In inflammatory diseases that cause atlantoaxial instability, laxity of which ligament contributes?

• A. Alar ligaments
• B. Transverse ligament of the atlas
• C. Tectorial membrane
• D. Nuchal ligament

Answer: (B)

Stability at the atlas–axis joint mainly comes from the transverse ligament of the atlas, which holds the dens against the anterior arch of C1 to prevent forward slipping of the atlas on C2. In inflammatory diseases such as rheumatoid arthritis, this ligament can become weakened or lax due to inflammatory changes and pannus formation. When the transverse ligament laxity occurs, the atlas can translate forward relative to the axis, leading to atlantoaxial instability and a real risk of spinal cord compression.

The other ligaments have different roles that aren’t the primary cause of this instability in inflammatory conditions. The alar ligaments limit rotation and side bending by connecting the dens to the occipital bones, so their laxity affects rotational control but isn’t the main driver of instability from inflammatory disease. The tectorial membrane provides posterior support behind the dens and contributes to stability, but its laxity is not the typical propagator of atlantoaxial instability in this context. The nuchal ligament supports the posterior neck and is not a primary stabilizer of the craniovertebral junction.