• Hisayoshi Tachihara, Miho Sekiguchi, Shin-ichi Kikuchi, and Shin-ichi Konno.
• Department of Orthopaedic Surgery, Fukushima Medical University School of Medicine, Fukushima, Japan. tachi@fmu.ac.jp
• Spine. 2008 Apr 1; 33 (7): 743-7.

Study DesignExperimental animal study.ObjectiveTo determine whether corticosteroids produce additional benefit to nerve root infiltration (NRI) for experimental lumbar disc herniation.Summary Of Background DataNRI is used for nonsurgical treatment of radicular symptoms caused by lumbar disc herniation or lumbar spinal canal stenosis. Various studies have shown that NRI using local anesthetic or combinations of local anesthetic and corticosteroid can provide both short- and long-term pain relief. However, whether corticosteroids produce additional benefit to NRI remains controversial.MethodsA total of 174 adult female Sprague-Dawley rats were used in this study. The left L5 nerve root and dorsal root ganglion (DRG) were exposed. For the nontreatment group, autologous nucleus pulposus was harvested from the tail and applied to the DRG. For treatment groups, 1% lidocaine (Lido group), 0.4% dexamethasone (Dexa group), 1% lidocaine + 0.4% dexamethasone (Lido + Dexa group), or saline (Saline group) was injected into the underlayer of epineurium just distal to the nucleus pulposus. At 2, 7, 14, and 21 days after surgery, withdrawal threshold was determined using the von Frey test for mechanical allodynia. Expression of tumor necrosis factor (TNF)-alpha in the DRG was examined by immunohistochemical analyses and immunoblotting.ResultsWithdrawal threshold decreased in the nontreatment group from day 2 to day 14. Conversely, Lido, Dexa, and Lido + Dexa groups showed no decreases in withdrawal thresholds, and no significant differences were observed among these 3 groups. Immunohistochemical analyses showed that TNF-alpha was localized in DRG neurons in all groups. Immunoblotting showed that expression of TNF-alpha in the DRG was lower in Lido, Dexa, and Lido + Dexa groups than in the nontreatment group. No significant differences were observed among these 3 groups.ConclusionNRI prevented mechanical allodynia. However, no additional benefit from using corticosteroid was identified, suggesting that corticosteroid may be unnecessary for NRI.

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