Atlanto-Occipital Joints
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Concave oval superior facets of atlas
Convex/rounded occipital condyles
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Horizontal plane
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Lateral Atlanto-Axial Joints
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Flat circular inferior facet of atlas
Flat circular superior facet of axis
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Horizontal plane
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Medial Atlanto-Axial Joints
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Dens of axis
Articular fossa for dens on posterior surface of anterior arch of atlas
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Frontal plane
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Cervical Facets (C3-7)
Permits extensive rotation as well as flexion, extension and lateral flexion.
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Flat, oval superior and inferior facets
Inferior face anterioinferior
Superior face posteriosuperior
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Frontal at about 45° to horizontal
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Thoracic Region (T1-12)
Permits rotation, flexion, extension, and lateral flexion but magnitude of motion is limited by the attachment to the ribs.
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Flat, oval superior and inferior facets
Inferior face anterior
Superior face posterior
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Frontal at about 60° to horizontal
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Upper Lumbar (L1-2)
Restricted rotation but allows forward and lateral flexion and extension.
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Oval and slightly concave superior facets
Oval and flat/slightly convex inferior facets
Inferior face laterally
Superior face medially
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Sagittal at about 90° to horizontal
Has cephalad and caudal menisci that attach to joint capsule
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Lower Lumbar (L4-5)
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Oval and slightly concave superior facets
Oval and flat/slightly convex inferior facets
Inferior facets of L4 face anteriolaterally, L5 faces more anterior than lateral
Superior facets of L4-5 face posteriomedially
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Diagnonal to sagittal and frontal at about 90° to horizontal
Has cephalad and caudal menisci that attach to joint capsule
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*articular cartilage of facet joints is hyaline cartilage that is thick centrally and thin peripherally
*jt. Capsule is dense irregular connective tissue containing collagen and elastic fibers
*collagen limits facet joint movement- jt. Distraction, rotation and superor translation of inferior facets on the superior facet of the vertebra below as during forward flexion
*elastic fibers prevent the capsule and synovial membrane from being pinched between the opposing facets, allow for movement between the facets, and return the capsule it its starting position.
*menisci in lumbar region can become trapped between opposing articular surfaces producing a painful blockage of motion at the vertebral segment
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INTERVERTEBRAL DISKS
*fibrocartilaginous joint between vertebral bodies
*Peripheral annulus fibrosis and central nucleus pulposus
ANNULUS FIBROSIS
*6-10 rings of Fibrocartilage
*collagen fibers in layers around nucleus are arranged loosely
*collagen fibers in outer layers are densely packed and run obliquely between vertebral bodies
*collagen fibers in the outermost 1-2 layers show a herringbone pattern which makes them strong in resisting tension
*peripheral-most fibers attach to the smooth edge (rim) of vertebral body with outermost fivers attaching to the periosteum and the anterior and posterior longitudinal ligaments
*other fibers attach to the hyaline cartilaginous end plate covering the rough articular surface of the vertebral body
FUNCTIONS OF THE ANNULUS FIBROSIS
*contains nucleus pulposus
*stabilization
*permits multidirectional movement
*shock absorbtion
NUCLEUS PULPOSUS
*gelatinous mass of collagen fibers imbedded in a mucopolysccharide and water
*absorbs and retains large quantities of water
*exchange of nutrients between disk and vertebral bodies
*in cervical and thoracic regions, nucleus lies centrally within disk
*in lumbar region, nucleus lies in the posterior ½ of disk
FUNCTIONS OF THE NUCLEUS PULPOSUS
*absorbtion and retention of water
*nutrition
*force transmission
*equalize unit stress in all directions to the annulus fibrosis
*permits a rocking type segmental movement between vertebral bodies
*movement between adjacent vertebrae is needed as is the ability of the AF and NP to expand
*NP expands at rest by drawing H2O & nutrients from blood vessels and lymphatics of the vertebral bodies
*as NP is loaded, the nutrient fluid is forced out into the AF and waste products out of the nucleus into the vertebral bodies
*flow of fluid inwardly during rest and outwardly during loading provides for nutritional needs of the disk
SACROILIAC JOINT
-synovial and fibrous articulation
-synovial articulation: auricular surface of sacrum (S1-3) and auricular surface of ilium lying anterior to PSIS and inferior to iliac tuberosity
-both auricular surfaces for the synovial portion have an irregular pattern of ridges and groves and both are covered with a thin layer of hyaline cartilage
Ligaments of the Spine
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Anterior Atlanto-occipital membrane
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Anterior arch of atlas with base of occiput
Continuous laterally with atlanto-occipital jt capsule
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Posterior Atlanto-occipital membrane
