OBJECTIVES To investigate the accuracy of placement of epidural injections using the lumbar and caudal approaches. To identify which factors, if any, predicted successful placement.

RESULTS Body mass index (BMI), grade of operator, and route of injection were predictors of a successful placement. 93% of lumbar and 64% of caudal epidural injections were correctly placed (p< 0.001). 97% of lumbar and 85% of caudal epidural injections clinically thought to be correctly placed were confirmed radiographically. For epidural injections where the clinical impression was “maybe”, 91% of lumbar injections, but only 45% of caudal injections were correctly placed. Obesity was associated with a reduced chance of successful placement (odds ratio (OR) 0.34 (95% confidence interval (CI) 0.17 to 0.72) BMI >30 vBMI <30). A more senior grade of operator was associated with a reduced chance of successful placement (OR 0.16 (95% CI 0.03 to 0.89) consultant v other). However, small numbers may have accounted for the latter result.

CONCLUSIONS The weight of the patient and intended approach need to be considered when deciding the method used to enter the epidural space. In the non-obese patient, lumbar epidural injections can be accurately placed withoutx ray screening, but caudal epidural injections, to be placed accurately, requirex ray screening no matter what the weight of the patient.