The Healing Process

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Chapter 5

• The Healing Process

2
Overview

• Injuries to the musculoskeletal system can result
  from a wide variety of causes. Each of the major
  components of the musculoskeletal system have
  varying capacities to heal

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Musculoskeletal Injuries

• Injuries to the soft tissues can be classified as
  primary or secondary
• Primary injuries can be self-inflicted, caused by
  another individual or entity, or caused by the
  environment
• Acute
• Chronic
• Acute on chronic

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Musculoskeletal Injuries

• Secondary injuries are essentially the
  inflammatory response that occurs with the
  primary injury

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Wound healing

• Fortunately, the majority of soft tissue injuries
  heal without complication in a predictable series
  of events
• However, healing abnormalities can occur. These
  abnormalities can be due to such complications
  as
• Infection
• Compromised circulation
• Neuropathy

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Wound healing

• Three main phases
• Inflammatory
• Proliferative
• Remodeling

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Inflammatory phase

• The reaction that occurs immediately after
  wounding includes a series of defensive events
  that involves the recognition of a pathogen and
  the mounting of a reaction against it. This
  reaction involves both coagulation and
  inflammation

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Inflammatory phase

• Coagulation. Apart from an initial period of
  vasoconstriction lasting for 5-10 minutes, tissue
  injury causes vasodilation, the disruption of
  blood vessels and extravasation of blood
  constituents, including platelets
• The main functions of the exudate are to
• Provide cells capable of tissue reconstruction
• Dilute microbial toxins
• Remove contaminants present in the wound

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Inflammatory phase

• Inflammation. Inflammation is mediated by
  chemotactic substances, including anaphylatoxins,
  which attract neutrophils and monocytes
• Neutrophils are white blood cells that bind to
  microorganisms, internalize them, and kill them
• Monocytes are white blood cells that develop into
  macrophages, and provide immunological defences
  against many infectious organisms

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Inflammatory phase

• The complete removal of the wound debris marks
  the end of the inflammatory process
• This stage can last from 1-6 days to longer than
  6 months

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• Common causes for a persistent chronic
  inflammatory response include
• Infectious agents
• Persistent viruses
• Hypertrophic scarring
• Poor blood supply
• Edema
• Repeated direct trauma
• Excessive tension at the wound site
• Hypersensitivity reactions

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Inflammatory phase

• Clinically, during the inflammatory phase there
  is pain
• At rest
• With active motion
• When specific stress is applied to the injured
  structure
• The pain, if severe enough, can result in muscle
  guarding, and a loss of function.

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Proliferative phase

• Characteristic changes during this phase include
• Capillary growth
• Granulation tissue formation
• Fibroblast proliferation with collagen synthesis
  and increased macrophage and mast cell activity

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Proliferative phase

• This phase lasts from 5 to 15 days, and often up
  to 10 weeks depending on the type of tissue, and
  the extent of damage.

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Remodeling phase

• The remodeling phase of wound healing involves a
  conversion of the initial healing tissue to scar
  tissue
• This lengthy phase of contraction, tissue
  remodeling and increasing tensile strength in the
  wound lasts for up to a year

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Remodeling phase

• Imbalances in collagen synthesis and degradation
  during this phase of healing may result in
  hypertrophic scarring or keloid formation
• If left untreated, the scar formed is less than
  20 of its original size
• Scarring that occurs parallel to the line of
  force of a structure is less vulnerable to
  re-injury than a scar, which is perpendicular to
  those lines of force

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Muscle healing

• The capacity of muscle for regeneration is based
  primarily upon the type and extent of injury
• Broadly speaking, there are three phases in the
  healing process of an injured muscle
• The destruction phase
• The repair phase
• The remodeling phase

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Ligament and tendon healing

• Healing of ligaments and tendons generally can be
  broken down into four overlapping phases
• I. Hemorrhagic
• II. Inflammatory
• III. Proliferation
• IV. Remodeling and maturation

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Articular cartilage healing

• The capacity of articular cartilage for repair is
  limited
• The repair response of articular cartilage varies
  with the depth of the injury

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Articular cartilage healing

• Injuries of the articular cartilage that do not
  penetrate the subchondral bone become necrotic
  and do not heal
• These lesions usually progress to the
  degeneration of the articular surface

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Articular cartilage healing

• Injuries that penetrate the subchondral bone
  undergo repair due to access to the bones blood
  supply
• These repairs are usually characterized as
• Fibrous
• Fibrocartilaginous
• Hyaline-like cartilaginous

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Bone healing

• The striking feature of bone healing, compared to
  healing in other tissues, is that repair is by
  the original tissue, not scar tissue
• Bone healing involves a combination of
  intramembranous and endochondral ossification

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Bone healing

• In classic histologic terms, fracture healing has
  been divided into two broad phases
• Primary fracture healing
• Secondary fracture healing

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Bone healing

• Primary healing involves a direct attempt by the
  cortex to reestablish itself once it has become
  interrupted
• Bone on one side of the cortex must unite with
  bone on the other side of the cortex to
  reestablish mechanical continuity

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Bone healing

• Secondary healing involves responses in the
  periosteum and external soft tissues with the
  subsequent formation of a callus
• The majority of fractures heal by secondary
  fracture healing