2.22 - Secondary Intention

Secondary intention occurs when there is substantial tissue loss and wound edges cannot be closely approximated.

secondary intention

healing of a significant area of injury with extensive tissue loss

• healing by secondary intention differ than healing by primary intention

  • intense inflammatory reaction

  • abundant granulation tissue

  • abundant accumulation of ECM during healing equating to significant area of scar tissue

  • contraction by myofibroblasts

• examples — abscess formation, ulceration

wound contraction

major feature of secondary intention mediated by myofibroblasts

• contraction to pull wound edges together, reducing wound defect in about 6 weeks

• contraction reduces size of the hole

steps in second intention

healing takes place similar to primary intention, but have the following differences:

• larger clot and scab

• more intense inflammation due to larger amount of injury and necrotic debris

• greater potential for inflammation-mediated injury

• greater volume of granulation tissue, generally equating to larger volume of ECM deposition and subsequent scar formation

• wound contraction mediated by myofibroblasts

  • within 6 weeks, defects is reduced by 90% its original size

wound strength

tensile strength of wound, which rises rapidly such that scar reaches 70-80% normal tissue tensile strength at three months

• increases rapidly over four-week period

• recovery of strength is related to deposition and modifications of collagen

  • cross-linking and increase in fiber size, dependent on vitamin C

fibrosis of parenchymal organs

primarily collagen deposition with collagen remodeling

• excessive collagen, with larger fiber size and cross-linking

• fibrosis = excessive collagen in injured organs

  • disease process is severe and renders portion of organ non-functional

  • examples —

    • fibrosis in heart following necrosis of myocardium resulting from an infarct

    • pulmonary fibrosis in alpha-1 antitrypsin deficiency

    • cirrhosis of liver related to alcohol, viral infection, or other inflammatory process

• scaring = excessive collagen in injured skin/mucosa