Disc penetration sign: an distinctive MRI feature as a predictor of surgical necessity in pyogenic spondylitis.

Purpose: Pyogenic spondylitis (PS) is a common spinal infection characterized by vertebral destruction and abscess formation, requiring timely intervention to mitigate irreversible neurological deficits. This study describes a novel MRI feature, termed the "Disc Penetration sign (DP)," defined as abscesses penetrating anteroposteriorly through the intervertebral disc space on sagittal MRI images, simultaneously compromising the anterior vertebral margins and spinal canal structures, aiming to evaluate its correlation with clinical manifestations to predict the necessity of early surgical intervention in PS patients with DP.

Methods: A retrospective cohort study was conducted, enrolling 137 patients diagnosed with pyogenic spondylitis at a tertiary hospital between 2013 and 2023. Based on MRI findings, patients were categorized into DP (n = 56) and non-DP (n = 81) groups. Two blinded clinicians independently classified the cases, with discrepancies resolved through consultation with a senior physician. Clinical indicators, laboratory parameters, imaging characteristics, microbiological profiles, and treatment modalities were analyzed. Multivariable logistic regression identified independent predictors of surgical intervention.

Results: Compared to the non-DP group, the DP group exhibited significantly elevated inflammatory markers, including ESR (74.30 vs. 51.46 mm/h, p < 0.001) and CRP (47.28 vs. 26.18 mg/L, p = 0.003). Paraspinal abscesses were more prevalent in the DP group (96.4% vs. 40.7%, p < 0.001). Microbiological identification revealed a higher pathogen-positive rate in the DP group (76.8% vs. 55.6%, p = 0.011), with Staphylococcus aureus predominating in both groups. The surgical intervention rate was significantly increased in the DP group (48.2% vs. 21.0%, p < 0.001), and multivariable logistic regression confirmed DP as an independent predictor of surgical necessity (adjusted OR = 2.47, 95% CI: 1.21-5.07, p = 0.032).

Conclusion: The Disc Penetration sign (DP) is a distinct MRI feature strongly associated with severe inflammatory burden, higher pathogen detection rates, and increased necessity for surgical intervention in pyogenic spondylitis.