Chapter 9: Mechanisms and Characteristics of Sports Trauma

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Chapter 9 Mechanisms and Characteristics of
Sports Trauma
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Mechanical Injury

• Trauma is defined as physical injury or wound
  sustained in sport, produced by internal or
  external force
• Mechanical injury results from force or
  mechanical energy that changes state of rest or
  uniform motion of matter
• Injury in sports can be the result of external
  forces directed on the body or can occur within
  the body internally

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• Tissue Properties
• Relative abilities to resist a particular load
• Strength, pressure of power is used to imply
  force (defined as a push or pull)
• Load can be a singular or group of outside
  internal forces acting on the body.
• Stress is resistance to a load
• Body tissues are viscoelastic and contain both
  viscous and elastic properties
• Point at which elasticity is almost exceeded is
  the yield point
• When exceeded mechanical failure occurs resulting
  in damage

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• Tissue Stresses
• Tension (force that pulls and stretches tissue)
• Stretching (pull beyond yield point resulting in
  damage)
• Compression (force that results in tissue crush)
• Shearing (force that moves across the parallel
  organization of tissue)
• Bending (force on a horizontal beam that places
  stress within the structure

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Soft Tissue Trauma

• Soft tissue or non -bony tissue is categorized as
  inert (noncontractile) and contractile tissue
• Inert tissues include, ligaments, skin,
  cartilage, capsules, fascia, dura mater and nerve
  roots
• Contractile tissue involves muscles and parts of
  including tendons

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Skin Injuries

• Break in the continuity of skin as a result of
  trauma
• Anatomical Considerations
• Skin (external covering) or integument represents
  the largest organ of the bogy and consists of 2
  layers
• Epidermis
• Dermis ( corium)
• Soft pliable nature of skin makes it easy to
  traumatize

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• Injurious Mechanical Forces
• Include friction, scraping, compression, tearing,
  cutting and penetrating
• Wound Classifications
• Friction blister
• continuous rubbing over skin surface that causes
  a collection of fluid below or within epidermal
  layer
• Abrasion
• Skin is scraped against rough surface resulting
  in capillary exposure due to skin removal
• Skin Bruise (contusion)
• Compression or crush injury of skin surface that
  produces bleeding under the skin

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• Laceration
• Wound in which skin has been irregularly torn
• Skin Avulsion
• Skin that is torn by same mechanism as laceration
  to the extent that tissue is completely ripped
  from source
• Incision
• Wound in which skin has been sharply cut
• Puncture
• Penetration of the skin by a sharp object

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Skeletal Muscle Injuries

• High incidence in athletics
• Anatomical Characteristics
• Composed of contractile cells that produce
  movement
• Possess following characteristics
• Irritability
• Contractility
• Conductivity
• Elasticity

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• Three types of muscle
• Cardiac
• Smooth
• Striated

Skeletal Muscle
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Acute Muscle Injuries

• Contusions
• Result of sudden blow to body
• Can be both deep and superficial
• Hematoma results from blood and lymph flow into
  surrounding tissue
• Localization of extravasated blood into clot,
  encapsulated by connective tissue
• Speed of healing dependent on the extent of damage

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• Can penetrate to skeletal structures causing a
  bone bruise
• Usually rated by the extent to which muscle is
  able to produce range of motion
• Strains
• Stretch, tear or rip to muscle or adjacent tissue
• Cause is often obscure
• Abnormal muscle contraction (result of 1)failure
  in reciprocal coordination of agonist and
  antagonist, 2) electrolyte imbalance due to
  profuse sweating or 3) strength imbalance
• May range from minute separation of connective
  tissue to complete tendinous avulsion or muscle
  rupture

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• Muscle Strain Grades
• Grade I - some fibers have been stretched or
  actually torn resulting in tenderness and pain on
  active ROM, movement painful but full range
  present
• Grade II - number of fibers have been torn and
  active contraction is painful, usually a
  depression or divot is palpable, some swelling
  and discoloration result
• Grade III- Complete rupture of muscle or
  musculotendinous junction, significant
  impairment, with initially a great deal of pain
  that diminishes due to nerve damage
• Pathologically, strain is very similar to
  contusion or sprain with capillary or blood
  vessel hemorrhage

