sacrum, coccyx & SI joints

sacrum

made of 5 vertebral segements

4 pairs of foramen nerves & blood vessel

size & curvature considerably from male to female

coccyx

3-5 segments

most of the time 4 segments

gives stabilization when sitting

sacroliliac joints (SI joints)

junction of iliac ala & sacral ala

“ear-like” shape w/ ridges & depressions

concave sacral surface joins w/ convex iliac surface

SI joint classification

synovial, amphiarthrodial joint

posteriorly & obliquely

how are SI joints angled?

ligaments

how are the superior portion of SI joints connected by?

synovial

what type of joint is the inferior portion of the SI joints?

dislocated coccyx

anterior or posterior

caused by high-energy trauma

pt w/ dislocated coccyx

what is this?

dislocated SI joint

high-injury polytrauma that often results in open book fx

pt w/ dislocated SI joint

what is this?

sacrum AP axial

Sacrum centered & seen entirety

Sacrum free of foreshortening, with the sacral curve straightened

Pubic bones not overlapping the sacrum

No rotation of the sacrum - symmetric alae

15 degree cephalad

what is the tube angle for a sacrum AP axial?

coccyx AP axial

Coccyx centered & seen entirety

Coccyx free of foreshortening, with the sacral curve straightened

no pubic bones overlapping

No rotation - by symmetric pelvis

no tube angle - forshortening

closed circles

repeat

critique this scarum AP axial

too much tube angle

too much overlapping of pubic bones

critique this scarum AP axial

good image

free from forshortening

foramen are open

critique this scarum AP axial

good image

critique this coccyx AP axial

6 X 8

what is the coccyx AP axial collimation?

10 degrees caudad

what is the tube angle for a coccyx AP axial?

no tube angle

pubic bones are over coccyx

should be in middle of pubic inlet

critique this coccyx AP axial

all anatomy on & can see the coccyx in the middle

rotation to the left = repeat

critique this coccyx AP axial

sacrum lateral

Closely superimposed posterior margins of the ischia & ilia, demonstrating no rotation

L5-S5

centering too superior

just got all anatomy on

nonrepeatable

critique this sacrum lateral

rotation - nothing lined up

all anatomy on

electronic marker

repeatable

critique this sacrum lateral

good image

no rotation

everything is on

critique this sacrum lateral

coccyx lateral

Closely superimposed posterior margins of the ischia & ilia, demonstrating no rotation

Bony trabecular detail & surrounding soft tissues

all anatomy

good image

critique this coccyx lateral

everything on

marker in corner

good image

critique this coccyx lateral

rotation - superimposition on coccyx

repeat

critique this coccyx lateral

12 X 10

what is the SI joint AP axial collimation?

30 cephalad

what is the tube angle for AP axial SI joints for males?

35 cephalad

what is the tube angle for AP axial SI joints for females?

AP axial SI joint

Lumbosacral junction & sacrum

Open intervertebral disk space between L5 and S1

Both sacroiliac joints

decrease tube angle

covering of left SI joint

repeat

critique this AP axial SI joint

good image

both SI joint are seen

no rotation

critique this AP axial SI joint

no tube angle

SI joints are too short - not long enough

repeat

critique this AP axial SI joint

RPO/LPO Oblique SI joints

Open sacroiliac joint space furthest from the IR with minimal overlap of the ilium & sacrum

Joint centered on the radiograph

elevated side

where should you place your marker for oblique SI joints?

under rotated

if the iliac tuberosity is overlapping sacral ala, how is the oblique SI joint rotated?

properly rotated

if the border of the sacrum just inside the inlet, how is the oblique SI joint rotated?

good image

joint is open & clear black line

critique this Oblique SI joints

over rotated

critique this Oblique SI joints

good image

critique this Oblique SI joints

superior articular process

what is #1?

base

what is #2?

sacral ala

what is #3?

sacral promontory

what is #4?

sacral foramen (anterior)

what is #5?

transverse lines

what is #6?

apex

what is #7?

coccyx/tailbone

what is #8?

inferior lateral angle

what is #9?

sacral foramen (posterior)

what is #10?

sacral hitatus

what is #11?

sacral cornu

what is #12?

median sacral crest

what is #13?

intermediate sacral crest

what is #14?

lateral sacral crest

what is #15?

auricular surface

what is #16?

sacral tuberosity

what is #17?

sacral canal

what is #18?

superior articular facet

what is #19?

apex

what is a?

sacral foramina

what is b?

superior articular process

what is c?

base

what is d?

sacrum

what is e?

ilium

what is f?

left sacroiliac joint

whar is g?

base

what is #1?

transverse process

what is #2?

apex

what is #3?

Co4

what is #4?

Co3

what is #5?

Co2

what is #6?

Co1

what is #7?

coccyx

what is #8?

sacrum

what is #9?

coccygeal cornua

what is #10?

sacral cornua

what is a?

coccyx

what is b?

coccygeal cornu

what is c?

sacrum

what is d?

articular surface

what is e?

promontory

what is f?

base

what is g?

super articular process

what is h?

median sacral crest

what is #1?

sacral horn

what is #2?

iliac crest

what is #1?

ilium

what is #2?

pelvic brim

what is #3?

acetabulum

what is #4?

ischium

what is #5?

pubic symphysis

what is #6?

pubic crest

what is #7?

pubic bone

what is #8?

ischial spine

what is #9?

sacroiliac joint

what is #10?