Important Joints Of Vertebral Column

IMPORTANT JOINTS OF VERTEBRAL COLUMN

Atlanto-occipital joints 

• It is ellipsoid type of synovial joint.
• It is formed b/w the occipital condyles & upper surface of lateral mass of atlas.
• Anterior atlanto-occipital membrane connects the anterior margin of foramen magnum to anterior arch of atlas.
• It is the continuation of anterior longitudinal ligament.
• Posterior atlanto-occipital membrane connects posterior margin of foramen magnu,m to posterior arch of atlas.
• Movements permitted at atlanto-occipital joint are:

1. Flexion & extension (nodding of head)
2. Lateral flexion (bending of neck)

Atlanto-axial joints

• There are three synovial joints b/w atlas & axis, one median & two lateral:

1. edian atlanto-axial joint:

2. Lateral atlanto-axial joints:

• These are plane synovial joints b/w lateral masses of atlas & upper facets of body of axis.
• The important ligament of these joints are:

1. Apical ligament
2. Alar ligament
3. Transverse ligament
4.  Membrane tectoria (is upward continuation of posterior longitudinal ligament)

• Transverse ligament forms the horizontal part of cruciform or cruciate ligament.
• Vertical part is formed by superior band of cruciate ligament (attached to occipit) & inferior band of cruciate ligament (attached to body of axis).
• Movements permitted at atlanto-axial joints are side to side rotation of head (looking towards right or left).

Joints below the level of axis

• All mobile presacral vertebrae (except atlas & axis) are articulating with each other by:
• Synovial joints b/w vertebral arches
• Cartilaginous joints b/w vertebral bodies

A) Joints b/w vertebral arches

• These are:

1. Facet joints (zygapophyseal joints):

• These joints are formed by superior & inferior articular facets of adjacent vertebrae.

2. Intervertebral syndesmosis:

• These are fibrous joints b/w vertebral arches where following ligaments connects adjacent vertebrae:-

1. Supraspinous ligament: b/w tips of spinous processes of adjacent vertebrae
2. Interspinous ligament: b/w two adjacent spinous processes from their roots to tips.
3. Ligamentum flavum: connects the laminae of adjacent vertebrae.
4. Intertransverse ligament: B/w two transverse processes of adjacent vertebrae.

B) Joints b/w vertebral bodies

Anterior longitudinal ligament:

• Attached to anterior margins of vertebral bodies.
• Anterior atlanto-occipital ligament is considered as continuation of anterior longitudinal ligament 

1. Posterior longitudinal ligament:

• Lies in vertebral canal & attached to posterior margins of vertebral bodies.
• Membrane tectoria is a continuation of posterior longitudinal ligament.
• It is one of the ligaments connecting the axis with occipital bone.

2. Intervertebral disc:

• It is a thick plate of fibrocartilage which has  parts:

1. Central nucleus pulsosus, remnant of notochord
2. Peripheral annulus fibrosus develops from sclerotome ventral). Disc is an avascular structure.
3. Prolapse of intervertebral disc is most common at lumbosacral region (L5,S1) followed by L4 L5 levels. 

Curvatures of vertebral column

• During fetal life & at birth the vertebral column shows a continuous curvature with the concavity direct forwards.
• In fully developed spine, thoracic & sacral curvatures are ‘concave forwards’ & hence are called primary curvatures.
• Cervical & lumbar curves are convex forwards (or concavity backwards) & are termed as ‘secondary curvatures’ because they develop after birth.
• Cervical curvature develops 3-4cmonths after birth & lumbar curvature develops 12-15 months after birth.