Objective: The objective of our study was to determine whether a method could be found to reduce iatrogenic radicular pain during needle placement in lumbar diskography.
Materials and methods: After obtaining permission from the institutional review board at the University of Pittsburgh Medical Center, we conducted a study using medical records and existing data that were recorded for quality control during lumbar diskography. A coaxial technique was being used for lumbar diskography. We evaluated data for 71 intervertebral disks in 26 patients in which the needle placement was randomly high (superior) or low (inferior), and the associated pain response during needle placement was recorded. In an attempt to minimize iatrogenic pain during needle placement, we identified a potentially "safe window" for needle placement on MRI of the lumbar spine. On oblique fluoroscopy of the lumbar spine, the safe window is a triangle formed by the superior articular facet medially, the superior endplate of the lower vertebra inferiorly, and an imaginary line joining the tip of the superior articular facet and the superolateral tip of the vertebral body. This safe window was then used for needle placement in another 73 intervertebral disks in 27 patients. Pain response to needle placement was recorded for quality control, and the medical records were retrospectively compared with the initial 71 intervertebral disks in which needle placement was random.
Results: In the initial group with random needle placement, lower extremity radicular pain occurred in 13 (18.3%) of 71 intervertebral disks with superior needle placement and in 23 (32.4%) of 71 intervertebral disks with inferior needle placement (total, 50.7%). The pain responses of the superior and inferior groups were not significantly different (p = 0.27). On MRI, the average distances between the nerve ganglion-fascicle-rami and the superior articular facets at the superior disk level were 1.1, 1.4, and 2.5 mm at L3-L4, L4-L5, and L5-S1, respectively. The average distances between the nerve ganglion-fascicle-rami and the superior articular facets at the inferior disk level were 3.0, 3.6, and 6.6 mm at L3-L4, L4-L5, and L5-S1, respectively. When the safe window was used, only five (6.8%) of 73 patients reported radicular pain. The decrease in radicular pain between the two groups was significant (p < 0.001).
Conclusion: Iatrogenic lower extremity radicular pain is common during random needle placement at lumbar diskography. High or low needle placement in the intervertebral disk could not predict whether radicular pain would be averted. We identified a safe window that can be used for needle placement during lumbar diskography to minimize iatrogenic lower extremity radicular pain and thereby improve the reliability of the test.