Atlanto-axial joint

Source: Wikipedia, the free encyclopedia.
Atlanto-axial joint
skeletal
Identifiers
Latinarticulatio atlantoaxialis mediana, articulatio atlantoaxialis lateralis
MeSHD001268
FMA25524
Anatomical terminology]

The atlanto-axial joint is a joint in the upper part of the neck between the atlas bone and the axis bone, which are the first and second cervical vertebrae. It is a pivot joint.

Structure

The atlanto-axial joint is a joint between the atlas bone and the axis bone, which are the first and second cervical vertebrae. It is a pivot joint.

There is a

transverse ligament of the atlas
.

Lateral and median joints

There are three atlanto-axial joints: one median and two lateral:[1]

  • The median atlanto-axial joint is sometimes considered a triple joint:[2]
    • one between the posterior surface of the
      odontoid process
    • one between the anterior surface of the ligament and the back of the odontoid process
  • The lateral atlantoaxial joint involves the
    arthrodial
    or gliding joint.

Ligaments

The ligaments connecting these bones are:

Capsule

The atlantoaxial articular capsules are thick and loose, and connect the margins of the lateral masses of the atlas with those of the posterior articular surfaces of the axis.

Each is strengthened at its posterior and medial part by an accessory ligament, which is attached below to the body of the axis near the base of the

odontoid process
, and above to the lateral mass of the atlas near the transverse ligament.

Clinical significance

Because of its proximity to the brain stem and importance in stabilization, fracture or injury to the atlanto-axial joint can cause serious problems. Common trauma and pathologies include (but are not limited to):

The dens: significant depression on the skull can push the dens into the brainstem, causing death. The dens itself is vulnerable to fracture due to trauma or ossification.

Transverse ligament: Should the

transverse ligament of the atlas fail due to trauma or disease, the dens is no longer anchored and can travel up the cervical spine, causing paralysis. If it reaches the medulla
death can result.
Alar ligaments
: stress or trauma can stretch the weaker alar ligaments, causing an increase in range of motion of approximately 30%.

Posterior atlanto-occipital membrane: genetic traits can sometimes result in ossification, turning the groove into a foramen.

Arthritis

Conservative management is usually effective, involving analgesics.[4] Surgery may be used in severe cases, and may have good outcomes.[4]

Abnormal widening

Normal atlanto-dental joint on projectional radiography.

A widening of the atlanto-axial joint, as measured between the posterior surface of the

odontoid process, indicates an injury to the transverse atlantal ligament.[5] Normally, this atlanto-dental distance is less than 2 mm, sometimes a maximum of 3 mm is accepted in men and 2.5 mm in women.[5]

References

  1. ISBN 978-3-13-114361-7
    . Retrieved 17 June 2010.
  2. ISBN 978-1-60831-384-6
    . Retrieved 17 June 2010.
  3. ^ "Lateral atlantoaxial joint". Medcyclopaedia. GE. Archived from the original on 2012-02-05.
  4. ^
    ISSN 1432-5195
    .
  5. ^
    PMID 17893223
    .

Bibliography

  • Dalley, Arthur F; Moore, Keith L. Clinically Oriented Anatomy Fourth Edition. Baltimore. Lippincott Williams & Wilkins, 1992.
  • Saladin, Kenneth S. Anatomy &Physiology: the Unity of Form and Function. New York. McGraw Hill, 2007.

External links
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