Local anaesthetics interrupt the pain-spasm cycle and reverberating nociceptor transmission, whereas corticosteroids have anti-inflammatory properties related to inhibition of prostaglandin synthesis, decreases in regional levels of inflammatory mediators and by causing a reversible local anaesthetic effect. Eventhough their antiinflammatory properties corticosteroids have been hypothesized to be of beneï¬t for nerve root infiltration. The emerging evidence also implies that the long-lasting therapeutic effect may be obtained with local anaesthetics with or without steroids. Tachihara et al. illustrated that no additional benefit from using corticosteroid was identified after nerve root infiltration. Thus, it is suggested that corticosteroids may be unnecessary for nerve root blocks. There are also adverse reactions in response to the administration of synthetic corticosteroids such as dermatologic conditions, osteonecrosis, peptic ulcer formation, weight gain, hyperglycemia, Cushing's syndrome and psychiatric symptoms varying from mild mood changes to completely developed psychosis.
In the present study, the aim was to evaluate the patients of pure piriformis syndrome treated with local anaesthetic alone or a combination of local anaesthetic and methylprednisolone.
Methods
This study conducted on retrospective evaluation of 31 patients diagnosed with piriformis syndrome, at the University of Inonu, School of Medicine, Departments of Physical Medicine and Rehabilitation and Pain Clinic, Malatya, Turkey between 2007 to 2009, who received a fluoroscopy guided piriformis muscle injection. All the patients were given detailed information on the procedure and informed written consent was obtained from all of them. The present study was approved by Local Ethics Committee.
Piriformis syndrome was diagnosed from the following: clinical history, physical examination, EMG findings and by excluding other pathological conditions of the lumbar, sacral, sacroiliac and hip joint areas by physical examination and magnetic resonance imaging or computed tomography if needed. Piriformis syndrome was suggested by pain on palpation of the sciatic notch and reproduction of pain with maneuvers that stretch or contract the piriformis muscle over the sciatic nerve such as forceful internal rotation of extended thigh (Freiberg's Maneuver) and active hip flexion, abduction or adduction and internal rotation by the patient lying with the painful side up, the painful leg flexed and knee resting on the table (Beatty's maneuver). All patients were examined by a single pain specialist and not referred by any other physician. Exclusion criteria included patients known allergies to local anaesthetic and bleeding diathesis.
Piriformis injections were carried out by a single pain specialist. The patients were placed prone on a fluoroscopy table. In a sterile fashion, the buttock area on the affected side was widely prepped and draped. AP view of the hemi-pelvis and acetabular region was obtained and then a metal marker is placed on 1/3 of lateral aspect of imaginary line between the greater trochanter and sacrum. Local infiltration with 0.5% prilocaine was used for local anaesthesia.
Two mL of radiographic contrast material (iohexol) was injected to obtain a satisfactory myogram (Figure 1). A syringe was prepared with 10 mL of 0.5% bupivacaine in local anaesthetic group or 9 mL of 0.5% bupivacaine + 40 mg methylprednisolone (10 mL total) in steroid group and injected into the piriformis muscle after negative aspiration for blood. Following the procedure patients should note relief of their usual pain. All patients were responded well to a single injection. The patients that were refractory to local anaesthetic and/or steroid medication were not considered as a sole piriformis syndrome and not included to the study.
After the procedure, the patients were observed to the recovery room for 1 hour and until any leg numbness subsides. If pain persisted a second injection was carried out with same fashion. The primary outcome parameter of the study was pain assessed by VAS, analgesic use, pain on movement and patient satisfaction. Follow-up examinations were conducted by telephone interview 6 months after local injection.
Analyses were performed using SPSS 16.0 version (SPSS Inc., Chicago, IL). The data deviated from the normal distribution were determined with the Kolmogorov-Smirnov test. Nonparametric data were evaluated with the Mann-Whitney U test. Proportions were compared with the Chi-square test. P value less than 0.05 was considered as significant.
Results
Medical records of 68 patients with piriformis syndrome were evaluated. Thirty-one patients fulï¬lled the inclusion criteria. The patient's characteristics including age, sex, weight, height, involved side and history of pain until injection were comparable between groups (Table 1). No signiï¬cant differences were noted regarding first diagnosis before admitting pain clinic, and conventional used treatment (Table 2).
Three patient from local anaesthetic group and two patients from steroid group needed to repeat injection (Table 2). The injections for these 5 patients were repeated in a couple of days. The other patients in both groups did not have a repeat injection. There were no significant differences between mean baseline VAS scores between the two groups of the study. There were significant differences between mean baseline and mean VAS scores obtained during telephone interview for both groups (p < 0.041). Pain VAS had improved by a means of 5.1 and 6.1 compared to the baseline level in the local anaesthetic and steroid groups, respectively.
