Die Dynamische Kopfverriegelungsschraube – DLS (Dynamic Locking Screw) – eine Weiterentwicklung der winkelstabilen Plattenosteosynthese

Abstract

Background: The plate-screw-interface of an angular stable plate osteosynthesis is very rigid. So far all attempts to decrease the stiffness of locked plating construct, e.g. the bridged plate technique, decrease primarily the bending stiffness. Thus, the interfragmentary motion increases only on the far cortical side by bending the plate.

To solve this problem the dynamic locking screw (DLS) was developed. Materials and Methods: Comparison tests were done with locking screws (LS) and DLS. Axial stiffness and interfragmentary motion were compared. For measurements we used a simplified transverse fracture model, consisting of POM C and an 11-hole LCP3.5 with a fracture gap of 3mm. 3D fracture motion was detected using an optical measurement device (PONTOS 5M/ GOM) consisting of two CCD cameras (2448 × 2048pixel) observing passive markers. Results: Applying an axial load of 150N the DLS reduced the axial stiffness by approximately 16 % while increasing the interfragmentary motion at the near cortical side significantly from approximately 282 μm (LS) to 423 μm (DLS). Conclusion: The use of DLS reduces the stiffness of the plate-screw-interface and thus increased the interfragmentary motion at the near cortical side without altering the advantages of angular stability and its strength.