The Skeletal System

1
Chapter 13

• The Skeletal System
• The rigid framework
• of the body

2
Clopton Havers (1691)
It is true, if we come to torture a bone with
the Fire, it seems to confess that it
consists of all the five Chymical Principles...
3
Composition and Structure of Bone Tissue

• Mechanical functions of bone
• provides a rigid skeletal framework to support
  and protect other tissues.
• forms a system of rigid levers (links) that can
  be moved by forces from the attached muscles
  (rotated by torques from the attached muscles).

4
Types of bones (206)

• Central or axial skeleton
• skull, vertebrae, sternum, and ribs
• Peripheral or appendicular skeleton
• bones of the arms and legs

5
Types of bones (overheads)

• Short bones
• limited gliding motions and shock absorption.
• Small, cubical structures (carpals, tarsals)

6
Types of bones

• Short bones
• Flat bones
• Protection, provide attachment sites
• Flat in shape (ie scapula)

7
Types of bones

• Short bones
• Flat bones
• Irregular bones
• Multi-functional
• odd shapes (ie vertebrae)

8
Types of bones

• Short bones
• Flat bones
• Irregular bones
• Long bones
• long shaft and bulbous heads (condyles,
  tubercles, or tuberosities)
• serve as levers for movement (ie tibia, femur,
  humerus, radius, ulna, clavicle, fibula,
  metatarsals, and the phalanges)

9
Material Constituents

• Calcium carbonate
• calcium phosphate
• collagen
• water

-stiffness -compressive strength
-flexibility (tensile strength)
-tensile compressive strength
10
Structural Organization (overhead)

• Cortical bone (compact)--Low porosity
• 5-30 of bone volume non-mineralized tissue.
• Trabecular (spongy\cancellous) High porosity
• 30 to gt 90 volume non-mineralized tissue.

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Structural Organization
12
Bone Comparison

• Cortical
• low porosity
• more stiff
• greater stress
• casing of all bones (epiphysis, irregular)
• diaphysis of long bones

• Trabecular
• high porosity
• more elastic
• greater strain
• interior of all bones

13
Load and Response

• Stress
• force per unit area

• Strain
• deformation
• amount of deformation divided by original length

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Generic Stress-Strain Relationship
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Bone Stress-Strain Relationship
Plastic Region
Elastic Region
Stress (load)
Fracture Threshold
Strain (deformation)
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Relative Bone Strength
Compression
Tension
Shear
17
Common bone injuries

• Fractures - with excessive loads, bone tends to
  fracture on the side loaded in tension.
• Simple - no break in skin.
• Compound - protrusion through the skin.
• Comminuted - fragmentation of the bone.
• Avulsions - bone chip pulled away
• Spiral - twisting break.
• Impacted - opposite ends compressed together.
• Stress - repeated low magnitude loading

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Site of Ankle Avulsion Fracture
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Avulsion fracture of the patella following
B-PT-B repair of the ispsilateral ACL
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Comminuted Fracture
Low Energy
High Energy
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Ankle Trouble
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Three Biological Phases to fracture healing

• Inflammatory Phase
• 3 to 7 days
• immobilize the bone
• activates cells for repair
• step by step process that is critical to
  successful union

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Three Biological Phases to fracture healing

• Inflammatory Phase
• Reparative Phase (bony union)
• about one month
• callus formation
• provisional gt bony

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Three Biological Phases to fracture healing

• Inflammatory Phase
• Reparative Phase (bony union)
• Remodelling Phase
• restoration of original contour

25
Bone Growth and Development

• Living bone is dynamic
• continually changes throughout lifespan.
• Longitudinal growth
• length increases occur at the epiphyses
• epiphyseal plates.
• produce new bone tissue until closing during
  adolescence or early adulthood.
• Circumferential growth
• Bones alter diameter throughout lifespan, with
  most rapid change before adulthood.

