Physical and biological aspects of fracture healing with special reference to internal fixation
- Question
- How do mechanical conditions at the fracture gap determine the type of tissue formed and the mode of bone healing?
- Design
- Experimental and theoretical review drawing on AO laboratory work.
- Patients
- Fracture healing under different fixation conditions.
- Intervention
- Concept of interfragmentary strain (change in gap length divided by original gap length)
- Comparison
- Absolute versus relative stability
- Primary outcome
- Not applicable (conceptual model)
- Key result
- Each tissue tolerates a different level of strain: granulation tissue tolerates high strain, cartilage intermediate and lamellar bone very little, so bone can only bridge the gap once strain falls below its tolerance.
- Limitations
- Simplified model; biological factors such as blood supply and later refinements to strain thresholds are not fully captured.
- Impact on practice
- Explains why absolute stability gives primary (direct) healing and relative stability gives callus (indirect) healing, and why small gaps under high strain fail; core to fixation principles taught to all trainees.