Sacrum/Coccyx (Quiz 2/Exam 2) Flashcards
The sacrum is considered false vertebra. Why?
it forms from 5 fused segments
The sacrum apex is an inferior trapezoid that transmits weight to the….
pelvis
What does the sacrum articulate with?
L5, coccyx, and L/R iliac portions of the coxae
Where is the base of the sacrum?
the top
What does the base of the sacrum articulate with?
inferior epiphysis and post zygopophyses of L5
What direction does the base of the sacrum face?
test q
anterosuperior in normal posture
The base of the sacrum has the superior epiphysis of S1, which is the ________IVD
23rd
Where is the sacral promontory?
anterior margin of the base of the sacrum
What is the chiropractic landmark in the sacrum?
base- looking for spondylolisthesis
What is the obstetrical landmark of the sacrum?
posterior pelvic inlet at the base of the sacrum (looking for baby to drop)
What are the features of sacral pre-zygopophyses?
-most inferior in the spinal column
-articulates with the L5 inferior articular surfaces
-also shows mammillary processes
What are the features of the sacral ala/wings?
-lateral masses of bone
-supports the lateral articular surfaces
-composed of both transverse and costogenic tissue
What are the features of sacral tuberosities (L/R)?
-posterolateral swellings on the superior alae
-impalpable under the PSISs
What are the sacral tuberosities (L/R) homologous to and articulate with?
test q
L5 transverses
What are the features of the sacral apex?
-inferior epiphysis of the S5 segment
-small, wide, oval articular facet
What does the apex of the sacrum articulate with?
coccygeal base
What are the features of the pelvic/ventral/anterior surface of the sacrum?
-smooth and concave
-in contact with pelvic viscera
-front of the kyphotic curve
-mini-concavities at each segment
-4 transverse ridges called intersegmental fusion lines
-4 pairs of anterior sacral foramina just lateral to the transverse ridges
-the foramina allow the passage of the anterior primary divisions of S1-S4 spinal nerves
What are the features of the dorsal surface of the sacrum? What is the dorsal surface homologous to?
-rough and convex
-many features that are homologous to arch processes
-homologous to fused vertebral arches
-median sacral crest is here
-4 distinct tubercles with inter-tubercular septa
-sacral hiatus
-sacral grooves
-intermediate articular crests (L/R)
-sacral cornua
-posterior sacral foramina (4 pairs)
-lateral sacral crests (L/R)
-lateral inferior angle of the sacrum
What is the median sacral crest of the dorsal surface homologous to?
S1-S4 SPs
Which sacral tubercle is the longest/largest?
1st sacral tubercle
Which sacral tubercle is the palpation landmark?
2nd sacral tubercle because its just median to the PSISs of the ilia
What are the features of the sacral hiatus on the dorsal surface?
-there is no 5th sacral tubercle, instead its the sacral hiatus
-its a gap in the posterior wall of S5
-its like a naturally occuring spina bifida
What does the sacral hiatus allow passage for?
test q
L/R S5 and Cc1 spinal nerves
What are the features of the sacral grooves (L/R) on the dorsal surface?
-just lateral to the median sacral crest
-shallow vertical valleys
-recessed laminae
What are the features of the intermediate/articular crests (L/R) of the dorsal surface?
-4 tubercles just lateral to the sacral grooves
-represents the post-zygopophyses of S1-S4 (test q)
-superior end= sacral pre-zygopophyses
What are the features of the sacral cornu on the dorsal surface?
-located at the inferior end of the intermediate sacral crest
-just lateral to the sacral hiatus
-rudimentary post-zygopophyses of S5
-articulates with the coccygeal cornua
What are the features of the posterior sacral foramina (4 pairs) of the dorsal surface?
-just lateral to the intermediate sacral crests
-passages for the posterior primary divisions of S1-S4 spinal nerves
-smaller and shallower than the anterior sacral foramina
What are the features of the lateral sacral crests (L/R) of the dorsal surface?
-prominent wavy ridges
-lateral to the posterior sacral foramina
-not composed of distinct tubercles
-superior end= sacral tuberosities
What is the lateral inferior angle of the sacrum on the dorsal surface?
sharp inferolateral angulation
What is the lateral inferior angle of the sacrum on the dorsal surface homologous to?
S5 transverses
What does the inferior angle of the sacrum on the dorsal surface articulate with?
rudimentary transverses of Cc1
What are the features of the lateral surface of the sacrum?
-also known as lateral articular or auricular surfaces
-auricular because it looks like an ear
-anteriorly convex, buckled oval
-very rough, irregular to increase stability
-rough bumpy inferior margin
-attachment for ligaments
-ends at the lateral inferior sacral ridges
What direction do the lateral surfaces (L/R) of the sacrum face?
test q
slightly posterolaterally
What do the lateral surfaces (L/R) of the sacrum articulate with?
test q
iliac auricular surfaces
What are the sexual differences in the sacrum?
Male
-narrower proportions
-larger S1 and sacral base
-larger auricular surfaces to increase stability
-smooth kyphotic curve
Female
-wider proportions
-smaller S1/sacral base
-smaller auricular surfaces that cover only S1/S2
-increases SI joint mobility to facilitate childbirth
-decreases stability due to lower average female weight
What is sacralization?
-partial or complete fusion of L5 to S1
-partial= arch/body/SPs partially fused
-complete= 6 segment sacrum with 4 lumbars
-partial is more common
-may be congenital or acquired
What is congenital sacralization?
-appears during embryonic development
-more likely to be complete (6 segments sacrum with 4 lumbars)
-stable, not progressive
What is acquired sacralization (usually adaptive to IVD trauma)?
-also known as ankylosis (pathological fusion)
-L5 looks like an L5, but the body or transverses may be fused
-progressive that becomes more complete with time
-usually clinically silent but may increase L4 IVD strain
-L4/L5 IVD is approx level with the superior iliac crest line
What is lumbarization?
-partial or complete failure of S1/S2 fusion
-partial=body/arch/alae partially fused
-complete= S1 transformed into an L6, sacrum has only 4 segments now
-partial is much more common than complete
-always congenital, never acquired
-never progressive
-may decrease SI joint stability and can LBP/problems
What are the features of the coccyx?
-apex inferior triangle of 3-5 segments, usually 4
-smallest vertebra, no neural foramen
-articulates only with the sacrum above
-mostly rudimentary
-6 surfaces- base, apex, ventral, dorsal, and 2 lateral
-transverse grooves/fusion lines (Cc1/Cc2 joint may persist)
-apex is a rudimentary centrum of the caudal segment
-important muscle and ligament attachment
-palpable just posterior to the anus
-has a cornua
-has rudimentary TPs
What are the features of the coccygeal cornua?
-rudimentary pre-zygopophyses of Cc1
-projects superiorly from the coccygeal base
-articulates with the sacral cornua
What do the rudimentary TPs of the coccyx articulate with?
lateral inferior angles
Where do the rudimentary TPs of the coccyx project?
laterally from Cc1, sometimes Cc2
