Ligaments.pptx

LIGAMENTS OF THE SPINE FUNCTIONS • PROVIDE STABILITY TO THE SPINE • ALLOW SMOOTH PHYSIOLOGICAL MOTION AND FIXED POSTURAL POSITIONS BETWEEN SEGMENTS • MINIMAL EXPENDITURE OF MUSCLE ENERGY • PROTECT NEUROLOGICAL STRUCTURES FROM EXCESSIVE FORCES WITHIN NORMAL ROM • RESIST DAMAGING HIGH SPEED,...

LIGAMENTS OF THE SPINE FUNCTIONS • PROVIDE STABILITY TO THE SPINE • ALLOW SMOOTH PHYSIOLOGICAL MOTION AND FIXED POSTURAL POSITIONS BETWEEN SEGMENTS • MINIMAL EXPENDITURE OF MUSCLE ENERGY • PROTECT NEUROLOGICAL STRUCTURES FROM EXCESSIVE FORCES WITHIN NORMAL ROM • RESIST DAMAGING HIGH SPEED, HIGH LOAD FORCES • ABSORB LARGE AMOUNTS OF ENERGY WHEN LOADS ARE SUDDENLY APPLIED TO THE SPINE • PROPRIOCEPTION FROM MECHANORECEPTORS AND NOCICEPTORS • CONTROL MUSCLE TONE • PREVENT POSITIONS THAT MAY LEAD TO INJURY HISTOLOGY • 60-70% WATER! • 75% DRY MASS – COLLAGEN • 90% - TYPE I – RESISTS TENSILE FORCES • ELASTIN • GAGS • *ELASTIN AND GAGS PROVIDE VISCOELASTICITY • VISCOELASTICITY – STRUCTURE HAS BOTH FLUID AND ELASTIC PROPERTIES THAT ARE TIME DEPENDENT; STRESS AND STRAIN ARE DEPENDENT ON LOADING RATE PHYSICAL PROPERTIES • EXHIBIT ELASTIC, VISCOELASTIC, AND PLASTIC BEHAVIORS DEPENDING UPON • LOCATION • FIBER DIRECTION • HISTOLOGY • MOST LIGAMENTS ARE UNIDIRECTIONAL, RESIST TENSILE FORCES, BUCKLE WITH COMPRESSION • RESIST VARIOUS FORCES EXERTED ON THE FSU BY DEVELOPING TENSION IN THEIR FIBERS DEFINITIONS • ELASTICITY • THE ABILITY OF A MATERIAL TO RETURN TO ITS NORMAL SHAPE AFTER BEING STRETCHED OR COMPRESSED • VISCOELASTICITY • THE PROPERTY OF A MATERIAL THAT ALLOWS IT TO BEHAVE BOTH AS A FLUID AND AN ELASTIC STRUCTURE, AND WHOSE DEFORMATION IS LOAD RATE DEPENDENT • PLASTICITY • THE PROPENSITY OF A MATERIAL TO UNDERGO PERMANENT DEFORMATION UNDER LOAD STRESS/STRAIN CURVE • GRAPH THAT PLOTS THE LOAD APPLIED TO A STRUCTURE (STRESS, Y-AXIS) AND THE RESULTING DEFORMATION (STRAIN, X-AXIS) • REFLECTS THE BEHAVIOR OF MATERIALS UNDER LOAD STRESS/STRAIN CURVE OF COLLAGEN • AT REST, SINGLE COLLAGEN FIBERS ARE BUCKLED • WAVY SHAPE REFERRED TO AS “CRIMP” • TOE PHASE • COLLAGEN FIBERS ARE STRAIGHTENED, CRIMP IS REMOVED • VERY LITTLE LOAD NEEDED LOAD/DISPLACEMENT CURVE OF COLLAGEN • LINEAR PHASE • INCREASED LOAD INCREASES STRESS WITHIN FIBERS • COLLAGEN FIBERS BEGIN TO RESIST ELONGATION • MORE LOAD NEEDED TO INCREASE STRAIN • CHEMICAL BONDS BETWEEN TROPOCOLLAGEN, COLLAGEN FIBRILS, AND PROTEOGLYCANS MAY BE DISRUPTED • AREA OF MICRO-FAILURE • COLLAGEN FIBRILS START TO BE STRAINED AND BROKEN BETWEEN 3-4% STRAIN • 4% STRAIN IS APPROXIMATE MAXIMUM DEFORMATION A FIBER AN SUSTAIN WITHOUT MICROSCOPIC DAMAGE LOAD/DISPLACEMENT CURVE OF COLLAGEN • MACRO-FAILURE PHASE • IF SUFFICIENT LOAD IS APPLIED AND SUBSTANTIAL BONDS BROKEN, COLLAGEN FIBER CEASES TO RESIST ELONGATION AND FAILS DEFORMATION OF LIGAMENTS • LIGAMENTS AND JOINT CAPSULES ARE MOSTLY COLLAGEN • BEHAVIOR IS COMPARABLE TO ISOLATED COLLAGEN FIBERS • TOE PHASE • MACROSCOPIC SLACK OF LIGAMENT IS REMOVED • LINEAR PHASE • COLLAGEN FIBERS REARRANGED • BONDS BETWEEN FIBERS AND PROTEOGLYCAN STRAINED • WATER DISPLACED • REQUIRES CONSIDERABLE ENERGY • MACRO-FAILURE • INCREASING STRESS CAUSES BONDS AND FIBERS TO FAIL STRESS/STRAIN CURVE RANGES • PHYSIOLOGIC RANGES • NEUTRAL ZONE (NZ) • FIBERS IN RELAXED STATE – CRIMPED • AS TENSION INCREASES THE ELASTIC LINKS BETWEEN ADJACENT STRANDS HELP INCREASE PARTICIPATION IN LOAD CARRYING THROUGH RECRUITMENT OF COLLATERAL FIBERS • ELASTIC ZONE (EZ) • STARTS WHEN CRIMP IS REMOVED • LIGAMENTS BEGIN TO RESIST FURTHER DEFORMATION STRESS/STRAIN CURVE RANGES • YIELD STRESS • POINT AT WHICH CHEMICAL BONDS BETWEEN TROPOCOLLAGEN AND COLLAGEN FIBRILS START TO BREAK DOWN • END OF ELASTIC ZONE, BEGINNING OF PLASTIC ZONE STRESS/STRAIN CURVE RANGES • TRAUMATIC RANGES • PLASTIC ZONE (PZ) • ZONE OF PERMANENT DEFORMATION • SIGNIFICANT NUMBER OF BONDS ARE BROKEN • REDUCTION IN STRENGTH AGAINST FURTHER ELONGATION • FAILURE • COMPLETE LOSS OF RESISTANCE TO ELONGATION • SMALL FORCES NEEDED TO TEAR APART FIBRILS AND MOLECULAR BONDS VISCOELASTICITY • THE PROPERTY OF A MATERIAL THAT ALLOWS IT TO BEHAVE BOTH AS A VISCOUS AND ELASTIC STRUCTURE, AND WHOSE DEFORMATION IS TIME DEPENDENT • THE LENGTH OF TIME A FORCE IS APPLIED TO A MATERIAL WILL CHANGE THE DEFORMATION OF THE MATERIAL OVER TIME • VISCOSITY – PROPERTY OF FLUIDS TO RESIST FLUID FLOW • ELASTICITY – PROPERTY OF SOLIDS THAT DESCRIBES THE ABILITY OF A MATERIAL TO RETURN TO ITS ORIGINAL SHAPE ONCE UNLOADED • ALL TISSUES OF THE HUMAN BODY ARE VISCOELASTIC!!! • TISSUES ARE COMPOSITES OF FIBERS AND GROUND SUBSTANCE VISCOELASTICITY CREEP • INCREASED STRAIN WITH CONSTANT STRESS • LOAD APPLIED AND HELD CONSTANT • INITIAL DEFORMATION WITH ONSET OF LOAD • ELONGATION CONTINUES TO OCCUR EVEN WHEN LOAD, AND THUS STRESS, IS CONSTANT • WHEN THE FORCE IS REMOVED THE LIGAMENT NORMALLY RETURNS TO RESTING