Perren's landmark 2002 review lays out the scientific foundation for biological internal fixation. It explains why controlled instability promotes callus healing, why implant contact destroys bone vascularity, and how these principles justify locked internal fixators and MIPO technique. The paper answers a fundamental question: when should you choose flexible stabilization over rigid compression, and why?
For decades, cortical porosity under plates was blamed on stress shielding, and the proposed fix was to use more flexible implants. Perren showed this was wrong: porosity width matches contact width exactly, and it resolves before the plate comes out — a mechanical unloading explanation cannot account for either finding.
This reframing changes the design target. When you pick up a locking plate today. LC-DCP, LISS, LCP. Its undercut geometry and point contacts exist because of this paper, not because engineers made plates thinner.
In practice: when you face a comminuted diaphyseal or periarticular fracture with good soft tissue bridges, biological fixation with indirect reduction is the method of choice. Do not strip the intermediate fragments to achieve anatomic reduction. The strain data show those fragments are better left alone, bridged, and allowed to heal by callus.
For simple fractures treated with flexible fixation, leave a slightly wider gap deliberately: a larger gap width reduces strain for a given displacement, keeping tissue differentiation within tolerable limits. The same 5 mm shift that ruptures cells in a tight gap is harmless across a wider one.
Perren's landmark 2002 review lays out the scientific foundation for biological internal fixation. It explains why controlled instability promotes callus healing, why implant contact destroys bone vascularity, and how these principles justify locked internal fixators and MIPO technique. The paper answers a fundamental question: when should you choose flexible stabilization over rigid compression, and why?
For decades, cortical porosity under plates was blamed on stress shielding, and the proposed fix was to use more flexible implants. Perren showed this was wrong: porosity width matches contact width exactly, and it resolves before the plate comes out — a mechanical unloading explanation cannot account for either finding.
This reframing changes the design target. When you pick up a locking plate today. LC-DCP, LISS, LCP. Its undercut geometry and point contacts exist because of this paper, not because engineers made plates thinner.
In practice: when you face a comminuted diaphyseal or periarticular fracture with good soft tissue bridges, biological fixation with indirect reduction is the method of choice. Do not strip the intermediate fragments to achieve anatomic reduction. The strain data show those fragments are better left alone, bridged, and allowed to heal by callus.
For simple fractures treated with flexible fixation, leave a slightly wider gap deliberately: a larger gap width reduces strain for a given displacement, keeping tissue differentiation within tolerable limits. The same 5 mm shift that ruptures cells in a tight gap is harmless across a wider one.