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DPT 726: Orthopaedic Foundations > Connective Tissue Biomechanics: Part II > Flashcards

Connective Tissue Biomechanics: Part II Flashcards

1
Q

Introduction

A
  • connective tissue is the building block of bone, ligament, tendon, cartilage, joint capsules, intervertebral discs
  • tissues affected by lifespan, injury, pathology, physical activity, hydration, sex
  • understanding biologic and mechanical nature of these tissues provides insights necessary for prevention and management of injuries to these structures-allows us to better balance stress and recovery in these tissues
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2
Q

CT and Musculoskeletal System

A
  • a junction between two or more bones
  • allow for varying degrees of motion: rotation, transfer and absorb force
  • allow for varying degrees of segmental growth
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3
Q

Osteoarthritis and Joints

A
  • cartilage becomes worn away, spurs grow out from edge of bone, and synovial fluid increases
  • stiff and sore joints
  • do right type of exercise to get the most amount of mileage out of joint
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4
Q

Synarthrosis

A
  • held together by dense irregular connective tissue
  • allows little or no motion
  • functions: bind bones together, transmit force with little joint motion
  • stability and force transmission decrease potential for injury
  • types: sutures, gomphoses, and syndesmoses
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5
Q

Sutures

A

-2 bones grow together separated by only thin layers of fibrous periosteum

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6
Q

Gomphosis

A

-binds teeth to bony sockets separated by only thin layers of fibrous periosteum

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7
Q

Syndesmosis

A
  • joint bound by ligament only

- most mobility of fibrous joints

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8
Q

Amphiarthrosis

A
  • cartilaginous joints
  • bones separated by hyaline or fibrocartilage
  • functions: joint stability, minimal to moderate movement, shock absorption
  • types: symphysis and synchrosis
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9
Q

Symphysis Joint

A

-segment of fibrocartilage joints bones

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10
Q

Synchondrosis

A

-hyaline cartilage joins bones

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11
Q

Diarthrosis

A
  • aka synovial joint
  • has fluid filled cavity which encapsulates the ends of the bones
  • possess a joint space
  • affords a large amount of motion: bone ends are not directly connected
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12
Q

Characteristics of Synovial Joints

A
  • synovial fluid provides lubrication and nutrition to cartilage and other structures within joint
  • hyaline cartilage covers ends of bones
  • articular capsule
  • vascular supply system supplies capsule but does not enter joint cavity
  • receptors provide proprioception
  • other elements include menisci, fat pads, labrum
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13
Q

Hinge Joint

A
  • movement about single axis
  • one degree of freedom
  • ex: humeroulnar joint
  • degrees of freedom mean how many motions are available at the joint
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14
Q

Pivot Joint

A
  • one segment is ring shaped
  • other is shaped so it can rotate within ring
  • ex: humeroulnar joint
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15
Q

Ellipsoid Joint

A
  • one segment has an elongated convex surface
  • the other is an elongated concave surface
  • ex: radiocarpal joint, ulnocarpal joint
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16
Q

Ball and Socket

A
  • one segment has a spherical convex end
  • other has concave surface
  • ex: hip joint
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17
Q

Plane Joint

A
  • bones are relatively flat allowing for gliding and some rotation
  • ex: carpal joints, subtalar joint
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18
Q

Saddle Joint

A
  • aka sellar joints
  • each segment has both convex and concave portions
  • ex: sternoclavicular joint
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19
Q

Condyloid Joint

A
  • shallower version of ball and socket joint

- ex: atlanto-occipital joint

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20
Q

Synovial Joint Capsule

A
  • functions to encapsulate joint
  • produces and contains synovial fluid
  • provides nutrition for articular cartilage
  • layers of capsule: fibrous/stratum fibrosum, synovial membrane/stratum synovium which has 3 layers subsynovial tissue and intima,
  • stratum synovium is not a true membrane and is poorly vascularized
  • type A synoviocytes clear joint of waste materials
  • type B synoviocytes provide viscosity to synovial fluid
  • synovial membrane lines entire joint cavity except over surfaces of articular cartilage menisci-absorb as well as secrete
  • outer fibrous capsule thickens in some areas to form ligaments
  • synovia-covered fat pads prevent creation of joint vacuum
21
Q

