Injection into the Space of Okada during Transforaminal Epidural Steroid Injections

Objective: Ensuring medication delivery to the epidural space is crucial for effective transforaminal epidural steroid injections. Epidural needle placement is determined by injecting a small amount of contrast at the final needle position. The purpose of this study is to illustrate the appearance of contrast flow in the retrodural retroligamentous space of Okada during computed tomography- and fluoroscopy-guided cervical and lumbar transforaminal epidural steroid injections. Design: This retrospective study will use a series of cases to demonstrate contrast within the space of Okada during epidural transforaminal steroid injections. Setting: Tertiary medical center. Subjects: Study subjects are adult patients who underwent transforaminal epidural steroid injection at our institution. Methods: Cases were identified through the use of a search engine of existing radiology reports at our institution. Epidural steroid injection procedural reports were searched for the terms "Okada"and "retrodural space."Images from the procedure were reviewed by the authors (all proceduralists with dedicated training in spinal injections) to confirm the presence of contrast within the space of Okada. Results: This case series illustrates six examples of contrast injection into the retrodural space of Okada during cervical and lumbar transforaminal epidural steroid injections. Conclusions: Contrast uptake in the retrodural space of Okada may be seen during transforaminal epidural injections. Although relatively uncommon, it is likely underrecognized. It is extremely important that providers who perform transforaminal epidural steroid injections be familiar with this non-epidural contrast flow pattern so they can adjust needle positioning to deliver steroid to the epidural space.