The Incidence of Inadvertent Intravascular Injection During Ultrasound-guided Cervical Medial Branch Blocks: a Fluoroscopically Controlled Study

Cervical medial branch blocks (CMBB) are commonly employed for the diagnosis and management of facet-related pain. The latter constitutes the most important cause of axial neck pain and has been implicated in 40% of all cases. In addition, the upper cervical joints can also cause cervicogenic headaches, an often-debilitating condition representing up to 20% of chronic headaches3. Well-defined pain referral patterns for each joint can help operators select the appropriate injection level. While fluoroscopy has long been the imaging standard for spinal procedures, ultrasound guidance (USG) is being increasingly adopted as an alternative and presents several advantages such as the ability to identify and avoid soft tissue structures such as blood vessels during needle insertion. From a clinical perspective, avoiding blood vessels and reducing the incidence of vascular breach can lessen the occurrence of intravascular injections that are associated with false negative diagnostic blocks. Indeed, a recent study examining the safety of USG CMBB reported a lower incidence of vascular breach than previous studies that had used fluoroscopic guidance. While these findings suggested a potential benefit associated with USG, further confirmatory studies employing digital subtraction angiography (DSA), the current imaging standard to detect intravascular spread, are required. We hypothesize that USG will be associated will a lower incidence of intravascular spread during primary needle placement than has been reported with fluoroscopic guidance.