What is the function of atlanto-occipital joint?
The atlanto-occipital joint (O-C1) acts as a pivot for the flexion/extension motion of the cranium, with 13 degrees average flexion/extension and 8 degrees lateral bending, thus allowing only a few degrees of axial rotation.
What type of joint is atlanto-occipital joint?
The atlanto-occipital articulation (also known as the C0-C1 joint/articulation) is comprised of a pair of condyloid synovial joints that connect the occipital bone (C0) to the first cervical vertebra (atlas/C1).
What is aa instability?
Atlanto-axial instability (AAI) is a condition that affects the bones in the upper spine or neck under the base of the skull. The joint between the upper spine and base of the skull is called the atlanto-axial joint. In people with Down syndrome, the ligaments (connections between muscles) are “lax” or floppy.
Which class of synovial joint is the most stable Why which is least stable and why?
– Plane joints are the most stable as they have the least range of motion.
What movement does the atlas allow?
The atlas and axis are specialized to allow a greater range of motion than normal vertebrae. They are responsible for the nodding and rotation movements of the head. The atlanto-occipital joint allows the head to nod up and down on the vertebral column.
What is atlantoaxial dislocation?
Atlantoaxial dislocation refers to a loss of stability between the atlas and axis (C1–C2), resulting in loss of normal articulation (Fig. 1). The atlantoaxial joints can lose stable articulation from traumatic, inflammatory, idiopathic, or congenital abnormalities.
How is atlantoaxial instability measured?
The ADI is determined by measuring the distance between the posterior edge of the anterior arch of C1 and the anterior edge of the dens. A value less than three mm is considered normal in adults and a value less than 4.5 mm is considered normal in children.
Which joint is considered the most stable?
The most stable joints are sutures. Sutures are synarthrodial joints which means that they are immovable. These joints are seen where the bones of the…
What is the most unstable synovial joint?
Ball and Socket Joints: These joints allow for the greatest range of motion. The joint involves a ball fitting into a concave surface. Because these joints allow for more motion, they are at greater risk for instability.
What does atlanto occipital dislocation mean?
Atlanto-occipital dislocation involves complete disruption of all ligamentous relationships between the occiput and the atlas. Death usually occurs immediately from stretching of the brainstem, which causes respiratory arrest. Radiographically, disassociation between the base of the occiput and the arch of C1 is seen.
How does atlanto occipital dislocation happen?
When severe flexion or extension exists at the upper cervical level, atlanto-occipital dislocation may occur. Atlanto-occipital dislocation involves complete disruption of all ligamentous relationships between the occiput and the atlas.
What is the difference between axis and atlas?
The atlas is the first cervical (neck) vertebra which is just under the head; it is named for Atlas, the Greek god who supported the world on his shoulders. The axis is the second cervical vertebra; it has what is called the odontoid process about which the atlas rotates.
How is atlantoaxial instability treated?
Posterior cervical spinal fusion can successfully treat symptomatic AAI in many cases. Surgery is most successful for treating patients with ligamentous instability and less successful in treating patients with osseous instability. Optimal results have been obtained in patients with severe pain and mild myelopathy.
What type of joint is the atlanto occipital joint?
Atlanto-occipital joint. Anterior atlantoöccipital membrane and atlantoaxial ligament. Posterior atlantoöccipital membrane and atlantoaxial ligament. The atlanto-occipital joint ( articulation between the atlas and the occipital bone) consists of a pair of condyloid joints. The atlanto-occipital joint is a synovial joint .
What is the atlanto-occipital articulation?
The atlanto-occipital articulation (also known as the C0-C1 joint / articulation) is comprised of a pair of condyloid synovial joints that connect the occipital bone (C0) to the first cervical vertebra (atlas/C1).
What is the function of the atlantoaxial joint?
The Atlanto-Occipital Joint (AO) is formed by the union of the Skull (C0) and the C1 bone. The Atlanto-Occipital Joint (AO) is composed of cartilage, ligaments, muscles and tendons. The principal function of the Atlantoaxial Joint is rotation.
What is the function of the atlantooccipital capsule?
The capsules of the atlantooccipital articulation surround the condyles of the occipital bone, and connect them with the articular processes of the atlas: they are thin and loose. The movements permitted in this joint are: