Tissue Healing and Intro to Physical Agents

• Tissue Healing

  A coordinated & complex process that occurs in response to injury

  
• Phases of tissue healing

  • Inflammation (Day 0-6)
  • Proliferation (Day 3-20)
  • Maturation / Remodeling (Day 9+)

  
• Inflammation

  Immediate protective response to the injury of perfused tissue

  
• Cardinal signs of inflammation

  • Calor (heat)
  • Rubor (redness)
  • Tumor (swelling)
  • Dolor (pain)
  • Functio laesa (loss of function)
• Inflammatory phase

  1. Hemostatic response

  2. Vascular response

  3. Cellular response

  4. Immune response
• Hemostatic response

  Controls blood loss when vessels are damaged
• Vascular response

  Rapid transient vasoconstriction followed by vasodilation and increased permeability of capillaries
• Prostaglandins

  Sensitize pain receptors, responsible for hyperalgesia
• Cellular response

  Leukocytes (white blood cells) clear the injured site of debris and microorganisms

  
• Immune response

  Macrophages present foreign antigens to T lymphocytes, T lymphocytes activate B cells, B cells make antibodies
• Proliferation phase

  1. Neovascularization

  2. Collagen production

  3. Wound contraction

  4. Epithelialization
• Neovascularization

  Development of new blood supply
• Collagen production

  Fibroblasts lay down an extracellular matrix and produce collagen
• Wound contraction

  Wound defect shrinks, facilitated by myofibroblasts

  
• Epithelialization

  Uninjured epithelial cells migrate from margins of wound to cover the wound

  
• Maturation phase

  1. Collagen turnover

  2. Collagen fiber orientation
• Collagen turnover

  Balance between collagen synthesis and lysis, type III replaced by type I
• Collagen fiber orientation

  Scar tissue attempts to mimic characteristics of the tissue it is healing, or is determined by internal and external forces
• Chronic inflammation is excessive or prolonged expression of cardinal signs of inflammation
• Acute vs chronic inflammation

  Acute: PMNs, platelets. Chronic: Macrophages, lymphocytes, plasma cells
• Factors that may contribute to chronic inflammation

  • Repetitive mechanical trauma
  • Presence of foreign body
  • Lack of stimulus for repair
  • Inadequate perfusion
  • Use of cytotoxic agents
• Localized chronic inflammation example

  Example: Osteoarthritis
• Systemic chronic inflammation example

  Example: Rheumatoid arthritis
• Factors affecting healing

  • Local factors
  • Systemic factors
• Healing of cartilage

  • Limited ability to heal due to lack of vasculature & lymphatics
  • Injury to cartilage or cartilage + subchondral bone
• Microfracture technique

  Clinical procedure to improve cartilage healing
• Healing of skeletal muscle

  • Skeletal muscle cannot proliferate, scarring but not healing
  • Myositis ossificans - heterotopic bone formation
• Healing of tendon

  • Repair potential is variable, depends on type of tendon and extent of damage
• Cartilage injury

  • Cartilage
  • Cartilage + subchrondral bone
• Microfracture

  Clinical Correlation for cartilage injury
• Cartilage has low blood supply
• Cartilage heals better with bone because bones are highly vascularized, allowing for formation of clots
• Fibroclasts

  Tries to heal cartilage
• Cartilage is made of Type 3 collagen
• Skeletal muscle injury

  • Blunt trauma
  • Violent contraction
  • Excessive stretch
  • Muscle wasting
• Skeletal muscle cannot proliferate, leading to scarring but not healing
• Myositis ossificans

  Heterotopic bone formation (calcified hematoma), most common in quadriceps and biceps
• Skeletal muscle cannot form new skeletal muscle cells
• Muscle inflammation occurs within the muscle
• Tendon repair

  • Variable repair potential
  • Depends on type of tendon
  • Extent of damage to tendon (& sheath)
  • Vascular supply
  • Duration of immobilization