Ultrasound-guided Pararadicular Injection in the Lumbar Spine: A Comparative Study of the Paramedian Sagittal and Paramedian Sagittal Oblique Approaches

Background: Ultrasound-guided nerve root blocks and transforaminal injections are well established, and several procedural feasibility studies have been reported. However, the contrast dispersion pattern during ultrasound-guided pararadicular injection has not been reported. We hypothesized that the paramedian sagittal oblique approach provides a superior intraforaminal contrast-spread pattern compared to the paramedian sagittal approach during ultrasound-guided pararadicular injections in the lumbar spine. Methods: Ninety injections were performed in 42 adult patients using pararadicular injections. Each injection was allocated to 1 of 2 groups. In the paramedian sagittal approach group, the transducer was positioned perpendicularly over the skin, and a bent needle was inserted using an in-plane technique. In the paramedian sagittal oblique approach group, the needle was advanced with the transducer tilted ~20 to 25° toward the pararadicular aditus plane. In both groups, the needle was advanced until the intertransverse ligament was punctured. Nonionic contrast media was injected under fluoroscopic guidance. Results: The contrast was injected in the targeted pararadicular compartment in 83 of 90 injections (92.2%). Among the successful pararadicular injections, the intraforaminal contrast pattern was detected in 17 cases (39.5%) in the paramedian sagittal approach group and in 35 cases (87.5%) in the paramedian sagittal oblique approach group (P < 0.001). Both groups showed significant pain reduction compared to the baseline (P < 0.001); however, the visual analog scale for pain showed significantly lower pain in the paramedian sagittal oblique approach group compared to the paramedian sagittal approach group (P = 0.036). Rates of ventral epidural flow, intra- and extraepineural pattern of contrast, and intravascular injections were similar between the two approaches. Conclusion: The paramedian sagittal oblique approach delivered a superior intraforaminal contrast-spread pattern and significantly greater pain relief than the paramedian sagittal approach during ultrasound-guided pararadicular injections in the lumbar spine.