title: Does nuclear tissue infected with bacteria following disc herniations lead to Modic changes in the adjacent vertebrae?
abstract: OBJECTIVE
  To investigate the prevalence of infected herniated nucleus material in lumbar disc herniations and to determine if patients with an anaerobic infected disc are more likely to develop Modic change (MC) (bone oedema) in the adjacent vertebrae after the disc herniation. MCs (bone oedema) in vertebrae are observed in 6 % of the general population and in 35-40 % of people with low back pain. These changes are strongly associated with low back pain. There are probably a mechanical cause and an infective cause that causes MC. Several studies on nuclear tissue from herniated discs have demonstrated the presence of low virulent anaerobic microorganisms, predominantly Propionibacterium acnes, in 7-53 % of patients. At the time of a herniation these low virulent anaerobic bacteria may enter the disc and give rise to an insidious infection. Local inflammation in the adjacent bone may be a secondary effect due to cytokine and propionic acid production.
  
  
  METHODS
  Patients undergoing primary surgery at a single spinal level for lumbar disc herniation with an MRI-confirmed lumbar disc herniation, where the annular fibres were penetrated by visible nuclear tissue, had the nucleus material removed. Stringent antiseptic sterile protocols were followed.
  
  
  RESULTS
  Sixty-one patients were included, mean age 46.4 years (SD 9.7), 27 % female. All patients were immunocompetent. No patient had received a previous epidural steroid injection or undergone previous back surgery. In total, microbiological cultures were positive in 28 (46 %) patients. Anaerobic cultures were positive in 26 (43 %) patients, and of these 4 (7 %) had dual microbial infections, containing both one aerobic and one anaerobic culture. No tissue specimens had more than two types of bacteria identified. Two (3 %) cultures only had aerobic bacteria isolated. In the discs with a nucleus with anaerobic bacteria, 80 % developed new MC in the vertebrae adjacent to the previous disc herniation. In contrast, none of those with aerobic bacteria and only 44 % of patients with negative cultures developed new MC. The association between an anaerobic culture and new MCs is highly statistically significant (P = 0.0038), with an odds ratio of 5.60 (95 % CI 1.51-21.95).
  
  
  CONCLUSIONS
  These findings support the theory that the occurrence of MCs Type 1 in the vertebrae adjacent to a previously herniated disc may be due to oedema surrounding an infected disc. The discs infected with anaerobic bacteria were more likely (P < 0.0038) to develop MCs in the adjacent vertebrae than those in which no bacteria were found or those in which aerobic bacteria were found.
authors: Research Department, Spine Centre of Southern Denmark, Hospital Lillebaelt, Middelfart, Institute of Regional Health Services Research, University of Southern Denmark, Clinical Locomotion Science Network, Ostre Houghvej 55, 5550, Middelfart, Denmark. Hanne.birgit.albert@slb.regionsyddanmark.dk
authors: Hanne B
authors: HB
authors: Albert
authors: Peter
authors: P
authors: Lambert
authors: Jess
authors: J
authors: Rollason
authors: Joan Solgaard
authors: JS
authors: Sorensen
authors: Tony
authors: T
authors: Worthington
authors: Mogens Bach
authors: MB
authors: Pedersen
authors: Hanne Schack
authors: HS
authors: Nørgaard
authors: Ann
authors: A
authors: Vernallis
authors: Frederik
authors: F
authors: Busch
authors: Claus
authors: C
authors: Manniche
authors: Tom
authors: T
authors: Elliott
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001847:Bone Diseases / Q000453:epidemiology*; D002444:Cefuroxime / Q000627:therapeutic use; D015331:Cohort Studies; D004487:Edema / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D016908:Gram-Positive Bacterial Infections / Q000150:complications* / Q000188:drug therapy; D006801:Humans; D007403:Intervertebral Disc / Q000382:microbiology*; D007405:Intervertebral Disc Displacement / Q000382:microbiology* / Q000473:pathology / Q000601:surgery; D017116:Low Back Pain / Q000453:epidemiology / Q000209:etiology; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011425:Propionibacterium acnes / Q000302:isolation & purification*; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D002444:Cefuroxime
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