From the Guidelines
To rule out osteomyelitis in a 14-month-old, a comprehensive approach combining clinical assessment, laboratory tests, and imaging studies is necessary, with MRI being the most sensitive imaging modality for detecting bone marrow edema within 24-48 hours of infection onset 1.
Clinical Assessment
Initial evaluation should include a thorough physical examination looking for localized tenderness, swelling, warmth, and limited movement of the affected area.
Laboratory Tests
Laboratory tests should be ordered including complete blood count (CBC) with differential, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and blood cultures before starting antibiotics. These inflammatory markers are typically elevated in osteomyelitis, with CRP rising and falling more rapidly than ESR, making it useful for monitoring treatment response 1.
Imaging Studies
Imaging studies should begin with plain radiographs, although these may appear normal in early infection. Ultrasound can detect subperiosteal fluid collections and soft tissue involvement.
- MRI is the most sensitive imaging modality and should be performed when available as it can detect bone marrow edema within 24-48 hours of infection onset 1.
- Bone scans are an alternative when MRI is unavailable, with a whole-body bone scan being typically advocated due to the common occurrence of multifocal osteomyelitis in young children 1.
Definitive Diagnosis and Treatment
In some cases, bone biopsy with culture may be necessary for definitive diagnosis, especially if blood cultures are negative or the patient has been on antibiotics. If osteomyelitis remains in the differential diagnosis despite negative initial workup, empiric antibiotic therapy (typically with cefazolin or clindamycin) may be initiated while awaiting culture results, with close follow-up to monitor clinical response 1.
From the Research
Approach to Rule Out Osteomyelitis
To rule out osteomyelitis in a 14-month-old, the following steps can be taken:
- Clinical presentation and laboratory results can be used, but they can be relatively unreliable and differ, making diagnosis challenging 2
- Imaging plays a pivotal role in the diagnosis of childhood osteomyelitis, with conventional imaging being the initial modality, although normal conventional imaging does not exclude osteomyelitis 2
- Cooperation between the clinician and radiologist is crucial in making the diagnosis 2
- Magnetic Resonance Imaging (MRI) can be used to support the diagnosis of osteomyelitis, with findings being definitive, probable, or suspected 3
- Blood and/or operative cultures can be used to identify the causative organism, with Salmonella species and methicillin-susceptible Staphylococcus aureus being common causes 3
- Serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell (WBC) count can be used to aid in diagnosis and follow-up, with CRP being a sensitive indicator of the effectiveness of therapy 4
Imaging Characteristics
Imaging characteristics of childhood osteomyelitis include:
- Conventional imaging being normal does not exclude osteomyelitis 2
- MRI findings being definitive, probable, or suspected 3
- Imaging playing a pivotal role in the diagnosis of childhood osteomyelitis 2
Laboratory Results
Laboratory results that can be used to aid in diagnosis and follow-up include:
- Serum C-reactive protein (CRP) being a sensitive indicator of the effectiveness of therapy 4
- Erythrocyte sedimentation rate (ESR) being elevated in most cases, with peak values being reached on days 3 to 5 4
- White blood cell (WBC) count being a poor indicator of acute hematogenous osteomyelitis, with only 35% of children having leukocytosis at the time of admission 4