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Predicting Epidural Space Spread Using Ultrasound Color Doppler Imaging in Interlaminar Epidural Steroid Injection: A Prospective Observational Study.

BACKGROUND
While the use of fluoroscopy-guided transforaminal epidural steroid injection (TFESI) to help spread the injectate toward the ventral side has increased, this procedure has a radiation risk. Recently, ultrasound has been widely used in the medical field; among ultrasound methods, color Doppler is useful for predicting the direction of the injectate.


OBJECTIVE
This study describes a novel technique employing color Doppler to help predict epidural space spread in interlaminar epidural steroid injection (ILESI).


STUDY DESIGN
Prospective observational study.


SETTING
The study took place at a single pain clinic within a medical center in Jeonju, Republic of Korea.


METHODS
We enrolled 35 patients scheduled for lumbar epidural steroid injection (ESI).  Ultrasound-guided epidural lateral parasagittal interlaminar injection was performed and real-time images using color Doppler were recorded during injections of 5 mL of 0.1% ropivacaine containing contrast dye with dexamethasone 5 mg (1 mL). Fluoroscopy-guided TFESI was performed if it was difficult to perform the procedure based on ultrasound images.


RESULTS
The analysis included 30 images from 30 patients. The observed sensitivity, specificity, positive predictive value, and negative predictive values of the ultrasound color Doppler were 100%, 89.5%, 84.6%, and 100%, respectively. The agreement with ultrasound color Doppler was 93.3%.


LIMITATIONS
The sample size was relatively small.


CONCLUSION
The main advantage of ultrasound-guided ILESI is the lack of radiation exposure and contrast medium requirement. Color Doppler may be a reliable imaging modality to predict epidural space spread during ultrasound-guided ILESI. It is worth predicting the spread in the anterior epidural space (AES) by first attempting ultrasound-guided ESI. If the injectate has not spread to the AES, fluoroscopy-guided TFESI may be a good option after confirming improvement of the patient's symptoms.