Inter-fragmentary Strain Theory of Perren

  • It is defined as “the ratio of relative displacement of fracture ends versus initial fracture gap width”.
  • It relates the tissue response to the local mechanical environment.
  • ε=d/G where ε-the inter-fragmentary strain, d-fracture ends displacement, & G– gap between ends.
  • ε=d/G≤2%        >Bone formation
    ε=d/G≤10%      >Fibrocartilage
    ε=d/G≤100%    >Granulation tissue
    ε=d/G>100%    >No tissue formation
  • Disadvantages of the Theory:
    Oversimplified theory
    2. Only Longitudinal Strain is considered
    3. Multidirectional principal strains are not even considered.

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