title: Lumbar lordosis and pars interarticularis fractures: a case-control study.
abstract: OBJECTIVE
  The aim of this study is to examine the relationship between lumbar lordosis and pars interarticularis fractures.
  
  
  METHODS
  In this retrospective case-control study we compare the angle of lumbar lordosis and the angle of the S1 vertebral endplate (as a measure of pelvic tilt) in patients with bilateral L5 pars interarticularis fractures with age- and sex-matched control cases with normal MRI examinations of the lumbar spine. Twenty-nine cases of bilateral L5 pars interarticularis fractures with matched control-cases were identified on MRI (16 male, 13 female, age 9-63 years). The angle of lordosis was measured between the inferior L4 and superior S1 vertebral endplates on a standing lateral lumbar spine radiograph for both groups.
  
  
  RESULTS
  The mean angle of lordosis about the L5 vertebra was 36.9° (SD = 6.5°) in the pars interarticularis fracture group, and 30.1° (SD = 6.4°) in the control group. The difference between the two groups was significant (mean difference 6.8°, Student's t test: P < 0.001). The mean angle of sacral tilt measured was 122.2° (SD = 10.16°) for controls and 136.4° (SD = 10.86°) for patients with pars defects. The difference in the means of 14.2° was statistically significantly different (P < 0.0001).
  
  
  CONCLUSIONS
  Sacral tilt represented by a steeply angled superior endplate of S1 is associated with a significantly increased angle of lordosis, between L4 and S1, and pars fractures at L5. Steep angulation of the first sacral vertebral segment maybe the predisposing biomechanical factor that leads to pincer-like impingement of the pars interarticularis and then spondylolysis.
authors: Norwich Radiology Academy, Cotman Centre, Colney Lane, Norwich, Norfolk, NR4 7UB, United Kingdom. william.bugg@nnuh.nhs.uk
authors: William G
authors: WG
authors: Bugg
authors: Mark
authors: M
authors: Lewis
authors: Arne
authors: A
authors: Juette
authors: John G
authors: JG
authors: Cahir
authors: Andoni P
authors: AP
authors: Toms
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D008141:Lordosis / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000293:injuries* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016103:Spinal Fractures / Q000209:etiology / Q000473:pathology*; D013169:Spondylolysis / Q000150:complications / Q000473:pathology*; D055815:Young Adult