title: Effects of single injection of local anesthetic agents on intervertebral disc degeneration: ex vivo and long-term in vivo experimental study.
abstract: BACKGROUND
  Analgesic discography (discoblock) can be used to diagnose or treat discogenic low back pain by injecting a small amount of local anesthetics. However, recent in vitro studies have revealed cytotoxic effects of local anesthetics on intervertebral disc (IVD) cells. Here we aimed to investigate the deteriorative effects of lidocaine and bupivacaine on rabbit IVDs using an organotypic culture model and an in vivo long-term follow-up model.
  
  
  METHODS
  For the organotypic culture model, rabbit IVDs were harvested and cultured for 3 or 7 days after intradiscal injection of local anesthetics (1% lidocaine or 0.5% bupivacaine). Nucleus pulposus (NP) cell death was measured using confocal microscopy. Histological and TUNEL assays were performed. For in vivo study, each local anesthetic was injected into rabbit lumbar IVDs under a fluoroscope. Six or 12 months after the injection, each IVD was prepared for magnetic resonance imaging (MRI) and histological analysis.
  
  
  RESULTS
  In the organotypic culture model, both anesthetic agents induced time-dependent NP cell death; when compared with injected saline solution, significant effects were detected within 7 days. Compared with the saline group, TUNEL-positive NP cells were significantly increased in the bupivacaine group. In the in vivo study, MRI analysis did not show any significant difference. Histological analysis revealed that IVD degeneration occurred to a significantly level in the saline- and local anesthetics-injected groups compared with the untreated control or puncture-only groups. However, there was no significant difference between the saline and anesthetic agents groups.
  
  
  CONCLUSIONS
  In the in vivo model using healthy IVDs, there was no strong evidence to suggest that discoblock with local anesthetics has the potential of inducing IVD degeneration other than the initial mechanical damage of the pressurized injection. Further studies should be performed to investigate the deteriorative effects of the local injection of analgesic agents on degenerated IVDs.
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Iwasaki
authors.affiliation: Department of Advanced Medicine for Spine and Spinal Cord Disorders, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sudo
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Division of Infection and Immunity, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Higashi
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohnishi
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Takeru
authors.initials: T
authors.lastname: Tsujimoto
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Norimasa
authors.initials: N
authors.lastname: Iwasaki
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects* / Q000627:therapeutic use; D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage* / Q000009:adverse effects* / Q000627:therapeutic use; D007267:Injections; D055959:Intervertebral Disc Degeneration / Q000188:drug therapy*; D008012:Lidocaine / Q000008:administration & dosage* / Q000009:adverse effects* / Q000627:therapeutic use; D009924:Organ Culture Techniques; D011817:Rabbits; D013997:Time Factors
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine; D002045:Bupivacaine