title: Plain film evaluation of degenerative disk disease at the lumbosacral junction.
abstract: OBJECTIVE
  Diagnosing degenerative disk disease (DDD) at the lumbosacral junction (LSJ) on plain films is often difficult, compared with other disk levels. The purpose of this study was to determine whether criteria for diagnosis of DDD at the LSJ can be established for plain films.
  
  
  METHODS
  We retrospectively reviewed 100 lumbar MRI scans of patients who also had lumbar plain films. Using MRI as the reference standard, the LSJ was classified as normal (n=35) or exhibiting mild (n=45) or severe (n=20) DDD by two radiologists using accepted criteria. Measurements were performed on the plain films by two other radiologists and the average measurements were tabulated according to the three categories of DDD defined by MRI. Plain film measurements included the anterior and posterior disk heights (ADH, PDH), Farfan's ratio, determined by adding ADH to PDH and dividing that number by the measured anteroposterior (AP) length of the inferior end plate of L5 [(ADH+PDH)/AP length of L5], and lumbosacral angle (LSA). Subsequently, five additional radiologists interpreted the radiographs by visual inspection only, for DDD at the LSJ, both before and, several weeks later, after being provided with the quantitative data for normal versus DDD.
  
  
  CONCLUSIONS
  There was a statistically significant difference between normal disk and increasing severity of DDD on radiographs using the parameters of PDH and Farfan's ratio. There was no statistically significant difference regarding ADH or LSA. Diagnostic accuracy by visual inspection was not significantly altered using the quantitative data for interpretation of DDD (68% correct before, 69.5% correct after). Analysis of results indicates that PDH is the most reliable and easily used criterion for detection of DDD at the LSJ. A PDH < or =5.4 mm on plain lateral film indicates DDD; PDH > or =7.7 mm indicates the absence of DDD on plain film.
authors.affiliation: Department of Radiology, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
authors.forename: E L
authors.initials: EL
authors.lastname: Cohn
authors.forename: E J
authors.initials: EJ
authors.lastname: Maurer
authors.forename: T E
authors.initials: TE
authors.lastname: Keats
authors.forename: R G
authors.initials: RG
authors.lastname: Dussault
authors.forename: P A
authors.initials: PA
authors.lastname: Kaplan
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000473:pathology; D017116:Low Back Pain / Q000000981:diagnostic imaging; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging* / Q000473:pathology; D013122:Spinal Diseases / Q000000981:diagnostic imaging* / Q000473:pathology