Alar Ligament Test is used to assess the alar ligament integrity. Rotation and side bending tighten the contralateral alar (e.g., rotation or side bending to the right tightens the left alar), whereas flexion typically tightens both alar ligaments.
How do you perform the Alar Ligament Test?
While the patient is in supine position, the posterior aspect of the transverse process of C2 is palpated with one hand, while the patient’s head is side bent or rotated.
See Also: Facet Joint Dysfunction
What does a positive Alar Ligament Test mean?
Under normal conditions, rotation & side bending tightens alar ligament. Thus, the spinous process should move immediately in the contralateral direction to side bending.
If the C2 transverse process does not move as soon as the head begins to rotate, laxity of the alar ligament should be suspected (most common in patient with RA)
To confirm the findings in Alar Ligament Test, the point of rotation is maintained, as the patient’s head is cradled by the clinician, and while monitoring the motion at the C2 segment, the clinician introduces side bending through the craniovertebral joints to slacken the alar ligament. Further rotation should now be possible.
The diagnostic value of Alar Ligament Test is as yet unknown.
Alar Ligament Anatomy
The alar ligaments connect the superior part of the dens to fossae on the medial aspect of the occipital condyles, although they can also attach to the lateral masses of the atlas.
A study of 44 cadavers found the orientation of the ligament to be superior, posterior, and lateral. In another study, upper cervical spine specimens were dissected to examine the macroscopic and functional anatomy of alar ligaments. The study found that the most common orientation was cauda-cranial, followed by transverse. In two of the specimens, a previously undescribed ligamentous connection was found between the dens and the anterior arch of the atlas, the anterior atlantodental ligament.
In 12 specimens, the ligament also attached via caudal fibers to the lateral mass of the atlas. The posteroanterior orientation of the ligaments in 17 of the 19 subjects was directly lateral from the dens to the occipital attachment or slightly posterior.
The function of the ligament is to resist flexion, contralateral side bending, and contralateral O-A rotation. In addition, the alar ligaments restrict anteroposterior translation of the occiput on C1 to some degree. Because of the connections of the ligament, side bending of the head produces a contralateral or ipsilateral rotation of C2, depending on the source.
Insufficiency of the alar ligaments increases the potential for occipitoaxial instability. The degree of instability can be determined in conjunction with other clinical findings, such as neurologic or vascular compromise, pain, and deformity.
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