title: Association of facet tropism with lumbar disc herniation.
abstract: OBJECTIVE
  Facet tropism is defined as asymmetry between left and right facet joints and is postulated as a possible cause of disc herniation. In the present study, the authors used a 3-T MRI to investigate the association between facet tropism and lumbar disc herniation at a particular motion segment. They also examined whether the disc herniated towards the side of the more coronally oriented facet joint.
  
  
  METHODS
  Sixty patients (18-40 years) with single level disc herniation (L3-L4, L4-L5, or L5-S1) were included in the study. Facet angles were measured using MRI of 3-T using the method described by Karacan et al. Facet tropism was defined as difference of 10° in facet joint angles between right and left sides. Normal disc adjacent to the herniated level was used as control. We also examined if disc herniated towards the side of more coronally oriented facet.
  
  
  RESULTS
  Twenty-five herniations were at L4-L5 level and 35 at L5-S1. Statistical analysis was performed using the Fischer Exact Test. At L4-L5 level, 6/25 cases had tropism compared to 3/35 controls (p = 0.145). At L5-S1 level, 13/35 cases had tropism as compared to 1/21 controls (p = 0.0094). Of 19 cases having tropism, the disc had herniated towards the coronally oriented facet in six (p = 0.11).
  
  
  CONCLUSIONS
  The findings of the study suggest that facet tropism is associated with lumbar disc herniation at the L5-S1 motion segment but not at the L4-L5 level.
authors.affiliation: Department of Orthopaedics, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, 110095, India.
authors.forename: Manish
authors.initials: M
authors.lastname: Chadha
authors.forename: Gaurav
authors.initials: G
authors.lastname: Sharma
authors.forename: Shobha S
authors.initials: SS
authors.lastname: Arora
authors.forename: Vivek
authors.initials: V
authors.lastname: Kochar
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D021801:Zygapophyseal Joint / Q000473:pathology*