title: Lumbar facet orientation in spondylolysis: a skeletal study.
abstract: METHODS
  Orientation of the lumbar articular facets at the L1-L5 level was measured and analyzed.
  
  
  OBJECTIVE
  To characterize the relationship between lumbar facet orientation and isthmic spondylolysis.
  
  
  BACKGROUND
  Whereas many studies have explored the relationship between facet orientation in the transverse plane and various spinal pathologies, there is insufficient data regarding this relationship and isthmic spondylolysis.
  
  
  METHODS
  A 3-dimensional digitizer was used to measure the transverse orientation of the lumbar facet joints at the L1-L5 level in 115 male individuals with bilateral isthmic spondylolysis (at L5) and 120 age and sex-matched normal control subjects from the Hamann-Todd Human Osteological Collection (Cleveland Museum of Natural History, Cleveland, OH). Statistical analysis included paired t tests and analysis of variance.
  
  
  RESULTS
  In both isthmic spondylolysis and control groups, considerable shifts were noticed from sagittally oriented articular facets at L1 to frontally oriented facets at L5. The change in orientation was significantly greater (up to 13 degrees at L4) in the isthmic spondylolysis group (right inferior facets). Three of the 4 articular facets of L5 (right and left inferior and right superior) were significantly more frontally oriented in isthmic spondylolysis compared to the control group. A greater tendency of asymmetry in facet orientation was noticed in the isthmic spondylolysis group.
  
  
  CONCLUSIONS
  Individuals with more frontally oriented facets in the lower lumbar vertebrae incorporated with facet tropism are at a greater risk for developing isthmic spondylolysis at L5.
authors.affiliation: Spinal Research Laboratory, Department of Physical Therapy, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv, Israel. yossefm@post.tau.ac.il
authors.forename: Youssef Maher
authors.initials: YM
authors.lastname: Masharawi
authors.forename: Deborah
authors.initials: D
authors.lastname: Alperovitch-Najenson
authors.forename: Nili
authors.initials: N
authors.lastname: Steinberg
authors.forename: Gali
authors.initials: G
authors.lastname: Dar
authors.forename: Smadar
authors.initials: S
authors.lastname: Peleg
authors.forename: Bruce
authors.initials: B
authors.lastname: Rothschild
authors.forename: Khalil
authors.initials: K
authors.lastname: Salame
authors.forename: Israel
authors.initials: I
authors.lastname: Hershkovitz
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D015331:Cohort Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008159:Lumbar Vertebrae / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015995:Prevalence; D015203:Reproducibility of Results; D018570:Risk Assessment; D012815:Signal Processing, Computer-Assisted; D013169:Spondylolysis / Q000453:epidemiology / Q000209:etiology / Q000473:pathology*; D021801:Zygapophyseal Joint / Q000473:pathology*