Document Detail

Holding power of variable pitch screws in osteoporotic, osteopenic and normal bone: are all screws created equal?
MedLine Citation:
PMID:  19747678     Owner:  NLM     Status:  MEDLINE    
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.
Rajesh Ramaswamy; Samuel Evans; Yona Kosashvili
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Publication Detail:
Type:  Comparative Study; Journal Article     Date:  2009-09-10
Journal Detail:
Title:  Injury     Volume:  41     ISSN:  1879-0267     ISO Abbreviation:  Injury     Publication Date:  2010 Feb 
Date Detail:
Created Date:  2010-01-28     Completed Date:  2010-09-14     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0226040     Medline TA:  Injury     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  179-83     Citation Subset:  IM    
Copyright Information:
Copyright 2009 Elsevier Ltd. All rights reserved.
Holland Orthopaedic and Arthritic Campus, Sunnybrook Medical Health Sciences Centre, University of Toronto, Ontario, Canada.
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MeSH Terms
Bone Density
Bone Diseases, Metabolic / pathology
Bone Screws / standards*
Bone and Bones / pathology
Equipment Design
Equipment Failure*
Equipment Failure Analysis / methods
Fracture Fixation, Internal / instrumentation*
Materials Testing / methods*
Reg. No./Substance:
0/Polyurethanes; 9009-54-5/polyurethane foam

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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