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Published on: March 7, 2014
The relationship between dens height and alar ligament orientation: a radiologic study
Peter G Osmotherly1, Olivia A Rawson, Lindsay J Rowe
1School of Health Sciences, The University of Newcastle, Callaghan, NSW, Australia. Peter.Osmotherly@newcastle.edu.au
Journal of Manipulative and Physiological Therapeutics
|April 16, 2011
Summary
Alar ligament orientation varies normally, but dens height does not cause this variation. This challenges assumptions in multiplanar stress testing for atlantoaxial instability.
Area of Science:
- Anatomy
- Biomechanics
- Radiology
Background:
- The alar ligament's orientation is crucial for atlantoaxial stability.
- Previous assumptions linked ligament orientation to dens height variations.
- Multiplanar stress testing protocols are based on these anatomical assumptions.
Purpose of the Study:
- To investigate the anatomical basis of alar ligament stress testing.
- To determine the relationship between dens height and alar ligament orientation.
- To evaluate the validity of current multiplanar stress testing assumptions.
Main Methods:
- Computed tomography (CT) scans of 42 subjects were analyzed.
- Dens height and alar ligament orientation were measured using standardized landmarks.
- Measurements were correlated to assess the relationship between dens height and ligament orientation.
Main Results:
- A consistent method using the digastric line yielded reliable ligament orientation measurements (mean 110.06°).
- No significant correlation was found between dens height and alar ligament orientation.
- This indicates anatomical variation in ligament orientation is not solely dependent on dens height.
Conclusions:
- Normal anatomical variation exists in both dens height and alar ligament orientation.
- Dens height variation does not appear to be the cause of alar ligament orientation variation.
- Findings suggest a need to re-evaluate the anatomical assumptions underlying alar ligament stress testing protocols.
