MRI-Based Investigation of Skin-Epidural Distance and Posterior Epidural Space Depth: The Role of Demographic and Anthropometric Factors

Background Precise identification of the skin-to-epidural distance (SED) is essential for safe and effective epidural anesthesia. This study aimed to evaluate the SED and posterior epidural space depth (PESD) at lower thoracic and lumbar levels using MRI, and to investigate their associations with demographic and anthropometric factors in an Iranian adult population. Methods In this cross-sectional study, 227 adult patients undergoing lumbar spine MRI were included. SED and PESD were measured at L2–S1 interspaces using MRI, and their correlations with age, sex, height, weight, and BMI were analyzed. Pearson correlation and multivariate linear regression were applied to identify significant predictors. Results The highest mean SED was observed at L3–L4 (57.05 ± 11.77 mm). BMI and weight showed strong positive correlations with SED across all levels. Age demonstrated a significant negative correlation with PESD at several levels. Multivariate analysis confirmed BMI and height as strong predictors of increased SED, while age was a negative predictor of PESD. Male gender was associated with shorter SED values at lower lumbar levels. Conclusions MRI-based assessment of SED and PESD reveals important correlations with BMI, height, and age. These findings support individualized estimation of epidural depth to enhance procedural safety, particularly in patients with varying body composition and age.