Atypical Cervical Vertebrae: C1/Atlas Flashcards
What is the name of the first cervical vertebrae?
atlas
What features are lacking at C1?
vertebral body,pedicles, a spinous process and the intervertebral disc
What muscle attaches to the anterior arch of C1?
longus colli
What ligaments will attach to the anterior arach of C1?
the anterior longitudinal ligament, anterior atlanto-occipital and anterior atlanto-axial ligaments
What is observed on the back of the anterior arch of C1?
the fovea dentis
What joint classifications are observed on the anterior arch C1?
fibrous (amphiarthrosis) syndesmosis joint and synovial pivot (diarthrosis trochoid) joint
What is the morphology of the superior articular facet?
they are elipitcal, closer together in front and often demonstrate an elevation subdividing the facet surface into two seperate surfaces
What is the oreintation of the superior articular facet of C1?
backward, upward and medial (BUM)
What is the joint classificaiton 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, and 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 is the contribution of the posterior arch to the circumference of C1?
about forty percent
What part of C1 represents the spinous process?
posterior tubercle of the posterior arch
What is the distance from the posteior tubercle of the posterior arch to the skin in each gender?
male: 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 attaches to the arcuate rim of C1?
the posteior atlanto-occiptal ligament
Ossification of the free margin of the posteior atlanto-occipital ligament results in which atypical bone classifiction?
accessory bone
What is the earlisest age of development where ossification of the anterior free margin of the posterior antlanto-occipital ligament was observed?
about age seven years old
What may be formed by ossification of the anterior free margin of the posterior atlanto-occipital ligament?
a partial 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
What is the general range of incidence of posticulus 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 ponticus versus an incomplete ponticulus posticus?
the incidence of a complete ponticulus posticus is about fifty percent; the incidence of an incomplete ponticulus posticus may be as high as forty-one percent?
What joint classification(s) may be observed on the posterior arch of C1?
fibrous (amphiarthrosis) syndesmosis joint
What is the location of the “zygapophysis” realtive to the atlanto-occipital and atlanto-axial intervertebral foramina?
it forms part of the anterior boundary of the intervertebral foramen in both cases
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 of C1 are absent?
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, obiquus 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 posterior 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 opening is identified when a complete lateral bridge is formed?
the retrotransverse foramen
What are the possible conents of the retrotransverse foramen?
the vertebral artery, a branch from the subocciiptal nerve and veins communicating with the venous sinuses of the neck
Which of the ponticles (bridges) of atlas is only observed in humans?
lateral bridges
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 mm
females: 72 mm
What is the distance from the posterior tubercle of the transverse process of C1 to the skin for each gender?
a little over 30 mm for both genders
What joint classifications are observed at C1?
fibrous (amphiarthrosis) syndesmosis joint, synovial (diarthosis) ellipsoidal joint, synovial pivot (diarthrosis trochoid) joint and synovial plane (diarthrosis arthodia) joint
How many synovial joint surfaces are observed at C1?
five
What synovial joint surfaces are aboserved at C1?
two superior articular facets, two inferior articular facets and the fovea dentis