26

• Osteoclasts
• resorb existing bone

• Osteoblasts
• form new bone

Critical factor in bone modelling/remodelling ba
lance of their action
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Bone Response to Stress

• Wolff's law (1892)
• tissue adapts to level of imposed stress
• increased stress
• hypertrophy (increase strength)
• decreased stress
• atrophy (decrease strength)
• FORM FOLLOWS FUNCTION
• Genetics, Body weight, physical activity, diet,
  lifestyle (see note clippings)

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The pattern of trabecular bone in the greater
trochanter neck of the femur head of the femur
reflects femurs roles muscle
attachment flexibility weight transfer support
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Atrophy

• Bone weight strength decreases
• Calcium content diminishes
• reduced BMD
• trabecular integrity is lost

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Bone stimulating factors

• Rate of loading
• Magnitude
• Frequency

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Is physical decline inevitable with aging?
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No. Genetics dominates. But lifestyle modulates
.
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Changing concept of old age.
34
Osteoporosis slide presentation(Aging(?), OA and
OP)
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Effect of Peak BMD on osteoporosis
BMD
Fracture Threshold
20
50
80
AGE (years)
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Effect of Peak BMD on osteoporosis
Menopause
BMD
Fracture Threshold
20
50
80
AGE (years)
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Effect of Peak BMD on osteoporosis
Typical peak BMD
BMD
Fracture Threshold
20
50
80
AGE (years)
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Effect of Peak BMD on osteoporosis
BMD
Low peak BMD
Fracture Threshold
20
50
80
AGE (years)
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Effect of Peak BMD on osteoporosis
High peak BMD
BMD
Fracture Threshold
20
50
80
AGE (years)
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Effect of Peak BMD on osteoporosis
Can the rate of BMD decrease be altered?
BMD
Fracture Threshold
20
50
80
AGE (years)
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DEXA Scans
Click here to read about DEXA scans
42
Calcium Intake
Check out this site with information on calcium
and osteoporosis
43
Joint Architecture Classification

• Synarthoses (immovable)
• Amphiarthroses (slightly movable)
• Diarthroses or synovial (freely movable)
• Get our attention

44
William Hunter (1743)
The bone ends are covered with a smooth
elastic crust, to prevent mutual abrasion
connected with string ligaments, to prevent
dislocation and enclosed in a bag that contains
a proper fluid deposited there for lubricating
the two contiguous surfaces.
45
Synovial Joint Features

• Articular (hyaline) cartilage
• covers articulating surfaces
• no blood vessels
• no nerves
• Serves 3 purposes
• reduces friction
• increases articulating area to reduce stress
• shock absorption

46
Synovial Joint Features

• Articular (hyaline) cartilage
• Articular (fibrous/joint) capsule
• double layer membrane surrounds synovial joint
• outer connects bones
• inner secretes synovial fluid
• may have definite ligaments

47
Synovial Joint Features

• Articular (hyaline) cartilage
• Articular capsule
• Synovial fluid
• clear, slightly yellow liquid
• lubricates joint
• nourishes cartilage

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Synovial Joint Features

• Articular (hyaline) cartilage
• Articular capsule
• Synovial fluid
• Fibrocartilage
• disc or partial disc between articulating bones.
• Intervertebral discs menisci
• increase surface area reduce stress
• improve fit of articulating surfaces
• limits translation or slip of bones
• shock absorption

49
Synovial Joint Features

• Articular (hyaline) cartilage
• Articular capsule
• Synovial fluid
• Fibrocartilage
• Tendon sheaths
• surround tendons located close to bones
• reduce stress on tendon
• maintain low friction

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Synovial Joint Features

• Articular (hyaline) cartilage
• Articular capsule
• Synovial fluid
• Fibrocartilage
• Tendon sheaths
• Bursae
• small synovial fluid filled capsules
• separate tendon from bone to reduce friction

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Mobility is a very precious gift. More complex
than the space shuttle.
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Total Hip Implants
Acetabular Component
Polyethylene Liner
Metal Shell
Head
Collar
Stem
Osteotomy Line
Femoral Component
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Osteoarthritis Slide Show
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Osteoarthritis Slide Show
Click on the info button to read on NSAIDs
55
Joint Stability

• ability to resist abnormal displacement of the
  articulating bones
• Dislocation - bones displace out of their normal
  positions.

