Osteomyelitis

Osteomyelitis in children is common enough to miss and serious enough to matter. In this episode of PEM Currents, we review a practical, evidence-based approach to pediatric acute hematogenous osteomyelitis, focusing on diagnostic strategy, imaging decisions including FAST MRI, and modern antibiotic management. Topics include age-based microbiology, empiric and pathogen-directed antibiotic selection with dosing, criteria for early transition to oral therapy, and indications for orthopedic and infectious diseases consultation. Special considerations such as MRSA, Kingella kingae, daycare clustering, and shortened treatment durations are discussed with an emphasis on safe, high-value care.

Learning Objectives

After listening to this episode, learners will be able to:

1. Identify the key clinical, laboratory, and imaging findings that support the diagnosis of acute hematogenous osteomyelitis in children, including indications for FAST MRI and contrast-enhanced MRI.

2. Select and dose appropriate empiric and pathogen-directed antibiotic regimens for pediatric osteomyelitis based on patient age, illness severity, and local MRSA prevalence, and determine when early transition to oral therapy is appropriate.

3. Determine when consultation with orthopedics and infectious diseases is indicated, and recognize clinical features that warrant prolonged therapy or more conservative management.

References

1. Woods CR, Bradley JS, Chatterjee A, et al. 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;10(8):801-844. doi:10.1093/jpids/piab027

2. Woods CR, Bradley JS, Chatterjee A, et al. Clinical practice guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2023 guideline on diagnosis and management of acute bacterial arthritis in pediatrics. J Pediatric Infect Dis Soc. 2024;13(1):1-59. doi:10.1093/jpids/piad089

3. Stephan AM, Platt S, Levine DA, et al. A novel risk score to guide the evaluation of acute hematogenous osteomyelitis in children. Pediatrics. 2024;153(1):e2023063153. doi:10.1542/peds.2023-063153

4. Alhinai Z, Elahi M, Park S, et al. Prediction of adverse outcomes in pediatric acute hematogenous osteomyelitis. Clin Infect Dis. 2020;71(9):e454-e464. doi:10.1093/cid/ciaa211

5. Burns JD, Upasani VV, Bastrom TP, et al. Age and C-reactive protein associated with improved tissue pathogen identification in children with blood culture-negative osteomyelitis: results from the CORTICES multicenter database. J Pediatr Orthop. 2023;43(8):e603-e607. doi:10.1097/BPO.0000000000002448

6. Peltola H, Pääkkönen M. Acute osteomyelitis in children. N Engl J Med. 2014;370(4):352-360. doi:10.1056/NEJMra1213956

Transcript

This transcript was provided via use of the Descript AI application

Welcome to PEM Currents, the Pediatric Emergency Medicine Podcast. As always, I’m your host, Brad Sobolewski, and today we’re covering osteomyelitis in children. We’re going to talk about diagnosis and imaging, and then spend most of our time where practice variation still exists: antibiotic selection, dosing, duration, and the evidence supporting early transition to oral therapy. We’ll also talk about when to involve orthopedics, infectious diseases, and whether daycare outbreaks of osteomyelitis are actually a thing.

So what do I mean by pediatric osteomyelitis? In children, osteomyelitis is most commonly acute hematogenous osteomyelitis. That means bacteria seed the bone via the bloodstream. The metaphysis of long bones is particularly vulnerable due to vascular anatomy that favors bacterial deposition.

Age matters. In neonates, transphyseal vessels allow infection to cross into joints, increasing the risk of concomitant septic arthritis. In older children, those vessels involute, and infection tends to remain metaphyseal and confined to bone rather than spreading into the joint.

For children three months of age and older, empiric therapy must primarily cover Staphylococcus aureus, which remains the dominant pathogen. Other common organisms include group A streptococcus and Streptococcus pneumoniae.

In children six to 36 months of age, especially those in daycare, Kingella kingae is an important and often underrecognized pathogen. Kingella infections are typically milder, may present with lower inflammatory markers, and frequently yield negative routine cultures. Kingella is usually susceptible to beta-lactams like cefazolin, but is consistently resistant to vancomycin and often resistant to clindamycin and antistaphylococcal penicillins. This has direct implications for empiric antibiotic selection.

Common clinical features of osteomyelitis include fever, localized bone pain, refusal to bear weight, and pain with movement of an adjacent joint. Fever may be absent early, particularly with less virulent organisms like Kingella.

