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Planchamp et al: Determination of cutoff values on computed tomography and magnetic resonance images for the diagnosis of atlantoaxial instability in small-breed dogs
Veterinary Surgery 4, 2022

🔍 Key Findings

  • Ventral Compression Index (VCI) ≥0.16 (extension) or ≥0.2 (flexion) was diagnostic for AAI with 100% sensitivity and >94% specificity
  • VCI had the highest diagnostic accuracy among all measured variables (AUC > 0.99)
  • C1-C2 overlap ≤2.7 mm (extension) or ≤1.8 mm (flexion) also diagnostic for AAI (sensitivity 84–96%, specificity 81–90%)
  • C1-C2 angle ≥176.9° (extension) or ≥187.4° (flexion) had high sensitivity and specificity (~95%)
  • Basion-dens interval ≥5.9 mm (extension) or ≥3.0 mm (flexion) provided moderate diagnostic accuracy
  • Cranial translation ratio (CTR) ≥0.18 classified dogs as potentially unstable (sensitivity 90%, specificity 78%)
  • VCI ≥0.23 reliably differentiated AAI from potentially unstable cases (sensitivity 94%, specificity 94%)
  • DALR ≤0.24 had high specificity (100%) but low sensitivity for AAI diagnosis

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← Articles

Planchamp et al: Determination of cutoff values on computed tomography and magnetic resonance images for the diagnosis of atlantoaxial instability in small-breed dogs
Veterinary Surgery 4, 2022

🔍 Key Findings

  • Ventral Compression Index (VCI) ≥0.16 (extension) or ≥0.2 (flexion) was diagnostic for AAI with 100% sensitivity and >94% specificity
  • VCI had the highest diagnostic accuracy among all measured variables (AUC > 0.99)
  • C1-C2 overlap ≤2.7 mm (extension) or ≤1.8 mm (flexion) also diagnostic for AAI (sensitivity 84–96%, specificity 81–90%)
  • C1-C2 angle ≥176.9° (extension) or ≥187.4° (flexion) had high sensitivity and specificity (~95%)
  • Basion-dens interval ≥5.9 mm (extension) or ≥3.0 mm (flexion) provided moderate diagnostic accuracy
  • Cranial translation ratio (CTR) ≥0.18 classified dogs as potentially unstable (sensitivity 90%, specificity 78%)
  • VCI ≥0.23 reliably differentiated AAI from potentially unstable cases (sensitivity 94%, specificity 94%)
  • DALR ≤0.24 had high specificity (100%) but low sensitivity for AAI diagnosis

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Multiple Choice Questions on this study

In Planchamp 2022 et al., on imaging-based AAI diagnosis, which measurement had the highest diagnostic accuracy in both head positions?

A. Ventral compression index (VCI)
B. C1-C2 overlap
C. Basion-dens interval
D. Cranial translation ratio (CTR)
E. Power ratio

Answer: Ventral compression index (VCI)

Explanation: The VCI had 100% sensitivity and >94% specificity in both flexed and extended positions, with AUCs near 1.0.
In Planchamp 2022 et al., on imaging-based AAI diagnosis, what cranial translation ratio (CTR) cutoff identified potentially unstable dogs?

A. ≥0.10
B. ≥0.12
C. ≥0.15
D. ≥0.18
E. ≥0.22

Answer: ≥0.18

Explanation: A CTR ≥0.18 classified dogs as potentially unstable (sensitivity 90.48%, specificity 78.08%).
In Planchamp 2022 et al., on imaging-based AAI diagnosis, which measurement best differentiated potentially unstable dogs from AAI-affected dogs?

A. Power ratio
B. Basion-dens interval
C. C1-C2 angle
D. Ventral compression index (VCI)
E. Clivus canal angle

Answer: Ventral compression index (VCI)

Explanation: VCI ≥0.23 had a sensitivity of 93.75% and specificity of 94.44% to distinguish AAI from potentially unstable dogs.
In Planchamp 2022 et al., on imaging-based AAI diagnosis, what was the reported specificity of VCI ≥0.16 in extension for diagnosing AAI?

A. 84.3%
B. 89.7%
C. 92.1%
D. 94.5%
E. 98.6%

Answer: 94.5%

Explanation: VCI ≥0.16 in extension had 100% sensitivity and 94.54% specificity.
In Planchamp 2022 et al., on imaging-based AAI diagnosis, what was the cutoff value of the VCI in dogs imaged in flexion?

A. ≥0.10
B. ≥0.16
C. ≥0.20
D. ≥0.30
E. ≥0.40

Answer: ≥0.20

Explanation: VCI ≥0.20 in flexion yielded 100% sensitivity and 96.67% specificity for diagnosing AAI.

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