Background: Lumbosacral transforaminal epidural steroid injections (LS-TFESIs) are an accepted procedure used in the comprehensive, conservative care for lumbar disc pathology and/or spinal stenosis induced low back pain with a radicular component. Historically, the terminology used
to describe the transforaminal technique of instilling medications into the epidural space and/or
exiting structures has varied. These procedures have also been referred to as either diagnostic or
therapeutic selective nerve root blocks (SNRBs). Although this procedure is typically used to “selectively” treat isolated pathology, the “SNRB” terminology suggests that one can selectively diagnose or treat a specific nerve root as a pain generator by anesthetizing or blocking it. It has
been recently demonstrated that L4 and L5 SNRBs are often non-“selective” by investigating the
extent of epidural contrast flow patterns after injecting 1.0 mL of contrast. Our study attempts
to identify the minimum injectate volume at which LS-TFESIs may still be considered “selective”
with no injectate extending to either the adjacent (superior and/or inferior) levels or to the contralateral side.
Objective: Quantitatively evaluate contrast flow level selectivity noted during fluoroscopically
guided lumbosacral transforaminal epidural steroid injections (LS-TFESIs).
Study Design: Prospective, nonrandomized, observational human study.
Methods: Thirty patients (female = 10, male = 20) undergoing LS-TFESIs were investigated. After
confirming appropriate spinal needle position with biplanar imaging, 4.0 mL of nonionic contrast
was slowly injected. Fluoroscopic images were recorded at 0.5 mL increments. These biplanar contrast flow images were evaluated to determine which 0.5 mL volume increment was no longer specific for the injected level. In particular, we documented when contrast extended either to a superior or inferior spinal segment or crossed the midline spine to the contralateral side.
Results: After injecting 0.5 mL of contrast, 30% of LS-TFESIs performed in this study were no
longer “selective” for the specified root level. After injecting 1.0 mL of contrast, 67% of LS-TFESIs performed in this study were no longer “selective” for the specified root level. After injecting
1.5 mL of contrast, 87% of LS-TFESIs performed in this study were no longer “selective” for the
specified root level. After injecting 2.5 mL of contrast, 90% of LS-TFESIs performed in this study
were no longer “selective” for the specified root level.
Conclusions: Diagnostic LS-TFESI or SNRB blocks limiting injectate to a single, ipsilateral segmental level cannot reliably be considered diagnostically selective with volumes exceeding 0.5mL.
Injectate volumes greater than 0.5mL are consistently non-selective and cannot be used reliably
for diagnostic block procedures in the epidural space.
Key words: Epidural steroid injections, selective nerve root block, transforaminal, contrast
flow
The Impact of Epidural Steroid Injections on the Outcomes of Patients Treated for Lumbar Disc Herniation
