CT fluoroscopy (CTF) is a powerful technology for performing image-guided procedures. It marries the benefits of cross-sectional imaging with real-time intraprocedural imaging to allow for highly precise image guidance. Procedures can usually be performed as quickly as conventional fluoroscopy-guided procedures and with equivalent or decreased radiation doses. CTF particularly excels in cases of difficult anatomy or patients with larger body habitus.
As adoption of CTF for spine procedures becomes more widespread, the benefits of the cross-sectional perspective have become more apparent. In this article, we report on a pitfall of epidural steroid injections (ESIs) that may result in off-target injection of medication. Entry into the retrodural space of Okada produces a false-positive loss of resistance that may be mistaken for entry into the epidural space. While easily discernable with CTF, the fluoroscopic imaging appearance of this type of injection may mimic an epidural injection, resulting in a failure to recognize it. We found that this pitfall was recognized with CTF at a rate 10-fold higher than with conventional fluoroscopy. Although the lack of a reference standard limits our ability to completely exclude technical differences as the explanation, the most likely explanation in our opinion is that this phenomenon is simply missed in many cases under fluoroscopy, a conclusion that fits with prior literature describing this injection type.
As we noted in the manuscript, the impact of this seemingly minor pitfall is not trivial when considered on an annual basis; for Medicare patients alone, more than 65,000 ESIs per year may be delivering medication off-target, unbeknownst to the proceduralist performing the injection. These are injections that would not be treating the intended target and would therefore likely be clinically ineffective.
However, as technical refinements to and developments in the use of CTF progress, the focus of research must now shift to the impact of this technology on clinical rather than technical outcomes. As is true for spine intervention in general, high-quality prospective research using validated outcome measures is critically needed in this area in order to ensure that the perceived technical advantages of CTF are translated into better care for patients.