LENGTH VISCOELASTICITY STRESS RELAXATION • DECREASED STRESS WITH CONSTANT STRAIN • ELASTIC STRAIN BECOMES PLASTIC STRAIN, WHICH REDUCES STRESS • WHEN LOAD IS REMOVED, THE LIGAMENT DOES NOT RETURN TO ORIGINAL SHAPE VISCOELASTICITY HYSTERESIS • DIFFERENCE IN RATE OF DEFORMATION VS. RATE OF RECOVERY – DUE TO VISCOSITY!! • WITH LOADING AND UNLOADING, TISSUES EXPERIENCE A LOSS OF ENERGY AS HEAT DUE TO REARRANGEMENT OF CHEMICAL BONDS • WHEN LOAD IS REMOVED, THERE IS NOT ENOUGH ENERGY SAVED TO RETURN LIGAMENT TO RESTING LENGTH VISCOELASTICITY – FATIGUE FAILURE • FATIGUE FAILURE • REPETITVE LOADING AND UNLOADING CYCLES LEADS TO LOSS OF ABILITY TO RESIST LOAD • WITH EACH CYCLE, THERE IS DECREASED RESISTANCE TO DEFORMATION LOAD RATE SENSITIVITY • THE LENGTH OF TIME A FORCE IS APPLIED TO A MATERIAL WILL CHANGE THE DEFORMATION OF THE MATERIAL OVER TIME • HIGH LOAD RATE – FORCE APPLIED OVER SHORTER AMOUNT OF TIME • LESS STRESS RELAXATION, HIGHER PEAK STRESS • LOW LOAD RATE – FORCE APPLIED OVER LONGER AMOUNT OF TIME • MORE STRESS RELAXATION, LOWER PEAK STRESS 8 LIGAMENTS OF THE FSU • IVD – COVERED IN DETAIL IN IVD LECTURE • ANTERIOR LONGITUDINAL LIGAMENT • POSTERIOR LONGITUDINAL LIGAMENT • LIGAMENTUM FLAVUM • INTERSPINOUS LIGAMENT • SUPRASPINOUS LIGAMENT • INTERTRANSVERSE LIGAMENT • CAPSULAR LIGAMENT ANTERIOR LONGITUDINAL LIGAMENT (ALL) • RUNS FROM BASILAR PROCESS -> C1 ANTERIOR TUBERCLE -> ANTERIOR VERTEBRAL BODIES -> SACRUM • FIRMLY ATTACHED TO BONEY ENDPLATES OF VERTEBRAL BODIES • SLIGHTLY ATTACHED TO ANNULAR FIBERS OF IVD • LAYERED • SUPERFICIAL LAYERS SPAN SEVERAL SEGMENTS • DEEP LAYERS SPAN BETWEEN INDIVIDUAL SEGMENTS AND FILL THE NATURAL CONCAVITY OF THE ANTERIOR VERTEBRAL BODIES • NARROWER AND THICKER IN THORACIC REGION • NARROWS AT THE LEVEL OF EACH DISC • FUNCTION: CONTROLS AND LIMITS SPINAL EXTENSION ANTERIOR LONGITUDINAL LIGAMENT (ALL) • TRACTION OF THE ALL CAN LEAD TO TRACTION SPURS AT ATTACHMENT SITES • APPEAR AS ANTERIOR LIPPING ON X-RAY • CAN BE DAMAGED IN HYPEREXTENSION INJURIES • BLENDS WITH PERIOSTEUM • IRRITATION CAUSES OSTEOBLASTIC ACTIVITY • CALCIFICATION OF THE LIGAMENT • FORMATION OF AN OSTEOPHYTE (LIPPING AND SPURRING) POSTERIOR LONGITUDINAL LIGAMENT (PLL) • RUNS FROM POSTERIOR BODY OF C2 -> POSTERIOR BODIES -> COCCYX • CONTINUES AS TECTORIAL MEMBRANE ABOVE BODY OF C2 • INTERWOVEN WITH ANNULAR FIBROSIS • THICKER IN THE THORACIC REGION • WIDER AT THE LEVEL OF THE DISC, NARROW AT THE