The Influence of Needle-insertion Depth on Successful Epidurogram and Clinical Outcome in Caudal Epidural Injections: A Randomized Clinical Trial

Caudal epidural injections have been commonly performed in patients with low back pain and radiculopathy. Conventional caudal epidural injections, which the needle is advanced into the sacral canal, present a potential risk of penetration of the epidural venous plexus or dura. The investigators hypothesized that a new caudal injection technique, which the needle only penetrates the sacrococcygeal ligament without being inserted into the sacral canal, might represent a safe alternative, with a lower incidence of intravascular injections and patient's discomfort during the procedure than the conventional technique. The study is designed to investigate the influence of the depth of the inserted needle on successful epidurogram and clinical outcome in caudal epidural injections under the ultrasound and digital subtraction angiography.