Anatomy & Physiology - Spine & SI Flashcards Preview

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Flashcards in Anatomy & Physiology - Spine & SI Deck (52):

Pars interarticularis

part of the lamina - area of thick cortical bone bridging the superior and inferior articular processes

IMPORTANT for transmitting load from POST to ANT

Susceptible to stress and compression fx


Anterior Longitudinal Ligament

anterior to vertebral bodies from sacrum to C2

- attaches segmentally to VERTEBRAL BODIES
- FUNCTION = resist extension

susceptible to hyperextension trauma


Posterior Longitudinal LIgament

runs posterior to vertebral bodies and continuous w/ tectorial membrane at C2

- attaches segmentally to DISC in fan-like pattern
-innervated by sinuvertebral nerve (same that innervates 1/3 of outer annulus of disc)
- FUNCTION: prevent posterior disc protrusion and segmental restraint to flexion


Ligamentum Flavum

connects two consecutive lamina

-attaches to anterior part of facet joint and becomes the joint capsule

FUNCTION: allow flexion to a certain extent & limit flexion
--> if it loses elasticity over time it may buckle & cause compression on nerve root


Interspinous LIgament

segmental attachment of spinous processes

innervated by medial branch of posterior (dorsal) rami

FUNCTION: assist w/ segmental stability, prevent seperation of two s.p's during flexion


Supraspinous Ligament

runs along the length of the spinous processes w/ segmental attachments via transverse fibers

- greatest risk of injury b/c furthest from axis of motion

most developed in the lumbar region

FUNCTION: resist flexion


Iliolumbar Ligament

attaches bodies of L4/L5 to ilium

FUNCTION: limit motion in lumbosacral region


What does a motion segment consist of?

a disc, two vertebral bodies, 2 facet joints and surrounding soft tissue

Superior vertebrae defines direction of movement
Rotation is defined by anterior part of vertebral body (not the direction of the spinous process)


Facet Joint Orientation

CS = 45deg to horizontal
- allows rotation, flex/ext

TS = coronal
- allow for rotation, prevents forward translation

LS = sagittal
- allow for flex/ext & resist rotation

L5/S1 = coronal

Greatest rotation = horizontal,
then coronal
Least = sagittal


Fryette's Law - Lumbar Spine

Side bending and rotation are coupled in OPPOSITE directions

Neutral spine = SB & ROT - OPP
Flexed spine = SB & ROT - SAME
Extended spine = SB & ROT - SAME


Erector Spinae

FUNCTION - back extension (main) + anterior tiliting + minimal stabilization of LS


Interspinalis & Intertransversarii

FUNCTION: fine tune segmental motion & provide proprioceptive feedback


Quadratus Lumborum

FUNCTION: lumbopelvic motion, especially rotation, side flexion, stabilizer in sustainted posture, stable base for diaphragm during inspiration



FUNCTION: segmental stability & LS/SI stability
- controls anterior shear


Transverse Abdominus

FUNCTION: anticipate motion, provide segmental stability, prevent anterior shearing


Internal vs. External Oblique

Internal -
FUNCTION - anterior pelvic tilt, initiate L rotation
--> originates from ASIS & t-l fascia, which is why it does an anterior pelvic tilt b/c contraction of I.O tenses t-l fascia

External -
FUNCTION - posterior pelvic tilt, initiate R rotation
--> all anterior attachments, so contraction will cause a posterior pelvic tilt


Thoracolumbar Fascia

Spinous process of T12 to PSIS and iliac crests
- envelop lumbar muscles

- attachment site
- stabilize against anterior shear/flexion
- "corset" action
- transmission of extension forces


Vertebral End-plate

cartilage above & below disc, tightly bound to disc

Highly innervated

Sharpy's fibers: annulus fibers that insert onto vertebral body

FUNCTION: hold disc in place


Nucleus Pulposus

mainly water allowing for deformation under compression
(contains proteoglycans which hold water)

TYPE II collagen


Annulus fibrosus

Type I Collagen that hold the nucleus pulposus in place
- Lamella: bundles of sheath around nucleus arranged in alternating diagonal patterns

