Technical Briefs

An Efficient and Accurate Prediction of the Stability of Percutaneous Fixation of Acetabular Fractures With Finite Element Simulation

[+] Author and Article Information
V. B. Shim

 Auckland Bioengineering Institute, University of Auckland, New Zealandv.shim@auckland.ac.nz

J. Böshme, P. Vaitl, C. Josten

Department of Trauma,  Plastic and Reconstructive Surgery, University of Leipzig, Germany

I. A. Anderson

 Auckland Bioengineering Institute, University of Auckland, New Zealand

J Biomech Eng 133(9), 094501 (Oct 04, 2011) (4 pages) doi:10.1115/1.4004821 History: Received April 18, 2011; Accepted June 23, 2011; Published October 04, 2011; Online October 04, 2011

Posterior wall fracture is one of the most common fracture types of the acetabulum and a conventional approach is to perform open reduction and internal fixation with a plate and screws. Percutaneous screw fixations, on the other hand, have recently gained attention due to their benefits such as less exposure and minimization of blood loss. However their biomechanical stability, especially in terms interfragmentary movement, has not been investigated thoroughly. The aims of this study are twofold: (1) to measure the interfragmentary movements in the conventional open approach with plate fixations and the percutaneous screw fixations in the acetabular fractures and compare them; and (2) to develop and validate a fast and efficient way of predicting the interfragmentary movement in percutaneous fixation of posterior wall fractures of the acetabulum using a 3D finite element (FE) model of the pelvis. Our results indicate that in single fragment fractures of the posterior wall of the acetabulum, plate fixations give superior stability to screw fixations. However screw fixations also give reasonable stability as the average gap between fragment and the bone remained less than 1 mm when the maximum load was applied. Our finite element model predicted the stability of screw fixation with good accuracy. Moreover, when the screw positions were optimized, the stability predicted by our FE model was comparable to the stability obtained by plate fixations. Our study has shown that FE modeling can be useful in examining biomechanical stability of osteosynthesis and can potentially be used in surgical planning of osteosynthesis.

Copyright © 2011 by by ASME
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Figure 1

Photo of osteosynthesis and loading and measurement setup

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Figure 2

(a) A sample photo from experiment. (b) Getting fragment movements in three directions—horizontal, vertical, and lateral—using photos taken at two different views. The actual movement of the fragment is from P1 to P2 from no load to full load conditions. The front view photo gives the triangle P1P4P3, allowing us to calculate horizontal and vertical movement. The side view photo gives the triangle P4P2P3, which allows us to calculate lateral movement.

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Figure 3

The far left column shows clouds of data points obtained from laser scanning. The center column shows the meshes for the fragment and fractured pelvis that were generated by geometric fitting to laser scanned data points. The red faces on the fragment mesh indicate where tied contact conditions were imposed in order to simulate the support provided by the screws. The final mesh is shown on the far right column.

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Figure 4

(a) Comparison between plate versus screws. (b) Comparison between experimental screw fixation versus FE predicted screw fixation.

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Figure 5

(a) Comparison between experimental plate fixation versus optimized screw fixation FE prediction. (b) Comparison between FE predictions from original and optimized screw positions. (c) Comparison between original screw positions and optimized positions.



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