Anatomical Evaluation of the Sacral Hiatus Using Ultrasound Imaging: Factors That Inhibit Needle Insertion During Caudal Epidural Block Procedures.

Abstract

Caudal epidural blocks often fail due to the difficulty of appropriate needle insertion. This study aimed to evaluate the anatomy of the sacral hiatus using ultrasound imaging. This was a retrospective study involving 76 patients with spinal disorders. The following factors were analyzed to see if they affected the palpability of the sacral hiatus: sex, body mass index (BMI), and the morphology of the sacral hiatus on ultrasound imaging. The difficulty of needle insertion and the factors that influenced it were investigated in 28 of the 76 patients, who underwent landmark-based caudal epidural block procedures performed by the same doctor. Among the 76 patients, the mean length of the sacral hiatus was 21.3±5.6mm, the mean distance from the skin to the sacral cornua was 5.2±3.4mm, and the mean angle of the sacral hiatus was 16.4±5.5 degrees. Sacral base protrusion was present and absent in 35 and 41 cases, respectively. The sacral hiatus exhibited good and poor palpability in 53 and 23 cases, respectively. The mean distance from the skin to the sacral cornua and BMI were found to significantly influence the palpability of the sacral hiatus. Only sacral base protrusion significantly influenced the difficulty of needle insertion. The mean distance from the skin to the sacral cornua and BMI were found to be associated with the palpability of the sacral hiatus, and sacral base protrusion was demonstrated to be associated with the difficulty of needle insertion into the sacral hiatus.