Sacrum Flashcards
What is the typical number of segments that unite to form the adult sacrum?
5
What is the generic size of the first sacral vertebral body from the base view?
transversely broad
What is the generic shape of the first sacral vertebral body from the base view?
reniform or kidney-shaped
What characteristics of S1 vertebral body and pedicle are similar to L5?
- On base view, the S1 TVP and costal element originate from the vertebral body, pedicle, and lamina-pedicle junction to form the sacral ala.
- In addition, the vertebral body of S1 is more wedge-shaped on lateral view with a much greater anterior height than posterior height.
How many synovial joint surfaces are present at the S1 vertebral body?
none
What is the outline of the S1 vertebral foramen and the sacral spinal canal from the base view?
triangular
Which is the greatest diameter of the vertebral foramen of the sacrum?
transverse
What part of the PNS is present in the S1 vertebral foramen?
cauda equina
What forms the sacral ala?
- costal element: anterior 2/3
- true transverse process: posterior 1/3
What is the joint classification for the spongy bone-intervertebral disc articulation?
cartilaginous (amphiarthrosis) symphysis
What is the joint classification for the longitudinal lig. attachments?
fibrous (amphiarthrosis) syndesmosis
How many fibrous (amphiarthrosis) syndesmosis joint surfaces are present on the S1 vertebral body?
4
What fibrous (amphiarthrosis) syndesmosis joint surfaces are present on the S1 vertebral body?
- superior and inferior anterior longitudinal lig. attachment sites
- superior and inferior posterior longitudinal lig. attachment sites
How many joint surfaces are present on the vertebral body of S1?
5
How many cartilaginous (amphiarthrosis) symphysis joint surfaces on present on the S1 vertebral body?
1
What muscle may attach to the S1 vertebral body?
psoas major
What is the orientation of the pedicle of S1?
primarily posterior
At what location on S1 vertebral body will the pedicle attach?
to the upper third or half of the vertebral body
What surface feature is located at the upper margin of the pedicle?
superior vertebral notch
Which spinal nerve will be accommodated on the superior vertebral notch of S1?
L5 spinal nerve
Which spinal nerve will be accommodated on the inferior vertebral notch of S1?
S1 spinal nerve
What is the reported angulation of the S1 articular facets?
they lie vertically in the coronal plane
What is the joint classification for the S1 zygapophysis?
synovial plane (diarthrosis arthrodia)
How many zygapophyseal joints are present on the S1 vertebra?
2
What is the position of the sacral zygapophysis in children?
lies in the coronal plane
What is the position of the sacral zygapophysis in adults?
lies in the coronal plane for L5/S1
What is the orientation of the S1 superior articular facet?
- backward, upward, medial (BUM)
- typically concave
What is the name given to the projection on the S1 superior articular process?
mammillary process
What muscles will attach to the sacral mammillary processes?
multifidis
From anterior view, the intervertebral discs of sacrum will be replaced by what feature?
transverse ridges
What is the name given to the openings that transmit the ventral sacral nerve rami?
anterior/ventral sacral foramina or ventral pelvic foramina
What is the size relationship between ventral and dorsal sacral foramina?
ventral sacral foramina are larger
What part of the sacral ala continues along the ventral surface of sacrum to about S4?
the costal element
What is the name of the region of bone lateral to the vertebral body of S5?
true transverse process
What constitutes the lateral mass of sacrum?
the bony region lateral to the ventral sacral foramina
The ventral surface of sacrum is curved in what direction?
it is curved posteriorly and appears concave
The dorsal surface of sacrum is curved in what direction?
it is curved posteriorly and appears convex
An imaginary line drawn along the dorsal midline of sacrum is identified as what?
median sacral crest
An imaginary line drawn from the superior articular process of S1 to the sacral cornu will form what feature??
intermediate sacral crest
What muscles may attach to the spinous processes of sacrum?
- latissimus dorsi
- iliocostalis lumborum
- longissimus thoracis
What muscles may attach to the median sacral crest?
