Pyomyositis of the iliacus muscle and pyogenic sacroiliitis after sacroiliac joint block -A case report-
A 70-year-old female patient visited our pain clinic. She had a previous medical history of hypertension and tension headache for 10 years. Seven years ago, the patient had undergone L3-S1 posterolateral spinal fusion surgery after being diagnosed with spinal stenosis and spondylolisthesis. The surgery, however, led to no improvement in the patient's lumbar back pain and lumbar radiculopathy. In order to treat the continuing low back pain, pelvic pain, and spread of radicular pain to both sides of the lower leg, several epidural and caudal blocks were performed. Although the lumbar back pain improved for 7 months with treatment, the patient continued to experience pelvic pain on both sides, corresponding to a score of 9 on the visual analogue scale (VAS) ranging from 0-10 (0 = no pain, 10 = most intense pain ever). Physical examination showed no signs of erythema, or infection. There was tenderness upon palpating both SIJs, but not on the hip joint. Patrick's and Gaenslen's tests were positive on both sides. We decided to perform SIJB for diagnostic and therapeutic purposes. We injected 0.5% mepivacaine 2 cc and triamcinolone acetate 10 mg into the SIJs. During the SIJB, we confirmed the referred pain the patient had complained of. Two hours after the procedure, the patient's pain level decreased to a VAS score of 0 and she was discharged.\nThree months later, the patient was re-admitted with a chief complaint of bilateral pelvic pain corresponding to a VAS score of 6. Physical examination showed the same results as previously. Recurrence of SIJD was suspected, and SIJB was planned. We performed SIJB on the left SIJ first to diagnose and treat the patient. After placement of non-invasive blood pressure and pulse oximetry monitors, the patient was placed on the fluoroscopy table in the prone position and both the hips and the pelvic region around the sacroiliac joints were disinfected widely with povidone iodine solution, after which we waited for 10 minutes. The physician cleaned his hands using a 62% ethanol gel, wore radiation protective gloves and disposable sterile gloves, and draped the patient. An anteroposterior fluoroscopic image of the SIJ was obtained. The fluoroscope was angled caudad, placing the posterior superior iliac spine and iliac crest to overlay the joint image, and was oblique to the contralateral side, placing the anterior and posterior aspects of the joint in line. A 23 gauge 6 cm disposable needle was advanced under coaxial technique and intermittent fluoroscopy until the joint was entered. After injection of 0.5 cc of contrast media, we confirmed that the needle was positioned in the capsule by the spread of the contrast media in the SIJ. A mixture of 0.5% mepivacaine 2 ml and triamcinolone acetonide 10 mg was injected. Following the same procedure, SIJB was then performed on the right side. The patient complained of ordinary referred pain on both sides at the time of the contrast media injection. After the injection of the mixture of 0.5% mepivacaine 2 cc and triamcinolone acetonide 10 mg, the pelvic pain on both sides decreased to a VAS score of 0. The patient did not complain of any other symptoms and her blood pressure was within normal limits. She was stabilized in bed for one hour and then discharged.\nThe patient was admitted to the emergency room two days after the final SIJB with chief complaints of left pelvic pain corresponding to a VAS score of 9 and fever (39.0℃). During the physical examination, the patient showed tenderness in the left hip. Blood pressure and heart rate were within normal limits. Laboratory tests showed the white blood cell count to be within normal limits, at 7.68 k/µl, but the neutrophil count was increased to 93.6%. Both ESR, at 35 mm/hr, and C-reactive protein (CRP), at 15 mg/dl, showed an increase. There were no specific findings on chest computed tomography (CT) or abdominal and pelvic CT, with the exception of L3-S1 posterior fusion. CT showed osteophytes and erosion in both SI joints and irregularity in the joint spaces, but there were no particular changes compared to the previous CT. Following admission, the patient was started on vancomycin hydrochloride 1 g intravenous (IV) every 12 hours. Pelvic magnetic resonance imaging (MRI) performed 3 days after the procedure showed high signal intensity edema and enhancement in a T2-weighted image at the left iliacus muscle, leading to a suspected diagnosis of myositis. There was no suspicion of infection or inflammation at the sacroiliac joint (). Methicillin-sensitive staphylococcus aureus (MSSA) was discovered in the blood culture taken 7 days after the procedure. Following this blood culture result, the patient's antibiotic therapy was changed from vancomycin to cefazolin sodium 2 g IV every 8 hours. After 17 days of continuous antibiotic therapy, the patient's ESR increased to 99 mm/hr and her CRP increased to 8.8 mg/dl. Taking these findings into consideration, the antibiotics were changed to ciprofloxacin 400 mg IV every 12 hours and rifampicin 450 mg P.O. every 12 hours. 27 days after the procedure, the patient's left pelvic pain decreased to a VAS score of 3. However, the patient's ESR and CRP remained elevated, at 93 mm/hr and 8.57 mg/dl, respectively, and she maintained a fever of at least 38.0℃ . Forty one days after the procedure, prosthetic infection at the site of the spinal fusion surgery performed 7 years ago was suspected, and 67Ga SPECT/CT was performed. At the fusion site, 67Ga SPECT/CT showed only mild uptake, which appeared to be inflammatory change. In addition, abnormal uptake was seen at the left SIJ, and septic sacroiliitis was suspected (). 58 days after the procedure, CRP normalized to 0.29 mg/dl and ESR decreased to 60 mm/hr, and the patient had no fever. Her pain decreased to a VAS score of 2 with a fentanyl 4.2 mg/10.5 cm patch and oral acetaminophen. The infection was thought to be under control, so the patient was discharged and placed on antibiotics and analgesics. She was directed to follow up as an outpatient.