Atypical Cervical Vertebrae: C1/Atlas Flashcards
What is the name of the first cervical vertebra?
atlas
What features are lacking at C1?
vertebral body, pedicles, a spinous process and the intervertebral disc
What osseous modification is observed to the front of the anterior arch of C1?
the anterior tubercle
What muscle attaches to the anterior arch of C1?
longus colli
What ligaments will attach to the anterior arch of C1?
the anterior longitudinal, anterior atlanto-occipital and anteior atlanto-axial ligaments
What is observed on the back of the anterior arch of C1?
the fovea dentis
What is the morphology of the superior articular facet of C1?
they are elliptical, closer together in front and often demonstrate an elevation subdividing the facet surface into two separate surfaces
What is the orientation of the superior articular facet of C1?
backward, upward, medial (BUM)
What is the joint classification of the atlanto-occipital zygapophysis?
synovial (diarthrosis) ellipsoidal joint
What are the morphological characteristics of the inferior articular facet of C1?
asymmetrical, slightly concave or flattened
What is the orientation of the inferior articular facet of C1?
backward, medial, downward (BMD)
What is the name of the rounded elevation on the medial aspect of the lateral mass of C1?
tubercle for the transverse atlantal ligament
What muscles attach to the lateral mass of C1?
levator scapula, splenius cervicis and rectus capitis anterior
What part of C1 represents the spinous process?
posterior tubercle of the posterior arch
What is the distance from the posterior tubercle of the posterior arch to the skin in each gender?
males: about fifty millimeters; females: about thirty-seven millimeters
What attaches to the posterior tubercle of the posterior arch of C1?
rectus capitis posterior minor muscle and ligamentum nuchae
What superior surface modifications of the posterior arch of C1 are present?
groove/sulcus for the vertebral artery and arcuate rim
What are the attachment sites of the posterior atlanto-occipital ligament?
it is attached to the arcuate rim of the posterior arch of atlas, to the superior articular process of the lateral mass of atlas and to the posterior margin of the foramen magnum of the occipital bone
What is the earliest age of development where ossification of the anterior free margin of the posterior atlanto-occipital ligament was observed?
about age 7 years old
Based on the amount of ossification of the anterior free margin of the posterior atlanto-occipital ligament what structures will form?
an incomplete ponticulus posticus or a complete ponticulus posticus
What other name may be used to identify a ponticulus posticus?
Kimmerle’s anomaly
What names are given to the opening formed by the ponticulus posticus?
arcuate foramen or retroarticular canal
Ponticulus posticus has observed in what ethnic populations?
all ethnic populations studied thus far
Wht is the general range of incidence of ponticulus posticus in the populations studied?
1%-41%
What is the gender bias now associated with ponticulus posticus?
female
What is the incidence of a complete ponticulus posticus versus and incomplete ponticulus posticus?
uthe incidence of a complete ponticulus posticus is aboue fifteen percent; the incidence of an incomplete ponticulus posticus may be as high as forty-one percent
What is observed on the undersurface of the posterior arch of C1?
“inferior vertebral notch” and an attachment site for the posterior atlanto-axial ligament
What is the location of the “zygapophysis” relative to the atlanto-occipital and atlanto-axial intervertebral foramina?
it forms part of the anterior boundary of the intervertebral foramen in both cases
What is the general appearance of the transverse process of C1?
triangular
What are the osseous parts of the transverse process of C1?
costal element, posterior tubercle, true transverse process
What osseous parts of the transverse process are absent at C1?
anterior tubercle and costotransverse bar
What muscles attach to the transverse process of C1?
rectus capitis anterior, rectus capitis lateralis, middle scalene, levator scapula, splenius cervicis, obliquus capitis superior, obliquus capitis inferior and intertransversarii muscles
What suboccipital muscles are known to have fascial projections attaching to the spinal dura?
rectus capitis posterior minor, rectus capitis posteior major, obliquus capitis inferior
What are the connections between suboccipital muscles and the spinal dura called?
myodural bridges
What are the lateral bridges of atlas connected to?
the lateral mass and the transverse process of atlas
What forms of the lateral bridges are observed in the population?
incomplete lateral bridges and complete lateral bridges
What opening is identified when a complete lateral bridge is formed?
the retrotransverse foramen
What are the possible contents of the retrotransverse foramen?
the vertebral artery, a brach from the suboccipital nerve and veins communicating with the venous sinuses of the neck
What is observed in the transverse foramen of C1?
vertebral artery, vertebral venous plexus, postganglionic sympathetic motor nerve fibers
What is the gender variation for measurements of the transverse diameter of C1?
males: 78 millimeters and females: 72 millimeters
Is there gender variation for the distance from the posterior tubercle of the transverse process of C1 to the skin?
not a significant difference
What is the distance from the posterior tubercle of the transverse process of C1 to the skin for each gender?
a little over 30 millimeters for both males and females
How many synovial joint surfaces are observed at C1?
five
What synovial joint surfaces are observed at C1?
two superior articular facets, two inferior articular facets and the fovea dentis
