Background Diagnostic and therapeutic injections of the zygapophyseal joint (z-joint) are routinely performed under radiologic guidance (eg, fluoroscopy, computed tomography). Technically, these procedures could also be completed using ultrasound guidance, but existing evidence insufficiently supports this alternative imaging method, and it cannot therefore be recommended as a standard practice. There has also been no published proof-of-concept study using a routine fluoroscopy control for ultrasound-guided z-joint injections.

Methods A cadaver study was performed to validate ultrasound as an imaging modality for z-joint injections. Fifty z-joint injections were performed on 5 nonembalmed specimens. In-plane ultrasound approach was implemented. Zygapophyseal joints were accessed through a needle placement under the joint capsule into the posterior synovial recess. Iohexol was thereby injected, and fluoroscopy was subsequently performed.

Results In 44 (88%) of 50 performed injections, the intra-articular spread of the contrast agent was clearly observed on the fluoroscopy image. In 6 (12%) of 50 cases, the contrast flow appeared in the soft tissues. In 4 of the 6 failed injections, the z-joint gap was not evident on an ultrasound image. No intravascular, nerve root, or epidural injections were observed.

Conclusions Ultrasound may be a viable alternative to fluoroscopy or computed tomography as a guidance method for lumbar z-joint injections.