Transition Zones Flashcards
What is/are the characteristics of occipitalization of C1?
The atlas may be partially or completely fused to the occiput
What is another way of implying occipitalization of C1?
Atlas Assimilation
What is the incidence of occipitalization of C1?
0.1% - 0.8%
When do the centers of ossification for the odontoid process first appear?
During the last trimester in utero
When do the bilateral ossification centers for the odontoid process fuse?
At or shortly after birth
What joint is formed between the odontoid process ossification centers and the centrum of C2?
Subdental Synchondrosis
Ossification between the odontoid process and centrum joint of C2 first appears at what age?
4
A joint between the odontoid process and centrum joint of C2 is last identified at what age?
7
What is the name given to the condition in which the joint formed between the odontoid process and centrum of C2 persists beyond age 7?
Os Odontoideum
What is the name given to the joint between the odontoid process and centrum of C2 which is still evident beyond age 7?
Persistent Subdental Synchondrosis
What is the name given to the joint formed between the tip of the dens and the odontoid process centers of ossification?
Tip of Dens Synchondrosis
At what age will the tip of the dens center of ossification appear?
Sometime in early adolescence
At what age will the tip of the dens fuse with the odontoid process?
Before age 12
If the joint formed between the tip of the dens and odontoid process centers of ossification persists beyond age 12, what is the condition called?
Terminal Ossicle
What is a basilar impression?
Persistence of the nonunion of the basilar and condylar parts of the chondrocranium such that the cartilage deforms due to the weight of the brain
What is a basilar invagination?
The upper cervical spine appears to be invaginated into the skull on x-ray analysis
What is the incidence of rib-related changes following dorsalization of C7?
From 1/2 to 2 and a 1/2 percent of the population
Do patients typically present with symptoms specific for dorsalization of C7?
No. They are typically asymptomatic
What is the gender bias suggested in dorsalization of C7?
Female
What alteration in C7 facet orientation may accompany dorsalization?
Superior Articular Facet of C7 may change from back, upward, and medial to that of a typical thoracic facet; back, upward and lateral.
The inferior articular facet is unchanged
What percent of the population many demonstrate thoracic like features at C7?
up to 46%
What T1 facet orientation changes may accompany cervicalization?
Superior articular facet may change from forward, medial and downward to forward, lateral and downward.
The inferior articular facet is unchanged
What is the incidence of lumbar ribs in the population?
Over 7% of the population demonstrates lumbar ribs
What L1 facet orientation changes may accompany dorsalization?
Superior articular facet may change from concave, back, upward and medial to flat, back upward and lateral
The inferior articular facet is unchanged.
What is the gender bias associated with dorsalization of L1?
Males are 2-3 times more affected
What T12 facet orientation changes may accompany lumbarization?
Superior articular facet may change from flat, back, upward and lateral to concave, back, upward and medial
The inferior articular facet is unchanged
What is the usual way of identifying the number of cervicals, thoracics, and lumbar vertebrae during imaging studies?
Identify the vertebrae with ribs– they will be thoracics
Those higher are cervicals and those lower are lumbars
What is the characteristic of lumbarization of S1?
The failure of synostosis between S1 and S2, squaring of the vertebral body of S1 and flaring of the sacral ala
What is the failure of synostosis between S1 and S2?
The segments do not completely fuse together
What is the squaring of the vertebral body of S1?
The S1 vertebral body has similar anterior and posterior heights, hence a lack of wedging
What is the flaring of the sacral ala?
The transverse process of the ala appears to elevate as though separating from the rest of the sacral ala
What articular facet changes, accompany lumbarization of S1?
None
What is the characteristic of sacralization of L5?
L5 may be partially or completely fused to the sacrum
What is the incidence of sacralization of L5 in the population?
41% to 85%
Which segment demonstrates the greatest morphological variation along the spine?
L5
What articular facet changes accompany sacralization of L5?
None
What is the incidence of variation within the sacrococcygeal region in the population?
Up to 14%
What is characteristic of sacralization of Co1?
Premature fusion of Co1 to the Sacrum
What is the characteristic of coccygealization of S5?
Seperation of S5 from sacrum and it’s premature fusion to Co1
