FAB Quiz #4 Lab

Location of PURPLE:

Sacral Base

Location of PURPLE:

Sacral Apex

Location of GREEN:

Sacral Promontory

Location of GREEN:

Superior Articular Processes

Location of GREEN:

Superior Articular Facet

Location of PURPLE:

Sacral Canal

Location of GREEN:

Sacral Foramina

Location of GREEN:

Auricular Surface

Location of GREEN:

Sacral Ridges

Location of GREEN:

Median Sacral Crest

Location of GREEN:

Intermediate (Medial) Sacral Crest

Location of GREEN:

Lateral Sacral Crest

Location of GREEN:

Sacral Hiatus

Location of GREEN:

Sacral Cornu

What is this landmark?

Alar (wings)

Kyphotic Curve

Motion allowed in SI Joint:

Small 1-4°, 1-2 mm of translation

Mainly in sagittal plane

Frontal/Coronal (Z): Motions

Adduction

Abduction

Lateral Flexion

Transverse/Horizontal (Y): Motions

Internal Rotation

External Rotation

Sagittal Plane (X): Motions

Flexion

Extension

Nutation:

Anterior-inferior nodding movement of sacral base

Counter-nutation:

Posterior-superior movement of sacral base

Lumbar flexion pairs with:

Sacral Counternutation (posterior-superior)

Lumbar extension pairs with:

Sacral nutation (anterior-inferior)

When the lumbar spine is in flexion, the sacral base moves ______.

Posterior-Superior (counter-nutation)

When the lumbar spine is in extension, the sacral base moves ______.

Anteiror-inferior (nutation)

Flexion of PSIS & Sacral Base:

PSIS: posterior & inferior

Sacral: anterior & inferior

Extension of PSIS & Sacral Base:

PSIS: anterior & superior

Sacral: posterior & superior

During flexion of the SI Joint, what is the motion of PSIS?

Moves posterior-inferior of PSIS

During extension of the SI Joint, what is the motion of PSIS?

Moves anterior-superior of PSIS

During flexion of the SI Joint, what is the motion of sacral base?

Anterior-inferior of the sacral base

During extension of the SI Joint, what is the motion of sacral base?

Posterior-superior of the sacral base

During gait (walking), when the right hip is in flexion, what is the motion of the left sacral base?

Sacral base nutation

Anterior-inferior

What are the 2 form closures of the sacroiliac joint?

Elevation and Depression

Keystone Effect

Define: Form Closure

Stability due to anatomy of the joint surfaces and shape of the bones

From of the bones

Define: Keystone Effect

“Keystone” shape of the sacrum, wider superiorly, wedged in between the ilia adds to the stability of the pelvic ring.

Form Closure

Define: Force Closure

Refers to the other forces acting across the SI joint to create stability for more demanding tasks that require more dynamic stability (gravity, joint compressions, muscles slings).