Objective: To determine the incidence of inadvertent lumbar facet joint injection during an interlaminar epidural steroid injection (ESI).
Materials and methods: A total of 686 interlaminar lumbar ESIs were performed from January 1, 2009 to December 31, 2009. Archived images from these cases were retrospectively reviewed on the PACS. Positive cases of inadvertent lumbar facet joint injection were identified by the characteristic sigmoid-shaped contrast pattern projecting over the posterior elements on the lateral view and/or ovoid contrast projecting over the facet joints on the anteroposterior (AP) view.
Results: Eight positive events were identified (1.2%). There was no statistically significant gender or lumbar level predilection. In 3/8 of the positive cases (37.5%), the inadvertent facet joint injection was recognized by the operator. The needle was repositioned as a result, and contrast within the posterior epidural space was documented by the end of the procedure. In 5/8 of the positive cases (62.5%), the patients reported an immediate decrease in the presenting pain.
Conclusions: The incidence of inadvertent lumbar facet joint injection during an interlaminar epidural steroid injection is low. Recognizing the imaging features of this event permits the operator to redirect the needle tip into the epidural space and/or identify the facet joint(s) as a source of the patient's presenting pain.