Clinical and ultrasound characteristics associated with pediatric osteomyelitis in comparison with soft tissue infection

To solve the difficulty in early differential diagnosis between pediatric osteomyelitis and soft tissue infection (STI), this study aimed to analyze the clinical and ultrasound characteristics of both diseases, screen independent differential risk factors, and explore the correlation between disease course, white blood cell (WBC) count and osteomyelitis risk. A retrospective analysis was performed on 236 pediatric patients (162 cases of osteomyelitis and 74 cases of STI) admitted to a single center from January 2018 to June 2025. Clinical data and ultrasound indicators were collected, and univariate and multivariate logistic regression were used to screen differential factors. Restricted cubic spline (RCS) analysis was applied to explore the nonlinear correlation of key indicators. Compared with the STI group, children with osteomyelitis had significantly longer symptom duration, higher erythrocyte sedimentation rate (ESR), and higher proportions of deep bone tenderness with refusal to bear weight/limp, cortical bone irregularity (CBI), increased periosteal blood flow (IPBF), and subperiosteal abscess (SA) (all P < 0.05). Conversely, the STI group presented with significantly higher levels of white blood cell (WBC), neutrophils, eosinophils, and monocytes. Multivariate logistic regression identified CBI, IPBF, and elevated ESR as independent risk factors for osteomyelitis, while neutrophils and eosinophils were independent protective factors against osteomyelitis. Restricted cubic spline analysis demonstrated that symptom duration and ESR were positively correlated with osteomyelitis risk, and the probability of osteomyelitis decreased significantly when WBC exceeded 12.996 × 10⁹/L. The clinical thresholds of symptom duration > 6 days and WBC > 12.996 × 10⁹/L achieved areas under the receiver operating characteristic curve (AUCs) of 0.617 and 0.579 for differentiating osteomyelitis from STI, respectively. Targeted ultrasound signs combined with clinical indicators can effectively differentiate pediatric osteomyelitis from STI. The nonlinear negative association between WBC and osteomyelitis risk provides a preliminary exploratory clue for clinical bedside rapid diagnosis.