Contrast flow in CT-guided lumbar interlaminar epidural steroid injections: does needle position effect the laterality of contrast flow?

Abstract

To evaluate the effect of needle position on the laterality of contrast flow in CT-guided lumbar interlaminar epidural steroid injections. A retrospective review of consecutive CT-guided interlaminar lumbar epidural steroid injections was performed. The terminal needle tip position (midline or lateral) and the laterality of epidural contrast were evaluated by two readers. Contrast flow pattern was classified as ipsilateral to needle trajectory, bilateral, or contralateral. Bilateral flow was further divided into asymmetric, symmetrical, or asymmetric to the contralateral side. Inter-reader agreement was calculated with the kappa statistic. The relationship of needle position to contrast laterality was calculated with the chi statistic. Pain scores were compared for bilateral and unilateral flows with a two-tailed T test for independent means. A total of 250 injections were included in 204 patients, with an age range of 24 to 93years. The most commonly injected level (145/250) was L4-L5. Agreement between the two readers was almost perfect and substantial (kappa 0.751-0.880). The majority of injections (154/250) demonstrated contrast flow ipsilateral to the needle trajectory, 90/250 demonstrated bilateral flow, and 6/250 had contralateral flow. Of the 90 cases with bilateral flow, 80% were performed with a midline terminal needle position (p < 0.001). There was no difference in immediate post-procedure pain scores between patients with ipsilateral or bilateral contrast flow. For interlaminar epidural steroid injections, a midline terminal needle tip position has a greater probability of producing bilateral contrast flow compared to a lateral terminal needle tip position.