From the (1) Second Radiology Department, Medical School, National and Kapodistrian University of Athens, University General Hospital “ATTIKON”, Athens, Greece; and the (2) First Department of Orthopaedics, National and Kapodistrian University of Athens, School of Medicine, University General Hospital “ATTIKON”, Athens, Greece
Manuscript Type: Original Article
Andreas F. Mavrogenis, MD
Associate Professor of Orthopaedics
First Department of Orthopaedics, National and Kapodistrian University of Athens, School of Medicine
1 Rimini str, 12462 Haidari/Athens, Greece
Tel.: +30 210 5831832
Fax: +30 2105326418
E mail: firstname.lastname@example.org
Grant Information: None
Conflict of interest: Authors declare that they have no conflict of interest
Piriformis syndrome (PS), which was first described by Yeoman in 1928, is a general term referring to patients with low back pain, sciatica and instability with a 6% incidence worldwide. This study aims to retrospectively evaluate the effectiveness of Computed Tomography (CT) – guided percutaneous infiltration in a series of consecutive patients with piriformis syndrome with symptoms refractory to conservative therapies.
Institutional database research identified 20 consecutive patients with piriformis syndrome refractory to conservative therapies who underwent CT – guided percutaneous infiltration with a mixture of long acting corticosteroid and local anesthetic. Pre-operational evaluation included physical examination and MRI. The correct position of the needle (22 Gauge spinal needle) was verified with CT scan post contrast medium injection. Pain, prior, one week/one, 6 and 12 months post were compared by means of a numeric visual scale (NVS) questionnaire.
Mean pain score prior to CT-guided percutaneous infiltration was 8.95±1.432 NVS units. This score was reduced to a mean value of 0.85±0.933 units at 1 week after, 0.90 ± 0.852 at 1 month, 1.10 ±1.165 at 6 months and 1.20±1.399 at 12 months of follow-up (p < 0.001). Two (2) patients out of twenty (10%) underwent a second infiltration, which was performed 7 and 10 days after the first one respectively. No complication was observed.
Computed tomography-guided infiltrations seem to be a feasible, efficacious and safe approach for pain reduction and mobility improvement in patients with symptomatic piriformis syndrome.
Keywords: Piriformis; pain; infiltration; corticosteroid
Piriformis syndrome (PS) was first described by Yeoman in 1928; it is a general term referring to patients with low back pain, sciatica and instability with a 6% incidence worldwide [1-5]. Biomechanical differences may explain a significant female (6:1) predominance of the syndrome: the quadriceps femoris muscle angle is wider in women compared to male population . PS is usually caused by alterations in the piriformis muscle, regional inflammations and anatomical variations (Figure 1) . Usually, patients present with buttock pain, commonly mimicking low back pain which compounds with bowel movements and hip adduction, or causes sitting intolerance [1, 4, 5]. Symptoms may also include scrotal pain (in male patients) and irritation in the labial majora or dyspareunia (in female patients). In most of the cases due to the piriformis complexity that includes the sacral plexus and the sciatic nerve, diagnosis is a result of exclusion . Subsequently, piriformis syndrome could always be included in the differential diagnosis of hamstring, lumbosacral and sacroiliac pain or injuries whilst pelvic masses, gout, bursitis, spinal stenosis and secondary sciatica (hematoma, aneurysm, fibrotic band) should be a diagnostic consideration [2, 5]. The Laseque’s sign (pain in the vicinity of the greater sciatic notch when the knee is extended and hip is flexed to 90 º), the absence of neurologic deficits and tenderness over the buttock, the sacroiliac joint and the sciatic notch are signs indicative of the syndrome [4, 6]. Electromyography (EMG) in 50% of the cases might demonstrate changes in gluteus maximous and piriformis muscle .
