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Vet Comp Orthop Traumatol 2018; 31(03): 182-187
DOI: 10.1055/s-0038-1639596
Original Research
Schattauer GmbH Stuttgart

Biomechanical Comparison between Preloaded Position Screw and Lag Screw Fixations for Their Compressive Effects in a Porcine Rib Fracture Model

Ya-Pei Chang   *
1   Graduate Institute of Veterinary Clinical Science, School of Veterinary Medicine, National Taiwan University, Taipei, Taiwan
2   Section of Small Animal Surgery, National Taiwan University Veterinary Hospital, Taipei, Taiwan
,
Chi-Yuan Ho   *
2   Section of Small Animal Surgery, National Taiwan University Veterinary Hospital, Taipei, Taiwan
,
Chao-Chang Chen
3   Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan
,
Lih-Seng Yeh
1   Graduate Institute of Veterinary Clinical Science, School of Veterinary Medicine, National Taiwan University, Taipei, Taiwan
2   Section of Small Animal Surgery, National Taiwan University Veterinary Hospital, Taipei, Taiwan
› Author Affiliations Funding This research received no grant from any funding agency in the public, commercial or not-for-profit sectors.
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Publication History

01 November 2017

30 January 2018

Publication Date:
03 May 2018 (online)

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Abstract

Objectives The aim of this study was to compare the compressive effect between preloaded position screws and lag screws in fracture fixation.

Methods Pairs of semi-cylindrical bone fragments were created on a porcine rib model to simulate fractured bones. The compressive forces of fracture fixation generated by preloaded position screws (P group) and conventional lag screws (L group) were recorded by a film stress sensor. In the P group, a pair of Angus bone holding forceps was used to compress the interfragmentary interface until reaching the preloading force of 1.3 MPa. Similar preloading procedure was applied on lag screw fixations to explore its potential of additional compressive force.

Results With 1.3 MPa preloading force and 0.2 Nm screw insertion torque force, the interfragmentary compressive force of P group was similar to that of L group. When the insertion torque force was increased to 0.4 Nm, all screws in the L group failed due to thread stripping. When screws in the P group were installed under 0.4 Nm torque and in the L group under 0.2 Nm torque, the P group generated significantly greater compressive force. With preloading device applied on lag screw installation, it did not further increase the interfragmentary compressive force.

Clinical Significance Compared with lag screws, preloaded position screws tolerated greater torque in screw installation and provided greater interfragmentary compressive force. The study suggests the applicability of preloaded position screws in fracture fixation requiring interfragmentary compression.

Keywords

preloaded stress - interfragmentary compression - position screw - lag screw - biomechanical

* Both authors contributed equally to this work.