Salmonella Nontyphi Subacute Osteomyelitis of the Triradiate Cartilage—An Unusual Case and Review of the Literature

To the Editors: Osteomyelitis caused by salmonella is an infrequent occurrence, typically associated with gastroenteritis. This is a case of a 9-year-old girl who initially sought medical attention for hip pain and limp. Initial blood work and ultrasound were in favor of septic arthritis; therefore, a hip aspiration and arthrotomy were performed. We diagnosed the patient with an atypical presentation of salmonella osteomyelitis affecting the triradiate cartilage. This report underscores the rarity of such cases in immunocompetent children and highlights successful management through a combination of antibiotic therapy and surgical debridement. Osteomyelitis remains one of the most challenging and prevalent musculoskeletal pediatric infections. According to the literature, the incidence appears to be increasing over the last decade, ranging from 1.7 to 8.2/100,000.1 In 17% of cases, adjacent pyomyositis occurs due to extension of infection or due to hematogenous dissemination, commonly affecting the thigh and pelvis.2 A previously healthy 9-year-old Caucasian female presented with a 4-week history of a worsening right trochanteric pain associated with a limp and body temperature of 38 °C every 8 hours, during the last week. At admission, she was unable to walk, palpation of the right trochanter evoked pain and she had a limited right hip abduction to 25° and internal rotation to 15°. She had a white blood cell count of 17 × 109/L, neutrophiles of 84,7%, C-reactive protein of 107 mg/L and erythrocyte sedimentation rate of 96 mm/h. The ultrasound revealed a hip effusion and hypoechogenicity in the gluteus medius. The patient underwent anterior hip aspiration, which revealed 2 cc of pus. Subsequently, arthrotomy and washout were performed using the Smith-Peterson approach and started on flucloxacillin 200 mg/kg/day qid plus clindamycin 40 mg/kg/day qid. Magnetic resonance T2-FatSat revealed a small intra-articular effusion and an abscess measuring 22 × 10 × 6 mm on the posterior wall of the triradiate cartilage with bone marrow hyperintensity indicative of acetabular osteomyelitis and triradiate cartilage involvement. Additionally, pyomyositis of the right gluteus muscle compartment was evident (Fig. 1). Salmonella enterica serotype 4,5,12:I was isolated from the synovial fluid. Antibiotics were changed for cefotaxime (50 mg/kg qid). After 2 weeks of intravenous antibiotics, she was able to tolerate weight and had no range of motion limitation. She was discharged on oral trimethoprim-sulfamethoxazole 75 mg/kg/day every 6 hours. After 6 weeks of antibiotic treatment, she regained a stable walking pattern and full range of motion. An ultrasound revealed no abnormalities, and she resumed normal activities at 3 months. We report a rare case of salmonella type B osteomyelitis in an immunocompetent child without risk factors affecting the triradiate cartilage. The diagnosis is clinical, with a high level of suspicion and laboratory confirmation. Children diagnosed with pelvic osteomyelitis normally present with hip, thigh, abdominal, or lumbar back pain and may present with fever and local signs of inflammation. However, 40% of the children are afebrile.3 Blood tests are required and may reveal an increase in inflammatory markers such as erythrocyte sedimentation rate, C-reactive protein and white blood cell count. However, these parameters may not be elevated or show only a slight elevation at the time of diagnosis.4 We present a salmonella enterica serotype 4,5,12:i. It antigenically and genetically resembles salmonella serotype typhimurium but lacks the second-phase flagellar antigen.5 Salmonella osteomyelitis combined with pyomyositis is rare. In this case report, we discuss osteomyelitis caused by a gram-negative microorganism, which is more commonly associated with enterocolitis. The authors highlight the importance of considering salmonella septic arthritis in the differential diagnosis, even in pediatric patients without any predisposing factors. The particularity of the case presented was the lack of gastrointestinal manifestations. Salmonella osteomyelitis, although rare, should be considered in the differential diagnosis of pediatric osteomyelitis, especially when atypical presentations are observed, even in immunocompetent children without risk factors. Timely diagnosis, appropriate antibiotic therapy and surgical intervention, when necessary, contribute to favorable outcomes.FIGURE 1.: Axial T2 sequence magnetic resonance imaging of the pelvis showing acetabular hyperintensity, synovitis and intra-articular liquid (arrow).