During the acute phase, physical therapy (including bed rest, stretching, massage, exercises, moist heat and/ or ultrasound) and medication (including non-steroid anti-inflammatory drugs, muscle relaxant drugs and neuropathic agents) consist the baseline of treatment [2, 5]. When conservative therapy is not effective, several authors are in favor of local steroid and anesthetic or botulinum (BTX-A) injection . Imaging guidance for the infiltration of the piriformis muscle includes fluoroscopy, ultrasound, computed tomography and Magnetic Resonance Imaging [4, 9, 10].
The purpose of this study is to retrospectively evaluate the effectiveness of Computed Tomography-guided percutaneous infiltration for piriformis syndrome in a series of consecutive patients, using a mixture of corticosteroid and local anesthetic.
Materials and methods
Patient selection and evaluation
Institutional database research identified 20 consecutive patients with piriformis syndrome refractory to conservative therapies who underwent CT – guided percutaneous infiltration with a mixture of long acting corticosteroid (triamcinolone acetonide 40mg/ml) and local anesthetic (Lidocaine Hydrochloride 2%). There were 12 male and 8 female patients with a mean age of 57.71 years (range 22-85 years). The patients were studied for a one year period. No patient was lost to follow-up. All patients gave written informed consent for their data to be included in this study
Diagnosis of PS was based on clinical history, physical examination and imaging findings. All patients presented with pain in the gluteal area and sciatica. During physical evaluation patients had indicative findings of PS, such as Laseque’s sign, buttock tenderness and knee pain in Beatty and Freiberg maneuvers respectively. X-Rays and multiplanar CT or MRI scans were performed in order to exclude other hamstring, lumbosacral or sacroiliac diseases/ causes of pain.
The diagnosis was made either by two interventional radiologists, with 10 and 15 years of experience respectively (12/20 patients), or by the referring orthopedic surgeon who identified the potential patients and verified their eligibility (8/20 patients). All patients had undergone different conservative therapies in the past six months without success. Evaluation of the patients’ medical records identified analgesics, non-steroidal anti-inflammatory drugs and physiotherapy as pre-enrolment conservative therapy. Exclusion criteria for the procedure included response to conservative treatment, irreversible coagulopathy, active, systemic or local infections and patient unwilling to consent to the procedure.
Percutaneous infiltration was always performed on an outpatient basis. Computed Tomography guidance with sequential scanning (120 Kv peak, 240 mAs wavelength and 2 mm slice thickness, scan length from anterior-superior spine to ischial spine to cover the piriformis muscle area) was used for planning, targeting and intra-procedural modification during the therapeutic session. Under local sterility, infiltration was performed with percutaneous posterior approach in all cases. After the initial CT scan, skin entry point was selected. A 22 Gauge spinal needle was advanced and its approach was evaluated with sequential CT scans. Once in the correct location, 1-3 ml of contrast medium was injected to verify extra-vascular needle location in proximity to the piriformis muscle (Figure 2). Following a mixture of long acting corticosteroid and local anaesthetic was injected (total volume injected was 2.5 cc including 1.5 cc of corticosteroid and 1 cc of local anesthetic). At the end of the procedure, a CT scan was performed with the same technical and anatomical parameters, to secure infiltration’s accuracy and depict potential complications. Each patient remained in the hospital for 30–45 min (only for observation) and was then discharged with suggestion of one day rest and then being free to engage in normal activities.
Patients follow up consisted of clinical visits at one week, one, 6 and 12 months after the procedure. Questions asked during the follow-up period concerned the pain reduction and mobility improvement and whether the procedure had decreased or totally relieved the symptoms they were treated for. Pain, was compared by means of a numeric visual scale (NVS) questionnaire. The primary outcome was defined as pain reduction, which was measured with numeric visual scale (NVS) questionnaires prior, one week/one, 6 and 12 months post therapy. The NVS is a 10-cm scale from 0 to 10 divided into 10 equal parts on which the patient subjectively assigns his or her pain on a scale of 0 (no pain) to 10 (worst pain patient can imagine). In addition, the inventory contains questions concerning the pain itself and its influence on the patient’s activity (sleep, occupation and housework, walking) and mobility impairment . Complications were classified and graded according standard international reporting standards . Mobility evaluation was further performed using four criteria: Normal mobility, moderate mobility (painful walking without English canes), limited mobility (mobility with English canes), and very limited mobility (impossible).