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• Tendon Injuries
• Wavy parallel collagenous fibers organized in
  bundles - upon loading (up to 8,700- 18,000 lbs)
  collagen straightens but will return to shape
  after loading
• Breaking point occurs at 6-8 of increased length
• Tears generally occur in muscle and not tendon
• Repetitive stress on tendon will result in
  microtrauma and elongation, causing fibroblasts
  influx and increased collagen production
• May evolve into chronic muscle condition ,
  weakening tendons

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• Muscle Cramps and Spasms
• Painful involuntary contraction
• Attributed to dehydration/electrolyte imbalance
• Reflex reaction caused by trauma
• Two types
• Clonic - alternating involuntary muscular
  contractions and relaxations in quick succession
• Tonic - rigid contraction that lasts a period of
  time
• May lead to muscle or tendon injuries

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Overexertional Muscle Problems

• Reflective in muscle soreness, decreased joint
  flexibility, general fatigue (24 hours post
  activity)
• Muscle Soreness
• Overexertion in strenuous exercise resulting in
  muscular pain
• Generally occurs following participation in
  activity that individual is unaccustomed

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• Two types of soreness
• Acute-onset muscle soreness - accompanies
  fatigue, and is transient muscle pain experienced
  immediately after exercise
• Delayed-onset muscle soreness (DOMS) - pain that
  occurs 24-48 hours following activity that
  gradually subsides (pain free 3-4 days later)
• Potentially caused by slight microtrauma to
  muscle or connective tissue structures
• Prevent soreness through gradual build-up of
  intensity
• Treat with static or PNF stretching and ice
  application within 48-72 hours of insult

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• Muscle Stiffness
• Does not produce pain
• Result of extended period of work
• Fluid accumulation in muscles, with slow
  reabsorbtion back into bloodstream, resulting in
  swollen, shorter, thicker muscles --resistant to
  stretching.
• Light activity, motion, massage and passive
  mobilization assists in reducing stiffness
• Muscle Cramps
• Related to hard conditioning
• Tonic - result of electrolyte imbalance or
  interruption of muscle synergism
• Clonic - stems from nerve irritation

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• Muscle Guarding
• Following injury, muscles within an effected area
  contract to splint the area in an effort to
  minimize pain through limitation of motion
• Involuntary muscle contraction in response to
  pain following injury
• Not spasm which would indicate increased tone due
  to upper motor neuron lesion in the brain

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Myofascial Trigger Points

• Area of tenderness in a tight band of muscle
• Develop as the result of mechanical stress
• Either acute strain or static postural positions
  producing constant tension in muscle
• Typically occur in neck, upper and lower back
• Pain with palpation, with predictable pattern of
  referred pain which may also limit motion
• Pain may increase with active and passive motion
  of involved muscle

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Chronic Musculoskeletal Injuries

• Progress slowly over long period of time
• Repetitive acute injuries can lead to chronic
  condition
• Constant irritation due to poor mechanics and
  stress will cause injury to become chronic

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• Myositis/fascitis
• Inflammation of muscle tissue
• Fibrositis or inflammation of connective tissue
• Plantar fascitis
• Tendinitis
• Gradual onset, with diffuse tenderness due to
  repeated microtrauma and degenerative changes
• Obvious signs of swelling and pain
• Tenosynovitis
• Inflammation of synovial sheath
• In acute case - rapid onset, crepitus, and
  diffuse swelling
• Chronic cases result in thickening of tendon with
  pain and crepitus

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• Ectopic Calcification (myositis ossificans)
• Striated muscle becomes chronically inflamed
  resulting in myositis
• Can result in muscle that lies directly above
  bone
• Osteoid material accumulates rapidly and will
  either resolve in 9-12 months or mature with
  repeated trauma
• With maturation, surgery is required for removal
• Common sites, quadriceps and brachial muscle

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• Atrophy and Contracture
• Atrophy is wasting away of muscle due to
  immobilization, inactivity, or loss of nerve
  functioning
• Contracture is and abnormal shortening of muscle
  where there is a great deal of resistance to
  passive stretch
• Generally the result of a muscle injury which
  impacts the joint, resulting in accumulation of
  scar tissue

