Chapter 4 Injury Mechanism and Classification of Injury

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Chapter 4

Injury Mechanism and Classification of Injury

Chapter 4

Injury Mechanism and Classification of Injury


Anatomic FoundationsAnatomic Foundations

• Anatomic position

• Joint movement

– Sagittal plane

– Frontal plane

– Transverse plane

• Directional terms

• Movement Terms

Anatomic position


Mechanism of InjuryMechanism of Injury

• Mechanism of Injury (MOI): How an injury occurs

• Components used to analyze MOI:

– Application of force

– Tissue type

• Severity of force


ForceForce

• 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


Force (cont’d)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


Mechanical Forces - InjuryMechanical 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


StressStress

• Stress = Force x Surface area affected

• Same force over a large area vs. a small area can have very different results

Stress


Injury TypesInjury 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


Check for Understanding!Check for Understanding!

Movements in the sagittal plane include flexion, extension, abduction, and adduction.

A.True

B.False



Which of the following is a correctly matched pair of terms? (Select all that apply)

A.Adduction – movement away from the midline of the body

B.Flexion – decreasing an angle

C.Extension – increasing an angle

D.Plantar flexion – movement of the forefoot toward the shin



When tissues sustain a force, what are the primary factors that determine the occurrence of an injury? (Select all that apply)

A.The magnitude of the force

B.The direction of the force

C.The material properties of the involved tissues

D.The length of time the force is applied



What are the three primary mechanical forces that produce injury?


Anatomical Properties of Soft TissueAnatomical 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


Anatomical Properties of Soft Tissue (cont’d)

Anatomical Properties of Soft Tissue (cont’d)

• Elastin

– Protein substance in connective tissue

– Adds elasticity

Collagen fibers


SkinSkin

• Epidermis

– Multiple layers

• Dermis

– Loose, multidirectional arrangement of collagen fibers


Skin Injury ClassificationSkin Injury Classification


Skin WoundsSkin 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


MusclesMuscles

• Produce skeletal movement and maintain postural alignment

• Viscoelastic

– Extensibility

– Elasticity

Muscle tissue


Muscle (cont’d)Muscle (cont’d)

• Irritability: ability to respond to a stimulus

– Electrochemical – nerve impulse

– Mechanical – external blow

• Contractility: ability to develop tension

– Isometric

– Concentric

– Eccentric


TendonsTendons

• 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


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


Contusions 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


Classification for ContusionsClassification for Contusions


StrainsStrains

• 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


Classification of StrainsClassification of Strains

<table 4.4, classifications of strains>


Muscle Cramps and SpasmsMuscle Cramps and Spasms

• Involuntary muscle contraction

• Cramp:

– Biochemical imbalance (dehydration) associated with muscle fatigue

– Painful

– Types

• Clonic – alternating contraction/relaxation

• Tonic – constant


Muscle Cramps and Spasms (cont’d)Muscle Cramps and Spasms (cont’d)

• Spasm:

– Reflex action caused by:

• Biochemical imbalance or

• Mechanical blow to nerve or muscle


Myositis and FasciitisMyositis 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)


Tendinitis and TenosynovitisTendinitis 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


Myositis OssificansMyositis Ossificans

• Mineral deposits in muscle associated with prolonged chronic inflammation

– Ectopic calcification

– Common site: quadriceps

• Calcific tendinitis: mineral deposits in the tendon


Overuse InjuriesOveruse Injuries

• Results from repetitive use

• Factors:

– Intrinsic

– Extrinsic


Overuse Injuries (cont’d)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


Anatomical Considerations of JointsAnatomical Considerations of Joints

• Articulation of two bones

• Classified by structure and function

• Structure

– Cartilaginous

– Fibrous

– Synovial


Anatomical Considerations of Joints (cont’d)

Anatomical Considerations of Joints (cont’d)

• Function: based on the amount of movement allowed

– Synarthoses

– Amphiarthroses

– Diarthroses


Diarthrodial JointsDiarthrodial Joints

• Components

– Articular cartilage

– Joint (synovial) cavity

– Articular capsule

– Synovial fluid

– Reinforcing ligaments

• Intrinsic or Extrinsic


Diarthrodial Joints (cont’d)Diarthrodial Joints (cont’d)

Joint components


Articular CartilageArticular 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


Joint CavityJoint Cavity

• Filled with synovial fluid


Articular CapsuleArticular 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.