Adverse effects were seen by 27% of the steroid and 6% of the placebo patients. These included drowsiness in 2 steroid group patients, and 1 local anaesthetic group patient, hypotension lasted in two days in 1 and mood changes in 1 steroid group patients. There were no other adverse effects such as fluctuations of glucose level, gastro-intestinal bleeding, osteonecrosis, infection, or requirement of additional medical treatment attributed to the investigational medications.
Discussion
Piriformis syndrome is not fully understood clinical syndrome and typically characterized by isolated sciatic pain limited to the buttock with radiation down the thigh, without sensory deficits or neurogenic cause. Robinson described six diagnostic features of piriformis syndrome which were: (I) history of the sacroiliac and gluteal trauma; (II) painful piriformis muscle, sacroiliac joint, greater sciatic notch with walking difficulty; (III) acute exacerbation of pain caused by stooping or lifting; (IV) tender and palpable piriformis muscle; (V) positive Lasegue sign; and (VI) muscle atrophy on the gluteal region. There is no generally accepted objective test for identifying the piriformis muscle syndrome. Trauma in the gluteal region have been considered as the main cause of piriformis muscle syndrome. Jawish et al. claim that piriformis muscle syndrome could be related to repetitive nerve trauma and exacerbated rotator muscle activity observed in patients with forced physical activity. To confirm the diagnosis, physical examination and imaging studies should be combined. As, piriformis syndrome is a diagnosis of exclusion, although the patients had radicular symptoms were exluded from the study, other imaging or correlation to exclude were more common causes of sciatic pain, such as lumbar disc herniation, posterior facet syndromes or spinal stenosis, had been obtained from our included patients.
The treatment goal is directed initially toward decreasing inflammation, associated pain, and spasm as pain originates due to the entrapment of the nerve root or to one of its branches, leading to the development of myofascial trigger point. This pain may also be due to energy crisis produced from a loss of oxygen and nutrient supply in the presence of an increased metabolic demand. This leads to the release of neuroactive biochemicals that sensitize nearby nerves that in turn initiate the motor and sensory of myofascial trigger point via the central nervous system resulting in mechanical hypersensitivity. Injection of the 10 mL local anaesthetic into the belly of the muscle as we used in our study may wash up such biochemicals. This injection may result in muscle relaxation and liberation of the entrapped nerve.
To our knowledge, our study is the ï¬rst clinical trial comparing the effectiveness of local anaesthetic and methylprednisolone added to the local anaesthetic. Naja et al. compared bupivacaine (9 mL 0.5% bupivacaine in a total volume of 10 mL) and bupivacaine plus clonidine (9 mL 0.5% bupivacaine and 1 mL 150 mg clonidine) in a randomized double-blind trial included 80 patients with piriformis syndrome who received a nerve stimulator guided piriformis injection. The mean VAS scores obtained after 6 months follow up were 4.5, 3.5 and 3.3 on walking, sitting and lying down, respectively. Better results with clonidine had been obtained. Benzon et al. retrospectively reviewed the charts of their patients who underwent piriformis muscle injections and described a technique for piriformis injection. After 80-100 mg methyl prednisolone or triamcinolone injection to the schiatic nerve and piriformis muscle, 18 of the 19 patients received positive responce to the injection, with significant pain relief ranging from a few hours to 3 months. The three patients diagnosed pure piriformis syndrome had 70-90% response to piriformis injection for 1-3 months. In Fishman et al. study all participants received an injection of 1.5 ml of 2% lidocaine and 0.5 ml (20 mg) of triamcinolone and improved an average of 71.1%, suggesting the efï¬cacy of corticosteroid and lidocaine injection combined with physical therapy in treating piriformis syndrome. Filler et al. reported 162 patients with pure piriformis syndrome given 10 mL of bupivacaine and 1 mL of celestone: 14.9% had sustained pain relief ranging from 8 months to 6 years without recurrence, 7.5% had 2 to 4 months of relief but required a second injection, 36.6% had 2 to 4 months of relief but experienced recurrence after a second injection, 25.4% of these patients benefited for only 2 weeks, and 15.7% received no benefit.
The result of this retrospective study pointed out that both bupivacaine alone and in combination with methylprednisolone have a significant effect in relieving chronic pain of pure piriformis syndrome and it was concluded that no additional benefit from using corticosteroid was identified after piriformis muscle injection.
