Pyogenic sacroiliitis is a relatively rare condition, ranging from 1–2% of all cases of septic arthritic conditions.123 Considering the complexity of its anatomical and biomechanical characteristics,4 conservative treatment with antibiotics alone is often unsuccessful.5 As a result, surgical treatment is often necessary; such treatment includes debridement/drainage and/or arthrodesis.678 Therefore, we have introduced a surgical technique using bilateral dual iliac screws to secure early ambulation and a maximal fusion success rate for the treatment of pyogenic sacroiliitis. This study has been reviewed by the appropriate ethics committee, and has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki.

A healthy 23-year-old female patient suffered from hip pain for 3 weeks. The patient had no history of recent illness and no significant past medical history. The pain was constant and severe (VAS 9–10), and was not relieved by resting or analgesics. Initial laboratory tests at a local clinic showed a leucocyte count of 8180/mm³, C-reactive protein (CRP) level of 67 mg/L (normal range 0–5 mg/L), and an erythrocyte sedimentation rate (ESR) of 75 mm/hour. Blood cultures were positive for Streptococcus agalactiae. The patient was initially treated at the local clinic with bed rest and intravenous antibiotics (ciprofloxacin 400 mg IV for 14 days, ceftriaxone 2 g IV for 28 days, along with oral metronidazole 500 mg for 14 days). Radiographs of the pelvis and sacroiliac joints were normal. MRI of sacroiliac joints after 42 days of intravenous antibiotics showed a focus of infection on the right side along with intramuscular abscess in the iliacus muscle, which connected into the right sacroiliac joint. Then, the patient was transferred to Severance Hospital for interventional treatment. Initial laboratory tests in the emergency room at Severance Hospital showed a leucocyte count of 5990/mm³, CRP level of 6.29 mg/L, and an ESR of 65 mm/hour. Then, percutaneous abscess drainage was done on the right intramuscular abscess in the iliacus muscle using a pig-tail catheter. The total amount of drained abscess was 22 mL for 8 days. As the patient's right sacroiliac pain symptoms did not improve after abscess drainage, she had difficulty in turning over on the bed. MRI was performed again to confirm abscess pocket shrinkage, but it revealed the remaining right sacroiliac arthritis (Fig. 1).

Finally, the patient underwent right sacroiliac arthrodesis with curettage and autologous iliac bone transfer mixed with ceftriaxone and vancomycin powders using the bilateral dual iliac screw fixation technique. An oblique skin incision was made bilaterally over the dual iliac screw entry points. The proximal iliac screw (Legacy pedicle screw system, Medtronic Sofamor Danek, Inc., Memphis, TN, USA) was inserted using the guidance of a C-arm, from the posterior superior iliac crest, to maximize the fixation force in terms of the larger screw diameter and longest screw length. Considering the sacroiliac joint anatomy, arthrotomy and curettage drainage of the sacroiliac joint were performed in that order. After copious irrigation (preferentially 10000 mL of normal saline), antibiotics mixed with autologous iliac bone were packed into the arthrotomized sacroiliac joints. Submuscular dual rod was inserted and assembled with an adequate amount of compressive force on the affected sacroiliac joint (Fig. 2).

The patient was able to sit up at a 45 degree angle from postoperative day 1. Her pain decreased to VAS 2 on postoperative day 5. Ambulation in a wheelchair or with walking aids was permitted 5 days after surgical treatment, with the patient wearing a back brace. CRP was normalized to 3.55 mg/L at 2 weeks after surgery.

Conservative treatment for pyogenic sacroiliitis using antibiotics alone is often unsuccessful in osteomyelitis of the pelvic bones.6910 In pyogenic sacroiliitis, these anatomical characteristics could be broken, and may lead to refractory infection and chronic painful joints. Therefore, proper and timely decisions to convert conservative treatment to surgical treatment are mandatory. The patient showed immediate pain improvement from preoperative VAS 9–10 to postoperative VAS 2 at postoperative day 5, which was enough to try ambulation and toileting activities using walking aids without the assistant of caregivers. Therefore, we recommend the bilateral dual iliac screw fixation method combined with incision drainage and arthrodesis using antibiotics mixed with autologous bone graft for the treatment of pyogenic sacroiliitis.