Rajesh Ramaswamy1, Samuel Evans, Yona Kosashvili. 1. Holland Orthopaedic and Arthritic Campus, Sunnybrook Medical Health Sciences Centre, University of Toronto, Ontario, Canada.
Abstract
INTRODUCTION: Biomechanical properties of four different commercially available small fragment cannulated screws (Twin fix (Stryker, Freiburg, Germany), Herbert, (Zimmer, Warsaw, USA), Omnitech (Unimedical, Torino, Italy), Barouk (Depuy, Warsaw, USA)), with variable pitch, used for fracture fixation were compared. MATERIALS AND METHODS: Polyurethane foam blocks of three different densities with mechanical properties similar to osteoporotic, osteopenic and normal bones were used to conduct the tests. Each screw was tested for pushout and pullout holding power after a primary insertion and for pullout after a repeated insertion into the respective foam blocks. RESULTS: The mean pullout and pushout strengths of all screws correlated to the foam density, and were significantly (p<0.001 and <0.001, respectively) better in foam with higher density. The mean pullout strength of each screw was consistently lower after reinsertion into the osteoporotic, osteopenic and normal bone densities by 4-30%, when compared to the index insertion (Fig. 4b). Yet, this difference was not found to be statistically significant (p=0.23). The Barouk screw performed significantly (p<0.0001) better than the other screws in all three different densities of foam for both for pushout and pullout after index insertion as well as for pullout tests after reinsertion. CONCLUSION: The holding power of screws is directly correlated to bone density, thread design and number of threads engaging the bone. Reinsertion through the same hole could reduce the ultimate pullout strength. The surgeon should consider the advantages and disadvantages of each implant, depending on the clinical situation and choose accordingly. Copyright 2009 Elsevier Ltd. All rights reserved.
INTRODUCTION: Biomechanical properties of four different commercially available small fragment cannulated screws (Twin fix (Stryker, Freiburg, Germany), Herbert, (Zimmer, Warsaw, USA), Omnitech (Unimedical, Torino, Italy), Barouk (Depuy, Warsaw, USA)), with variable pitch, used for fracture fixation were compared. MATERIALS AND METHODS:Polyurethane foam blocks of three different densities with mechanical properties similar to osteoporotic, osteopenic and normal bones were used to conduct the tests. Each screw was tested for pushout and pullout holding power after a primary insertion and for pullout after a repeated insertion into the respective foam blocks. RESULTS: The mean pullout and pushout strengths of all screws correlated to the foam density, and were significantly (p<0.001 and <0.001, respectively) better in foam with higher density. The mean pullout strength of each screw was consistently lower after reinsertion into the osteoporotic, osteopenic and normal bone densities by 4-30%, when compared to the index insertion (Fig. 4b). Yet, this difference was not found to be statistically significant (p=0.23). The Barouk screw performed significantly (p<0.0001) better than the other screws in all three different densities of foam for both for pushout and pullout after index insertion as well as for pullout tests after reinsertion. CONCLUSION: The holding power of screws is directly correlated to bone density, thread design and number of threads engaging the bone. Reinsertion through the same hole could reduce the ultimate pullout strength. The surgeon should consider the advantages and disadvantages of each implant, depending on the clinical situation and choose accordingly. Copyright 2009 Elsevier Ltd. All rights reserved.
Authors: Daniel Kyle Palmer; David Rios; Wyzscx Merfil Patacxil; Paul A Williams; Wayne K Cheng; Serkan İnceoğlu Journal: Int J Spine Surg Date: 2012-12-01
Authors: Jochen Erhart; Ewald Unger; Philip Schefzig; Peter Varga; Inga Trulson; Anna Gormasz; Alexander Trulson; Martin Reschl; Michael Hagmann; Vilmos Vecsei; Winfried Mayr Journal: PLoS One Date: 2016-06-03 Impact factor: 3.240