it does not include some diagnostic tests , such as local steroid injection , which is a widely used tool for establishing the diagnosis .
they are comprised of 5 items : buttock pain with / without sciatica during prolonged sitting ; tenderness of the piriformis muscle ; positive provocative tests ; positive findings on ct or mri ; and pain relief with a local injection .
additionally , caudal or epidural block was tried at least once before surgery in our study .
we suggest to exclude a diagnosis of ps with any of the following findings : symptoms of neurologic claudication ; positive lasgue 's or straight leg raise test ; sensory changes on nerve root innervation ; radiculopathy on emg ; or an effective caudal or epidural block .
the sciatic nerve compression by the piriformis muscle or surrounding fibrous bands is different from the nerve root compression of spinal origin .
absent clinical findings due to nerve root compression is important in the diagnosis of ps .
initial nonoperative treatment of ps includes medications ( nonsteroidal anti - inflammatory drugs , muscle relaxants , and other medications effective in neuropathic pain , such as pregabalin or gabapentin ) , physiotherapy , eswt , injections of local anesthetics and corticosteroids , and the more recently investigated option of botulinum neurotoxin injections.8 ) in our study , eswt was applied in patients with buttock pain more than twice with an interval of 1 week until pain subsides significantly .
eswt was undertaken with 2,000 pulses each time at 1 week interval totaling 4,000 to 6,000 pulses .
our clinical results demonstrated that the most effective modality in treatment of ps for reducing buttock pain was eswt .
we had satisfactory clinical results after release of the piriformis muscle and neurolysis of sciatic nerve in patients with refractory sciatica that fail to respond successfully to conservative treatments .
intraoperatively , identification of the piriformis muscle among short external rotator muscles and posterior retraction after complete resection of the muscle are important .
careful dissection of fibrous tissues around the sciatic nerve is also essential to avoid damaging the nerve proper or the dilated vaso nervorum .
deep gluteal syndrome ( dgs ) is a disease entity that is characterized by pain or dysesthesia in the buttock area , hip , or posterior thigh and/or radicular pain due to a nondiscogenic sciatic nerve entrapment in the subgluteal space.22 ) its main pathology is fibrous bands around the sciatic nerve formed by various pathological conditions , such as piriformis syndrome , obturator internus / gemellus syndrome , or ischiofemoral impingement .
the causes of dgs include traumatic , iatrogenic , inflammatory / infectious , vascular , and gynecological processes , and tumors / pseudotumors .
therefore , the treatment of dgs is decompression of the sciatic nerve via open or endoscopic surgery .
it is not clear whether resection of the piriformis muscle has additional benefits over decompression of the sciatic nerve in ps .
however , the recurrence of sciatic nerve adhesions can be avoided when the muscle is resected.1 ) endoscopic surgery for adhesiolysis of the sciatic nerve has several advantages over open methods , including less invasiveness and less postoperative pain.23 ) however , endoscopic sciatic nerve release is technically demanding and has limited efficacy for release of a severely adherent sciatic nerve . considering that
no prospective , randomized trial has evaluated surgical treatment outcomes of ps , the important finding of our study was the significant decrease in symptoms after surgery . to achieve good results , the indications for surgery ( no response to physical therapy and at least one injection )
should be determined upon proper diagnosis ( based exclusively on clinical and spine evaluations ) .
surgery is an important treatment option for unresolved ps because of its low morbidity and simplicity . to overcome the limitations of our work , a prospective study with a greater number of cases and a longer follow - up period
should be performed to establish the gold standard methods for the diagnosis and treatment of ps ; furthermore , several modalities for diagnosis of ps should be developed . in conclusions ,
the diagnosis of ps is obscure and elusive , but a systematic approach is helpful .
if a diagnosis is determined correctly , surgical treatment can be a good option in patients with refractory pain , particularly sciatica , despite application of appropriate conservative treatment modalities .
 backgroundpiriformis syndrome ( ps ) is an uncommon disease characterized by symptoms resulting from compression / irritation of the sciatic nerve by the piriformis muscle . 
 uncertainty and controversy remain regarding the proper diagnosis and most effective form of treatment for ps . 
 this study analyzes the diagnostic methods and efficacy of conservative and surgical treatments for ps.methodsfrom march 2006 to february 2013 , we retrospectively reviewed 239 patients who were diagnosed with ps and screened them for eligibility according to our inclusion / exclusion criteria . 
 all patients underwent various conservative treatments initially including activity modification , medications , physical therapy , local steroid injections into the piriformis muscle , and extracorporeal shock wave therapy for at least 3 months . 
 we resected the piriformis muscle with / without neurolysis of the sciatic nerve in 12 patients who had intractable sciatica despite conservative treatment at least for 3 months . 
 the average age of the patients ( 4 males and 8 females ) was 61 years ( range , 45 to 71 years ) . 
 the average duration of symptoms before surgery was 22.1 months ( range , 4 to 72 months ) , and the mean follow - up period was 22.7 months ( range , 12 to 43 months ) . 
 we evaluated the degree of pain and recorded the responses using a visual analog scale ( vas ) preoperatively and 3 days and 12 months postoperatively.resultsbuttock pain was more improved than sciatica with various conservative treatments . compared with preoperatively 
 , the vas score was significantly decreased after the operation . 
 overall , satisfactory results were obtained in 10 patients ( 83% ) after surgery.conclusionsps is thought to be an exclusively clinical diagnosis , and if the diagnosis is performed correctly , surgery can be a good treatment option in patients with refractory sciatica despite appropriate conservative treatments . 
METHODS
Surgical Approach
Clinical Evaluation
RESULTS
DISCUSSION