Chapter 5 mechanisms of injury
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Chapter 5 - Mechanisms of Injury. Physical process responsible for a given action, reaction or result. Why is it necessary to determine the mechanism of injuries?. Important for the diagnosis, rehabilitation and prevention of injuries. Depends persons perspective

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Chapter 5 - Mechanisms of Injury

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Chapter 5 - Mechanisms of Injury

Physical process responsible for a given action, reaction or result


Why is it necessary to determine the mechanism of injuries?

Important for the diagnosis, rehabilitation and prevention of injuries


Depends persons perspective

Mechanism often acts in combination

Establish cause and effect relationship

Sport medicine classification

Contact or impact

dynamic overload

overuse

structural vulnerability

inflexibility

muscle inbalance

rapid growth

Injury Mechanism


Mechanical Loading

  • Loads greater than physiological lead to injuries

  • Chronic injuries

    • cumulative trauma

    • repetitive stress

  • Acute injuries


Principles of Injuries

  • Catch-all terms

    • shinsplints

    • tennis elbow

    • jumper’s knee

  • Level of dysfunction

    • catastrophic injuries

  • Progression

    • untreated or lack to time to heal lead to more severe injuries


Clinical classifications

help assign common characteristics to injuries

Severity linked to amount of tissue damage

Mild & moderate: partial disruption, tissue is able to accept loads

Ligaments

grade 1 mild

negligible structural

minimal time loss

grade 2 moderate

partial rupture

swelling tenderness

up to 6 wk time

grade 3 severe

complete, gross swelling, 8 wk min

Assessment of Severity


Injury Principles

  • Micro vs macrotrauma

  • Primary: direct consequence of trauma

  • Secondary

    • injury surface after original trauma

    • accommodation to primary injury (adaptation of loads)

  • Tissue structure


Age

acute injuries: young

chronic: older

Gender

Genetics

Fitness level

Nutrition

Psychological

Human interaction

Fatigue

physical & mental

Environment

Equipment

protective

contributes to injuries

Previous injury

Disease

Drugs

Rehabilitation

Anthropometrics

Skill level

Experience

Pain

Contributing factors


Tissue Injury

  • Inflammation: pathological process

    • vascular response

    • increase capillary permeability (swelling)

  • Pain: swelling related pressure on nerve endings (more in confined spaces)


Vasodilatory phase

flow of fluid/plasma proteins into tissue

Plasma proteins

fibrinogen

Functions

dilutes & inactivates toxins

nutrients to inflammatory cells

antibodies, proteins

Control of inflammation

Chemicals mediators

histamine, serotonin, bradykin, prostagladins, plasmin etc.

Other Cells

Phagocytes (fungal and bacterial infection)

Lymphocytes (antigens)

Tissue Injury


Why inflammation?

Body’s first line of defense against injuries


Bone

  • Any conditions that affects osteocyte performance

  • Osteonecrosis: cessation of blood flow

    • vessel disruption

    • occlussion

    • injury or pressure to arterial walls

  •  matrix, bone strength

  •  likelihood of fracture


Bone

  • Osteoporosis

  • Major public health issue

  • Affect mostly trabercular bone

  • Bone of axial skeleton

  • Multifactor

  • Clinical conditions


Bone

  • Fracture (break): applied loads exceeds bone’s ability

  • Resistance

    • material properties

    • geometry

    • anisotropic effects

    • porosity

  • Type of loading

    • acute vs chronic


Fractures

  • Indirect or direct

  • Risk and type of bone

  • Diagnosis

    • site

    • extent of injury

    • configuration

    • fragments (displaced)

    • environmental (open closed)

    • complications

    • etiological


Fractures

  • Healing phases:

    • inflammation

    • union of bony ends (3wk)

    • callus remodeling (6 wks)


Articular Cartilage

  • Excessive loading

    • loss of cartilage matrix

    • chondral fractures

    • osteochondral fracture

  • Inability to repair


Articular Cartilage

  • AO

    • non inflammatory

    • weight bearing joints

    • deterioration of AC

    • osteophytes formation

    • cartilage fibrillation

  • Artificial Joints

    • cemented or non


Fibrocartilage

  • Distributes forces at joints

  • Shock absorber

  • Improve joint fit

  • menisci

  • intervertebral disks


Tendon

  • Force transfer

  • Injuries

    • direct (cuts)

    • indirect (excessive loads applied to unit)

  • Musculotendinous injuries: Strain

    • Mild, moderate, severe

    • severe: precede by microdamage


Repetitive overloading: inflammatory response or tendinitis

Also could affect tendon sheath, peritenon etc.

Healing

Inflammation

Synthesis of collagen and GAG (matrix)

Cyclic loading (2-3 wk)

Progressive stress

Peritenonitis

Tendinosis (intratendinous degeneration dut ot atrophy)

Tendinitis (Symptomatic degeneration vascular disruption and inflammation

Tendon


Ligaments

  • Ligament injuries

    • sprain

    • partial tears

    • complete tears

  • Healing

    • bleeding & inflammation (fibrin, fibroblas scar cells)

    • proliferation of building material (scar tissue)

    • matrix remodeling

      • smaller fibers

      • lack organization


Muscle

  • Injuries

    • Acute muscular strain

      • overstreching or overloading

      • force, rate, application

      • moderate:partial tear

      • severe: complete tear, hemorrage, swelling

    • contusions

      • intramuscular bleeding

      • myositis ossificans

    • exercise induced injury

      • DOMS 24-72 hr after exercise

      • eccentric


Skin

  • Abrasions

  • Contusions

  • Penetrating wounds

    • obscure deeper damage

  • Lacerations

  • Infection

  • Excessive bleeding


Not musculoskeletal

Greatest potential for dysfunction

Injuries

chemical

thermal

ischemic

mechanical

entrapment

trauma: compressive or tensile

Temporary or complete axonal discontinuity

Motor impairment can lead to secondary injuries

Nervous tissue


Nervous Tissue


Nervous Tissue

  • Compartment or entrapments of nerves or vessels

    • Increase pressure transmitted

    • Enclosed spacing

  • Symptons

    • numbness, tingling & pain

    • decreased vessel perfusion

  • Inflammation: positive feedback loop


Joint Injuries

  • Excessive loading

  • Dislocation (luxation)

  • Partial dislocation (subluxation)

  • Synovitis

  • Arthritis

    • OA

    • RA

    • Gouty


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