Synovial Joint Fluid

A
  • viscous, pale, yellow, clear fluid
  • component of plasma to which glycoproteins and hyaluronic acid have been added
  • also present in synovial sheaths and bursae
  • has no fibrinogen so does not clot
  • functions: absorbs and transmits forces, nourishes articular cartilage, decreases friction between joint surfaces, provides a medium for diffusion of nutrients and waste between articular cartilage and synovial membrane
  • principle components: water, proteoglycans, hyaluronic acid, lubricin
22
Q

Embryonic Development of Synovial Joints

A
  • articular disk of mesenchymal tissue appears at the future site of joint
  • dense tissue surrounds the primitive joint plate and is forerunner of the joint capsule
  • clefts or spaces are evident by 7th or 8th week of embryonic life filled with tissue fluid
  • active intrauterine movement is crucial for joint health
23
Q

Joints and Exercise

A
  • short-term effects of clinical exercise: articular cartilage thickens (improved force dissipation), 2-3 times increase in volume of synovial fluid in a joint
  • evidence supports endurance exercise’s benefits over strength training on ligament strength
  • DJD (osteoarthritis): thinning articular cartilage, thickening compact bone under articular cartilage, possible genetic aging and environmental factors impact DJD development, regular runners do not have greater incidence of osteoarthritis
24
Q

Articular Cartilage

A
  • hyaline cartilage
  • pearly white, partially translucent
  • viscoelastic tissue: elastic solid, viscous liquid
25
Q

Histological Structure of Articular Cartilage

A
  • completely devoid of blood vessels, lymphatic vessels, and nerve fibers
  • chondrocytes live normally in immunologic isolation
26
Q

Histological Structure of Articular Cartilage

A
  • gel matrix: tissue fluid primarily water, collagen, proteoglycans
  • cartilage is hydrophilic: fluid can move in and out, gives cartilage its turgidity
  • hyaline cartilage has percentage of type II collagen: provides great strength, especially in compression
  • proteoglycans are hydrophilic: glue collagen fibers together, provide resillence and elasticity
27
Q

Histologic Structure of Articular Cartilage

A
  • chondrocytes: produce both collagen and proteoglycans, more metabolically active early in life
  • chondrocytes respond to many stimuli: AROM, PROM, hormones, drugs
  • Immobilization leads to stasis of synovial fluid, disuse atrophy of cartilage
28
Q

Articular Cartilage

A
  • creates extremely small coefficient of friction
  • motion occurs between two thin fluids rather than surfaces of articular cartilage
  • variable thickness
  • bundles of collagen fibers form arcades
29
Q

Menisci

A
  • exist in knee
  • comprised of fibrocartilage rather than hyaline articular cartilage
  • provide greater articular joint surface area
  • extra-cellular matrix consists of mainly type I collagen
30
Q

Ligaments

A
  • composed of dense regular connective tissue
  • contain an abundance of type I collagen
  • have remarkable tensile strength
  • neither ligaments nor tendons tear out of bone
  • function to connect bone to bone, add to the mechanical stability of joints, help to guide joint motion
31
Q

Comparative Composition of Ligaments and Tendons

A
  • similar in water and solid makeup

- more alike than different

32
Q

Biomechanical Characteristics of Ligaments

A
  • possess high tensile strength yet injuries due to even higher tensile loads
  • flexibility allows motion around bony architecture
  • stress-strain properties apply to ligaments
  • length may change over time secondary to viscoelasticity, creep, immobilization, etc
  • heating to 60* C leads to irreversible shrinkage: thermal capsulorrhaphy, used to rx joint laxity
  • failure occurs through ligament’s body of through avulsion fracture
33
Q

Effects of Aging on Ligaments

A
  • rupture typically by avulsion before adolescence

- rupture to ligament body after maturation

34
Q

Hormonal Effects on Ligaments

A
  • ACTH and cortisone lower GAG content
  • cortisol decreases synthesis of type I collagen
  • relaxin softens pelvic ligaments released during pregnancy
  • estrogen may affect tensile strength of ligaments
35
Q

Effects of Immobilization of Ligaments

A
  • decreased stiffness (slope of curve)
  • reduction of load at failure
  • increased rate of avulsion fracture over failure of ligament body
  • decrease in collagen fiber size
  • alteration in collagen orientation
  • decrease in number of collagen cross links
  • water and GAG content decreased
36
Q

