Evaluation of Skin-to-Epidural Distance With Ultrasonography at Different Vertebral Levels in Infants: A Prospective Observational Study

Epidural analgesia is an effective method for perioperative pain management in pediatric patients and is widely used to reduce postoperative pain and opioid requirements. In infants, however, epidural procedures may be technically challenging because spinal anatomical structures are smaller and continue to change during early development. Variability in vertebral anatomy, ligament thickness, and spinal cord termination level may increase the difficulty of predicting epidural depth during neuraxial procedures. Even small differences in needle depth may be clinically important in this age group.

Ultrasonography has become an increasingly important tool in pediatric regional anesthesia because it provides real-time visualization of spinal anatomy without radiation exposure or harmful effects on the body. Preprocedural ultrasonographic assessment may help identify anatomical landmarks and estimate epidural depth before needle insertion. Previous studies have demonstrated that ultrasound measurements may correlate with actual epidural needle depth in pediatric patients. However, available data regarding normative skin-to-epidural distance measurements in infants remain limited, particularly at different vertebral levels and with different ultrasound imaging planes.

In infants, identification of the epidural space using conventional loss-of-resistance techniques may be more difficult than in older children and adults because tissue resistance changes may be less distinct. In addition, spinal anatomy changes rapidly during infancy, and measurements obtained at one vertebral level may not reflect measurements at other levels. Evaluation of multiple vertebral levels and imaging planes may therefore provide more comprehensive anatomical information for pediatric epidural procedures.

This study is designed to evaluate ultrasonographic skin-to-epidural distance measurements at multiple lumbar and thoracolumbar vertebral levels in infants undergoing elective surgery under general anesthesia. Measurements will be obtained using two commonly used ultrasound imaging planes to better characterize epidural depth in this population. The study will also evaluate the relationship between ultrasonographic measurements and demographic characteristics such as age, body weight, height, and gestational age.

Ultrasonographic evaluations will be performed during routine perioperative preparation under general anesthesia without additional invasive intervention for study purposes. In participants who undergo epidural catheter placement as part of routine clinical management, ultrasonographic measurements will additionally be compared with clinically measured epidural needle depth. Findings from this study may contribute to the development of more reliable reference data for infant epidural procedures and may support safer and more individualized pediatric regional anesthesia practices.