ATR2010 Module 2: Injury Process

There is no universal acceptable definition of sports injury. Injuries are characterized by…

1. Sport participation: game, practice, or sanctioned event (conditioning or weight-lifting)

2. Body area involved: head, knee, shoulder, ankle

3. Mechanism: applied mechanical force(s) that cause injury (trauma) to tissues, factors include speed, size, and vectors (directions) of forces

4. Tissue damaged: muscle, connective (ligament, fascia, cartilage, bone) neural, etc

5. Severity: mild (grade 1/first degree), moderate (grade 2 or 2nd degree), or severe (grade 3 or 3rd degree)

Identifying risks as causative factors in injury

• Intrinsic risk factors: Age, Gender, Physical, Psychological, Injury history

• Extrinsic risk factors: environment, equipment, conditioning and training errors

• Some can be controlled (weak or inflexible muscles), others cannot (age)

Intrinsic risk factors

• Age: chronological and biological

• Gender (biological s*x)

  • Heritable traits: genetics

• Physical: body size/morphology

  • Weak muscles

  • Lax “loose” or unstable joint

  • Fitness level

  • Resiliency

• Psychological

  • Psyche/affect (attitudes)

  • Persona (personality traits)

  • Dispositional

• Injury history: are you injury prone?

Extrinsic risk factors

• Environment

  • Type of activity

  • High risk exposures

  • Training conditions

  • Weather

• Equipment (ex. restrictive clothing, gear)

• Conditioning and training errors

  • Overtraining or undertraining

  • Diet and hydration

  • Insufficient rest and recovery

Mechanical forces of injury (3 types)

1. Compressive: direct blow, blunt forces, crush

2. Tension (tensile): stretching or pulling apart

3. Shear (friction): rubbing or twisting

• Connective tissues are more resistant to tensile forces, and less resistant to compressive/shear forces

• Pulling a muscle/tendon = tensile force

• Therefore, injuries usually occur as a result of a combination of forces

• Critical forces?

Concept of “critical force”

• Soft tissue injuries (ligament, tendon, muscle) and bone

• In most injury cases: tendons, ligaments, and bone are progressively weakened by micro-damage (chronic attenuation) accumulated during each sub-maximal loading cycle before it can be repaired (insufficient recovery)

• Leads to acute macro-trauma

  • From chronic micro-trauma

  • Tear, fracture, or rupture

• KEY: Prevention

Threshold for damage or injury (yield point)

• Macro-trauma: single force

• Micro-trauma: multiple, repetitive forces (fatigue)

• Question of how much stress a structure can withstand without failing

Critical forces may vary within the same tissue depending upon:

• Genetics: familial predisposition

• Age

• Temperature

• Skeletal maturity

• Previous injury

Tensile loading, compression, and shear

• Tensile loading: stretching rope from both ends

• Connective tissues are most resistant to tensile forces and less resistant to compressive/shear forces

• Each structure or tissue (muscle/tendon) has a different critical force or threshold level of resistance before they yield to failure

Injury categories

1. Acute

2. Chronic

3. Acute on chronic

4. Chronic on acute

5. Catastrophic

Acute injury

injury characterized by rapid onset, resulting from a macro-traumatic event, typically involves tissue trauma followed by pain, swelling, and loss of function

Chronic injury

Injury characterized by slow, insidious onset, resulting from a series of micro-traumatic events, gradual development of structural damage, develop over time and are often associated with repetitive, cyclic activities, such as running, commonly called “overuse injuries.” Common sites include Achilles (ankle), patellar (knee), and the rotator cuff tendon (shoulder)

Acute on chronic

Chronic injury with lingering symptoms (microtrauma), episodes of microtrauma, e.g. Achilles tendon

Chronic on acute

Acute injury that becomes a chronic condition (ex ankle sprain that leads to instability with frequent episodes of giving out)

Catastrophic

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Acute Injury diagram

Chronic and/or acute on chronic injury diagram

Main types of injuries

• Sprains (ligaments)

• Strains (muscles/tendons)

• Contusions (soft tissues usually)

• Fractures (bone tissue)

• Dislocations (joints)

• Concussions (brain)

Sprains

• Structural damage to ligaments

• First degree: mild with no swelling

• Second degree: ligament damage, pain, and dysfunction

  • Limping, swelling, more signs and symptoms of injury

• Third degree: complete tear of ligaments

  • Lot of symptoms, lot of swelling, lot of pain, cannot put weight on it

Strains

• Structural damage to tendon, muscle, or musculotendinous junction

• First degree strain: mild with no swelling, pain noticeable with use

• Second degree strain: more extensive soft-tissue damage, pain, and moderate loss of function

• Third degree strain: complete rupture, significant swelling and loss of function

Contusions

• Commonly referred to as bruises, may involve skin, muscle, and/or bone

• Contusions associated with pain, stiffness, swelling, ecchymosis, and hematoma

• Black and blue is a sign of internal bleeding, indication that area is healing, red blood cells on surface

Fractures

Structural damage (breaks or cracks) to bone tissue

Types of fractures: Closed, Open, Stress, Salter-Harris

Types of fractures

• Closed: Do not penetrate skin’s surface, usually not displaced fracture.

• Open: displaced fracture, complete fracture, breaks skin and exposes tissue to outside environment. Risk of infection.

• Stress: indicates wear and tear

• Salter-Harris: growth plate fractures, adolescents and pre-adolescents

Dislocations

Displacement of bone surfaces comprising a joint

• Subluxation: partial displacement

• Luxation: total displacement

• Usually involves structural damage to ligaments

• All dislocations should be diagnosed and treated by physician

Concussion

• Mild Traumatic Brain Injury (mTBI)

• Microscopic damage to axon bundles

• Temporary disruption in brain function

Classification of sports

• American Academy of Pediatrics (AAP) developed classifications for sports (mostly for supervision of high school sports)

  • Contact/collision: soccer, football

  • Limited contact/impact: volleyball, baseball

  • Non-contact: cross-country, golf, swimming

• Determine priority for coverage (medical supervision)

• Sport-specific recommendations for coverage

Pathophysiology of tissue injury

When damaged, vascularized tissue reacts w/ a predictable sequence or cascade of biochemical events

• Begins immediately and can last indefinitely

• Tendon and cartilage have very low vascularity, hard to heal on its own

Stages:

1. Inflammation - immediate (24-48hrs, can last months to years): acute, degeneration, demolition phase

2. Proliferation - lasts days to a week: post-acute, repair, and regeneration

3. Remodeling - long term remodeling and maturation of tissue: chronic, fibrosis

Overlapping of stages, transition periods

• Tensile strength very low at the beginning

• Many different types of healing cells

• Immediately after injury like moving into an apartment, unloading all different kinds of things at first → then slowly becomes more organized

• Peak of fibroblast activity in the middle: synthesizes collagen which acts as glue that holds the body together

First 48 hours of injury cascade

Initial injury (first degree)

1. Arachidonic acid cascade: Prostaglandin, histamine, bradykinin, thromboxane. Brings in a lot of molecules that further drive inflammatory response

2. Vascular cascade: capillaries get leaky, vasodilation, increase in permeability, swelling/edema

3. Coagulation cascade: clotting and coagulation, hematoma, protective response to stop bleeding, ischemia (impaired bloodflow) and hypoxia (low oxygen)

4. Leukocyte cascade: leukocyte (white blood cell) infiltration → clean up area, break down debris, potentially cause damage through phagocytosis (eating cells)

5. Secondary injury (second degree)

Ice: limits bloodflow, makes area feel cold, stinging, burns, numbness to distract from pain