Pain scores and mobility-quality of life scores are expressed as median and mean ± standard deviation. Confidence interval was 95%. Variables were tested against normality with Kolmogorov-Smirnov and Shapiro-Wilk tests of Normality. Related Samples Wilcoxon Signed Rank Test was used to compare pain scores and mobility-quality of life scores before the infiltration and during follow up. P values less than 0.05 were considered to indicate a statistically significant difference. Statistical analyses were performed with IBM SPSS Statistics 21.
Descriptive statistics of the study are reported in Table 1. Technical success was achieved in all 20 patients who underwent the infiltration procedure. There were no clinically significant complications noted in our study. Patients prior and at each follow-up self-reported a brief pain inventory containing a 0-10 NVS questionnaire and questions on terms of pain reduction, effect upon mobility and life quality. Mean pain score prior to CT-guided percutaneous infiltration was 8.95±1.432 NVS units. This score was reduced to a mean value of 0.85±0.933 units at 1 week after, 0.90 ± 0.852 at 1 month, 1.10 ±1.165 at 6 months and 1.20±1.399 at 12 months of follow-up (Figure 3), (p < 0.001). No statistically significant differences were observed regarding sex or age. Pain, mobility, activity (sleep, occupation/ houseworks and walking) and general clinical condition were recorded prior, 1 week post the session and in1, 6 and 12 months. End point was one year post treatment. Details of pain reduction and mobility improvement are summarized in Table 2. End point was one year post treatment.
Despite the long term clinical experience, PS remains a diagnostic and management dilemma with some authors even doubting its existence as an entity . Piriform muscle’s complexity and alterations constitute a possible explanation for the production of symptoms (Figure 3), [2-6]. The piriform muscle is a pyramid-shaped external rotator, weak abductor and flexor of the hip; normally, it originates from the pelvic surface of the sacral segments S2–S4, the sacro-iliac joint, the anterior sacro-spinous ligament and the sacro-tuberous ligament . It passes through the greater sciatic notch to insert onto the greater trochanter of the femur. The sciatic nerve exits the pelvis below the belly of the muscle. In cases of congenital alterations, the sciatic nerve may divide proximally, pass through the belly of the muscle through its tendons or between a congenitally bifid muscle [2, 6].
PS clinical features are always a point of criticism. Laseque’s sign is considered as the most reliable clinical feature of the syndrome [2-4] Freiberg, Pace, Beatty signs, the FAIR test, internal/ external tenderness, dyspareynia and tonic external rotation of the hip are all considered as specific signs of the syndrome, but present with various sensitivity among individual studies ( 13-100%) [3-6]. Prolonged H latency in the adducted and flexed hip is also indicative of piriformis syndrome .
Patients who do not respond to a baseline of conservative treatment are elligible for local anesthetic and/ or steroid injections. [4,15]. To present, surgery is considered as the last approach, to secure the decompression of isciatic nerve from fibrous bands and reduce the tension of the piriformis muscle .
The present study is in favor of percutaneous infiltration injection. Regarding patients self –reports, we observed significant statistical difference upon pain reduction prior and after the procedure. A mixture of steroid/ anesthetic is preferred because corticosteroids block selectively the transmission of nociceptive fibers and usually act 72 hours after the injection. The initial pain relief derives from the local anesthetic which reduces the spasm and relax the muscle . Our method presented 100% technical success, and no major complications were mentioned.
