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, spinous process and intervertebral disc
what is thought to represent the pedicle at C1?
anterior arch
what muscle attaches to the anterior arch of C1?
longus colli
what ligaments will attach to the anterior arch of C1?
anterior longitudinal, anterior atlanto-occipital and anterior atlanto-axial ligaments
what is observed on the back of the anterior arch of C1?
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 surfaces into two separate surfaces
what is the orientation of the superior articular facet of C1?
backward, upward, medial (BUM)
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 is the distance from the posterior tubercle of the posterior arch to the skin in each gender?
males: about 50 millimeters; females: about 37 millimeters
what attaches to the posterior tubercle of the posterior arch of C1?
rectus capitis posterior minor muscle and ligamentum nuchae
what attaches to the arcuate rim of C1?
posterior atlanto-occipital ligament
ossification of the free margin of the posterior atlanto-occipital ligament results in which atypical bone classification?
accessory 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
what may be formed by ossification of the anterior free margin of the posterior atlanto-occipital ligament?
partial or 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 ponticulus posticus in the populations studied?
1%-41%
what is the gender bias now associated with ponticulus posticus?
female
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 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 captitis 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 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?
lateral mass and the transverse process of atlas
what opening is identified when a complete lateral bridge is formed?
retrotransverse foramen
what are the possible contents of the retrotransverse foramen?
vertebral artery, a branch from the suboccipital 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 millimeters and females: 72 millimeters
what is the distances 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
what joint classifications are observed at C1?
fibrous (amphiarthrosis) syndesmosis joint, synovial (diarthrosis) ellipsoidal joint, synovial pivot (diarthrosis trochoid) joint and synovial plane (diarthrosis arthrodia) joint
how many synovial joint surfaces are observed at C1?
5
what synovial joint surfaces are observed at C1?
two superior articular facets, two inferior articular facets and fovea dentis