A normal white blood cell count does not exclude osteomyelitis. Only about one-third of children present with leukocytosis. CRP and ESR are generally more useful, particularly CRP for monitoring response to therapy.

No single CRP cutoff reliably diagnoses or excludes osteomyelitis in children. While CRP is elevated in most cases of acute hematogenous osteomyelitis, the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America note that high-quality data defining diagnostic thresholds are limited. A CRP above 20 milligrams per liter is commonly used to support clinical suspicion, with pooled sensitivity estimates around 80 to 85 percent, but no definitive value mandates the diagnosis. Lower values do not exclude disease, particularly in young children, as CRP is normal in up to 40 percent of Kingella kingae infections.

CRP values tend to be higher in Staphylococcus aureus infections, especially MRSA, and higher levels are associated with complications such as abscess, bacteremia, and thrombosis, though specific cutoffs are not absolute.

In summary, CRP is most useful for monitoring treatment response. It typically peaks two to four days after therapy initiation and declines rapidly with effective treatment, with a 50 percent reduction within four days seen in the majority of uncomplicated cases.

Blood cultures should be obtained in all children with suspected osteomyelitis, ideally before starting antibiotics when feasible. In children, blood cultures alone can sometimes identify the pathogen.

Plain radiographs are still recommended early, not because they’re sensitive for acute osteomyelitis, but because they help exclude fracture, malignancy, or foreign body and establish a baseline.

MRI with and without contrast is the preferred advanced imaging modality. MRI confirms the diagnosis, defines the extent of disease, and identifies complications such as subperiosteal abscess, physeal involvement, and concomitant septic arthritis. MRI findings can also guide the need for surgical consultation.

Many pediatric centers now use FAST MRI protocols for suspected osteomyelitis, particularly from the emergency department. FAST MRI uses a limited sequence set, typically fluid-sensitive sequences like STIR or T2 with fat suppression, without contrast. These studies significantly reduce scan time, often avoid the need for sedation, and retain high sensitivity for bone marrow edema and soft tissue inflammation.

FAST MRI is particularly useful when the clinical question is binary: is there osteomyelitis or not? It’s most appropriate in stable children without high concern for abscess, multifocal disease, or surgical complications. If FAST MRI is positive, a full contrast-enhanced MRI may still be needed to delineate abscesses, growth plate involvement, or adjacent septic arthritis. If FAST MRI is negative but clinical suspicion remains high, further imaging may still be necessary.

The Pediatric Infectious Diseases Society and the Infectious Diseases Society of America recommend empiric antibiotic selection based on regional MRSA prevalence, patient age, and illness severity, with definitive therapy guided by culture results and susceptibilities.

Empiric therapy should never be delayed in an ill-appearing or septic child. In well-appearing, stable children, antibiotics may be briefly delayed to obtain imaging or tissue sampling, but this requires close inpatient observation.

For children three months and older with non–life-threatening disease, empiric therapy hinges on local MRSA rates. In regions with low community-acquired MRSA prevalence, generally under 10 percent, reasonable empiric options include cefazolin, oxacillin, or nafcillin.

When MRSA prevalence exceeds 10 to 20 percent, empiric therapy should include an MRSA-active agent. Clindamycin is appropriate when local resistance rates are low, while vancomycin is preferred when clindamycin resistance is common or the child has had significant healthcare exposure.

For children with severe disease or sepsis, vancomycin is generally preferred regardless of local MRSA prevalence. Some experts recommend combining vancomycin with oxacillin or nafcillin to ensure optimal coverage for MSSA, group A streptococcus, and MRSA. In toxin-mediated or high-inoculum infections, the addition of clindamycin may be beneficial due to protein synthesis inhibition.

Typical IV dosing includes cefazolin 100 to 150 milligrams per kilogram per day divided every eight hours; oxacillin or nafcillin 150 to 200 milligrams per kilogram per day divided every six hours; clindamycin 30 to 40 milligrams per kilogram per day divided every six to eight hours; and vancomycin 15 milligrams per kilogram every six hours for serious infections, with appropriate monitoring.

Ceftaroline or daptomycin may be considered in select MRSA cases when first-line agents are unsuitable.

