181   Computed Tomography Parameters for Atlanto-occipital Dislocation in Adult XXXX : The Occipital Condyle-C1 Interval.

@entity1 @entity3029
INTRODUCTION: Our goal was to identify and compare the normal occipital-condyle-C1 interval (CCI) in healthy adults with the CCI in adults with @entity3029 ( @entity3029 ) and establish a highly sensitive and specific cutoff value to diagnose @entity3029 radiographically. METHODS: Eighty-one @entity1 (59 non- @entity3029 , 22 @entity3029 ) were included. Measurements obtained from thin-cut computed tomography scans of the craniovertebral joint to assess @entity3029 included: CCI, condylar sum, and standard diagnostic tools. RESULTS: Non- @entity3029 @entity1 were 50.8% (n = 30) male and 49.2% (n = 29) female, mean age was 42.4    16 years (range 19-87 years). @entity3029 @entity1 were 45.5% (n = 10) male and 54.5% (n = 12) female with a mean age of 38.2    9.7 years (range 20-56 years). Interrater reliabilities were all above 0.98 (95% CI) for CCI measurements. A total of 1296 measurements were made of the CCI in 81 @entity1 . The mean CCI for non- @entity3029 @entity1 was 0.89    0.12 mm, the single largest CCI measurement was 1.4 mm, and the largest mean for either right or left CCI was 1.2 mm. The mean condylar sum was 1.8    0.2 mm, and the largest condylar sum value was 2.2 mm. Linear regression with age predicted an increase in CCI of 0.001 mm/y (P < .05). The mean CCI in @entity3029 @entity1 was 3.35    1.8 mm (range 1.5-6.4 mm). A cutoff value for @entity3029 was determined at 1.5 mm for the CCI and 3.0 mm for the condylar sum, both with a sensitivity of 1 and false-negative rate of 0. Sensitivity for Powers, Wholey, Harris, Sun, Wackenheim, and Lee tests were determined to be 0.55, 0.46, 0.27, 0.23, 0.41, and 0.41, respectively. CONCLUSION: The revised CCI (1.5 mm) and condylar sum (3.0 mm) cutoff values have the highest sensitivity and specificity for the diagnosis of @entity3029 in the adult population.
