Correlation of correct needle placement in caudal epidural space and anatomical structures of sacral canal in paediatric patients: An observational study

BACKGROUND AND AIMS: Caudal epidural block (CEB) is commonly performed using surface landmark-based technique in the paediatric patients, with a good success rate. Failure to perform CEB is usually attributable to anatomic variations. The aim of this study was to perform measurements of the anatomical landmarks that are generally used to perform CEB and find a relation between these measurements and successful needle placement. METHODS: This was an observational study that included 114 patients, aged up to 15 years. Ultrasonography (USG) scan of the sacrococcygeal region with measurement of cornu height, skin to cornu distance, inter-cornu distance (ICD), vertical and oblique size of hiatus were done. Needle placement for CEB was done using the usual palpatory hiatal approach. Needle position was checked by using ultrasound. Spearman correlation coefficient and multi-variate logistic regression were used for measuring the correlation and predictors of correct needle placement, respectively. RESULTS: Correct placement of needle was found in 84% patients. Statistically significant correlation was found between all the anatomical parameters. Regression analysis revealed that only ICD had a statistically significant contribution (OR1.67, 95% CI 1.024–2.7; P = 0.04) in predicting an incorrect needle placement. If ICD was less than 12.5 mm, it predicted a difficult needle placement; all the children were less than 1.5 years in age; AUC was 77%, P = 0.001, sensitivity 83% and specificity 76.5%. CONCLUSION: ICD can be used as predictor of difficult needle placement for CEB. USG guidance may be of help while performing CEB in children less than 1.5 years.