P0580 - Contiguous Osteomyelitis of distal extremities in children.

Background: In previously healthy children, most cases of osteomyelitis are hematogenous. Non-hematogenous osteomyelitis can, however, occur as a result of contiguous spread of infection from soft tissue or via direct inoculation of infection into the bone from trauma. Contiguous osteomyelitis in children has not been well studied in relation to infection in distal extremities.

Purpose: To evaluate the burden and features of contiguous osteomyelitis in pediatric patients with cellulitis or abscess of hands and feet.

Methods: 41 children, ages of 0-18 years, treated from 2009 to 2019 for cellulitis/abscess of the hands or feet, who either had a Magnetic Resonance Imaging at presentation, or a Roentgenogram of the affected area performed at least ten days after onset of symptoms, were included in this study. Case definition of contiguous osteomyelitis was based on MRI findings of both low signal intensity in the marrow on T1-weighted images and high signal intensity in the marrow on T2-weighted images, with continuity of soft tissue abnormality; or with findings of periosteal reaction/cortical erosion or bone lucency on the Roentgenogram. A comparison between two groups of patients, with and without underlying osteomyelitis by continuity, was determined by using a two-tailed T-test. A P-value of <0.05 was considered to be statistically significant.

Results: 20 of 41 patients (48.8%) were diagnosed with underlying contiguous osteomyelitis. Forty patients had preceding trauma, the most common cause among those with osteomyelitis was contusion or crush injury (36.8%), and abrasion or laceration among those without osteomyelitis (28.6%), p>0.05. There was no statistical difference between the two groups of patients in the frequency of trauma-to-presentation period < 5 days; treatment with antibiotics for > 48 hours prior to admission; in location of infection in the upper or lower extremity; presence of abscess or cellulitis, fever, elevated WBC count, elevated CRP or bacteremia.
In the group of patients with osteomyelitis, the most common location of infection was the phalanx (75%); the most common organism in 12 cases with positive culture was Staphylococcus aureus, followed by Streptococcus pyogenes. Mixed flora infection was identified in 41.7% of patients.

Conclusion: In concordance with previous reports, contiguous osteomyelitis in our patients was rarely associated with systemic symptoms or leukocytosis. Our study has demonstrated that in pediatric patients with soft tissue infection of distal extremities requiring hospitalization, it was not possible to clinically differentiate between those who had and did not have associated osteomyelitis. Soft tissue infection of distal extremities with underlying contiguous osteomyelitis is a novel association not previously described in any pediatric cohort study. Imaging is not standard practice in managing cellulitis/abscess. However, imaging of hands/feet in pediatric patients hospitalized with cellulitis/abscess should be strongly considered to determine the appropriate duration of treatment.