Evaluation of the L2 spinal nerve root infiltration as a diagnostic tool for discogenic low back pain.

BACKGROUND To assess whether unilateral L2 infiltration with local anesthetic can be used to identify patients who will have negative discograms and thus eliminate the need for the discogram. Discogenic low-back pain is considered to have afferent pathways in the sinuvertebral nerves, mainly originating from the ventral rami of the spinal nerves. There is evidence that pain arising from the lower lumbar intervertebral discs may be transmitted through the sympathetic afferent fibers contained in the L2 spinal nerve root. Provocative discography, within the context of other clinical data, is the current "gold standard" by which to diagnose discogenic low-back pain, but a far more invasive procedure than L2 infiltration. OBJECTIVE To evaluate the correlation between unilateral second lumbar (L2) spinal nerve root infiltration with local anesthetic and provocative discography in patients with chronic low back pain. STUDY DESIGN A prospective, observational study. METHODS All patients scheduled for discography were asked to participate in having local anesthetic infiltration of the L2 spinal nerve root at least two weeks prior to discography, until forty subjects were enrolled. Discography was performed after the patient's pain level returned to baseline. RESULTS Local anesthetic infiltration of the L2 spinal nerve root was predictive of provocative discography results in only 46.5% of the subjects (26% true positives, and 20.5% true negatives). In 53.5% of the subjects, L2 infiltration was not predictive of discography results (20.5% false positives, and 33% false negatives). CONCLUSIONS The results showed that unilateral L2 infiltration is not predictive of discogenic low-back pain when compared to discography, the current "gold-standard" for diagnosis.