Ultrasound, CT and MRI guided injections tend to replace blind or fluoroscopically- guided injections as they provide good visualization of the piriform muscle and the ability to measure the needle depth [17-21]. Several studies support the efficacy of ultrasound- guided injections, proposing this technique as a fast and low cost modality [17, 18]. CT-guided percutaneous infiltration is the preferable technique in our department. Despite the radiation effect, computed tomography-guided injection provides an efficacious combination of precise landmark for the piriformis muscle, direct approach of the pain area and relatively low cost. Magnetic resonance lacks radiation, but requires compatible needles and increases the cost and the duration of the procedure [20, 21]. Another point of controversy is the type of drug chosen for injection. Several studies support the superiority of Botulinium (BTX) when compared to steroid/ local anesthetic drugs, regarding pain relief and life quality [22-24]. Corticosteroids have also undeniably lower cost comparing to BTX injections .
Limitations of our study include its retrospective nature, the small sample of patients and the lack of control group. Further studies are required to compare large series of patients with conservative and interventional approaches and/or the efficacy of CT-guided injections of steroid/ local anesthetic compared to the CT-guided injection of botulinum as well.
Computed tomography-guided infiltrations constitute a feasible, efficacious and safe approach for pain reduction and mobility improvement in patients with symptomatic piriformis syndrome. Computed tomography guidance secures the precise needle placement and minimizes major complications with excellent results upon pain relief.
Declarations of interest: None.
Ethical approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent: Informed consent was obtained from all individual participants included in the study.
Disclosures: all authors have approved the final article
- Yeoman W. The relation of arthritis of the sacro-iliac joint to sciatica, with an analysis of 100 cases. Lancet 1928; 2: 1119-1122.
- Kirschner JS, Foye PM, Cole JL. Piriformis syndrome, diagnosis and treatment. Muscle Nerve. 2009 Jul;40(1):10-8.
- Jawish RM, Assoum HA, Khamis CF. Anatomical, clinical and electrical obdervations in piriformis syndrome. J Orthop Surg Res. 2010 Jan 21;5:3.
- Masala S, Crusco S, Meschini A, Taglieri A, Calabria E, Simonetti G. Piriformis syndrome: long-term follow-up in patients treated with percutaneous injection of anesthetic and corticosteroid under CT guidance. Cardiovasc Intervent Radiol. 2012 Apr;35(2):375-82.
- Robinson ES, Lindley EM, Gonzalez P, Estes S, Cooley R, Burger EL, Patel VV. Piriformis syndrome versus radiculopathy following lumbar artificial disc replacement. Spine (Phila Pa 1976). 2011 Feb 15;36(4):E282-7.
- Hopayian K, Song F, Riera R, Sambandan S. The clinical features of the piriformis syndrome: a systematic review. Eur Spine J. 2010 Dec;19(12):2095-109.
- Fishman LM, Zybert PA. Electrophysiologic evidence of piriformis syndrome. Arch Phys Med Rehabil. 1992 Apr;73(4):359-64.
- Santamato A, Micello MF, Valeno G, Beatrice R, Cinone N, Baricich A, Picelli A, Panza F, Logroscino G, Fiore P, Ranieri M. Ultrasound-Guided Injection of Botulinum Toxin Type A for Piriformis Muscle Syndrome: A Case Report and Review of the Literature. Toxins (Basel). 2015 Aug 10;7(8):3045-56.
- Kelekis AD, Somon T, Yilmaz H, Bize P, Brountzos EN, Lovblad K, Ruefenacht D, Martin JB. Interventional spine procedures. Eur J Radiol. 2005 Sep;55(3):362-83.
- Santiago FR, Kelekis A, Alvarez LG, Filippiadis DK. Interventional procedures of the spine. Semin Musculoskelet Radiol. 2014 Jul;18(3):309-17.
- Mystakidou K, Cleeland C, Tsilika E, Katsouda E, Primikiri A, Parpa E, Vlahos L, Mendoza T. Greek M.D. Anderson Symptom inventory: validation and utility in cancer patients. Oncology 2004; 67(3-4):203-10.
- Filippiadis DK, Binkert C, Pellerin O, Hoffmann RT, Krajina A, Pereira PL. Cirse Quality Assurance Document and Standards for Classification of Complications: The Cirse Classification System. Cardiovasc Intervent Radiol. 2017 Aug;40(8):1141-1146.