LEVEL OF THE VERTEBRAL BODY • FUNCTION: RESISTS SPINAL FLEXION LIGAMENTUM FLAVUM • HISTOLOGY • 80% ELASTIC FIBERS (MOST PURE ELASTIC FIBER IN THE HUMAN BODY) • 20% COLLAGEN • AKA “YELLOW LIGAMENT” • PAIRED LIGAMENTS THAT RUN FROM ANTERIOR/INFERIOR BORDER OF THE LAMINA ABOVE TO POSTERIOR/SUPERIOR LAMINA BELOW • CONNECT BORDERS OF ADJACENT LAMINA FROM C2 TO S1 • THICKER IN THORACIC REGION • WITH AGING – DECREASE IN ELASTIC FIBERS AND INCREASE IN COLLAGEN FIBERS LIGAMENTUM FLAVUM • FUNCTION • PRETENSION (RESTING TENSION) IN NEUTRAL POSITION • PREVENTS BUCKLING OF THE LIGAMENT INTO THE SPINAL CANAL DURING FULL EXTENSION • PRODUCES RESTING COMPRESSION ON THE DISC THAT HELPS STABILIZE THE SPINE INTERSPINOUS LIGAMENT • CONNECT ADJACENT SPINOUS PROCESSES FROM ROOT TO APEX • THORACIC SPINE - LONG AND NARROW • LUMBAR SPINE - BROAD AND THICK • CERVICAL SPINE - LIGHTLY DEVELOPED BUT EXPANDED ANTERIOR TO POSTERIOR (LIGAMENTUM NUCHAE) • FUNCTION: RESIST SPINAL FLEXION SUPRASPINOUS LIGAMENT • RUNS FROM LIGAMENTUM NUCHAE AT C7 -> SACRUM ALONG TIPS OF SPINOUS PROCESSES • ROUND, SLENDER STRAND • THICKER AND BROADER IN LUMBAR SPINE • ONLY LIGAMENT WHOSE MECHANICAL PROPERTIES HAVE BEEN STUDIED IN VIVO • FUNCTION: RESIST SPINAL FLEXION AT FULL FLEXION • TENSION IS GRADUALLY INCREASED DURING TRUNK FLEXION • MAXIMUM TENSION AT FULL FLEXION INTERTRANSVERSE LIGAMENT • RUN BETWEEN ADJACENT TRANSVERSE PROCESSES • WELL DEFINED IN THORACIC REGION AS ROUNDED CORDS • POORLY DEFINED IN LUMBAR AND CERVICAL REGIONS, BLEND WITH INTERTRANSVERSARII MM • FUNCTION: SUBJECT OF DEBATE! • BIOMECHANICALLY – PROBABLY HELP LIMIT CONTRALATERAL LATERAL FLEXION • BOGDUK – NOT “TRUE” LIGAMENTS, CREATE MEMBRANOUS SEPTUM BETWEEN ANTERIOR AND POSTERIOR MUSCULATURE CAPSULAR LIGAMENT (ARTICULAR CAPSULE) • ATTACHED JUST BEYOND THE MARGINS OF THE ARTICULAR PROCESSES • FIBERS RUN PERPENDICULAR TO THE PLANE OF THE FACET JOINTS • SHORTER AND TAUT IN THE THORACIC AND LUMBAR REGION • LOOSER IN THE CERVICAL SPINE • INNERVATED BY MECHANORECEPTORS AND NOCICEPTORS • FUNCTION: PROVIDE FLEXION STABILITY LOAD DEFORMATION CURVE OF FSU LIGAMENTS – LUMBAR SPINE • LIGAMENTS SITUATED RELATIVELY CLOSE TO CENTER OF ROTATION HAVE STEEPER SLOPES • MORE STIFF • STIFFNESS – ABILITY OF A STRUCTURE TO RESIST DEFORMATION • LIGAMENTS POSITIONED FURTHER AWAY FROM AXIS OF ROTATION HAVE LESS STEEP SLOPE • MORE FLEXIBLE • FLEXIBILITY – ABILITY OF A STRUCTURE TO DEFORM UNDER LOAD