Mechanisms of Injury Flashcards

1
Q

How are injuries classified?

A

Cause-based or tissue-based

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2
Q

What are the cause-based classifications of injuries?

A

1) Primary
- Direct/extrinsic
- Indirect/intrinsic
- Overuse

2) Secondary (re-injury)
- Short term
- Long term

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3
Q

What is the cause of a primary direct/extrinsic injury?

A

External causes, such as a collision with another athlete or piece of equipment

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4
Q

What can primary direct/extrinsic injuries result in?

A

Fractures, joint dislocation, ligament/muscle injury and skin abrasions

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5
Q

What is a primary indirect/intrinsic injury?

A

An injury caused by the athlete to themselves, e.g. inadequate warm-up

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6
Q

What is a primary overuse injury?

A

When apposing structures are in constant contact resulting in frictional wear between the structures e.g. bursitis

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7
Q

What are secondary short term and long term injuries?

A

Short term: Injury following previous mismanagement

Long term: Injury that leads to degenerative problems e.g. osteoarthritis

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8
Q

What are the tissue-based classifications of injuries?

A

Soft tissue, hard tissue, special tissue/organ

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9
Q

What is classified as soft tissue?

A
  • Skin
  • Musculotendon unit/tenoperiosteal
  • Muscle compartments
  • Joints (ligaments/tendons)
  • Intervertebral discs
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10
Q

What is classified as hard tissue?

A
  • Bone

- Cartilage (hyaline, articulate, epiphyseal)

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11
Q

What is classified as special tissue/organs?

A
  • Brain/nerves
  • Eyes/nose/sinus/larynx/teeth
  • Thoracic/abdominal/pelvic organs
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12
Q

Describe the characteristics of collagen

A
  • Most abundant protein in the body
  • Linear, stable, water insoluble
  • Cross-linked fibres
  • Withstands high longitudinal stress
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13
Q

What are the 6 forms of collagen based on?

A

Molecular chain structure, location and function

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14
Q

Where is type 1 and 2 collagen located?

A

Type 1: Synovium, bone, tendon, skin and eyes

Type 2: Cartilage, eyes

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15
Q

What is the relationship between the collagen type number and the fibre diameter?

A

As the collagen type number increases, the fibre diameter decreases (e.g. type 1 is the largest)

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16
Q

What type of collagen is used for repair injuries?

A

Type 3

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17
Q

What are the three phases of general pathology repair?

A
  • Acute inflammation response
  • Matrix and cellular proliferation
  • Remodelling and maturation
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18
Q

When does the acute inflammation response phase occur and how long does it last?

A

0-72 hours post injury, can last up to 6 days

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19
Q

How is acute inflammation treated?

A

RICER

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20
Q

What are the steps of the acute inflammation response phase?

A

1) Damaged tissues release histamines, increases blood flow to the area
2) Histamines cause capillaries to leak, releasing phagocytes and clotting factors into the area
3) Phagocytes engulf the bacteria, dead cells and cellular debris (phagocytosis)
4) Platelets move out of the capillary to seal the wounded area

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21
Q

What is the effect of aspirin on the healing process?

A

It delays the healing process

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22
Q

What are the steps of phagocytosis?

A

1) Microbe adheres to phagocyte
2) Phagocyte forms pseudopods
3) Phagocytic vesicle containing antigen fuses with a lysosome (phagolysosome)
4) Microbe in fused vesicle is killed and digested by lysosomal enzymes
5) Indigestible and residual material is removed by exocytosis

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23
Q

What are the functions of inflammation?

A
  • Destroys injurious agents
  • Dilutes toxic chemicals
  • Cleans up necrotic waste
  • Paves the way for repair
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24
Q

What are the steps of the matrix and cellular proliferation phase?

A
  • Proliferation of capillaries and fibroblasts
  • Collagen/proteoglycan matrix production
  • Formation of granulation tissue
  • Capillary network budding
  • Fibroblasts produce type 3 collagen
  • Contraction of wound
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25
Q

What is the role of fibronectin in the matrix and cellular proliferation phase?

A

Acts as an anchoring compound

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26
Q

When does the matrix and cellular proliferation phase occur?

A

72hrs - 6 weeks + post-injury

27
Q

When does the remodelling and maturation phase occur?

A

6 weeks - months post-injury

28
Q

What does the length of the remodelling and maturation phase depend on?

A

Person’s conditioning, rehabilitation completed and the tissue damaged

29
Q

What are the steps of the remodelling and maturation phase?

A
  • Contraction continues
  • Reorientation of collagen fibrils (becomes much more organised)
  • Collagen matures
  • Cell numbers decrease
30
Q

What is the effect of a musculotendinous injury?

A

Increased stiffness of terminal sarcomeres and membrane infolding is no longer reproduced

31
Q

How long should a musculoteninous injury be immobilised for and why?

A

1-5 days. Immobilisation in a shortened position for more than 7 days causes stiffness from intramuscular collagen and loss of sarcomeres

32
Q

What are the guidelines for mobilisation?

