Chapter 4 Injury Mechanism and Classification of Injury

1. Chapter 4 Injury Mechanism and Classification of Injury

2. Anatomic Foundations • Anatomic position • Joint movement • Sagittal plane • Frontal plane • Transverse plane • Directional terms • Movement Terms Anatomic position

3. Mechanism of Injury • Mechanism of Injury (MOI): How an injury occurs • Components used to analyze MOI: • Application of force • Tissue type • Severity of force

4. Force • Force: a push or pull acting on a body (e.g., gravity, friction) • Force acting on a body causes: • Acceleration • Deformation • Factors that determine injury: • Magnitude of force • Material properties of tissues involved

5. Force (cont’d) • Small load = elastic response • Large load = plastic response • Yield point = load exceeds the ultimate failure point of the tissue resulting in mechanical failure • Anisotropic = material is stronger in resisting force from certain directions than others

6. Mechanical Forces - Injury • Compression • Force that crushes tissues • Tension • Force that pulls and stretches tissues • Shearing • Force that moves across the parallel design of the fibers Mechanisms of injury

7. Stress • Stress = Force x Surface area affected • Same force over a large area vs. a small area can have very different results Stress

8. Injury Types • Acute Injury • Single force • Characterized by a definitive moment of onset • Force = macrotrauma • Chronic Injury • Repeated forces • Characterized by becoming more problematic over time (Gradual onset over time) • Forces = microtrauma

9. Check for Understanding! Movements in the sagittal plane include flexion, extension, abduction, and adduction. • True • False

10. Check for Understanding! Which of the following is a correctly matched pair of terms? (Select all that apply) • Adduction – movement away from the midline of the body • Flexion – decreasing an angle • Extension – increasing an angle • Plantar flexion – movement of the forefoot toward the shin

11. Check for Understanding! When tissues sustain a force, what are the primary factors that determine the occurrence of an injury? (Select all that apply) • The magnitude of the force • The direction of the force • The material properties of the involved tissues • The length of time the force is applied

12. Check for Understanding! What are the three primary mechanical forces that produce injury?

13. Anatomical Properties of Soft Tissue • Collagen • Primary component of skin, tendon, ligaments • Protein substance strong in resisting tensile forces • Wavy configuration that allows for an elastic type deformation or stretch but, otherwise, is inelastic

14. Anatomical Properties of Soft Tissue (cont’d) Collagen fibers • Elastin • Protein substance in connective tissue • Adds elasticity

15. Skin • Epidermis • Multiple layers • Dermis • Loose, multidirectional arrangement of collagen fibers

16. Skin Injury Classification

17. Skin Wounds • Blisters • Accumulation of fluid between epidermis and dermis • Caused by repeated application of shear in one or more directions • Skin bruises • Accumulation of blood within skin • Results from compression sustained during a blow

18. Muscles Muscle tissue • Produce skeletal movement and maintain postural alignment • Viscoelastic • Extensibility • Elasticity

19. Muscle (cont’d) • Irritability: ability to respond to a stimulus • Electrochemical – nerve impulse • Mechanical – external blow • Contractility: ability to develop tension • Isometric • Concentric • Eccentric

20. Tendons • Muscle to bone • Dense connective tissue with unidirectional bundles of collagen & some elastin • Collagen – parallel arrangement • Helps in resisting high, unidirectional tension loads from the attached muscle • 2X as strong as muscle it serves • Yield point 5-8% in length

21. Tendons (cont’d) Collagen arrangements in tendon and ligament tissue

22. Contusions • MOI: compression • Can be both deep and superficial • Must be cautious and aware of more severe injuries associated with repeated blows • S&S: • Onset - acute • Ecchymosis: if superficial • Hematoma • Restrictions in ROM • Pain – localized • Swelling • Associated nerve compression

23. Classification for Contusions

24. Strains • Damage to muscle or tendon • Key factor: magnitude of force and structure's cross-sectional area • MOI: • Abnormally high tensile force • Most common site for tears: near the musculotendinous junction

25. Classification of Strains <table 4.4, classifications of strains>

26. Muscle Cramps and Spasms • Involuntary muscle contraction • Cramp: • Biochemical imbalance (dehydration) associated with muscle fatigue • Painful • Types • Clonic – alternating contraction/relaxation • Tonic – constant

