A rare case of acetabulum osteomyelitis mimicking bone sarcoma.

A 57-year-old man presented to the authors' department with pain over the right hip joint over a 3-month period. External magnetic resonance imaging showed a structure in the right acetabulum that was highly suspicious for a bone sarcoma. External 3-phase bone scintigraphy substantiated the suspected diagnosis. A computer tomography-guided biopsy was performed. Microbiologic examination showed a Staphylococcus aureus strain. Histopathologic findings showed chronic fibrous osteomyelitis. Because of doubts about these findings made by radiologists, open biopsy with retrieval of bony samples from the acetabulum and hip joint puncture was repeated. At that time, the serum C-reactive protein level was 48.8 mg/dL and the white blood cell count was 5600 × 10⁶/L. Microbiologic examination showed a S aureus and a Staphylococcus epidermidis strain in both regions. Results of blood cultures were negative. Based on these findings, the decision was made to perform a septic femoral head and neck resection. After meticulous debridement, necrosectomy, and pulsatile lavage, a gentamicin and vancomycin-impregnated cement spacer was implanted. Postoperatively, systemic antibiotic treatment with cefuroxime and rifampicin was administered for 4 weeks, followed by 2 weeks of oral antibiotics. Mobilization was allowed under toe-touch bearing of the operated extremity. The further postoperative course was uneventful. Prosthesis implantation was performed after 3 months. White blood cell count and C-reactive protein values were normal at the time of surgery. Histologic and microbiologic examination of tissue samples taken intraoperatively showed no evidence of persistent infection. At follow-up after 1 year, the patient had no complaints and has no local or systemic signs of infection.