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Posterior arch of atlas with occiput
Continuous with lateral atlanto-occipital ligament
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Anterior atlanto-axial membrane
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Body of axis to anterior arch of atlas
Continuous with atlanto-axial jt capsule
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Posterior atlanto-axial membrane
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Posterior body of axis to posterior arch of atlas
Continuous with atlanto-axial jt capsule
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Lateral atlanto-occipital ligament
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Transverse process of atlas with occipital bone and strengthens atlanto-occipital jt
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Tectorial membrane
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Continuation of posterior longitudinal ligament connects posterior arch of axis to occipital bone covers cruciform, alar and apical ligaments
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Cruciform ligament
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Consists of transverse ligament of atlas, superior band and inferior band
Superior band attaches to occipital bone
Inferior band attaches to body of axis
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Transverse ligament of atlas
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Cups posterior surface of dens
attaches to posterior surface of anterior arch of atlas on each side of the medial atlanto-axial joint
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Alar ligaments (paired)
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Attach to sides and posterior surface of dens and run laterally with superior band attaching to occiput, middle band to lateral mass of atlas, inferior band to axis
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Apical ligaments
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Anterior to the superior band of cruciform ligament
Connects apex of dens to occiput
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Anterior longitudinal ligament
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Attaches to anterior rim of vertebral bodies and anterior aspect of IVD
Runs from sacrum to atlas
Becomes anterior atlanto-occipital membrane
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Posterior longitudinal ligament
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Attaches to posterior rim of vertebral bodies and posterior aspect of IVD
Anterior surface of spinal canal from sacrum to axis
Becomes tectorial membrane
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Ligament flava
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Paired segmental elastic ligaments on posterior aspect of spinal canal
Sacrum to axis
Connects lamina of adjacent vertebrae
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Supraspinous ligament
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Attaches to tips of spinous processes from C7
continuous with ligamentum nuchae to about L4
Replaced by erector spinae fascia
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Interspinous ligaments
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Inferior and superior aspects of adjacent SP from C7 to L5-S1
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Ligamentum nuchae
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Complex fibrous septum that runs along posterior midline of neck from C7 to occiput
Connects tips and superior and inferior aspects of cervical SP to the occiput
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Intertransverse ligament
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Connects TP of adjacent vertebrae
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Iliolumbar ligament
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Starts as muscle, ligament by 40
TP of L5(males)/L4-5 (females) to superior SIJ and ilium
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Sacrotuberous ligament
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Runs obliquely from posterior surface of PIIS and Posteriolateral aspect of lower sacrum and upper coccyx to the medial aspect of the Ischial tuberosity and Ischial ramus
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Sacrospinous lgament
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Runs obliquely from posteriolateral surface of lower sacrum and coccyx to Ischial spine
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Interosseus SI ligament
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Connects the iliac and sacral tuberosities at the fibrous SI jt
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Short dorsal SI ligament
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Run horizontally from dorsolateral aspect of the superior part of the sacral tuberosityto the dorsal aspect of the tuberosity of the ilium
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Long dorsal SI ligament
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Runs obliquely from the dorsolateral aspect of the inferior part of the sacral tuberosity and the dorsal surface of the sacrotuberous ligament to the PSIS
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Ventral SI ligament
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Runs horizontally from the ventrolateral margin of the sacrum to ventral aspect of the auricular surface of the ilium
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Facet Joint Motion
-forward bending exposes some 40% of the facet joint area
-functional left sidebending causes more upward sliding of the right facet than does forward bending
-rotation to the right causes right facet distraction and left facet compression; left facet slide forward with vertebrae tilting into left side bending
-FWD BENDING: upward movement of inferior articular processes; slides up and forward