Impingement
Subluxation
Dislocation
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Joint Stability

• ability to resist abnormal displacement of the
  articulating bones
• Contributing factors
• shape of articulating surfaces
• close-packed position position of max contact
• knee, wrist, interphalangeal full extension
• ankle full dorsiflexion
• loose-packed position position other than c-p
• most prone to dislocation, cartilage damage

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Joint Stability

• ability to resist abnormal displacement of the
  articulating bones
• Contributing factors
• shape of articulating surfaces
• arrangement of ligaments muscles
• concept of rotary stabilizing components of
  muscle/ligament tension
• rotary component that causes/tends to cause
  rotation
• stabilizing acts parallel to the bone

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Flexibility ROM at a joint
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Joint Flexibility

• Factors influencing joint flexibility
• Shape of articulating bones
• other soft tissue stiffness mass
• muscle current tone
• ligaments arranged in direction of expected pull
• fatty tissue
• temperature warmer more pliant
• past injury collagen alignment integrity
• clothing
• AGE??? vs inactivity

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Why is flexibility important?

• Basic component of a fitness profile.

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Why is flexibility important?

• Basic component of a fitness profile.
• allows for greater choice of movement patterns
• slides of gymnasts
• elderly shoulder ROM independence
• Osteoarthroses
• contractures (ie cerrebral palsy)
• sprain ankle inflammation

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Why is flexibility important?

• Basic component of a fitness profile.
• allows for greater choice of movement patterns
• reduce risk of injury
• absorb energy over a greater distance (time)
• CAVEAT Risk of injury increased with ROM high,
  or low
• slide next overhead

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From Cowan et al, 1988, ref 304
64
Why is flexibility important?

• Basic component of a fitness profile.
• allows for greater choice of movement patterns
• reduce risk of injury
• Increase forceful performance
• apply force over a greater distance (time)
• violation of principle of summation of joint
  force
• violation of principle of IMPULSE

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Techniques for increasing joint flexibility
Best Advice Use It Dont Lose It
66
How best to stretch?
67
Techniques for increasing joint flexibility

• Review neural innervation
• Golgi tendon organs (figure 5-11)
• located in junctions between muscles and tendons
• responsive to tension in tendon
• inhibits tension development in active muscle

68
Techniques for increasing joint flexibility

• Review neural innervation
• Golgi tendon organs
• Muscle spindles (figure 5-12)
• located parallel to the muscle fibers in the
  belly of the muscle
• responsive to lengthening of fibers (rate
  length) Stretch Reflex
• activate stretched muscle, inhibit antagonist
  (reciprocal inhibition)

69
Techniques for increasing joint flexibility

• Review neural innervation
• Golgi tendon organs
• Muscle spindles
• Flexibility training goal
• do not invoke stretch reflex (do not activate the
  muscle group to be stretched) HOW???
• activate golgi tendon organs (further inhibit the
  muscle group to be stretched (reduce tonus))
  HOW???

70
Types of stretching

• Active - stretching muscles, tendons, ligaments
  by active development of tension in the
  antagonist muscles
• Passive - stretching muscles, tendons,
  ligaments by a force other than tension in the
  antagonist muscles (gravity, another segment,
  another person)

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Types of stretching

• Ballistic - a series of quick, bouncing
  movements.
• Static - a slow controlled stretch held over time
  (10-30s, 3 to 4 reps)
• Proprioceptive Neuromuscular Facilitation -
  alternating contraction and relaxation of the
  muscles being stretched.
• Contract-relax pull-contract