Posterior fibers are thinner to allow for flexion, also a common site for posterior disc protrusions

HIGHLY innervated (outer 1/3) by sinuvertebral nerve


Disc Mechanics (5)

1. Compression (normal)
- WB activities and muscle contraction
- equilibrium between push & pull

2. Distraction (normal)
- separation of vertebral bodies

3. Rocking (normal or pathological)
- bending the disc anterior & posterior

4. Rotation (pathological)
- half of annulus on slack & other half on stretch

5. Shear (pathological)
- takes place w/ rotation (lateral shearing)


Lumbosacral Joint

L4, L5 and S1 - facets oriented in CORONAL plane and coupling of SB & ROT to the same side (diff from LS)

L5/S1 = primary WB joint

Motion restricted by iliolumbar ligament - especially excessive sacral flexion


5 joints of lumbopelvic region

1. lumbosacral
2. sacroiliac (x2)
3. pubic symphysis
4. hip joints (x2)
5. coccyx


Sacroiliac Joints
- joint surfaces

Sacrum: Inverted L shape
- Short arm (superior) = depth of sacrum - in vertical plane
- Long arm (inferior) = length of sacrum w/n S2/S3 in A-P plane

Ilium: corresponding L shape


SI Joints

transfer load from trunk to legs and absorb/dissipate forces from LE before they reach the spine

Major WB joint (as well as L5/S1)


SI Joint Stability (4 things)

1. Articulating surfaces
- sacral surface has thick hyaline cartilage
- ilial surface has fibrocartilage

2. Two joint stypes
- anterior (1/3 of joint) = synovial
- posterior (2/3 of joint) = syndesmosis - held together by interosseus membrane which allows for very little motion

3. Joint surfaces un-smooth (friction)

4. Extensive ligaments


Anterior SI ligament

WEAKEST and most susceptible to injury

FUNCTION: limit anterior gapping

test w/ anterior distraction


Posterior Interosseus Ligament

deepest and STRONGEST

FUNCTION: limit posterior gapping

test w/ anterior compression


Long dorsal (posterior) SI ligament

connects PSIS to lateral segments of S3 and S4

FUNCTION: prevent counternutation (backward tiliting)

blends w/ multifidus, ES, and t-l fascia which is why those structures are important for the stability of the SI joint


Sacrotuberous ligament

attaches PIIS medially down to S3 and S4 and to ischial tuberosity

FUNCTION: prevent nutation

blends w/ biceps femoris tendon so contraction of this muscle will increase stability of SI joint by increasing tension in ligament


Sacrospinous ligament

attaches ischial spine to lateral margins of the sacrum & coccyx

FUNCTION: prevent nutation

blends to form capsule of the SIJ


Muscles of the Pelvic Girdle
- inner vs outer

Inner tube = local muscles
(TrA, multifidus, diaphragm and pelvic floor muscles)

Outer = global muscles
(4 systems - longitudinal, anterior & posterior oblique, and lateral)

Piriformis - only muscle w/ direct attachment to SIJ
- function = ER
- can cause SI problems

Biceps femoris attaches to sacrotuberous ligament so can cause counternutation of sacrum or prevent nutation


Sacroiliac Biomechanics

Sacrum moving on ilium during LUMBAR motions

Flexion = sacral nutation then counternutation
Extension = sacral counternutation
Axial rotation = reciprocal motion of unilateral ipsilateral nutation and counternutation
(picture hypothetical oblique axis)

Nutation = sacrum gliding anterior & inferior
Counternutation = posterior & superior


Iliosacral Biomechanics

Ilium moving on the sacrum during HIP motions

Flexion = posterior rotation
Extension = anterior rotation


Longitudinal System - outer tube muscles of the pelvic girdle

Erector spinae
t-l fascia
biceps femoris (sacrotuberus ligament)


