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BACKGROUND AND PURPOSE:Cervical epidural steroid injections are approached with trepidation because of concerns over safety, including direct spinal cord injury. CT fluoroscopy is an alternative to conventional fluoroscopy that could potentially help reduce the risk of injury by providing improved localization of the needle tip. We sought to determine rates of technical success and risk of complications in our initial cohort of patients treated with cervical interlaminar ESI performed under CTF guidance.

CT fluoroscopy is an alternative method to perform cervical interlaminar steroid injections that allows precise needle placement in the epidural space.

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We very much appreciate the comments of Drs. Ng et al in response to our article "CT Fluoroscopy-Guided Cervical Interlaminar Steroid Injections: Safety, Technique, and Radiation Dose Parameters."Dr. Ng and colleagues question the necessity of CT guidance given the large number of successful injections they have performed under conventional fluoroscopic (CF) guidance, and suggest that injection above the C7-T1 level can be safe under CF guidance. We do not doubt that such procedures can be performed safely in experienced hands. Many authors would disagree with this opinion, however. [1][2][3][4] Such authors cite a number of anatomic and technical reasons for their objections, as summarized in our manuscript, which may be overcome by using CT fluoroscopy (CTF). Nevertheless, the purpose of our article is not to advocate for 1 type of image guidance over another, because comparative safety and effectiveness data have not been established. Any position taken on this issue would be based on opinion (ie, level 5 evidence), at best. Nor is it our intent to supplant CF guidance for those interventionalists who successfully use it to perform injections, but rather to provide an alternative method for those with reservations about the safety of the procedure.We fully agree with Dr. Ng and colleagues that radiation dose must be closely scrutinized with any procedure. We take issue with the dose estimates they propose, however. Dose comparison between CF and CTF is not straightforward, due to narrow beam collimation and scan lengths of Ͻ1 cm used with CTF. In CT, conversion factors have been used to convert dose-length product to effective dose (ED), but these are not reliable when scan lengths of less than 2 cm are used, and can result in the incorrect estimation of ED by up to a factor of 30. 5For this reason, estimates based on phantom studies may be more reliable. A direct comparison of lumbar CF and CTF guided injections at our institution using an anthropomorphic phantom demonstrated that the ED from the CTF portion of a lumbar injection was half that of the ED for the same procedure performed with CF.6 Ultimately, the small differential risk of radiation-related cancer induction between procedures must be balanced against any potential safety benefit related to the procedure, which as yet remains undetermined. Such overall safety comparisons are therefore premature. Next, the authors argue that injection at C7-T1 is equivalent to injections at higher cervical levels, though the authors admit that despite this argument they do perform injections as high as C2-3 when anatomy permits. One may speculate as to the validity of this assertion, which is based on indirect evidence, and whether the delivered concentration of injected steroid medication is really equivalent when it reaches a level by remote epidural spread as opposed to direct injection. In the end, though, we are not aware of any study that directly addresses the fundamental question of clinical outcomes using these 2 different approaches.As for the potentia...