Neonatal anatomy relevant for lumbar and caudal epidural blocks

Abstract

Many anaesthesiologists not used to working with paediatric patients may lack the knowledge of relative depths or position of key anatomical structures, as it is known that the anatomy of children differ to some degree from that of adults. A thorough knowledge of the anatomy of paediatric patients is therefore essential for safe and successful performance of epidural blocks. The aims of this study were to observe and quantify the important landmarks and structures, associated with both the lumbar and caudal epidural blocks. The vertebral column of 40 neonatal cadavers were dissected and measurements were taken in both a prone and flexed (between 40o-50o) position. Information regarding Tuffier’s line (TL), the surface area of the L1/L2 to L5/S1 interlaminar spaces, and the vertebral level and distance from the apex of the sacral hiatus (ASH) to the conus medullaris (CM) and the dural sac (DS), were then obtained. It was found that, when prone, the L2/L3 and L3/L4 interlaminar spaces have the largest surface areas, 9.61-12.68mm2 and 9.73-12.54mm2, respectively. Flexion caused the greatest change (approximately 23.52%) at the L3/L4 interlaminar space. On average, the CM was found to be at the middle third of the L2 vertebra. The distance from the ASH to the CM was between 36.05-41.61mm when prone and 40.99-48.88mm when flexed. TL was found to be at the L4/L5 interlaminar space when prone. When flexed, this level moved caudally, ending at the upper third of L5. In all cases the DS was found to be within the caudal space. On a prone cadaver the distance from the ASH to the DS was between 8.88-11.79mm. This increased to 10.45-12.99mm when flexed. This study hopes to complement what is already known of the neonatal vertebral column and to shed some light on the changes that occur when the neonate is flexed during the conduction of either single-shot lumbar or caudal epidural blocks, or for the insertion of a continuous epidural catheter via the caudal or lumbar route.