title: Advanced interlocking systems to improve heavy-load-bearing characteristics of flexible intramedullary nailing.
abstract: Flexible intramedullary nailing (FIN) is a minimally invasive and widespread standard method for osteosynthesis of pediatric long bone fractures. In the case of unstable fractures of the lower extremity, interlocking systems need to be used to prevent axial shortening and subsequent perforation of the nail at its insertion site. In the present study, four different screw-fixed interlocking systems for FINs (Hofer TwinPlug with two 3-mm titanium interlocking screws, Hofer FixPlug with 3-mm titanium interlocking screw, Hofer Plug with 3.5-mm titanium interlocking screw, and Hofer Plug with 3-mm titanium interlocking screw) in comparison with the commonly used Ender stainless steel nails (locked with 3.5-mm screw) were experimentally investigated in cadaveric lamb tibiae, regarding their load characteristics and failure modes in the case of heavy loading. The specimens were subjected to sequential axial cyclic loading of 5000cycles with stepwise increase of the load amplitude until failure. Migration of locking screws and internal damage of bone tissue was quantified by micro-computed tomography (CT) imaging. Ender nails failed on average at a peak load of 800 N, TwinPlugs at 1367 N, FixPlugs at 1222 N, Plugs 3.5mm at 1225 N and Plugs 3.0mm at 971 N. TwinPlugs, FixPlugs, and Plugs 3.5mm failed in a slow manner over several hundred loading cycles, whereas Ender nails and Plugs 3.0mm exhibited abrupt failure without any prior indication. Our results confirm that axial stability of FIN can be further improved by screw-fixed plugs by simultaneously avoiding shortcomings of an eye-locked system, which the Ender nails are. Considering biomechanical results, plug interlocking systems with 3.5-mm screws should be favored over conventional Ender nails and plugs with 3-mm screws.
authors: Institute of Building Construction and Technology, TU Wien, Karlsplatz 13/206-4, 1040 Vienna, Austria. Electronic address: leopold.berger@tuwien.ac.at.
authors: Leopold
authors: L
authors: Berger
authors: Department of Orthopedics and Orthopedic Surgery, Medical University of Graz, Auenbruggerplatz 5/6, 8036 Graz, Austria.
authors: Johannes
authors: J
authors: Eichler
authors: Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Muenster, Westphalian-Wilhelms University, Muenster, Germany.
authors: E Jonathan S
authors: EJS
authors: Ryll
authors: Department of Traumatology, Medical University of Graz, Auenbruggerplatz 5/6, 8036 Graz, Austria.
authors: Stefan
authors: S
authors: Fischerauer
authors: Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Muenster, Westphalian-Wilhelms University, Muenster, Germany.
authors: Michael J
authors: MJ
authors: Raschke
authors: Institute of Building Construction and Technology, TU Wien, Karlsplatz 13/206-4, 1040 Vienna, Austria.
authors: Andreas
authors: A
authors: Kolbitsch
authors: Department of Pediatric and Adolescence Surgery, Medical University of Graz, Auenbruggerplatz 34, 8036 Graz, Austria.
authors: Christoph
authors: C
authors: Castellani
authors: Department of Orthopedics and Orthopedic Surgery, Medical University of Graz, Auenbruggerplatz 5/6, 8036 Graz, Austria.
authors: Annelie-Martina
authors: AM
authors: Weinberg
mesh_terms: D001858:Bone Nails; D001863:Bone Screws; D013193:Stainless Steel; D016474:Weight-Bearing
chemical_list: D013193:Stainless Steel
keywords: Cyclic testing; Flexible intramedullary nailing (FIN); Fracture; Interlocking system; Long bone; Pediatric