Osteomyelitis (pediatrics): Clinical sciences

Osteomyelitis refers to bony inflammation caused by an underlying infection. In children, osteomyelitis is usually caused by Staphylococcus aureus, but it can also be caused by other bacterial pathogens, such as Group A Streptococcus.

Children most commonly present with acute hematogenous osteomyelitis, meaning the infection spreads from the blood to the bone.

Osteomyelitis often involves the metaphyseal region of tubular bones like the femur, due to the increased vascularity of the growth plate.

In order to determine appropriate treatment, it’s important to distinguish stable patients from those with a rapidly progressive infection or worsening clinical status.

Now, if a pediatric patient presents with a chief concern suggesting osteomyelitis, you should first perform an ABCDE assessment to determine if the patient is unstable or stable. If unstable, stabilize their airway, breathing, and circulation.

Next, obtain IV access and start IV fluids. Begin continuous vital sign monitoring, including pulse oximetry, blood pressure, and heart rate. If needed, provide supplemental oxygen; and start antibiotics if your patient shows signs of sepsis.

Alright, let’s go back to the ABCDE assessment and look at stable patients. First, obtain a focused history and physical examination.

History may include fever, or a recent trauma or infection. The patient or caregivers typically report pain in the affected bone and pseudoparalysis, meaning they are unable to bear weight or have reduced use of the affected extremity.

Also keep in mind that nonverbal or pre-verbal children might only exhibit nonspecific symptoms, such as fussiness, decreased activity, or decreased appetite.

Physical examination typically reveals edema, warmth, and tenderness over the affected bone. At this point, you should suspect osteomyelitis.

Here’s a clinical pearl! In neonates, osteomyelitis often causes septic arthritis of adjacent joints, due to the presence of vascular channels connecting the bone and joint.

When compared to older children, neonates are also more likely to develop multifocal osteomyelitis and septicemia. Neonatal osteomyelitis is commonly caused by group B Streptococcus or E. coli, due to perinatal exposure to these organisms.

Now, once you suspect osteomyelitis, your next step is to obtain labs. Labs include CBC, CRP, ESR, and blood culture. Also order imaging studies, such as a plain radiograph or possibly MRI.

Okay, let’s move on to lab results! The CBC might reveal increased WBCs, and platelets might be elevated or low. The CRP and ESR are usually elevated, and the blood culture might be positive, though it often does not grow any pathogens.

Meanwhile, X-rays may reveal no positive findings, but you might detect bony lucencies, periosteal reaction, or soft tissue swelling. If you ordered an MRI, findings might reveal bone marrow edema, soft tissue swelling, and possibly a rim lining an abscess cavity, referred to as a “penumbra sign.”

Here’s a clinical pearl! Although an X-ray is often ordered during the initial evaluation of osteomyelitis, plain radiographs often do not show clear evidence of osteomyelitis during early stages of infection.

The first noticeable changes of soft tissue swelling and loss of fat planes may not become visible until day 3; and periosteal thickening, focal osteopenia, and osteolytic lesions are only seen after day 10. Since X-ray findings lag behind the clinical presentation, MRI is the preferred imaging modality if you need additional evidence to support the diagnosis.

Now, based on these findings, you can make a diagnosis of osteomyelitis. Your next step is to assess your patient’s clinical status.

First, let’s look at clinically stable patients with no concern for a rapidly progressive infection. In these patients, your next step is to assess for evidence of an abscess on the X-ray or MRI.

If you don’t identify an abscess, or if there’s an abscess no more than 2 centimeters in diameter.

If this is the case your next step is to obtain an aspirate or bone biopsy for culture and Gram stain.

Now, here’s a clinical pearl! While it’s ideal to obtain cultures before you administer antibiotics, don’t delay treatment beyond 48 to 72 hours if your patient is stable, and begin antibiotics immediately if your patient is unstable!