title: Radiographic assessment of lumbar facet distance spacing and spondylolysis.
abstract: METHODS
  Spondylolytic defects at L5 are influenced by insufficient differential spacing between the inferior articular facets of L4 and superior facets of S1. These structures then impinge on the intervening L5 pars interarticularis during hyperlordosis, contributing to fracture and resorption of the pars.
  
  
  OBJECTIVE
  Articular facet spacing was evaluated on clinical radiographs of normal and spondylolytic patients.
  
  
  BACKGROUND
  Spondylolysis ranges from a hairline fracture through the pars to a complete pseudarthrotic defect. Insufficient increase in the distance between articular facets from L4-L5 to L5-S1 has been associated with chronic lytic defects in a skeletal sample.
  
  
  METHODS
  Anteroposterior radiographs of 39 patients with L5-S1 spondylolysis were compared with radiographs from 42 normal individuals. Differences in transverse distances between lumbar articular facets and pedicles were compared using 2-tailed t tests.
  
  
  RESULTS
  Patients with spondylolysis exhibited a smaller increase in interfacet distance from the L3-L4 facet joints to the L5-S1 joints than do normal patients, even relative to vertebral size.
  
  
  CONCLUSIONS
  Spondylolytic fractures at L5 are influenced by an inadequate increase in interfacet distances between adjacent vertebrae. Individuals lacking sufficient increase in lower lumbar transverse interfacet dimensions are at greater risk of developing and maintaining spondylolytic defects.
authors.affiliation: Department of Anthropology, University of Missouri, Columbia, MO 65212, USA. wardcv@missouri.edu
authors.forename: Carol V
authors.initials: CV
authors.lastname: Ward
authors.forename: Bruce
authors.initials: B
authors.lastname: Latimer
authors.forename: Dirk H
authors.initials: DH
authors.lastname: Alander
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Parker
authors.forename: James A
authors.initials: JA
authors.lastname: Ronan
authors.forename: Anne D
authors.initials: AD
authors.lastname: Holden
authors.forename: Cary
authors.initials: C
authors.lastname: Sanders
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging; D013169:Spondylolysis / Q000000981:diagnostic imaging*