Biomechanical Performance of Headless Compression Screws: Fixos Ø4.0, 5.0 & 7.0 mm compared to Synthes Ø4.5 & 6.5 mm HCS

Introduction: The screw biomechanical performance plays a crucial role on the early interfragmentary stability and, in turn, on the fracture healing outcome. To assess the biomechanical performance of the headless compression screws Fixos 4.0, 5.0 & 7.0 mm, interfragmentry compression force and pull-out strength were determined and compared to the Synthes 4.5 & 6.5 mm HCS. Materials & Method: Interfragmentary compression force and pull-out strength were determined in a synthetic bone material. Results: The interfragmentary compression force generated by the Fixos screws was higher than the force of the Synthes HCS (by 47%, 75% and 72%, for group Ø4.0-4.5, Ø4.5-5.0 and Ø6.5-7.0 mm, respectively). In addition, the pull-out strength associated to Fixos screws was higher than the pull-out strength of the Synthes HCS by 27% and 9%, for group Ø4.5-5.0 and Ø6.5-7.0 mm, respectively. For group Ø4.0-4.5 mm, the pull-out strength of Fixos screw was 9% lower. Discussion and conclusion: These results demonstrate improved biomechanical performance (i.e. better interfragmentary stability) of the Fixos screws compared to the similar size Synthes HCS with exception of the pull-out strength in the smallest tested screws. However, the smaller diameter of the Ø4.0mm Fixos screw may be more appropriate for certain situations.