27. Muscle Cramps and Spasms (cont’d) • Spasm: • Reflex action caused by: • Biochemical imbalance or • Mechanical blow to nerve or muscle

28. Myositis and Fasciitis • MOI: repeated movements irritate the tissues • Myositis: • Inflammation of muscle tissue (e.g., shin splints) • Fasciitis: • Inflammation of the fascia (e.g., plantar fasciitis)

29. Tendinitis and Tenosynovitis • Tendinitis: inflammation of a tendon • Related to aging and degenerative changes • S&S: pain and swelling with tendon movement • Tenosynovitis: inflammation of the tendon sheath • Acute: rapid onset, crepitus, local swelling • Chronic: same as acute, thickened tendon, nodule formation in sheath

30. Myositis Ossificans • Mineral deposits in muscle associated with prolonged chronic inflammation • Ectopic calcification • Common site: quadriceps • Calcific tendinitis: mineral deposits in the tendon

31. Overuse Injuries • Results from repetitive use • Factors: • Intrinsic • Extrinsic

32. Overuse Injuries (cont’d) • Classification • Stage 1: pain after activity only • Stage 2: pain during activity, does not restrict performance • Stage 3: pain during activity, restricts performance • Stage 4: chronic unremitting pain, even at rest

33. Anatomical Considerations of Joints • Articulation of two bones • Classified by structure and function • Structure • Cartilaginous • Fibrous • Synovial

34. Anatomical Considerations of Joints (cont’d) • Function: based on the amount of movement allowed • Synarthoses • Amphiarthroses • Diarthroses

35. Diarthrodial Joints • Components • Articular cartilage • Joint (synovial) cavity • Articular capsule • Synovial fluid • Reinforcing ligaments • Intrinsic or Extrinsic

36. Diarthrodial Joints (cont’d) Joint components

37. Articular Cartilage • Ends of bones covered by hyaline cartilage…solid type of connective tissue • More resistant to deformation than fibrous connective tissue and more resilient than bone • No blood supply; nourished by synovial fluid

38. Joint Cavity • Filled with synovial fluid

39. Articular Capsule • Cuff of fibrous tissue • Primarily bundles of collagen • Primary function: hold bones together • Inner layer: synovial membrane • Produces synovial fluid that lubricates the joint.

40. Synovial Fluid • Functions • Lubricate joint • Reduce friction • Nourish joint

41. Ligaments • Bone to bone • Intrinsic • Extrinsic • Maintain anatomical integrity and structural alignment • Collagen and elastin intermixed (contain elastin – more elastic than tendons) • Viscoelastic

42. Ligaments (cont’d) • Resists large tensile loads along the long axis of the ligament and smaller loads from other directions – static stabilizers • Fail in fast loading situations • Strongest in their middle and weakest at their ends • Healing process – slow due to a limited blood supply

43. Classification of Diarthrodial Joints • Plane • Hinge • Pivot • Condyloid • Saddle • Ball-and-socket

44. Injury to the Ligament • Compromises the ability of the ligament to stabilize the joint • MOI: • High tensile force • S&S: • Pain; point tenderness; swelling; loss of function; instability

45. Classification of Sprains <table 4.5, classification of sprains>

46. Dislocations and Subluxations • Joint forced beyond normal limits • MOI: tension • Increased susceptibility for chronic or recurrent dislocations • S&S: • Pain • Swelling • Point tenderness • Deformity • Loss of limb function

47. Osteoarthritis • Degeneration of articular cartilage • S&S: • Pain • Limited movement • No definitive cause; rather, several contributing factors

48. Bursitis • Inflammation of bursa • Acute or chronic • MOI: • Compression • S&S: • Localized swelling • Point tenderness • Warm to touch

49. Soft Tissue InjuryCheck for Understanding! The discoloration or swelling outside a joint in the surrounding soft tissue is termed: • Bruising • Ecchymosis • Edema • Effusion

50. Soft Tissue Injury Check for Understanding! The ability of a muscle to be stretched or increased in length is termed: • Contractility • Elasticity • Plasticity • Extensibility