For methicillin-susceptible Staphylococcus aureus, first-generation cephalosporins or antistaphylococcal penicillins remain the preferred parenteral agents. For oral therapy, high-dose cephalexin, 75 to 100 milligrams per kilogram per day divided every six hours, is preferred. Clindamycin is an alternative when beta-lactams cannot be used.

For clindamycin-susceptible MRSA, clindamycin is the preferred IV and oral agent due to excellent bioavailability and bone penetration, and it avoids the renal toxicity associated with vancomycin.

For clindamycin-resistant MRSA, vancomycin or ceftaroline are preferred IV agents. Oral options are limited, and linezolid is generally the preferred oral agent when transition is possible. Daptomycin may be used parenterally in children older than one year without pulmonary involvement, typically with infectious diseases and pharmacy input.

Beta-lactams remain the drugs of choice for Kingella kingae, Streptococcus pyogenes, and Streptococcus pneumoniae. Vancomycin has no activity against Kingella, and clindamycin is often ineffective.

For Salmonella osteomyelitis, typically seen in children with sickle cell disease, third-generation cephalosporins or fluoroquinolones are used. In underimmunized children under four years, consider Haemophilus influenzae type b, with therapy guided by beta-lactamase production.

Doxycycline has not been prospectively studied in pediatric acute hematogenous osteomyelitis. There are theoretical concerns about reduced activity in infected bone and risks related to prolonged therapy. While short courses are safe for certain infections, the longer durations required for osteomyelitis increase the risk of adverse effects. Doxycycline should be considered only when no other active oral option is available, typically in older children, and with infectious diseases consultation. It is not appropriate for routine treatment.

Many hospitals automatically consult orthopedics when children are admitted with osteomyelitis, and this is appropriate. Early orthopedic consultation should be viewed as team-based care, not failure of medical management.

Consult orthopedics when MRI shows abscess or extensive disease, there is concern for septic arthritis, the child fails to improve within 48 to 72 hours, imaging suggests devitalized bone or growth plate involvement, there is a pathologic fracture, the patient is a neonate, or diagnostic bone sampling or operative drainage is being considered. Routine surgical debridement is not required for uncomplicated cases.

Infectious diseases consultation is also often automatic and supported by guidelines. ID is particularly valuable for antibiotic selection, dosing, IV-to-oral transition, duration decisions, bacteremia management, adverse reactions, and salvage regimens. Even in straightforward cases, ID involvement often facilitates shorter IV courses and earlier oral transition.

Osteomyelitis is generally not contagious, and clustering is uncommon for Staphylococcus aureus. Kingella kingae is the key exception. It colonizes the oropharynx of young children and spreads via close contact. Clusters of invasive Kingelladisease have been documented in daycare settings.

Suspicion should be higher in children six to 36 months from the same daycare, with recent viral illness, mild systemic symptoms, refusal to bear weight, modest CRP elevation, and negative routine cultures unless PCR testing is used. Public health intervention is not typically required, but awareness is critical.

There is no minimum required duration of IV therapy for uncomplicated acute hematogenous osteomyelitis. Transition to oral therapy should be based on clinical improvement plus CRP decline. Many children meet criteria within two to six days.

Oral antibiotics must be dosed higher than standard outpatient regimens to ensure adequate bone penetration. Common regimens include high-dose cephalexin, clindamycin, or linezolid in select cases. The oral agent should mirror the IV agent that produced clinical improvement.

Total duration is typically three to four weeks, and in many cases 15 to 20 days is sufficient. MRSA infections or complicated cases usually require four to six weeks.

Early oral transition yields outcomes comparable to prolonged IV therapy with fewer complications. Most treatment-related complications occur during parenteral therapy, largely due to catheter-related issues.

Take-home points: osteomyelitis in children is a clinical diagnosis supported by labs and MRI. Empiric antibiotics should be guided by age, illness severity, and local MRSA prevalence. Early transition to high-dose oral therapy is safe and effective when clinical response and CRP support it. Orthopedics and infectious diseases consultation improve care and reduce variation. FAST MRI is changing how we diagnose osteomyelitis. Daycare clustering is uncommon except with Kingella kingae.

That’s all for this episode. If there are other topics you’d like us to cover, let me know. If you have the time, leave a review on your favorite podcast platform. It helps more people find the show and learn from it. For PEM Currents, this has been Brad Sobolewski. See you next time.