title: The lateral buttress: an anatomic feature of the lumbar pars interarticularis.
abstract: METHODS
  A morphometric study of the lateral buttress region of the lumbar pars interarticularis from L1-L5 on 10 dried lumbar spines was performed.
  
  
  OBJECTIVE
  To qualitatively describe and quantitatively evaluate this portion of the pars and to discuss its clinical and surgical relevance.
  
  
  BACKGROUND
  The "lateral buttress" is a bony bridge connecting the superolateral edge of the inferior facet to the pedicle/transverse process junction, offering structural support to the pars interarticularis at upper lumbar levels. To date, no anatomic study has evaluated this structure.
  
  
  METHODS
  Direct measurements using vernier calipers were taken at each level, L1-L5, from 10 dried lumbar spines. Surface area of the buttress was calculated and compared statistically for differences between each level, as well as normalized relative to L3.
  
  
  RESULTS
  The surface areas of the buttresses at L1-L3 were similar, measuring near 80 +/- 10 mm2. At L4, it measured 50 +/- 10 mm2. And at L5, it measured 15 +/- 5 mm2. These differences were statistically significant. Normalized data showed the buttress at L4 to be 40% smaller and at L5 to be 80% smaller than at upper levels.
  
  
  CONCLUSIONS
  This study provides descriptive and anatomic data regarding the lateral buttress portion of lumbar pars interarticularis. The broad buttress of the upper lumbar levels offers support to the pars but can confuse anatomic guidelines for pedicle screw placement and paraspinal approaches. The narrow buttress of lower lumbar levels makes pedicle screw placement and the paraspinal approach easier, but it lessens support to the pars, making spondylolysis and iatrogenic instability more likely.
authors.affiliation: Northeastern Ohio Universities College of Medicine, Summa Health Systems, Akron, Ohio, USA. bradweiner@earthlink.net
authors.forename: Bradley K
authors.initials: BK
authors.lastname: Weiner
authors.forename: Matthew
authors.initials: M
authors.lastname: Walker
authors.forename: William
authors.initials: W
authors.lastname: Wiley
authors.forename: John A
authors.initials: JA
authors.lastname: McCulloch
mesh_terms: D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology; D008161:Lumbosacral Region; D012016:Reference Values; D013131:Spine / Q000033:anatomy & histology*