Synovial FluidSynovial Fluid

• Functions

– Lubricate joint

– Reduce friction

– Nourish joint


Ligaments Ligaments

• Bone to bone

– Intrinsic

– Extrinsic

• Maintain anatomical integrity and structural alignment

• Collagen and elastin intermixed (contain elastin – more elastic than tendons)

– Viscoelastic


Ligaments (cont’d)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


Classification of Diarthrodial JointsClassification of Diarthrodial Joints

• Plane

• Hinge

• Pivot

• Condyloid

• Saddle

• Ball-and-socket


Injury to the LigamentInjury 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


Classification of SprainsClassification of Sprains

<table 4.5, classification of sprains>


Dislocations and SubluxationsDislocations 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


Osteoarthritis Osteoarthritis

• Degeneration of articular cartilage

• S&S:

– Pain

– Limited movement

• No definitive cause; rather, several contributing factors


Bursitis Bursitis

• Inflammation of bursa

• Acute or chronic

• MOI:

– Compression

• S&S:

– Localized swelling

– Point tenderness

– Warm to touch


Soft Tissue InjuryCheck for Understanding!


The discoloration or swelling outside a joint in the surrounding soft tissue is termed:

A.Bruising

B.Ecchymosis

C.Edema

D.Effusion


Soft Tissue Injury Check for Understanding!

Soft Tissue Injury Check for Understanding!

The ability of a muscle to be stretched or increased in length is termed:

A.Contractility

B.Elasticity

C.Plasticity

D.Extensibility




Joint capsules are fluid-filled sacs that serve to reduce friction in the tissues surrounding the joints.

A.True

B.False




Which of the following statements is true? (Select all that apply)

A.A tear of a ligament is referred to as a sprain.

B.A muscle spasm is brought on by a biochemical imbalance, sometimes associated with muscle fatigue.

C.Overuse injuries are more often attributed to intrinsic rather than extrinsic factors.

D.The onset of bursitis can be acute or chronic.




Strains and sprains that produce moderate discomfort, tenderness, swelling, ecchymosis, detectable joint instability, and/or muscle weakness are categorized as:

A.1st degree

B.2nd degree

C.3rd degree

D.Severe


Anatomical Properties of BoneAnatomical Properties of Bone

• Primary constituents:

– Calcium carbonate

– Calcium phosphate

– Collagen

– Water


Anatomical Properties of Bone (cont’d)Anatomical Properties of Bone (cont’d)

• Structure:

– Diaphysis

– Epiphysis

– Membranes

• Periosteum

– Medullary cavity

– Apophysis

Bone macrostructure



• Bone growth:

– Longitudinal

• Continues until epiphysis closes

– Diameter

• Continues to grow throughout life

– New bone formed via the periosteum; bone is resorbed around the medullary cavity

• Osteoblasts: form new bone

• Osteoclasts: resorb bone




Anatomical properties of Bone (cont’d)Anatomical properties of Bone (cont’d)

• Composition

– Cortical

• Compact bone tissue of high density (low porosity)

• Outside

• Can withstand greater stress but less strain

– Cancellous

• Bone tissue of low density (high porosity)

• Inside

• Can tolerate more strain


Bone Injury ClassificationsBone Injury Classifications

Bone injury mechanisms


Bone Injury Classifications (cont’d)Bone Injury Classifications (cont’d)

• Fracture: Disruption in the continuity of bone

• S&S:

– Rapid swelling

– Ecchymosis

– Deformity or shortening of the limb

– Precise point tenderness

– Grating or crepitus

– Guarding or disability


Bone Injury Classifications (cont’d)Bone Injury Classifications (cont’d)

• Type of fracture dependent upon:

– Force applied

– The health and maturity of the bone at the time of injury

• Bone susceptible to:

– Compression, tension, shear, bending, and torsion


Types of FracturesTypes of Fractures


Stress FractureStress Fracture

• MOI: repeated lower magnitude forces

• Can become worse over time

• Begins as a small disruption in the outer layers of cortical bone and ending as complete cortical fracture with possible displacement