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Synovial Joints

• Anatomical Characteristics
• Consist of cartilage and fibrous connective
  tissue
• Joints are classified as
• Synarthrotic - immovable
• Amphiarthrotic - slightly moveable
• Diarthrotic - freely moveable (synovial
  articulations)
• Synovial Joint characteristics
• Capsule or ligaments
• Capsule is lined with synovial membrane
• Hyaline cartilage
• Joint cavity with synovial fluid
• Blood and nerve supply with muscles crossing joint

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• Joint Capsule
• Bones are held together by a fibrous cuff
• Consists of bundles of collagen and function to
  maintain relative joint position
• Extremely strong and can withstand cross
  sectional forces
• Will be slack or taut depending on joint movement

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• Ligaments
• Sheets or bundles of collagen that form
  connection between two bones
• Both intrinsic (inside the capsule) and extrinsic
  (outside the capsule)
• Similar composition to tendons
• Strong in the middle, weak at the ends
• When placed under undo stress may result in
  avulsion injury
• Viscoelastic properties are primary factor in
  ligamentous injuries

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• Constant compression or tension causes ligament
  deterioration while intermittent stress
  strengthens
• Repeated microtrauma overtime makes capsule and
  ligaments more susceptible to major acute
  injuries
• Act as protective backup for joint
• Primary protection is dynamic action of muscle
• Under fast loading conditions, ligament will
  fail, however, they provide maximal protection
  during rapid movements
• Will adapt based on Rouxs law of functional
  adaptation (organ will adapt structurally to
  alteration qualitative or quantitative of
  function)

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• Synovial Membrane
• Lines articular capsule
• Single layer of flattened cells and villi
• Secretes and absorbs fluid - serves as lubricant
• Fluid contains hyaluronic acid (changes
  viscosity)
• Fast movement - thins fluid
• Slow movement - fluid thickens
• Articular Cartilage
• Provides firm flexible support - semifirm
  connective tissue with primarily ground substance
• No direct blood or nerve supply

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• Fibrocartilage makes up vertebral disks,
  symphysis pubis and menisci
• Elastic external ear and eustachian tubes
• Hyaline composes nasal septum, larynx, trachea,
  bronchi, and articular ends of bone
• Covers ends of bones in diarthrodial joints which
  serves as cushion and sponge
• Can undergo compression and return to normal
  shape
• Degeneration producing microtrauma can occur
  following abnormal compressive forces
• Receives nourishment from synovium
• Provides motion control, stability and load
  transmission

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• Additional Synovial Joint Structures
• Fat
• Pads located in elbow, knee, to fill spaces
  between bones that form joints (lie between
  synovial membrane and the capsule)
• Articular Disks
• Additional fibrocartilanginous disks
• Vary in shape and size and connected to capsule
• Exist in joints that operate in 2 planes of
  motions
• Aid in dispersion of synovial fluid
• Meniscus

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• Nerve Supply
• Capsule, ligaments, outer aspects of synovial
  membrane and fat pads are well supplied
• Inner structures (synovial membrane, cartilage
  and articular cartilage) also supplied
• Myelinated mechanoreceptors provide joint
  position sense in fibrous capsule
• Non-myelinated fibers supply blood vessels and
  pain receptors

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• Types of Synovial Joints
• 6 types
• ball and socket - allows movement in all plane
  (hip)
• hinge - allows for flexion and extension (elbow)
• pivot - rotation about and axis (cervical atlas
  and axis)
• ellipsoidal - elliptical convex and concave
  articulation (wrist)
• saddle - reciprocally convex-concave
  (carpometacarpal joint of thumb)
• gliding - all sliding back and forth (carpal
  joints)
• hinge, pivot, ellipsoidal, saddle, and gliding

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• Functional Synovial Joints
• Differ in their ability to withstand trauma
  depending on skeletal, ligamentous, and muscular
  organization
• Synovial Joint Stabilization
• Muscle tension helps to limit synovial joint
  movement
• With stretching of the capsule, muscle reflex
  contractions prevent overstretching
• Nerve supply is governed by Hiltons Law
  (capsule, skin and muscle have same nerve supply)
• Ligaments can extend due to right angle
  structural design but are not elastic

