title: A Novel Radiographic Indicator of Developmental Cervical Stenosis.
abstract: BACKGROUND
  Developmental cervical stenosis of the spinal canal predisposes patients to neural compression and loss of function. The Torg-Pavlov ratio has been shown to provide high sensitivity but low specificity for identifying developmental cervical stenosis. A more sensitive and specific radiographic index has not been reported to our knowledge. The objective of this study was to develop and provide an objective, sensitive, and specific radiographic index to assess for developmental cervical stenosis.
  
  
  METHODS
  The C3 through C6 levels of the cervical spine were analyzed on lateral radiographs of 150 adult patients to determine the spinolaminar line-to-lateral mass distance (SL), lateral mass-to-posterior vertebral body distance (LM), spinolaminar line-to-vertebral body (canal) diameter (CD), and vertebral body diameter (VB). Ratios of these measurements were calculated to eliminate magnification effects. The corresponding true spinal canal diameter was measured using computed tomography (CT) midsagittal sections. Receiver operating characteristic (ROC) curve analysis was performed to identify a radiographic measurement ratio with optimal sensitivity and specificity, using a true canal diameter of <12 mm to define developmental cervical stenosis.
  
  
  RESULTS
  Several of the measured ratios demonstrated a strong correlation with the true canal diameter at all cervical levels. However, ROC curve analysis showed that only an LM/CD ratio of ≥0.735 indicated a canal diameter of <12 mm (developmental cervical stenosis). The sensitivity of this ratio at C5 was 83% and its specificity at C5 was 74%. An LM/CD ratio of ≥0.735 measured only at the C5 level also indicated developmental cervical stenosis at any cervical level from C3 through C6 with 76% sensitivity and 80% sensitivity. Other ratios, including the Torg-Pavlov ratio, did not demonstrate an adequate statistical profile to indicate developmental cervical stenosis. The accuracy of the LM/CD ratio was not adversely affected by the patient's sex.
  
  
  CONCLUSIONS
  This analysis provided a novel index for identifying developmental cervical stenosis: the C5 lateral mass/canal diameter (LM/CD) ratio. We believe that this ratio is the best radiographic measurement available to screen for developmental cervical stenosis in the adult spine patient population. It provides an objective radiographic screening tool for physicians to detect developmental cervical stenosis and decide whether additional imaging or surgical referral is appropriate.
  
  
  METHODS
  Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Duke Orthopaedics of Raleigh, Raleigh, North Carolina.
authors.forename: Phillip H
authors.initials: PH
authors.lastname: Horne
authors.affiliation: Hospital for Special Surgery, New York, NY.
authors.forename: Lukas P
authors.initials: LP
authors.lastname: Lampe
authors.affiliation: Hospital for Special Surgery, New York, NY.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Nguyen
authors.affiliation: Hospital for Special Surgery, New York, NY.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Herzog
authors.affiliation: Hospital for Special Surgery, New York, NY.
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Albert
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013130:Spinal Stenosis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed