TRANSITION ZONES OF THE VERTEBRAL COLUMN - Transition zone characteristics Flashcards
What are the transition zones of the vertebral column?
occipitocervical, cervicothoracic, thoracolumbar, lumbosacral, and sacrococcygeal zones
What are the possible transition zone - segmental combinations?
cervicalization of occiput, occipitalization of C1
dorsalization of C7, cervicalization of T1
lumbarization of T12, dorsalization of L1
sacralization of L5, lumbarization of S1
coccygealization of S5, sacralization of Co1
What is/are the characteristics of cervicalization of occiput?
an increase in occipital bone size, formation of new or larger lines, on the occipital bone
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% to 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 forms between the odontoid process ossification centers and the centrum of C2?
the subdental synchondrosis
Ossification between the odontoid process and centrum joint of C2 first appears at what age?
4 years old
A joint between the odontoid process and centrum of C2 is last identified at what age?
7 years old
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 the 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
What is the terminal ossicle?
a persistence beyond age 12 of the joint formed between the tip of the dens and odontoid process centers of ossification
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/are the characteristics of dorsalization of C7?
the addition of a rib and changes in superior articular facet orientation are typical
What is the incidence of rib-related changes following dorsalization of C7?
from one-half to two and one-half percent of the population
What is the gender bias suggested in dorsalization of C7?
female
What alteration in C7 facet orientation may accompany dorsalization?
the superior articular facet of C7 may change from back, upward, and medial (BUM) to that of a typical thoracic facet…back, upward, and lateral (BUL); the inferior articular facet is unchanged
What alteration in C6 facet orientation may accompany dorsalization?
C6 demonstrates a change in inferior articular facet orientation from forward, lateral, and downward (FoLD) to forward, medial, and downward (ForMeD) ; the superior articular facet is unchanged
What percent of the population may demonstrate thoracic-like features at C7?
up to 46%
What rib-related changes may accompany cervicalization of T1?
the first rib may decrease in mean relative length or become absent
What will result from fusion of a short rib to the T1 transverse process
the transverse foramen
What T1 facet orientation changes may accompany cervicalization?
the superior articular facet may change from back, upward, and lateral (BUL) to back, upward, and medial (BUM) ; the inferior articular facet is unchanged
What C7 facet orientation changes may accompany cervicalization?
the inferior articular facet may change from forward, medial, and downward (ForMeD) to forward, lateral, and downward (FoLD) ; the superior articular facet is unchanged
What is the incidence of cervicalization of Tq in the population?
up to 28%
What rib-related changes may accompany dorsalization of L1?
elongated bones shaped like ribs may appear
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?
the superior articular facet may change from concave, back, upward, and medial (BUM) to flat, back, upward, and lateral (BUL); the inferior articular facet is unchanged
What T12 facet orientation changes may accompany dorsalization?
the inferior articular facet may change from convex, forward, lateral, and downward (FoLD) to flat, forward, medial, and downward (ForMeD) ; the superior articular facet is unchanged
What is the gender bias associated with dorsalization of L1?
males are two to three times more affected
What rib-related changes may accompany lumbarization of T12?
a significant shortening of the mean relative length of 113mm of the twelfth rib or it becomes absent
What T12 facet orientation may accompany lumbarization?
the superior articular facet may change from flat, back, upward, and lateral (BUL) to concave, back, upward, and medial (BUM) ; the inferior articular facet is unchanged
What T11 facet orientation changes may accompany lumbarization?
the inferior articular facet may change from flat, forward, medial, and downward (ForMeD) to convex, forward, lateral, and downard (FoLD) ; the superior articular facet is unchanged
What unique characteristics of lumbarization of S1 were stressed in class?
squaring of the vertebral body of S1 and flaring of the sacral ala
What is squaring of the vertebral body of S1?
the S1 vertebral body has similar anterior and posterior heights, hence a lack of wedging
What is 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 is 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 is the incidence of variation within the sacrococcygeal region in the population?
up to 14%
What is characteristic of sacralization of Co1?
the premature fusion of Co1 to the sacrum
