1317. Early identification of avascular necrosis in pediatric acute hematogenous osteomyelitis using gadolinium-enhanced subtraction MRI
Authors: Alawi Ahmed Al , Raniga Sameer , Michelow Ian , Alhinai Zaid 
Published: December 2022

Abstract

Background
Current literature cites avascular necrosis as one of the rare and late complications of pediatric acute hematogenous osteomyelitis (AHO). Gadolinium-enhanced subtraction (GES) MRI sequences could potentially detect avascular necrosis more frequently and at an earlier time point in the course of pediatric AHO. Such an advantage could aid in the identification of patients at risk for chronic complications early in the course of disease. GES sequences are produced by subtracting pre-gadolinium images from the corresponding gadolinium-enhanced sequences.

Methods
Pediatric patients managed at Sultan Qaboos University Hospital between January, 2015 and April, 2022 with a confirmed diagnosis of AHO were reviewed. Patients were included in the analysis if GES MRI sequences were included in the initial diagnostic evaluation. Clinical presentation and outcomes were compared between patients with evidence of avascular necrosis on initial GES MRI and those without.

Results
Eleven patients were identified with a diagnosis of AHO for whom which GES MRI sequences had been obtained. Median age was 5 years (IQR 4-9), and 10 (91%) patients were males. Evidence of avascular necrosis on initial MRI (Figure 1) was identified in 6 (55%) patients. Patients with avascular necrosis showed a trend towards higher markers of inflammation (median absolute neutrophil count 10.7 vs 5.0, P = 0.052). Patients with avascular necrosis had significantly longer lengths of stay (median 16 days vs 9, P = 0.030), longer IV antibiotic treatment durations (median 14 days vs 7, P = 0.009) and longer oral antibiotic treatment durations (median 206 days vs 26, P = 0.036) (Table 1). Progression to chronic osteomyelitis occurred frequently, and only among patients with evidence of avascular necrosis on initial GES MRI (P = 0.008). Table 1
Comparison of clinical presentation and outcomes between patients whose initial MRI showed evidence of avascular necrosis on gadolinium-enhanced subtraction sequences, and patients whose imaging did not. *Represented as median (interquartile range). **For two patients, follow-up time at the time of writing was insufficient to determine if chronic osteomyelitis had developed. Figure 1Images A, B and C- Coronal MRI of the proximal femur in a child with uncomplicated acute hematogenous osteomyelitis. A- Pre-Gd T1, B- Post-Gd T1 and C- subtraction. Images show bone marrow edema with enhancement without any evidence of ischemia or necrosis (blue parenthesis). Images D, E and F- Sagittal MRI of the distal tibia in a child with complicated acute hematogenous osteomyelitis. D- Pre-Gd FAT SAT T1, E- Post-Gd FAT SAT T1 and F-subtraction. Images show bone marrow edema with a large central non-enhancing region of bone marrow suggestive of ischemia/necrosis (yellow rectangles).

Conclusion
GES MRI readily detected avascular necrosis in a large percentage of patients during the initial presentation of pediatric AHO, suggesting a much higher prevalence and an earlier presence of this complication than previously thought. The presence of avascular necrosis appeared to correlate highly with later progression to chronic osteomyelitis, providing for a promising early predictor of later complications. The findings of this study need to be validated in a larger, prospective cohort.

Disclosures
All Authors: No reported disclosures.