OsteopeniaOsteopenia

• Reduced bone mineral density

• Predisposes individual to fracture

– Particularly stress fractures

• Possible causes:

– Amenorrhea, hormonal factors, dietary insufficiencies


Classification of Epiphyseal InjuriesClassification of Epiphyseal Injuries• Classifications

– Injury to growth plate could result in alteration in normal growth

– Acute injury

• Types I-V

Epiphyseal injuries


Classification of Epiphyseal Injuries (cont’d)


• Osteochondrosis

– Disruption of blood supply to epiphysis

– Idiopathic

– Causing necrosis and possible deformity

– Example: Legg-Calvé-Perthes disease




• Apophysitis

– Osteochondrosis of apophysis

– Idiopathic or traumatic avulsion fracture

– Example:

• Sever’s disease

• Osgood-Schlatter disease


Bone Tissue Injury Check for Understanding!

Bone Tissue Injury Check for Understanding!

In a comminuted fracture, the bone fragments into several pieces.

A.True

B.False


Bone Tissue InjuryCheck for Understanding!


Osteopenia is a condition:

A.That is exclusive to an older adult population

B.That predisposes an individual to stress fractures

C.That only involves females

D.That inhibits longitudinal bone growth




Epiphyseal injuries can include damage to the: (select all that apply)

A.Epiphyseal plate

B.Ligaments

C.Articular cartilage

D.The apophysis


Anatomical Properties of NervesAnatomical Properties of Nerves

• Nervous System

– CNS:

• Brain

• Spinal cord

– PNS:

• 12 pairs of cranial nerves

• 31 pairs of spinal nerves, along with their branches


Anatomical Properties of Nerves (cont’d)Anatomical Properties of Nerves (cont’d)

• Spinal nerves

– Roots

• Posterior – afferent

• Anterior – efferent

Spinal nerves


Nerve Injury ClassificationsNerve Injury Classifications

• MOI: Tensile or compression force

• Neurapraxia (grade 1)

– Localized conduction block: temporary loss of sensation and/or motor

– Resolves within days to a few weeks


Nerve Injury Classifications (cont’d)Nerve Injury Classifications (cont’d)

• Axonotmesis (grade 2)

– Significant motor and mild sensory deficits

– Lasts at least 2 weeks

• Neurotmesis (grade 3)

– Motor and sensory deficit

– Lasts up to 1 year



• Compression:

– More complex; dependent upon:

• Force magnitude and duration

• Direct or indirect

• Nerve injuries result in a variety of afferent symptoms

– Hyperesthesia

– Hypoesthesia

– Paresthesia



• Neuralgia

– Chronic pain along nerve course

• Healing: if completely severed, healing does not occur


The Neurological Basis of PainThe Neurological Basis of Pain

• Sources

– Somatic, visceral, and psychogenic

• Nociceptors: produce pain sensation

– Mechanosensitive: initiate pain by acute trauma

– Chemosensitive: causes persistent pain in chronic injuries and the early stages of healing


The Neurological Basis of Pain (cont’d)The Neurological Basis of Pain (cont’d)

• Fibers transmitting pain

– A fibers

– C fibers

– T cells

• Gate control theory of pain


The Neurological Basis of Pain (cont’d)The Neurological Basis of Pain (cont’d)

• Factors than mediate pain

– Brain production of opioid peptides and endorphins

– Cognitive and affective filters

• Referred pain

– Pain perceived at a location remote from the site actually causing the pain

• Radiating pain

– Pain felt both at its source and along a nerve




The posterior branches are the afferent (sensory) nerves that transmit information from sensory receptors in the skin, tendons, ligaments, and muscles to the central nervous system.

A.True

B.False




___________ is perceived at a location remote from the site of the tissues actually causing the pain.

A.Radiating pain

B.Cognitive pain

C.Acute pain

D.Referred pain




Grade II nerve injuries that produce significant motor and mild sensory deficits that last at least two weeks are termed:

A.Neurapraxia

B.Axonotmesis

C.Neurotmesis

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Chapter 4 Injury Mechanism and Classification of Injury