A
  • Don’t mobilise until the repair tissue is sting enough (gradual process)
  • Light stretching helps elongate new sarcomeres
  • Should involve stretching for 30 minutes daily (passive then active)
33
Q

Where is microfatigue most common?

A

In heavily repetitive loading areas

34
Q

What is the cause of spontaneous tendon rupture and who is most at risk?

A

The degenerative pathology of collagen fibrils, older people

35
Q

What is the mature composition of ligaments and tendons?

A
  • Large diameter type 1 collagen fibrils, tightly packed
  • Small amounts of type 3 collagen
  • Elastic fibres
  • Proteoglycan gel (fluid matrix)
36
Q

What are the three regions of a strain curve and what does it represent?

A

Toe, linear and rupture. Represents the relationship between injury and load deformation

37
Q

Describe the toe region of the strain curve

A

Collagen crimp is flattened by 3-4%, but no damage occurs due to elastic properties

38
Q

Describe the linear region of the strain curve

A

Partial rupture of cross links, 5-10% strain of initial length

39
Q

What are the two grades of the linear region of the strain curve?

A

Grade 1 = 0-50% fibre disruption

Grade 2 = 50-80% fibre disruption

40
Q

Describe the term ‘fibre disruption’

A

When the yield point is reached and deformation of fibres continues after the load has been removed (i.e. permanent changes)

41
Q

Describe the rupture region of the strain curve

A

10-20% strain of initial length, results in Grade 3 injury (>80% fibre disruption)

42
Q

What are the indicators of each grade of ligament/tendon injury?

A

Grade 1: Little bit of pain
Grade 2: Asking for ice/strapping
Grade 3: Past strapping, requiring rest/rehab/surgery

43
Q

What are the three phases of repair for ligaments and tendons?

A
  • Acute inflammation (0-72 hours)
  • Proliferation (4-6 weeks)
  • Remodelling and maturation (6 weeks - 12 months)
44
Q

What occurs during the acute inflammation phase of ligament and tendon repair?

A
  • Injury gap is filled with erythrocytes and leucocytes (swelling)
  • Monocytes and macrophages predominate for phagocyctosis
  • Fibroblasts commence deposition of type 3 collagen
45
Q

What occurs during the proliferation phase of ligament and tendon repair?

A
  • Fibroblasts predominate
  • Increased H2O content (replacing proteoglycan gel)
  • Increased collagen, peaks during weeks 3-6
46
Q

What is the result of increased scar collagen in ligament and tendon repair?

A

Increased tensile strength of ligament matrix

47
Q

What occurs during the remodelling and maturation phase of ligament and tendon repair?

A
  • Decrease in fibroblasts
  • H2O returns to normal
  • Scar matrix continues to mature slowly
48
Q

What is intrinsic muscle injury usually attributed to?

A

Inadequate muscle length/strength and proprioception and muscle fatigue

49
Q

Where do the majority of muscle injuries occur and why?

A

Lower limb two-joint muscles, i.e. quads, hamstrings, calves. Due to complex reflexes (co-contraction and co-relaxation)

50
Q

When does muscle sarcomere disruption at the Z lines occur?

A

When continually using eccentric exercise

51
Q

What are muscle contusions?

A

Common extrinsic injuries that follow the 3 phases of tissue repair

52
Q

Why is immobilisation of muscle injuries important?

A

Allows granulation tissue to form with enough tensile strength to survive early muscle contraction

53
Q

Why is mobilisation of muscle injuries important?

A

Required for muscle fibres to gain tensile strength and orientate through the reabsorbing connective scar tissue

54
Q

What are some of the causes of stress fractures?

A

Overtraining, not enough rehab, overloading, change in environment

55
Q

What are some of the symptoms of stress fractures?

A

Point tenderness, swelling, pain, visible deformity

56
Q

What are avulsion fractures associated with?

A

Loading tendons/ligaments

57
Q

What are the two types of acute fractures?

A

Open: Tissue damage, bone may penetrate through skin
Closed: No displacement of bones (still aligned)

58
Q

How long should fractures be immobilised in children and adults?

A

Children: 4-6 weeks
Adults: 6-8 weeks

59
Q

What are the four steps of bone repair?

A

1) Hematoma formation (bleeding)
2) Fibrocartilaginous callus formation
3) Bony callus formation
4) Bone remodelling

60
Q

What are the three types of cartilage injury?

A

1) Superficial lacerative injury
2) Defect down to subchondral bone
3) Blunt trauma

61
Q

Describe super lacerative cartilage injuries

A
  • Laceration down to calcified zone (bone level)
  • No acute inflammation (due to no blood supply)
  • Lesions unchanged over years/further damage
  • No osteoarthritis (as not at bone level)
62
Q

Describe cartilage injuries that reach the subchondral bone

A
  • Inflammatory reaction (blood supply)
  • New subchondral bone plate forms
  • Defect fills with type 1 & 3 collagen & new type of proteoglycan
  • New matrix is not as strong
63
Q

Describe blunt trauma cartilage injuries

A
  • Trauma below fracture level
  • Can cause chondrocyte changes, which alter matrix
  • Can lead to chondromalacia (e.g. runners knee)