Evidence brief
Physical and Biological Aspects of Fracture Healing
Interfragmentary strain theory explains healing
Strain = change in gap / original gap
Strain >10%: fibrous tissue formation
Strain 2-10%: fibrocartilage/cartilage
Strain <2%: direct bone healing possible
Perren's strain theory provides the biomechanical basis for understanding why different fracture fixation methods lead to different healing patterns.
Classic basic science question. Strain tolerance: bone 2%, cartilage 10%, fibrous tissue 100%. Absolute stability (<2% strain) = primary/direct healing. Relative stability (2-10%) = secondary/callus healing. Know examples: compression plating (absolute), IM nailing (relative).
Perren SM. Physical and biological aspects of fracture healing with special reference to internal fixation. Clin Orthop Relat Res. 1979;(138):175-196.
Level V
Expert opinion or mechanism-based reasoning