- Halpin RJ, Ganju A. Piriformis syndrome: a real pain in the buttock? Neurosurgery. 2009 Oct;65(4 Suppl):A197-202.
- Michel F, Decavel P, Toussirot E, Tatu L, Aleton E, Monnier G, Garbuio P, Parratte B. Piriformis muscle syndrome: diagnostic criteria and treatment of a monocentric series of 250 patients. Ann Phys Rehabil Med. 2013 Jul;56: 371-83.
- Cramp F, Bottrell O, Campbell H, et al. Non-surgical management of piriformis syndrome: a systematic review. Phys Ther Rev. 2007; 12: 66-72.
- Filippiadis DK, Kelekis A. A review of percutaneous techniques for low back pain and neuralgia: current trends in epidural infiltrations, intervertebral disk and facet joint therapies. Br J Radiol. 2016;89(1057):20150357.
- Reus M, de Dios Berná J, Vázquez V, Redondo MV, Alonso J. Piriformis syndrome: a simple technique for US-guided infiltration of the perisciatic nerve. Preliminary results. Eur Radiol. 2008 Mar;18(3):616-20.
- Chen CP, Shen CY, Lew HL. Ultrasound-guided injection of the piriformis muscle. Am J Phys Med Rehabil. 2011 Oct;90(10):871-2.
- Ozisik PA, Toru M, Denk CC, Taskiran OO, Gundogmus B. CT-guided piriformis muscle injection for the treatment of piriformis syndrome. Turk Neurosurg. 2014;24(4):471-7.
- Fritz J, Chhabra A, Wang KC, Carrino JA. Magnetic resonance neurography-guided nerve blocks for the diagnosis and treatment of chronic pelvic pain syndrome. Neuroimaging Clin N Am. 2014 Feb;24(1):211-34.
- Filler AG, Haynes J, Jordan SE, Prager J, Villablanca JP, Farahani K, McBride DQ, Tsuruda JS, Morisoli B, Batzdorf U, Johnson JP. Sciatica of nondisc origin and piriformis syndrome: diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment. J Neurosurg Spine. 2005 Feb;2(2):99-115.
- Fanucci E, Masala S, Sodani G, Varrucciu V, Romagnoli A, Squillaci E, Simonetti G. CT-guided injection of botulinic toxin for percutaneous therapy of piriformis muscle syndromewith preliminary MRI results about denervative process. Eur Radiol. 2001;11(12):2543-8.
- Fishman LM, Anderson C, Rosner B. BOTOX and physical therapy in the treatment of piriformis syndrome. Am J Phys Med Rehabil. 2002 Dec;81(12):936-42.
- Yoon SJ, Ho J, Kang HY, Lee SH, Kim KI, Shin WG, Oh JM. Low-dose botulinum toxin type A for the treatment of refractory piriformis syndrome. Pharmacotherapy. 2007 May;27(5):657-65.
Figure 1. Axial T1-weighted MRI of the pelvis shows variation of the size between the two piriformis muscles with the left muscle (white asterisk) being significantly larger.
Figure 2AB. Axial CT scan of the pelvis of a 48 years old symptomatic female patient suffering from piriformis syndrome shows:
(A) A 22 Gauge spinal needle was advanced anterior to the right piriformis muscle and 1-3 ml of contrast medium (white arrow) was injected to verify extra-vascular needle location in proximity to the muscle. (B) CT scan after the infiltration shows the dispersion of contrast medium (white arrow) anterior to the right piriformis muscle at the location where the nerve runs
Figure 3. Pain scores in a 0-10 points numeric visual scale.
Table 1. Descriptive statistics at baseline and follow-ups of the patients included in this series.
|Valid N (listwise)||20|
Table 2. Details of the patients included in this series.
|Patients (no.)||Before||1 week||1 month||6 months||1 year||Before||1 year|
|17||10||0||1||0||0||Very limited (impossible)||Normal|