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• Joint structure vs. ligament contribution to
  joint stability
• Muscles absorb forces involved in load
  transmission and may provide dynamic stabilizing
  through integration into joint capsule and by
  crossing joints
• Articular Capsule and Ligaments
• Help maintain anatomical integrity and structural
  alignment of joints
• Ligaments have spiral arrangement of collagenous
  tissue
• Ligaments tend to be stronger in the middle and
  weak at the ends
• Respond quicker than muscle to over-stretching

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• Synovial Joint Trauma
• Major factor in injury is viscoelastic properties
  of ligaments and capsule
• While constant compression is damaging, periodic
  tension increases overall strength of tissue
• Subject to same mechanical forces that cause
  injury
• Synovial Joint Injury Classifications
• Acute Joint Injuries
• Sprains
• Result of traumatic joint twist that causes
  stretching or tearing of connective tissue
• Graded based on the severity of injury

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• Grade I - some pain, minimal loss of function, no
  abnormal motion, and mild point tenderness
• Grade II - pain, moderate loss of function,
  swelling, and instability
• Grade III - extremely painful, inevitable loss of
  function, severe instability and swelling, and
  may also represent subluxation
• Can result in joint effusion and swelling, local
  temperature increase, pain and point tenderness,
  ecchymosis (change in skin color) and possibly an
  avulsion fracture
• Most vulnerable joints include ankles, knees, and
  shoulders
• Sometimes difficult to distinguish between sprain
  and tendon strain
• Repeated joint twisting could result in arthritis
  or chronic inflammation

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• Acute Synovitis
• Synovial membrane can be acutely injured via
  contusion or strain
• Irritation of membrane results in increased fluid
  production and swelling occurs
• Results in joint pain along with skin sensitivity
• With proper treatment, effusion and pain will
  diminish
• Subluxations, Dislocations and Diastasis
• High level of incidence in fingers and shoulder
• Subluxations are partial dislocations causing
  incomplete separation of two bones
• Luxation presents with total disunion of bone
  apposition between articular surfaces
• Diastisis is the disjointing of 2 parallel bones
  or rupture of a solid joint (symphysis pubis)

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• Factors associated with dislocations - 1) loss of
  limb function, 2) gross deformity, 3)swelling and
  point tenderness
• X-ray is the only absolute diagnostic technique
  (able to see bone fragments from possible
  avulsion fractures, disruption of growth plates
  or connective tissue
• Dislocations (particularly first time) should
  always be considered and treated as a fracture
  until ruled out
• Once a dislocation, always a dislocation

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• Chronic Joint Injuries
• Stem from microtrauma and overuse
• Include, osteochondrosis, osteoarthritis, and in
  adolescence epiphyseal injuries
• Major cause involves failure of muscle to control
  or limit deceleration
• To prevent, a combination of chronic fatigue and
  training should be avoided, and protective gear
  should be used to enhance absorption of impact
  forces

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• Osteochondrosis
• Also known as osteochrondritis dissecans and
  apophysitis (if located at a tubercle/tuberosity)
• Causes not well understood
• Degenerative changes to epiphyses of bone during
  rapid child growth
• Possible cause includes 1)aseptic necrosis
  (disrupted circulation to epiphysis, 2) fractures
  in cartilage causing fissures to subchondral
  bone, 3) trauma to a joint that results in
  cartilage fragmentation resulting in swelling,
  pain and locking
• With the apophysis, an avulsion fracture may be
  involved, including pain, swelling and disability

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• Osteoarthritis
• Wearing away of hyaline cartilage as a result of
  normal use
• Changes in joint mechanics lead joint
  degeneration (the result of repeated trauma to
  tissue involved)
• May be the result of direct blow, pressure of
  carrying and lifting heavy loads, or repeated
  trauma from an activity such as running or
  cycling
• Commonly affects weight bearing joints but can
  also impact shoulders and cervical spine
• Symptoms include pain (as the result of
  friction), stiffness, prominent uprising in the
  morning, localized tenderness, creaking, grating,
  and often is localized to one side of the joint
  or generalized joint pain

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• Bursitis
• Fluid filled sac that develops in area of
  friction
• Sudden irritation can cause acute bursitis, while
  overuse and constant external compression can
  cause chronic bursitis
• Signs and symptoms include swelling, pain, and
  some loss of function
• Repeated trauma can lead to calcification and
  degeneration of internal bursa linings
• Capsulitis and Synovitis
• Capsulitis is the result of repeated joint trauma
• Synovitis can occur acutely but will also develop
  following mistreatment of joint injury
• Chronic synovitis can result in edema, thickening
  of the synovial lining, exudation can occur and
  a fibrous underlying develops --motion may be
  restricted and joint noises may occur

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Skeletal Trauma

• Anatomical Characteristics
• Dense connective tissue matrix
• Outer compact tissue
• Inner porous cancellous bone including Haversian
  canals

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• Bone Functions
• Body support
• Organ protection
• Movement (through joints and levers)
• Calcium storage
• Formation of blood cells (hematopoiesis)
• Types of Bone
• Classified according to shape
• Flat bones - skull, ribs, scapulae
• Irregular bones - vertebrae and skull
• Short bones- wrist and ankle
• Long bones - humerus, ulna, tibia, radius,
  fibula, femur
• - bones most commonly injured

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• Gross Structures
• Diaphysis -shaft - hollow and cylindrical
• - covered by compact bone)
• - medullary cavity contains yellow
• marrow
• Epiphysis - composed of cancellous bone and
• has hyaline cartilage
  covering
• - provides areas for muscle
  attachment
• Periosteum - dense, white fibrous covering which
• penetrates bone via
  Sharpey fibers
• - contains blood vessels and
  osteoblasts

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• Microscopic Structures
• Calcium salts impregnate intracellular bone
  substance (makes bone hard)
• Osteocytes located in hollow spaces are called
  lacunae
• Haversian systems are the structural units of
  bone
• Compact bone has interspersed lamellae to fill
  spaces between canals
• Cancellous bone has numerous open spaces between
  thin processes of trabeculae
• Trabeculae serve as scaffolding and align along
  points of stress within the bone to add
  structural strength
• Blood circulation connects perisosteum with
  haversian canals through Volkmanns canal
• Medullary cavity and bone marrow are supplied
  directly by one or more arteries

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• Bone Growth
• Ossification occurs from synthesis of bones
  organic matrix (work of osteoblasts and
  osteoclasts)
• Involves the epiphyseal growth plates located at
  the ends of long bones
• As cartilage matures, immature osteoblasts
  replace to ultimately form bone
• Deforming forces, premature injury and growth
  plate dislocation can alter growth patterns
  and/or result in deformity of bone
• Bone diameter increases via the activity of
  osteoblasts adding to the exterior while
  osteoclasts break down bone in medullary cavity
• At full size, bone maintains state of balance
  between osteoblastic and -clastic activity

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• Changes in activity and hormonal levels can alter
  balance
• Bone loss begins to exceed external bone growth
  overtime
• As thickness decreases, bones are less resistant
  to forces --osteoporosis
• Bones functional adaptation to stresses follows
  Wolffs Law --every change in form and function
  or in its function alone is followed by changes
  in architectural design

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• Bone Injuries
• While have viscoelastic properties, bone is
  fairly rigid and serves as a poor shock absorber
• Brittle nature increases under tension rather
  than compression
• Cylindrical nature of bones make them very strong
  - resistant to bending and twisting
• Anatomical Weak Points
• Stresses become concentrated in areas where
  changes in shape and direction occur
• Gradual changes in shape are much more
  advantageous

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• Load Characteristics
• Bones can be stressed or loaded to fail by
  tension, compression, bending, twisting and
  shearing
• Either occur singularly or in combination
• Amount of load also impact the nature of the
  fracture
• More force results in a more complex fracture
• While force goes into fracturing the bone, energy
  and force is also absorbed by adjacent soft
  tissues
• Some bones will require more force than others
• Bones magnitude of stress and strain in most
  prevalent at it outer surface and decreases to
  zero at its center

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• Bone Trauma Classifications
• Periostitis - inflammation of the periosteum,
  result primarily of contusions and produces rigid
  skin overlying muscle (acute and chronic)
• Acute bone fractures - partial or complete
  disruption that can be either closed or open
  (through skin) serious musculoskeletal condition
• Type of fractures include, depressed, greenstick,
  impacted, longitudinal, oblique, serrated,
  spiral, transverse, comminuted, blowout, and
  avulsion
• Stress fractures- no specific cause but with a
  number of possible causes
• Overload due to muscle contraction, altered
  stress distribution due to muscle fatigue,
  changes in surface, rhythmic repetitive stress
  vibrations

