• Stefan Döbele, Carsten Horn, Stefan Eichhorn, Arne Buchholtz, Andreas Lenich, Rainer Burgkart, Andreas K Nüssler, Martin Lucke, Daniel Andermatt, Rudolf Koch, and Ulrich Stöckle.
• Klinik für Orthopädie und Unfallchirurgie, Abteilung für Unfallchirurgie, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675, München, Germany. doebele@tum.de
• Langenbecks Arch Surg. 2010 Apr 1; 395 (4): 421-8.

BackgroundThe 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 MethodsComparison tests were performed with locking screws (LS) and DLS. Axial stiffness, bending 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 3 mm. Three-dimensional fracture motion was detected using an optical measurement device (PONTOS 5 M/GOM) consisting of two CCD cameras (2,448 x 2,048 pixel) observing passive markers.ResultsThe DLS reduced the axial stiffness by approximately 16% while increasing the interfragmentary motion at the near cortical side significantly from 282 microm (LS) to 423 microm (DLS) applying an axial load of 150 N.ConclusionThe use of DLS reduces the stiffness of the plate-screw interface and thus increases the interfragmentary motion at the near cortical side without altering the advantages of angular stability and the strength.

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