Atlanto-Occipital Joints Concave oval superior facets of atlas

Atlanto-Occipital Joints	Concave oval superior facets of atlas Convex/rounded occipital condyles	Horizontal plane
Lateral Atlanto-Axial Joints	Flat circular inferior facet of atlas Flat circular superior facet of axis	Horizontal plane
Medial Atlanto-Axial Joints	Dens of axis Articular fossa for dens on posterior surface of anterior arch of atlas	Frontal plane
Cervical Facets (C3-7) Permits extensive rotation as well as flexion, extension and lateral flexion.	Flat, oval superior and inferior facets Inferior face anterioinferior Superior face posteriosuperior	Frontal at about 45° to horizontal
Thoracic Region (T1-12) Permits rotation, flexion, extension, and lateral flexion but magnitude of motion is limited by the attachment to the ribs.	Flat, oval superior and inferior facets Inferior face anterior Superior face posterior	Frontal at about 60° to horizontal
Upper Lumbar (L1-2) Restricted rotation but allows forward and lateral flexion and extension.	Oval and slightly concave superior facets Oval and flat/slightly convex inferior facets Inferior face laterally Superior face medially	Sagittal at about 90° to horizontal Has cephalad and caudal menisci that attach to joint capsule
Lower Lumbar (L4-5)	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	Diagnonal to sagittal and frontal at about 90° to horizontal Has cephalad and caudal menisci that attach to joint capsule
*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

*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

*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

*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

-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

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	Flexion	Extension	Right Side Bend	Right Rotation
Atlanto-Occipital	Occipital condyles Roll anteriorly Glide posteriorly	Occipital condyles Roll posteriorly Glide anteriorly	Occipital condyles Roll right Glide left	ROC moves slightly back LOC moves slightly forward
Atlanto-Axial	Facets move forward	Facets move backward	Atlas slides right	RF moves back LF moves forward
C2/3-T2/3	Facets slide up and forward	Facets slide down and back	RF slides down and back LF slides up and forward	RF slides down and back LF slides up and forward
T3/4-T11/12	Facets slide up	Facets slide down	RF slides down LF slides up	RF distracts LF compresses and acts as fulcrum
Lumbar	Facets slide up	Facets slide down	RF slides down LF slides up	RF distracts LF compresses and acts as fulcrum

Vertebrae Forward Flexion	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
Vetebrae Backward Extension	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
Vertebral Side Bending/Lateral Flexion (in cervical spine, coupling occurs- when head and neck are bent right, SP go left.)	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
Vertebrae Rotation	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
SI joint	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

Loads on the 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

*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.

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.

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.

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  Full Fibrocartilage articular disc that is connected to anterior joint capsule (attachment of superior head of lateral pterygoid)
  
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  Posterior disc attached to superior and inferior lamina
  
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  Superior lamina = elastic, stretches when disc moves anteriorly and recoils to move disc posteriorly
  
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  Inferior lamina= collagen, tightens when disc moves anteriorly to restrict the amount of anterior movement and slackens when disc moves posteriorly
  

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= 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

*Fragile material absorbs little energy before it breaks

*brittleness is not necessarily related to strength (can be brittle- little formation but strong as in a drill bit)

*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	Found in dermis of skin, bone tendon, ligament, Fibrocartilage, and fascia Forms 90% of collagen in body and functions to resist tension and stretching
Type II collagen	Found in hyaline cartilage and elastic cartilage Function is to resist pressure
Type III collagen	Found in CT of organs- liver, spleen, lungs, intestines Also in blood vessels, nerves and muscles Function is structural support Important in wound closure
Type IV collagen	Found n basement membrane of epithelium Function is to support tissue and act as a filter
Type V collagen	Found in basal lamina of smooth and skeletal muscle cells and Schwann and Glia cells Functions as support system in these structures