-BWD BENDING: downward movement of inferior articular processes; slides down and back contacting the lamina below
-LEFT ROTATION: gapping at left facet, right facet acts as a fulcrum
-SIDEBENDING/ROTATION: downslide of inferior articular facets on side to which cervical spine rotates; upslide on opposite side
Region
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Flexion
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Extension
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Right Side Bend
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Right Rotation
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Atlanto-Occipital
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Occipital condyles Roll anteriorly
Glide posteriorly
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Occipital condyles
Roll posteriorly
Glide anteriorly
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Occipital condyles Roll right
Glide left
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ROC moves slightly back
LOC moves slightly forward
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Atlanto-Axial
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Facets move forward
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Facets move backward
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Atlas slides right
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RF moves back
LF moves forward
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C2/3-T2/3
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Facets slide up and forward
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Facets slide down and back
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RF slides down and back
LF slides up and forward
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RF slides down and back
LF slides up and forward
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T3/4-T11/12
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Facets slide up
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Facets slide down
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RF slides down
LF slides up
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RF distracts
LF compresses and acts as fulcrum
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Lumbar
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Facets slide up
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Facets slide down
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RF slides down
LF slides up
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RF distracts
LF compresses and acts as fulcrum
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Vertebrae Forward Flexion
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Anterior tilting (rocking) of vertebral body over NP
Compression & bulging of anterior IVD (AF)
Tension on posterior IVD (AF)
NP deforms posteriorly
IV foramen increases
SP separate
Decreased compression on facet jt
Tension on supraspinous, interspinous, intertransverse, ligamentum flava, posterior longitudinal ligament
Slack on anterior longitudinal ligament
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Vetebrae Backward Extension
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Posterior tilting (rocking) of vertebral body of NP
Compression and bulging of the posterior IVD (AF)
Tension on anterior IVD (AF)
IV foramen decreases
SP converge
Increased compression on facet jt
Slack in supraspinous, interspinous, intertranverse, ligamentum flava, posterior longitudinal ligament
Tension on anterior longitudinal ligament
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Vertebral Side Bending/Lateral Flexion
(in cervical spine, coupling occurs- when head and neck are bent right, SP go left.)
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Lateral tilting of vertebral body over nucleus on side toward movement
Compression and bulging of IVD on side toward movement
Tension on IV on side opposite movement
Nucleus deforms to side opposite movement
IV foramen decreases on side of movement
IV foramen increases on side opposite movement
Increased compression on facet jt on side of movement
Decreased compression on facet jt on side opposite movement
Tension on intertransverse lig on side opposite movement
Slack on intertransverse lig on side of movement
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Vertebrae Rotation
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Increased compression on NP
Shear stress on AF
Increased compression on facet opposite to rotation
Decreased compression on facet joint on side of rotation
Tension on jt capsule on side of rotation
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SI joint
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Movement limited to 1-3 degrees
Movement mainly at anterioposterior direction
Rotation and translation occur
Nutation- movement of sacrum related to ilium as during fwd bending of trunk and squatting
Torsion- movement of ilium relative to sacrum as in lying supine and brining the knee to the chest
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Loads on the Spine
Cervical Spine
*Loads at the AO jt are lowest in full extension and highest in full flexion
*Loads at C7-T1 are least when head is facing forward and chin is tucked
*Loads at C7-T1 are slightly greater when the head is in the correct posture, greater still when the head is extended and greatest at full flexion
Lumbar Spine
*Loads are least when lying supine
*Loads are low with relaxed standing, greater with supported sitting, and still greater with unsupported sitting
*Compression loads on the lumbar spine are greatest near the toe off stage in walking
*Loads increase on the lumbar spine as the velocity of walking increases
Muscle Actions
Forward trunk flexion from standing
Abs and ilipsoas move trunk forward while gravity pulls downward. Erector spinae eccentrically control downward movement. At 60 degrees of trunk flexion, pelvis rotates anteriorly at hips. Glute max and hamstrings eccentrically control anterior pelvic rotation.