Anterior oblique system - outer tube muscles of pelvic girdle

Internal and external obliques
abdominal fascia
contralateral adductors


Posterior oblique system - outer tube muscles of pelvic girdle

Latissimus dorsi
Contralateral glute max
t-l fascia


Lateral system - outer tube muscles of the pelvic girdle

Glute med & min
contralateral adductors


Lumbar Spine flexion
-facet motion
- limiters
- mechanics
- clinical implication

- Facets glide superior
- opens foramen & facet joints

- Limited by: PLL, LF, ISL, SSL (all posterior ligaments), tension on post part of disc, bony block

- Mechanics: initiated by abdominals, then "flexion-relaxation phenomenon" - TLF stretches, deactivating the ES to prevent overactivation

- Clinical implication: repetitive flexion can cause disc injuries, avoid w/ certain diagnoses (usually during acute stage)


Lumbar Spine Extension
- facet motion
- limiters
- Mechanics
- Clinical implication

- Facets glides inferior
- closes facets & narrows foramen

- Limited by: approximation of spinous processes or facet joints

- Mechanics: initiated & maintained by back extensors while abdominals work eccentrically

- Clinical Implication: avoid w/ stenosis, OA of facet joints, excessive lordosis
--> excessive loading on pars interarticularis common during hyperextension & sporting activities
--> repetitive extension can damage facet joints


Lumbar Spine Rotation
- facet motion
- limiters
- clinical implication

- Ipsilateral facets move inferior (caudal) and contralateral facets glide superior (cranial)
- LS = gapping on ipsilateral side
- CS = gapping on contralateral side

- Limited by: approximation of contralateral facet, stretch of joint capsule or disc rotation

- Clinical implication: optimal stimulus IF w/n pain-free, optimal range, rotational manual therapy due to opening of lateral foramen (LS - same side)


Lumbar Spine Side Flexion
- facet motion
- coupled w/?

- Ipsilateral facet glides inferior (caudal) and contralateral facet glides superior (cranial)

- Fryette's Law = SB & ROT of LS are coupled in opposite directions UNLESS...
- spine is flexed or extended then coupled in SAME direction


Upper CS Biomechanics - Flexion & Extension

- occipital condyles glide posterior
- C1 moves inferior
- C2 translates anterior

- occipital condyles glide anterior
- C1 moves superior
- C2 translates posterior on C3


Upper CS Biomechanics - SB

- occipital condyle glides anterior
- nothing at AA?


Upper CS Biomechanics - Rotation

50% of cervical rotation comes from C1-C2!
The AA joint is the "no" joint

- occipital condyles glide posterior
- C1 translates to opposite side
- ipsilateral facet glides posterior
- CL facet glides anterior


Upper CS Motion Coupling

SB & Rotation occur in OPPOSITE directions

when you have SB to the right you will have a rotation to the left
- can use to differentiate between UCS vs. LCS problems


Lower CS Biomechanics - Flexion/Extension

- vertebral body translates anterior
- Facets glide anterior

- vertebral body translates posterior
- Facets glide posterior


Lower CS Biomechanics - SB/ROT
- Coupled motion

- ipsilateral facet glides inferior
- CL facet glides superior

Rotation is same biomechanics because in LCS coupled motion, SB and rotation occur in the SAME direction
- when you SB to the left it gaps the right foramen, when you rotate to the left, it will also gap the right foramen


Thoracic Spine Biomechanics - Flex/Ext

- vertebral body translates anterior

- vertebral body translates posterior

Motion increases in the LOWER SEGMENTS


Rib Biomechanics - Flex/Ext

- anterior rib translates inferior
- posterior rib translates superior
- plus ANT rotation

- anterior rib translates superior
- posterior rib translates inferior
- plus POST rotation


Thoracic Spine Biomechanics - SB/ROT

- ipsilateral facet extends (inferior-lateral)
- CL facet flexes (superior-medial)

Coupled motion - SB & rotation of the TS occur in the SAME direction
- CTJ and TLJ will follow respective biomechanics


Rib Biomechanics - SB/ROT

- ipsilateral rib translates inferior and rotates posterior
- CL rib translates superior and rotates anterior