BIOMECHANICAL STUDIES FOR THE DYNAMIZATION OF LOCKING PLATE SYSTEMS USING A SIMPLE OVERDRILLING TECHNIQUE

The locking compression plate (LCP) supports bridge plating in complex fractures or osteoporotic bones, promoting secondary bone healing via callus formation while preserving blood supply by maintaining a gap between the plate and bone. However, the high stiffness of LCP constructs may inhibit interfragmentary motion, leading to suboptimal callus formation or atrophic non-union. To address this problem, Singapore General Hospital (SGH) has developed a technique to introduce dynamization into locking plate systems. Our first study compared the stiffness of locking compression plate (LCP) constructs with and without elongated figure-of-8 holes of the similar diameters drilled into the near cortex. Drilling these holes reduced axial stiffness by 16% but did not affect bending stiffness or maximum strength under axial or bending loads. The findings suggest that elongated holes in the near cortex alter axial stiffness without compromising overall construct strength or fatigue performance. In the second study, we investigated the effect of eccentric over-drilling the near cortex in locked plate constructs with holes of varying diameter to reduce stiffness and enhance fracture healing. The technique was found to decrease axial stiffness by 34.2% and significantly reduced bending and torsional rigidity, while maintaining construct strength. Thus, this cost-effective method allows controlled compression across the fracture site, offering a practical solution to “dynamize” locked plates and promote better healing without the need for complex or expensive implant modifications. The advantage of these studies was that we used standardised sawbone models instead of cadavers to limit differences in terms of anatomical variations and mechanical quality of the bone. However, the main limitation of our studies is that the mechanical properties of the bone-implant construct which is dependent on fracture healing was not accounted for. Dynamic locking screws (DLS) has been introduced with the aim to enhance secondary bone healing by allowing controlled axial micro-motion but often failed due to design issues causing unpredictable stiffness, excessive or insufficient motion, and mechanical complications like screw loosening or breakage. These challenges ultimately limited their clinical reliability and adoption. In contrast, we believe our technique is simple to implement during surgery and does not require any modifications to the implant.