Biomechanics: Force and Load Directions Quiz

Aetiology and Biomechanics

• Aetiology is the study of causation or origination
• Stress is the load or cross-sectional area of the tissue
• Strain is the amount of deformation, which can be caused by different force directions:
  • Compression: force along the axial plane (top to bottom)
  • Tension: pulling forces along the axis
  • Shear: force is applied parallel in the object, causing sliding and displacement
  • Torsion: causes twisting, typically one end is fixed and the other is moving
  • Bending: atypical loading pattern, load is different on one side to the other

Types of Tissue Injuries

• Abrasion: skin tissue injury, usually the result of a shear force (e.g., scrap against concrete)
• Contusion: injury to underlying tissue, usually a bruise on the muscle, typically resulting from a force from a blunt object
• Laceration: cut or tear in the skin having rough edges, caused by forces from a sharp and/or hard object
• Strain: an elongation of muscle or tendon beyond the elastic limit, where actual tearing or breaking of some fibers is present, caused by excessive tensile force
• Puncture: small break in the skin from a pointed object, force that is perpendicular to the skin and focused on a small area
• Sprain: stretching and tearing of ligaments or capsular tissue, caused by tensile, shear, or rotary force that pushes the tissue fibers beyond the elastic region
• Inflammation: irritation or swelling causing pain and additional friction, usually a repeated micro-trauma due to tensile strain for muscles and tendons
• Fracture: disruption to the normal matrix of bone tissue, caused by shear, compression, torsional, or tensile forces, or a combination of them
• Subluxation: partial dislocation, injury to a joint which forces it to move beyond its normal limit of motion, usually due to a tensile or compressive force, with some shear to torsional force
• Dislocation: more severe injury where articulating bones have lost their alignment, force may be tensile or compressive and usually involves some shear or torsional loading

Injury Grading

• Hamstring Strain:
  • Grade 1: simple pull/elongation of the muscle
  • Grade 2: partial tear
  • Grade 3: avulsion/complete tear
• Lateral Ankle Sprain:
  • Grade 1: stretching, small tears
  • Grade 2: larger but incomplete tear
  • Grade 3: complete tear

Fracture Types

• Impact Force Fractures (Direct):
  • Forces from outside the body
  • Transverse fractures: these occur at a slight angle, caused by a tapping mechanism, small forces over a small area
  • Crushing mechanism: large forces over a large area, results in an extensive comminuted fracture
• Active Force Fractures (Indirect):
  • Due to active forces originating within the body
  • Traction mechanism: transverse or avulsion fracture as a result of tensile loading
  • Bending mechanism: bending occurring of the bone causing either an oblique or butterfly fracture
  • Rotational mechanism: occurs due to torsional loading causing a spiral fracture
  • Transverse and oblique fracture: combo of loading patterns causing axial compression and angulation
  • Angulation with torsion and axial loading causing a compound fracture

Injury Control Process

• 1. Establish the extent of the incidence and severity
• 2. Establish the aetiology and mechanisms of the injury
• 3. Introduce a preventative measure
• 4. Assess its effectiveness by repeating Step 1

Injury Reporting Scale

• Level 1: niggles/pain
• Level 2: modifications in class
• Level 3: off class < 3 days
• Level 4: off class > 3 days