Chapter 5 - Mechanisms of Injury

1. Chapter 5 - Mechanisms of Injury Physical process responsible for a given action, reaction or result

2. Why is it necessary to determine the mechanism of injuries? Important for the diagnosis, rehabilitation and prevention of injuries

3. 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

4. Mechanical Loading • Loads greater than physiological lead to injuries • Chronic injuries • cumulative trauma • repetitive stress • Acute injuries

5. 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

6. 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

7. 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

8. 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

9. Tissue Injury • Inflammation: pathological process • vascular response • increase capillary permeability (swelling) • Pain: swelling related pressure on nerve endings (more in confined spaces)

10. 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

11. Why inflammation? Body’s first line of defense against injuries

12. 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

13. Bone • Osteoporosis • Major public health issue • Affect mostly trabercular bone • Bone of axial skeleton • Multifactor • Clinical conditions

14. Bone • Fracture (break): applied loads exceeds bone’s ability • Resistance • material properties • geometry • anisotropic effects • porosity • Type of loading • acute vs chronic

15. Fractures • Indirect or direct • Risk and type of bone • Diagnosis • site • extent of injury • configuration • fragments (displaced) • environmental (open closed) • complications • etiological

16. Fractures • Healing phases: • inflammation • union of bony ends (3wk) • callus remodeling (6 wks)

17. Articular Cartilage • Excessive loading • loss of cartilage matrix • chondral fractures • osteochondral fracture • Inability to repair

18. Articular Cartilage • AO • non inflammatory • weight bearing joints • deterioration of AC • osteophytes formation • cartilage fibrillation • Artificial Joints • cemented or non

19. Fibrocartilage • Distributes forces at joints • Shock absorber • Improve joint fit • menisci • intervertebral disks

20. Tendon • Force transfer • Injuries • direct (cuts) • indirect (excessive loads applied to unit) • Musculotendinous injuries: Strain • Mild, moderate, severe • severe: precede by microdamage

21. 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

22. 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

23. 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

24. Skin • Abrasions • Contusions • Penetrating wounds • obscure deeper damage • Lacerations • Infection • Excessive bleeding

25. 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

26. Nervous Tissue

27. 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

28. Joint Injuries • Excessive loading • Dislocation (luxation) • Partial dislocation (subluxation) • Synovitis • Arthritis • OA • RA • Gouty