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A finite element analysis of two novel screw designs for scaphoid waist fractures.
Journal article

A finite element analysis of two novel screw designs for scaphoid waist fractures.

  • Varga P AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland; Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gußhausstraße 27-29, A-1040 Vienna, Austria. Electronic address: peter.varga@aofoundation.org.
  • Zysset PK Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gußhausstraße 27-29, A-1040 Vienna, Austria; Institute for Surgical Technology & Biomechanics, Universität Bern, Stauffacherstrasse 78, CH-3014 Bern, Switzerland.
  • Schefzig P Department of Trauma Surgery, Medical University of Vienna, Austria.
  • Unger E Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
  • Mayr W Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
  • Erhart J Department of Trauma Surgery, Medical University of Vienna, Austria.
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  • 2015-12-15
Published in:
  • Medical engineering & physics. - 2016
Biomechanics
Finite element method
Fracture healing
Scaphoid
Screw osteosynthesis
Bone Screws
Compressive Strength
Female
Finite Element Analysis
Fractures, Bone
Humans
Materials Testing
Prosthesis Design
Rotation
Scaphoid Bone
X-Ray Microtomography
English The scaphoid is the most often fractured carpal bone. Scaphoid fracture repair with a headless compression screw allows for early functional recovery. The rotational stability of a single screw may be limited, having a potential negative impact on the healing process. Two novel screws have been designed to provide improved rotational stability compared to the existing ones. Using a computational finite element model of a scaphoid osteotomy, we compared the efficacy of one simple screw and the two new screws in restricting inter-fragmentary motion (IFM) in three functional positions of the wrist and as a function of inter-fragmentary compression force. The in-plane IFM was primary rotational and was better restricted by the new screws compared to the conventional one when the inter-fragmentary compression force was below 15-20 N, but provided no clear benefit in total flexion independently of the compression force. To better understand the differences in the non-compressed case, we analyzed the acting moments and investigated the effects of the bending and torsional screw stiffness on IFM. By efficiently restricting the inter-fragmentary shear, the new screws may be clinically advantageous when the inter-fragmentary compression force is partially or completely lost and may provide further benefits toward earlier and better healing of transverse waist fractures of the scaphoid.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/278672
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