Sacral Spine

ROM at SIJ

1-4 degrees rotation, 1-2mm of translation

Pubis makes up ______- of acetabulum

1/5th

The iliac makes up _____ of acetabulum

2/5ths

The sacrum have how many foramina

4 pairs, anterior and posterior primary rami of sacral nerves

Bony landmarks of innominates

ASIS, AIIS, PSIS, Iliac crest, coccyx (muscle and ligament attachment)

The innominate bone is considered an __________ of the lower extremity

An extension of the lower extremity

What is SIJ nutation

Anterior Sacral on ilial rotation, posterior iliac on sacral rotation or both performed simultaneous

Articular surfaces of sacroiliac joint and joint capsule

Change from smooth to rough which enhances resistance against vertical shear forces, joint capsule becomes more fibrotic and less mobile with age

The structure of the pelvis is a ________. Components are 4 bones and 3 joints ________

Closed osteoarticular ring Bones- Sacrum, coccyx, 2 innominates (ilium, ischium) Joints- 2 Sacroiliac joints, pubic symphysis

Posterior layer of thoracolumbar fascia

Covers posterior surface of muscles including erector spinae, multifidi and lats attaches to SP's L1-5, sacrum and ilium

Short and long posterior sacroiliac ligaments

Cross posterior SIJ, many short fibers blend with interosseous ligament

Sacrospinous ligament

Deep to sacrotuberous ligament

Abdominal muscles that affect SIJ

Diaphragm, pelvic floor, rectus abdominis, obliquus abdominis internus and externus, transverse abdominis

Back muscles that reinforce SIJ

Erector spinae and Lumbar multifidus

Ischium is the ___ of acetablum

Floor, 2/5ths of acetablum

Thoracolumbar fascia role

Functional stability

Leg and arm muscles affecting SIJ

Hip extensor muscles (Biceps femoris and glute), lats, Iliacus and piriformis

Which inominate bone articulates with sacrum

Ilium

Laxity

Increased ROM of joint

What innominate bone do you sit on

Ischium

Sacrotuberous ligament

Large, blends with biceps femoris tendon (lateral hamstring)

Men and Sacrum

Larger Sacroiliac joint surfaces, increased congruency (stability), taller and more narrow pelvis

Coccyx purpose

Muscle and ligament attachment

Rotation of SIJ occurs ________

Near sagittal plane, around near medial-lateral axis of rotation (transverses the interosseous ligament)

The sulcus is _______

Near the PSIS and look like dimples in low back area

Nutation SIJ kinematics

Nutation increases articular stability Close packed position is full nutation Nutation torque created by (gravity, ligaments(passive when stretched), and muscle activation)

What is counternutation

Posterior sacral on ilial rotation, anterior iliac on sacral rotation or both performed simultaneously

The base of the Sacrum is ______ and is the most ______ and has what facets

S1, cephalad (superior), has 2 facets (face posterior) articulate with L5

The inferior lateral angles of the sacrum are ________

S3-S5 area, muscle and ligament attachments

The apex of the sacrum is _______ and articulates with

S5, most caudal, articulates with coccyx

Sacroiliac vs iliosacral joint

Sacrum moving on iliac- sacroiliac Iliac moving on sacrum- iliosacral

Sacroiliac joint innervation

Sensory nerve fibers, dorsal rami of L5-S3 spinal nerve roots, less often ventral rami of L4-S2

Women and sacrum

Smaller Sacroiliac joint surfaces, increased mobility, shorter and wider pelvis

Iliolumbar ligament

Stabilizer of lumbosacral joint, blends with parts of anterior sacroiliac ligament, reinforces anterior SIJ

Function of sacrum

Support abdomen and spinal column (within pelvic ring), link vertebral column to lower extremities

The sacroiliac joint is a _____ joint

Synovial/diarthrodial joint, freely mobile joint in childhood, becomes modified synarthrodial joint in puberty and adulthood

Anterior sacroiliac ligament

Thickening of anterior and inferior capsule, reinforces anterior SIJ

Interosseous ligament

Very dense and short, fills gape between posterior and superior SIJ

Movment of SIJ occurs during

Walking, labor and delivery and during pregnancy (weight gain, lordsis and hormone induced ligamentous laxity)

Sacrum is part of vertebral column and describe dimensions

Wider superior vs inferior, wider anterior vs posterior, has 5 fused vertebrae

Anterior and middle layers of thoracolumbar fascia

named according to position relative to quadratus lumborum, attach to TP's of L-spine and to iliac crests