Upper cervical spine

Question 1

Atlas

OA

Answer 1

Structure:
- Composed of 2 large lateral masses
- Connected by anterior and posterior arches

Tubercles:
- Posterior tubercle is larger than the anterior
- Anterior tubercle serves as attachment for the anterior longitudinal ligament

Facet orientation:
- Superior articular facets:
- Concave → accommodate the convex occipital condyles
- Inferior articular facets:
- Flat or slightly convex

Motion:
- Facet orientation favors motion in the sagittal plane
- Extension > Flexion due to facet alignment

Question 2

OA Joint

Answer 2

Superior articular surfaces of atlas (C1) are:
- Kidney-shaped
Oriented in the horizontal plane
Often described as “female” shaped to receive the “male” occipital condyles

Motions Possible:
- Joint allows flexion/extension, side bending, and axial rotation

Primary Motion:
- Despite multi-directional capability, motion is primarily in the sagittal plane
- Mainly nodding (flexion/extension)

Stability:
- Highly ligamentous support contributes to controlled, limited motion

Question 3

OA arthrokinematics

Answer 3

Flexion => posterior glide of occipital condyles

Extension => anterior glide of occipital condyles