Types of Ligamentous Injuries

A
  • 1st degree: few symptoms, some pain, does not affect joint stability
  • 2nd degree: often experience high pain, some joint instability, partial rupture of ligament, strength and stiffness decreased by 50%
  • 3rd degree: may have severe pain, but often less pain sooner after injury, joint stability is compromised, complete rupture of ligament, linked to early DJD
37
Q

Tendons

A
  • comprised of dense CT
  • contain an abundance of type I collagen
  • have remarkable tensile strength
  • tendons are wrapped in synovial sheaths at sites of friction
  • neither tendons nor ligaments tear out of bone
  • fx: attach muscle to bone, transmit tensile load from muscle to bone, serve as dynamic restraint to joint motion, enable muscle belly to act a distance from a joint
38
Q

Tendon Related Structuctures

A
  • fibrous sheaths: canals which allow tendon gliding, ex: located in long tendons of hands and feet, located only where tendons change direction has increased friction or lube is needed
  • reflection pulleys: tense reinforce fibrous sheaths, located in areas that tendons change direction
  • synovial sheaths: small access tunnels for tendons at bone, reduce excess friction, composed of 2 thin sheets which form a closed duct system which traps peritendinous fluid
39
Q

Peritendinous Sheath

A
  • aka paratenon
  • located in tendons without synovial sheath
  • surrounds tendon to decrease friction
40
Q

Tendon Bursae

A
  • located at points where tendon comes in contact with bony prominence
  • serves to reduce friction of tendon on bone
41
Q

Structural Characteristics of Tendons

A
  • paratenon functions as elastic sheath
  • permits free movement of tendon within surrounding tissue
  • very high tensile strength
  • mesotenon (vincula)
  • epitenon: then surrounds each fiber bundle and forms the tendon
  • endotenon: surrounds each tendon fiber, binds them together into bundles, allows free gliding of each fiber, large water and PG is needed for friction free sliding, also creates pathway for blood, nerve, and lymphatic supplies
42
Q

Osteotendinous Junction

A
  • four zones exist at this junction: tendon, fibrocartilage, mineralized fibrocartilage, bone
  • failure here typically occurs thru avulsion fracture
43
Q

Myotendinous Junction

A

-junction of the muscle and the tendon
-forces are transmitted between muscle and tendon
-collagen in tendon and muscle join at finger like projections: increases surface area 10-20 times, increases strength of this junction
-still the MTJ is the weakest segment of muscle tendon unit
-susceptible to injury
surface area of MTJ is 30-40% greater in type II fibers: basis for high force and velocity movement, allows MTJ to transmit high loads without increasing strain at this junction

44
Q

Biomechanical Characteristics of Tendons

A
  • possess high tensile strength: yet injuries due to even higher tensile loads
  • flexibility allows motion around bony architecture
  • stress-strain properties apply to tendons
  • length may change over time secondary to viscoelasticity, creep, immobilization, poor motor recruitment patterns, etc
  • failure occurs through tendon’s body or through avulsion fracture
45
Q

Effects of Aging on Tendons

A
  • rupture typically by avulsion before adolescence

- rupture to tendon body after maturation

46
Q

Hormonal Effects on Tendons

A
  • ACTH and cortisone lower GAG content
  • cortisol decreases synthesis of type I collagen
  • estrogen may affect tensile strength of tendons-link to SSRI use in some research
47
Q

Effects of Immobilization on Tendons

A
  • decreased stiffness (slope of curve)
  • reduction of load at failure
  • increased rate of avulsion fracture over failure of ligament body
  • decrease in collagen fiber size
  • alteration in collagen orientation
  • decrease in number of collagen cross-links
  • water and GAG content decreased
48
Q

Chronic Effects of Diabetes on Tendons

A
  • tendon contractures 29%
  • tenosynovitis 59%
  • joint stiffness 40%
  • capsulitis 15%
49
Q

Types of Tendinous Injuries

A
  • strain: results from excessive tensile load to myotendinous unit; counterpart to sprain in ligaments
  • tendonitis: chronic overuse of tendon leads to microscopic tears within collagen matrix-gradually weakens tissue over time; often used interchangeably with tendinosis: limited understanding of tendinopathies by medical community
  • eccentric loading of important part of therapeutic exercise for strain and tendinitis-particularly for highly active patients
  • tenosynovitis: inflammation of fluid filled sheath that surrounds a tendon

DPT 726: Orthopaedic Foundations (14 decks)

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