Trunk extension from full flexion
Erector spinae very active at full flexion in stabilizing spine. During initial 30 degrees of extension, pelvis rotates posteriorly at hips. Glute max and hamstrings concentrically produce pelvic rotation. Last 60 degrees of extension is produced by concentric contraction of erector spinae.
Trunk side bending
QL, erector spinae and abs on side of movement initiate side bending to same side. Gravity pulls trunk further to same side. ES, QL on opposite side act eccentrically to control the rate and distance of gravity produced sidebending. Return to erect posture is produced by concentric activity of the ES and QL on the side opposite the gravity produced side bending.
Line of Gravity (LOG)
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Atlanto-Occipital Jt
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Lower C-Spine (C3-7)
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Thoracic Spine
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Lumbar Spine
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Sacroiliac Joint
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passes through dens of C2, bodies of T1, T12, S2
Maximal gravitational torque occurs at C5, T8, L3 where apex of each spinal curve are furthest from LOG
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LOG: anterior
Moment: flexion
Passive forces: ligamentum nuchae
tectorial membrane
Active forces: posterior neck musckes
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LOG: posterior
Moment: extension
Passive forces: anterior longitudinal ligament
Active forces: anterior scalene
Longus capitis
Longus colli
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LOG: anterior
Moment: flexion
Passive forces: posterior longitudinal ligmament
Ligamentum flavum
Supraspinous ligmanet
Active forces: extensors
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LOG: posterior
Moment: extension
Passive forces: anterior longitudinal ligament
Active forces: rectus abdominus
IAO
EAO
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LOG: anterior
Moment: flexion
Passive forces: sacrospinous ligament
Sacrotuberous ligament
Sacroiliac ligament
Active forces: TA
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Excessive Anterior Pelvic Tilt
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Excessive Lumbar Lordosis
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Excessive Thoracic Kyphosis
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Excessive Cervical Lordosis
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Increased compression of posterior bodies
Increased L5-S1 disk pressure
Increased lumbosacral angle
Potential slippage of L5 on S1
Ab stretched
Iliopsoas shortened
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Increased compression of posterior bodies
Increased compression of facet jts
Increased disk pressire
Narrowing of IV foramen
Increased tension on anterior AF
ALL stretched
PLL, interspinous, lig. Flavum, lumber extensors shortened
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Increased compression of anterior bodies
Increased disk pressure
Increased tension on facet capsule and posterior AF
Dorsal back and scap muscles stretched
ALL shortened
Anterior shoulder girdle and upper Abs shortened
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Increased compression of posterior bodies
Increased compression of facet joints
Increased disc pressure
Narrowing of IV foramen
Increased tension on anterior AF
ALL stretched
Posterior spinal ligaments shorten
Posterior neck muscles shorten
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TEMPOROMANDIBULAR JOINT
Full Fibrocartilage articular disc that is connected to anterior joint capsule (attachment of superior head of lateral pterygoid)
Posterior disc attached to superior and inferior lamina
Superior lamina = elastic, stretches when disc moves anteriorly and recoils to move disc posteriorly
Inferior lamina= collagen, tightens when disc moves anteriorly to restrict the amount of anterior movement and slackens when disc moves posteriorly
Jaw Opening and Closing
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Stage 1
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11-25 mm between incisors
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Anterior rotation of mandibular condyle in fossa and on disc
Disk does not move
Superior and inferior lamina are relaxed
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Stage 2
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40-50 mm between incisors
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Anterior rotation and anterior translation of the mandibular condyle over articular eminence
Anterior translation of the articular disc with condyle as condyle moves over articular surface
Superior lamina stretches
Inferior lamina tightens
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Initial Jaw Closing
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40-50 mm to 11-25 mm
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Posterior rotation and posterior translation of mandibular condyle back into mandibular fossa
