Sione, a young Pacific Islander boy, is brought to the emergency department with a 3-day history of acute onset, progressively worsening central chest pain.
He points to his sternum when you ask him where the pain is. and tells you that it is made worse by deep breathing and movement.
His sternum is warm to touch and exquisitely tender, inferior to the manubrium. There is no overlying bruising, erythema, or skin changes.
He has had a cough and some mild coryzal symptoms, though there was nothing exciting to hear when you listen to his chest.
You are unsure what to make of this, so order some tests. As the results trickle in, you wonder if this is just costochondritis.
The initial workup showed evidence of inflammation, with an elevated white cell count (WCC) of 12.9 (neutrophils 12.8), CRP of 18, ESR of 38, and ferritin of 327. The rest of the blood, including troponin and LDH, is normal.
This is his sternum X-ray.
The chest x-ray was normal, but the sternal views show ill-defined soft tissue and bony changes of the inferior sternum.
How common is sternal osteomyelitis?
Paediatric chest pain is uncommon and responsible for only 0.6% of child emergency department presentations. Compared to adults, non-cardiac causes are much more likely, accounting for 99% of all cases.
In the largest reported series, PSO was more common in boys and peaked at age one though it should be considered across the age spectrum. Consider PSO in children with pre-sternal swelling, tenderness, erythema, and chest pain though these features are non-specific and may be seen in other musculoskeletal conditions like costochondritis
How does sternal osteomyelitis occur?
Paediatric primary sternal osteomyelitis (PSO) is exceedingly rare with 100 cases reported globally and only seven cases in the Australian context. It occurs because of haematogenous spread and bacterial seeding. This is different from secondary osteomyelitis which is usually due to direct innocculation from trauma
Although adults with immunodeficiency, intravenous drug use and diabetes mellitus are at risk, affected children usually have no predisposing factors.
How is sternal osteomyelitis diagnosed?
Clinical suspicion is key as the WCC may be normal in 44% of cases and other inflammatory markers such as CRP and WCC do not correlate with the risk of PSO.
All these patients need cultures to identify the causative organism and guide management. The most common organisms are Staphylococcus aureus, Kingella kingae (in children younger than 3) and Salmonella enteritidis (in sickle cell disease).
Although bone biopsies are gold-standard, blood cultures are more appropriate in kids though they are only positive in 30% of cases (compared with 61% for tissue cultures. It might be worth obtaining tissue cultures in blood culture negative PSO, if standard treatment fails, or if they need surgical intervention.
MRI is superior to CXR. Plain imaging only identified a third of cases with CXR changes occurring late, 10-21 days after infection onset.
Magnetic resonance imaging of the chest demonstrating 3rd sternal segment enhancement and evidence of surrounding inflammatory phlegmon.
Here’s the MRI. it shows abnormal marrow oedema and marked enhancement in the 3rd sternal segment and lower end of the 2nd sternal segment, with an anterior subperiosteal collection. These findings are consistent with a diagnosis of sternal osteomyelitis.
Children don’t routinely need an echocardiogram unless you suspect endocarditis is suspected e.g., persistent positive blood culture results. Hence, echocardiography was felt not to be indicated in our patient.
How is it treated?
The inpatient team start vancomycin as empirical coverage and his pain began to improve by day 4. Although the initial blood cultures were negative, a second set taken the next day, before commencing antibiotics, returned a Gram-positive coccus – methicillin-susceptible Staphylococcus aureus (MSSA)
Intravenous flucloxacillin is the empirical antibiotic therapy of choice and covers MSSA. It was reasonable to start empiric vancomycin in case of MRSA before sensitivities are back due to Sione’s background. Given the unusual architecture of flat bone, experts recommend a 7-to-14-day course of IV antibiotics. If the clinical condition and inflammatory markers improve then they can be switched over to oral antibiotics for a further two weeks.
Surgical debridement is recommended for complicated osteomyelitis with significant bone destruction, medical treatment failure, or an abscess greater than 2cm.
Learning Points
Consider sternal osteomyelitis in your differential of central chest pain, particularly in vulnerable patientsÂ
CXRs, blood cultures and inflammatory markers may be normal in PSOÂ
MRI is the preferred imaging modality
Start intravenous flucloxacillin empirically then switch to oral targeted therapy guided by the clinical picture.Â
References
Children’s Health Queensland Hospital and Health Service. Differentials of Paedatric Chest Pain. Sept 5, 2022. Accessed Jul 1, 2023. https://www.childrens.health.qld.gov.au/wp-content/uploads/PDF/guidelines/gdl-00740.pdf
The Royal Children’s Hospital Melbourne. Chest Pain. Feb, 2022. Accessed Jul 2, 2023. https://www.rch.org.au/clinicalguide/guideline_index/chest_pain/
Schweitzer A, Della Beffa C, Akmatov MK, Narchi H, Abaev YK, Sherry DD, Pessler F. Primary osteomyelitis of the sternum in the pediatric age group: report of a new case and comprehensive analysis of seventy-four cases. Pediatr Infect Dis J. 2015 Apr;34(4):e92-e101. doi: 10.1097/INF.0000000000000597. PMID: 25764104.
RodrÃguez Lorenzo P, Fernández MartÃnez B, Pérez Alba M, RamÃrez Jaén C, Meana MorÃs AR, Pérez Méndez C. Primary sternal osteomyelitis. Arch Argent Pediatr. 2023 Feb 9:e202201449. English, Spanish. doi: 10.5546/aap.2022-01449.eng. Epub ahead of print. PMID: 36724129.
Jang YN, Sohn HS, Cho SY, Choi SM. Primary Sternal Osteomyelitis caused by Staphylococcus aureus in an Immunocompetent Adult. Infect Chemother. 2017 Sep;49(3):223-226. doi: 10.3947/ic.2017.49.3.223. Epub 2017 May 23. PMID: 28608656; PMCID: PMC5620390.
Street M, Puna R, Huang M, Crawford H. Pediatric Acute Hematogenous Osteomyelitis. J Pediatr Orthop. 2015 Sep;35(6):634-9. doi: 10.1097/BPO.0000000000000332. PMID: 25333907.
The Royal Children’s Hospital Melbourne. Bone and joint infection. Aug, 2021. Accessed Jul 2, 2023. https://www.rch.org.au/clinicalguide/guideline_index/Osteomyelitis_Septic_Arthritis/
Woods CR, Bradley JS, Chatterjee A, Copley LA, Robinson J, Kronman MP, Arrieta A, Fowler SL, Harrison C, Carrillo-Marquez MA, Arnold SR, Eppes SC, Stadler LP, Allen CH, Mazur LJ, Creech CB, Shah SS, Zaoutis T, Feldman DS, Lavergne V. Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 Guideline on Diagnosis and Management of Acute Hematogenous Osteomyelitis in Pediatrics. J Pediatric Infect Dis Soc. 2021 Sep 23;10(8):801-844. doi: 10.1093/jpids/piab027. PMID: 34350458.