- latissimus dorsi
- iliocostalis lumborum
- longissimus thoracis
What features may be identified along the intermediate sacral crest?
- mammillary process of S1
- sacral cornu of S5
What does the sacral cornu represent?
the inferior articular process and facet of S5
What is the name of the inferior opening of the sacral spinal canal?
sacral hiatus
An imaginary line drawn from the TVP of S1 to the inferior lateral sacral angle will form what feature?
lateral sacral crest
What features may be identified along the lateral sacral crest?
- S1 transverse tubercle
- sacral tuberosity of S2
- transverse tubercles of S3, S4, and S5
What is the sacral tuberosity?
the enlarged transverse tubercle of S2
What is the name of the joint formed by the sacral tuberosity?
accessory sacro-iliac joint
What feature is associated with the transverse tubercle of S5?
the inferior and lateral (inferolateral) sacral angle
What muscles may attach to the TVPs of sacrum?
- multifidis
- iliocostalis lumborum
What muscles may attach to the lateral sacral crest?
- multifidis
- iliocostalis lumborum
What muscle is said to attach to the dorsal surface of sacrum?
iliacus
What feature is identified on the lateral surface of S1-S3?
auricular surface
What bone articulates with the auricular surface of sacrum?
the ilium of the innominate bone
What classification of joint is formed by the auricular surface of sacrum?
synovial plane (diarthrosis arthrodia)
What feature does the anterior surface of the superior epiphyseal rim of S1 form?
sacral promontory
The continuation of the anterior longitudinal lig. below S3 forms what lig.?
the anterior sacrococcygeal lig.
The continuation of the posterior longitudinal lig. below S3 forms what lig.?
the deep posterior sacrococcygeal lig.
What lig. is attached to the sacral hiatus?
superficial posterior sacrococcygeal lig.
What forms the apex of sacrum?
S5 vertebral body
What synovial joint classification is present at sacrum?
synovial plane (diarthrosis arthrodia)
What synovial joint surfaces are present at sacrum?
- two superior articular facets
- two auricular surfaces
What joint classifications are typically present at sacrum?
- fibrous (amphiarthrosis) syndesmosis
- synovial plane (diarthrosis arthrodia)
- cartilaginous (amphiarthrosis) symphysis
What forms the posterior boundary for the fifth sacral spinal nerve intervertebral foramen?
- sacral cornu
- coccygeal cornu
- superficial posterior sacrococcygeal lig.
- intervertebral disc
What forms the anterior boundary for the fifth sacral spinal nerve intervertebral foramen?
- vertebral body S5
- vertebral body Co1
- deep posterior sacrococcygeal lig.
- intervertebral disc
What is the homolog for the ligamentum flavum at S5?
superficial posterior sacrococcygeal lig.
What forms the inferior boundary for the spinal canal?
the union of the superficial posterior and deep posterior sacrococcygeal lig.
What lig. is formed by the union of the superficial posterior sacrococcygeal and deep posterior sacrococcygeal lig. at Co1?
posterior sacrococcygeal lig.
What lig. is a homolog of the intertransverse lig. at S5?
lateral sacrococcygeal lig.
What lig. divides the sciatic foramen into the greater and lesser sciatic foramina?
sacrospinous lig.
Which lig. has a broad attachment along the lateral margin of sacrum and coccyx and then attaches to the ischial tuberosity?
sacrotuberous lig.
What lig. represents a thickening of the fibrous capsule of the sacro-iliac joint?
anterior sacro-iliac lig.
What lig. is the strongest of the sacro-iliac lig. and is penetrated by the dorsal rami of the sacral spinal nerves?
interosseous sacro-iliac lig.
Which lig. will attach the intermediate sacral crest of S1, lateral sacral crest of S2 to the posterior superior iliac spine?
short posterior sacro-iliac lig.
Which lig. attaches the lateral sacral crest of S3 and S4 to the posterior superior iliac spine?
long posterior sacro-iliac lig.
What is the homolog for the superior articular process and facet at Co1?
coccygeal cornu
What is the homolog for the capsular lig. at S5?
intercornual lig.