Posterior translation of articular disc with condyle as condyle returns to fossa
Superior lamina recoils pulling disc posteriorly into fossa
Inferior lamina slackens as disc moves posterior into fossa
Lateral pterygoid contractions to control the rate of posterior disc movement
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Terminal Jaw Closing
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11-25 mm to full closure
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Posterior rotation of mandibular condyle in fossa and on disc
Disc is within fossa
Superior and inferior lamina are relaxed
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Tissue Mechanics
Load-Deformation Curve describes the relationship between the amount of stress/force and the amount of strain/deformation
TOE REGION
-start of curve
-material is slack
-small amount of stress produces proportionally more strain
ELASTIC/LINEAR REGION
-material is tightening
-amount of stress is proportional to amount of strain
-when stress is released, material returns to original shape
-ability of a material to return to it’s non-deformed starting point define the elastic region of the material
PLASTIC REGION
-material is damaged
-degree of damage increases as the stress increases
-amount of strain/deformation increasing more relative to increase in stress
-necking point occurs in plastic region where the degree of material change is so extensive that the amount of deformation remans large with a decrease in stress
-material in plastic region is permanently deformed and will not return to it’s original position when the stress is removed
FAILURE is the point where the material completely breaks or ruptures
Stress/Strain curve for elastic material- as stress is applied, material deforms…when the stress is stopped, material returns to original size and shape….work lost during this process to deform the material is not completely recaptured once the forced are removed. Work lost is the area under the curves.
Young’s Modulus of Elasticity
E=Stress/Strain
Defines stiffness (resistance to deformation)
High Young’s Modulus= high stiffness
Low Young’s Modulus= low stiffness
Resilience
Resilience is the mechanical work lost during deformation
R= work – change in work/work
Greater loss of work= less resilience
Less work lost= greater resilience
R=1 is perfectly resilient
1 2 3 4
1= good resilience and elastic
2= less resilient but still elastic
3= poor resilience, not elastic
4= not resilient, not elastic…good Damping
Damping is the opposite of resilience- styrofoam D=1-R
Toughness is resistance to mechanical failure
*amount of energy a material will absorb before it breaks
*toughness is not necessarily equal to strength
*strength is the magnitude of the force needed to break a material
Fragility is the opposite of toughness
*Fragile material absorbs little energy before it breaks
Brittleness describes materials that deform very little before failure
*brittleness is not necessarily related to strength (can be brittle- little formation but strong as in a drill bit)
Ductility is the ability of a material to deform progressively in tension without breaking
*old bone is more brittle than young bone
*young bone is more DUCTILE than old bone because young bone deforms farther when tension stress is applied than old bone.
CONNECTIVE TISSUE PROPER
-CT is made up predominantly of collagen fibers
-CT is formed from tropocollagen molecules (each has 3 polypeptide chains called alpha units that are wound about each other to form a triple helix)
-Tropocollagens are packed end to end and stacked side to side to form collagen fibril
-bound together by intra and inter chain bonds or cross-links between lysine and hydroxlysine
-cross links also bind fibrils together
-cross links contribute to high tensile strength, stability and stiffness of collagen so that collagen fibers with many cross-links are stiffer than collagen fibers with few cross-links
Type I collagen
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Found in dermis of skin, bone tendon, ligament, Fibrocartilage, and fascia
Forms 90% of collagen in body and functions to resist tension and stretching
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Type II collagen
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Found in hyaline cartilage and elastic cartilage
Function is to resist pressure
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Type III collagen
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Found in CT of organs- liver, spleen, lungs, intestines
Also in blood vessels, nerves and muscles
Function is structural support
Important in wound closure
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Type IV collagen
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Found n basement membrane of epithelium
Function is to support tissue and act as a filter
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Type V collagen
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Found in basal lamina of smooth and skeletal muscle cells and Schwann and Glia cells
Functions as support system in these structures
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