Introduction to Sacrum Flashcards
lumbarization of the sacrum
when S1 and S2 do NOT fuse
sacralization of the lumbar spine
when L5 fuses to S1
superior aspect
base
inferior aspect
apex
anterior surface
concave
posterior surface
convex
medial row/crest
fusion of sacral articular processes
lateral rows/crests
fusion of sacral transverse processes
inferolateral angle (ILA)
curve at the end of the lateral rows
sacral canal
contains the cauda equina and for bilateral sacral foramina for the ventral and dorsal rami of the sacral spinal nerves S1-S4
sacral hiatus
defect near the apex, where the lamina failed to close
coccyx
made up of 4 vertebrae
lowest part of the spinal column
coccyx attaches to the sacral apex via the sacrococcygeal joint
ganglion impair = where right and left sympathetic chains join rests on anterior aspect of the coccyx
palpatory bony landmarks
sacral base
sacral sulci
ILA
sacral sulci
to bilateral palpable grooves medial and slightly superior to the PSIS
sacrotuberous ligament
attaches sacrum to ischial tuberosity
works w/ sacrospinous ligament stabilize anterior motion, preventing posterior superior rotation
sacrospinous ligament
attaches sacrum to ischial spine
works w/ sacrotuberous ligament stabilize anterior motion, preventing posterior superior rotation
iliolumbar ligament
attaches 4th and 5th lumbar vertebra to iliac crests
stabilizes posterior motion restricting anterior motion of of L4/L5
upper part blends in with the sacroiliac ligament
primary - intrinsic m of the pelvic diaphragm
levator ani group pubococcygeus m puborectalis m iliococcygeus m cocygeus mm
secondary - mm considered to have partial attachment to the true pelvis
rectus abdominis transverse abdominis internal and external oblique quadratus lumborum also m of the posterior anterior and medial compartments of the lower extremity
dura mater
layers of fibrous CT
tension in this CT has a direct effect on the cranial and sacral bone motion which it attaches to
dural connections b/w cranium and sacrum (C1 and C2 to S2)
force closure
holding an object by pressure on the sides
created by mm, lig, and fascia surrounding the SI joint
form closure
stacking or the use of a roman arch as a self supporting structure
the sacrum acts as the keystone of the arch being wedged b/w iliums
superior
respiratory - axis for respiratory motions as well as nutation and counternutation from SBS flexion/extension
middle
postural or sacroiliac axis for flexion/extension in sitting and standing
inferior
iliosacral axis for rotation of the iliums on the sacrum
at the level of the inferior pole of the lower sacral articulation
oblique axes of motion
where dynamic/torsional motion occur
named for the cephalad side
respiratory motion
around superior transverse axis
with inhalation sacral base moves posteriorly while sacral apex moves anteriorly
decreased lumbar lordosis
w/ exhalation sacral base moves anteriorly while sacral apex moves posteriorly (increased lumbar lordosis)
postural motion
in standing and seated positions
around middle transverse axis
flexion and extension corresponding to anatomical nomenclature same terminology as used with the spine
postural motion - flexion
forward bending
sacral base moves anterior sacral apex moves posterior
postural motion - extension
backward bending
sacral base moves posterior, apex moves anterior
craniosacral flexion (couternutation)
influenced by the dura the sacral base moves posteriorly and the apex moves anteriorly
craniosacral extension (nutation)
sacral base moves anteriorly and the apex moves posteriorly
dynamic motion
occurs when walking
occurs around oblique axes
sacral base moves forward on one side then the other side around the oblique axes
as this occurs the innominates are constantly rotation in opposite directions to one another (one rotates anteriorly, the other posteriorly)
