Discussion:
Sternal osteomyelitis is rare and usually occurs after sternotomy following cardiac surgery. Primary sternal osteomyelitis has rarely been described in individuals with intravenous drug use, immunodeficiency, acne fulminans, palmoplantar pustulosis, SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, and osteomyelitis), and vascular access infections.⁴ It is classified as *primary* when no other focus of infection is present and *secondary* when associated with procedures such as sternotomy, trauma, or mediastinitis. Few cases of primary sternal osteomyelitis have been reported in international literature.²
Patients often present with fever, localized pain, tenderness, and swelling over the affected sternal area. While complete blood counts may be normal in two-thirds of cases, CRP and ESR are typically elevated. Blood cultures are frequently negative, but bone or abscess samples yield positive results in 65% of cases.⁵
Our patient presented with fever, chest pain, and tender swelling, suggesting osteomyelitis as the provisional diagnosis. A lack of proper clinical observation can delay diagnosis and lead to complications such as mediastinitis, chronic osteomyelitis, and chest wall deformities.⁶ Immediate antibiotic therapy is recommended when osteomyelitis is suspected, even before confirmatory investigations.
Ultrasound is a valuable tool in identifying soft tissue collections and periosteal involvement. In our resource-limited setting, ultrasonography revealed a hypoechoic collection adjacent to the sternum, which guided the diagnosis. Taneja et al. (1992) demonstrated the utility of ultrasound in detecting early osteomyelitis, distinguishing it from soft tissue abscesses and cellulitis.⁸ Radiographs are often normal in early stages, with changes like periosteal reactions becoming visible after two weeks,⁹ as seen in this case.
Treatment involves empirical antibiotics targeting *Staphylococcus aureus*, followed by targeted therapy based on culture and sensitivity results. Early short-course intravenous therapy, followed by oral antibiotics, is effective.¹⁰ In our case, intravenous flucloxacillin was initiated empirically and later combined with clindamycin after culture results. The patient received a total of six weeks of antibiotics, including one week intravenously and five weeks orally, with full recovery. Transitioning to oral antibiotics requires clinical stability, absence of severe complications, and a significant reduction in CRP levels.¹¹
Surgical intervention is reserved for cases with abscesses or when conservative treatment fails. It involves drainage and debridement, performed under aseptic conditions.¹² In this case, no surgical intervention was needed, and the patient responded well to medical management.
In conclusion, sternal osteomyelitis is rare. Strong clinical suspicion, along with basic imaging modalities like ultrasonography, can facilitate early diagnosis even in resource-limited settings. Prompt antibiotic therapy often ensures a favorable outcome without complications.