gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019)

22. - 25.10.2019, Berlin

Novel Variable Fixation technology changes the interfragmentary stability of bone segments stabilized with locking plates

Meeting Abstract

  • presenting/speaker Andre Frank - University Hospital Münster, Münster, Germany
  • Michael Plecko - Trauma Hospital Styria, UKH Graz, Graz, Austria
  • Stefano Brianza - Biomech Innovations, Nidau, Switzerland
  • Michael J. Raschke - University Hospital Münster, Münster, Germany
  • Dirk Wähnert - University Hospital Münster, Münster, Germany

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019). Berlin, 22.-25.10.2019. Düsseldorf: German Medical Science GMS Publishing House; 2019. DocAB48-595

doi: 10.3205/19dkou437, urn:nbn:de:0183-19dkou4371

Veröffentlicht: 22. Oktober 2019

© 2019 Frank et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe



Objectives: Standard locking screws have been reengineered into a new locking screw technology, called Variable Fixation. This new technology aims at promoting secondary fracture healing stimulating the formation of bone callus. Variable Fixation Locking Screws (VFLS) feature a degradable sleeve changing the stability of fracture fixation over the healing time. The screws provide initially high interfragmentary stability and later progressive dynamisation of the fracture gap. The goal of this study was to compare the performance of Variable Fixation technology with that of standard locking screw technology in a diaphyseal bridge plating configuration. Constructs featuring VFLS have been tested both in initial condition (intact sleeve) and in final condition (fully-resorbed sleeve). We hypothesized that 1) with intact sleeve, Variable Fixation technology provides interfragmentary stability comparable to that provided by standard locking technology, that 2) with sleeve resorption there is a significant increase in allowed interfragmentary displacement and that 3) it is possible to get intermediate effects using the two technologies as indicated.

Methods: Five different configurations have been tested under combined axial compression - bending load and under torsion. Bone substitute fragments have been fixed leaving a 5 mm gap with a 6-hole 4.5/5.0 narrow LCP (DePuy Synthes 424.561) and either (A) six locking screws (DePuy Synthes 413.342), or (B) three locking screws and three VFLS (Biomech Innovations, S540042S) or (C) six VFLS. Constructs B and C, featuring VFLS, have been tested both with intact sleeve and with fully-resorbed sleeve (Figure 1 [Fig. 1]). Machine data and an optical measurement system have been used to detect differences in stiffnesses and interfragmentary displacements among groups.

Results and conclusion: No difference among groups was found concerning axial and torsional stiffnesses and interfragmentary displacements when VFLS screws feature an intact sleeve. The same test performed on samples featuring three and six VFLS with fully-resorbed sleeves showed a progressive decrease in both axial and torsional stiffnesses as well as higher interfragmentary displacements. In conclusion, at the beginning of the treatment Variable Fixation technology provides biomechanical conditions similar to those provided by the state of the art locking technology. With a fully-resorbed sleeve, the construct stiffnesses decrease and the interfragmentary displacements increase. Mixing the two technologies as indicated provides intermediate effects. Variable Fixation technology changes the stability of fracture fixation going from initial rigid fixation to progressive dynamisation of the fracture gap.