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• Bone becomes susceptible early in training due
  to increased muscular forces and initial
  remodeling and resorption of bone
• Progression involves, focal microfractures,
  periosteal or endosteal response (stress fx)
  linear fractures and displaced fractures
• Typical causes include
• Coming back to competition too soon after injury
• Changing events without proper conditioning
• Starting initial training too quickly
• Changing training habits (surfaces, shoes.etc)
• Variety of postural and foot conditions
• Early detection is difficult, bone scan is
  useful, x-ray is effective after several weeks

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• Major signs and symptoms include focal tenderness
  and pain, (early stages) pain with activity,
  (later stages) pain becomes constant and more
  intense, particularly at night, positive
  percussion tap test
• Common sites involve tibia, fibula, metatarsal
  shaft, calcaneus, femur, pars interarticularis,
  ribs, and humerus
• Management varies between individuals, injury
  site and extent of injury
• More easily managed and healed if on compression
  side of bone vs. tension (may result in complete
  fx)

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• Epiphyseal Conditions - three types can be
  sustained by adolescents (injury to growth plate,
  articular epiphysis, and apophyseal injuries)
• Occur most often in children ages 10-16 yrs. Old
• Classified by Salter-Harris into five types (see
  photo on next slide)
• Apophyseal Injuries - Young physically active
  individuals are susceptible
• Apophyses are traction epiphyses in contrast to
  pressure epiphyses.
• Serve as sites of origin and insertion for
  muscles
• Common avulsion conditions include Severs
  disease and Osgood-Schlatters disease

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Nerve Trauma

• Abnormal nerve responses can be attributed to
  injury or athletic participation
• The most frequent injury is neuropraxia produced
  by direct trauma
• Lacerations of nerves as well as compression of
  nerves as a result of fractures and dislocations
  can impact nerve function

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• Anatomical Characteristics
• Provides sensitivity and communication from the
  CNS to muscles, sense organs and various systems
  in the periphery
• Neuron cell body has a large nucleus with
  branched dendrites which respond to
  neurotransmitter substances
• Each nerve cell has an axon that conducts nerve
  impulse
• Axons are encased in neurilemmal sheaths (Schwann
  and satellite cells)
• Various neurological cells in CNS help to form
  framework for nervous tissue

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• Nerve Injuries
• Two main causes of injury - compression and
  tension
• May be acute or chronic
• Physical trauma causes pain and can result in a
  host of sensory responses (pinch, burn, tingle,
  muscle weakness, radiating pain)
• Long term problems (neuritis) can go from minor
  nerve problems to paralysis
• Pain can be referred as well

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Body Mechanics

• Body move very effectively in upright position -
  able to overcome great forces even with
  inefficient lever system
• Body must overcome inertia, muscle viscosity and
  unfavorable angles of pull
• Mechanical reasons for injury - hereditary,
  congenital, or acquired defects may predispose
  athlete to injury
• Body build, structural make-up, habitual
  incorrect application of skill may also
  predispose individual to injury

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• Microtrauma and Overuse Syndrome
• Injuries as a result of abnormal and repetitive
  stress and microtraumas fall into a class with
  certain identifiable syndromes
• Frequently result in limitation or curtailment of
  sports involvement
• Often seen in running, jumping, and throwing
  activities
• Some of these injuries while small can be
  debilitating
• Repetitive overuse and stress injuries include
• Achilles tendinitis, shin splints, stress fx,
  Osgood-Schlaters disease, runners and jumpers
  knee, patellar chondromalacia and apophyseal
  avulsion

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• Postural Deviations
• Often an underlying cause of injury
• May cause unilateral muscle use as well as bony
  and soft tissue asymmetries
• Results in poor pathomechanics
• Imbalance is manifested by postural deviations as
  body tries to regain balance relative to CoG
• Injury generally becomes chronic and
  participation must stop
• Athletic trainer should attempt to correct
  postural conditions
• Postural conditions can make athletes exceedingly
  more prone to injury