Intro to Sacrum DSA Flashcards
Landmarks of the anterior sacrum?
Anterior Sacral Foramina
Sacral Promintory
Transverse lines
Sacral Apex
Base
Sacral Ala
Landmarks of the posterior Sacrum?
auricular surface of the SI joints.
spinous processes of S1-S5
Posterior Sacral Foramen.
Inferior Lateral Angle
Sacral canal (near the base) –> goes all the way to the sacral hiatus
What are the lines of the posterior sacrum?
`Median Sacral Crest
Intermediate Sacral Crest
Lateral Sacral Crest
what are the edges of the sacral hiatus called?
Sacral Comu
Coccyx has what muscular attachments?
Coccygeus M.,
Gluteus Maximus M.
Levator Ani
How is the sacrum formed?
what bones are part of the sacrum?
when does the arch/costal part fuse?
what about this and the rest of the sacrum?
when do the plates fuse and in what direction?
What about the dura, where is that at?
formed by the union of 5 modified vertebrae (35 ossification centers)
Costal elements, vertebral arch, Centrum, lateral epiphysis
bony arch + costal part between 2 and 5
they unite with the centrum at age 8.
epiphyseal plates fuse after puberty, beginning with lowest segments and working up.
the dura attaches at the OA/AA and it comes down through the whole spinal column and attaches at the posterior portion of the body of S2!
What are the bony articulations of the sacrum?
5th lumbar (superiorly)
coccyx (inferiorly)
Innominate bones (Auricular surface)
What are the joints of the sacrum?
Right and left SI joints
L5-S1 intervertebral disc
Sacrococcygeal joint.
After puberty, what happens to the SI joint in males? females?
2nd decade?
3rd decade? what about males?
4th decade? Males?
Males = well developed and strong
females = less developed allowing mobility for childbirth
second decade = crescent shaped ridge develops along the iliac surface that interdigitates with the depression on the sacral side.. adding stability and limiting mobility
the ridge becomes more pronounced decreasing ROM… males might have degenerative changes
males: degenerative changes on the sacral side.. also can see fibrous ankylosis that may further limit it.
Where is the SI joint located?
about at S2
Where is the apex of the SI joint?
what kind of joint is it?
at the anterior aspect, where the two “arms” meet up.
diarthrodial joint –> because synovial fluid and matching articular surfaces
it’s different than any other joint because it’s hyaline cartilage and the other part is fibrocartilage.
What’s to note about the iliac surface of the SI joint?
it’s fibrous posteriorly, giving rise to the interosseous ligaments
fibrocartilage
What are the ligaments of the SI joint?
posteriorly what does it blend with?
anteriorly what does it blend with?
posterior sacroiliac ligament –> inferior fibers from the 3rd and fourth sacral sacral segments, ascend to the PSIS and posterior end of the internal lip of the iliac crest.
STL and the thoracolumbar fascia.
Anterior Sacroiliac ligament –> connects the 3rd sacral segment to the lateral side of the pre-auricular sulcus.
blends with the iliolumbar ligament.
what’s thicker, anterior or posterior sacroiliac ligament?
posterior
Interosseous sacroiliac ligament?
major bond between the bones, filling the irregular space posterosuperior to the joint
these are the straps going from the SI joint to the sacrum posteriorly
What is long dorsal SI ligament?
what does it have a relationship with?
connects the PSIS to the lateral aspect of the 3rd and fourth sacral segment
erector spinae
posterior layer of thoracolumbar fascia
sacrotuberous ligament
What is counternutation?
when can this happen?
this is where the Long Dorsal SI ligament becomes stretched when the sacrum is rotated in a posterior manner relative to the ilium.
early stages of pregnancy… aging and degenerative changes.. backwards torsion or unilateral/bilateral sacral extensions
what’s on the anterior aspect of the sacrospinous ligament?
Coccygeus M.
Where is the sacrospinous ligament located?
sacrotuberous ligament?
ischial spine to lateral margins of the sacrum where it blends with the sacrotuberous ligament
runs from lower sacral tubercles to ischial tuberosity
what attaches to the STL?
some of the gluteus Maximus muscle and the tendon of the biceps femoris.
As we react to gravity, what is helping to stabilize us from going too far posterior?
Sacrospinous and STL stabilize the posterior rotation of the sacral. apex around the transverse axis
What’s connecting to the superior sacrum/iliac crest region?
Inferior/Inferolateral region?
Longissimus, Iliocostalis, Latissimus Dorsi, multifidis, interspinalis lumborum,
Piriformis, External Anal Sphincter, Coccygeus, Levator Ani
Action of the piriformis?
externally rotates the thigh when the hip joint is flexed; assists in holding the femoral head in the acetabulum
Sciatic nerve relationship to the piriformis?
piriformi hypertonicity can cause sciatic.
so there is referred pain down the posterior thigh.
Nervous system of the pelvis? include their spinal lengths too
Lumbar Plexus (L1-4)
Sacral Plexus (L5-S4)
Coccygeal Plexus (S5-Coccygeal nerve)
Inferior mesenteric ganglion, superior hypogstric ganglion, ganglion impar.
What are the couple forces that are keeping the sacrum against those innominate?
Form closure = dealing with the specific properties of the articular surfaces of the SIJ. –> size, shape, and attitude to fit together.
Force closure = compression produced by body weight, muscle action, and ligament force, and gravity
What do the postural muscles act on as the SI joint?
like seat belts
helps with the SI joint stability.
What are the 3 transverse axes?
most superior = Respiratory Axis (also called Superior Transverse (ST) axis) –> attaches posterior to the point of attachment of the dura at S2
middle transverse axis (MT) = Postural –> anterior S2
IT (inferior transverse axis) (movement of ilia on sacrum)–> inferior auricularr surface of S3
what allows movement along the Superior Transverse axis?
where is it located?
sacrum moves around this one through inhalation and exhalation
posterior to the point of attachment of the dura at S2
What allows movement along the middle transverse axis
nutation and counternutation in the standing position
anterior aspect of S2
what allows movement along the IT axis?
Ilia movement on the sacrum
What happens to the sacrum if you flex the lumbar spine?
extend the lumbar spine?
you extend the sacrum
flex the sacrum
this is all due to compensation.
Again, what is Counternutation?
nutation?
when the base of the sacrum moves posteriorly and the apex moves anteriorly
base moves anteriorly, apex moves posteriorly
nutation and counternutation and flexion / extension of the sacrum
counter = extension
nutation = flexion
What happens if you have a compression on the right occipital condyle?
causes a side bending sacrum to the right, lifting and elevating the left side.
“nervous” infants have what?
76% had a fixed extension sacrum and 49% had a flexion cranial base.
Lumbarization?
first sacral segment becomes like an additional lumbar vertebra articulating with the second sacral segment.
Lumbarize S1 means it’s not fusing with S2 so it looks like an extra vertebra
Sacralization?
incomplete separation and differentiation of the 5th lumbar vertebra.. so the 5th is connected to S1.
Batwing deformity?
if the transverse processes of L5 are atypically large, causes pseudoarthrosis with the sacrum and or ilium
can be bilateral or unilateral
