The Anatomy, Technique, Safety, and Efficacy of Image-Guided Epidural Access

Epidural steroid injections have demonstrable efficacy and safety in treatment of radicular pain syndromes; transforaminal access has greater evidence of efficacy than interlaminar approaches. The interventionalist must understand epidural and foraminal anatomy and imaging to insure delivery of medication to the target, the ventral epidural space at the site of neural compression. This obligates pre-procedural planning. When performed with appropriate risk mitigation strategies, epidural injections by either access are safe. For transforaminal access, the use of dexamethasone as the injectate, and infraneural approaches, provides safety advantages.

Inter-rater reliability of MRI superior articular process angle measurement for use in the modified approach to cervical transforaminal epidural steroid injections

Background

Upper extremity radicular pain is commonly treated with a cervical transforaminal epidural steroid injection (CTFESI). Recently, a new technique, the modified approach CTFESI, has been developed with a theoretical safety advantage to avoid the neurovascular structures. This approach requires an angle measurement of the superior articular process (SAP) on MRI. The inter-rater reliability of this angle measurement among practicing physicians is yet to be investigated.

Objective

The purpose of this study was to determine the inter-rater reliability of SAP angle measurements on MRI.

Methods

Three raters independently measured the SAP angle on 50 cervical MRIs. A two-way, mixed effects, absolute agreement, single rater statistical model was used to determine the intraclass correlation coefficient (ICC) between all three raters, as well as between each pair of raters.

Results

Inter-rater reliability among all raters showed good reliability with an ICC ​= ​0.837709 (95% CI 0.75-0.9, p ​< ​0.001). Similarly, good inter-rater reliability was found between each of the pairs of raters.

Conclusion

This study demonstrates good inter-rater reliability of MRI SAP angle measurement among clinicians for use in the modified CTFESI approach.

The Fluoroscopic-Guided Cervical Transarticular Epidural Steroid Injection

ABSTRACT

The epidural space is commonly accessed via an interlaminar or transforaminal approach to administer corticosteroids for radicular pain. An alternative is a transarticular approach, which may be considered when conventional access to the epidural space is either not desired or contraindicated. This approach has been described in the cervical spine using computed tomography guidance but not fluoroscopic guidance. We describe a cervical transarticular approach to the epidural space under fluoroscopy and review the computed tomography-guided literature. The risks of transarticular epidural injections are likely low given that when performed prudently, they avoid direct contact with the vertebral artery, spinal medullary arteries, venous plexus, spinal cord, and nerve roots.

Single center experience on the rate of discontinuation and safety of cervical transforaminal epidural steroid injections using the modified approach in an office setting without sedation

Background

Cervical transforaminal epidural steroid injections (CTFESI) are commonly used in the treatment of upper extremity radicular pain. Recently, a modification of the conventional technique has been developed and validated which has a theoretical safety advantage of less risk of needle contact of the spinal nerve and vertebral artery. The new approach involves a needle trajectory under fluoroscopic guidance which is directly based upon the specific superior articular process angle measurement on MRI.

Objective

The purpose of this study was to evaluate the discontinuation rate of the modified approach CTFESI procedure in a non-sedated patient population. The study was also undertaken to confirm the safety of the procedure in an office-based setting.

Methods

A retrospective review was performed of the authors' (DL, SH) practice to identify all CTFESI using the modified approach, performed between October 2018 through January 2021 through a query of the investigators' (DL and SH) electronic medical record system. Any discontinued CTFESI procedure was identified. The reason for discontinuation was determined through medical record review. In addition, any significant neurologic or cardiovascular event occurring during or immediately following any completed or discontinued CTFESI was identified. Mild vasovagal reaction was not considered a significant complication.

Results

A total of 973 CTFESI procedures were performed using the modified approach during the study period. Twelve procedures, 1.2% (95% CI 0.7-2.1%) were discontinued. Nine were aborted due to vascular flow not resolved with needle repositioning. Only three, 0.3% (95% CI 0.1-0.9) were aborted due to patient intolerance. There were zero significant neurologic or cardiovascular complications.

Conclusion

The performance of the modified approach CTFESI appears to be well tolerated with a very low rate, 0.3%, of discontinuation due to intolerance in non-sedated patients. The zero incidence of neurologic or cardiovascular complication contributes to the current literature on the safety of this procedure.

Contrast flow patterns based on needle tip position during cervical transforaminal epidural injections

BACKGROUND

Few studies have evaluated the effect of final needle position on contrast flow patterns during the performance of cervical transforaminal epidural steroid injections (TFESIs).

OBJECTIVE

To analyze fluoroscopically guided cervical TFESI contrast flow patterns based upon final needle tip position.

DESIGN

Retrospective, observational in vivo study.

SETTING

Outpatient private practice physical medicine and rehabilitation spine clinic.

PARTICIPANTS

One hundred consecutive patients undergoing cervical TFESIs.

INTERVENTIONS

Cervical TFESIs.

MAIN OUTCOME MEASURES

Categories of contrast flow patterns including epidural, intraforaminal, "sufficient to inject," and "predominantly epidural and/or intraforaminal," based upon final needle tip position.

RESULTS

Two independent observers reviewed images from 100 consecutive patients and classified injectate flow patterns stratified by needle tip position. The interrater reliability for all categories of interest was moderate, with kappa values from 0.61 to 0.76. More medially placed needles (middle third and lateral third of the articular pillars) resulted in higher rates of epidural contrast flow (75%; 95% confidence interval [CI]: 56%-94%; and 60%; 95% CI: 47%-73%) compared to needles placed lateral to the articular pillars (26%; 95% CI: 8%-44%), and higher rates of "predominantly epidural and/or intraforaminal" flow patterns with needles placed in the middle one third (75%; 95% CI: 56%-94%) and lateral one third of the articular pillars (47%; 95% CI: 34%-60%) compared to flow patterns when needles were placed lateral to the articular pillars (17%; 95% CI: 2%-32%). No needles were placed in the medial third of the articular pillars.

CONCLUSIONS

More medially placed needle tips result in more optimal flow patterns during cervical TFESIs. The importance of this finding is unknown as clinical outcomes were not measured.