Original Research
A Biomechanical Comparison of Internal Fixation Techniques for Ankle Arthrodesis

https://doi.org/10.1053/j.jfas.2014.06.002Get rights and content

Abstract

The purpose of the present study was to compare the primary bending stiffness characteristics of 5 different ankle arthrodesis fixation techniques: 3 compression screws, an anterior locking plate, a lateral locking plate, an anterior locking plate with a compression screw, and a lateral locking plate with a compression screw. A total of 25 full-scale anatomic models consisting of fourth-generation composite tibiae and tali were tested using an Instron 4505 Universal Testing System. We hypothesized that the use of a compression screw with a locking plate would add considerable stiffness to the fixation construct compared with the use of a locking plate alone. The data have shown that an anterior or lateral plate with a compression screw provides significantly greater stiffness than both a plate and 3 compression screws used individually. No significant difference was seen between the anterior plate with a compression screw and the lateral plate with a compression screw. No significant differences were found among the use of an anterior plate, a lateral plate, or 3 compression screws. We have concluded that when using a locking plate in an anterior or lateral configuration, the addition of a compression screw will considerably increase the primary bending stiffness of ankle arthrodesis.

Section snippets

Materials and Methods

Testing was performed on full-scale anatomic models consisting of fourth-generation composite tibiae and tali (Pacific Research Laboratories, Vashon WA). The models were prepared for arthrodesis with planar resection of the tibial and talar articular surfaces to a maximum depth of 3 mm. The medial malleolar articular surface was also resected to a maximum depth of 1 mm, with a planar cut at a 90° angle to the prepared tibial surface. All specimens were placed in neutral anatomic alignment

Results

A total of 25 fourth-generation saw bones were tested, 5 each used for each of the 5 different fixation constructs. With dorsiflexion loading, the greatest stiffness was provided by the ALP-S (60.76 ± 12.63 N/mm), which was significantly stiffer than all other fixation methods (p < .001), and provided a bending stiffness 71% greater than the anterior plate alone (p < .001). The addition of a compression screw resulted in a significant increase in bending stiffness (p < .001) for the anterior

Discussion

The results of the present study highlight several important findings. The initial hypothesis was supported by the data showing that a compression screw could add considerable stiffness to a locking plate fixation technique for ankle arthrodesis in certain cases. The addition of a compression screw added significant stiffness to arthrodesis constructs in which the plate was on the compression side of loading (i.e., the anterior plate under dorsiflexion and the lateral plate under eversion).

Acknowledgments

We thank Tuesday Kuykendall for her assistance with the Instron testing system and the Materials Science and Engineering Department, University of Washington, Seattle, WA.

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    Financial Disclosure: The hardware used was donated by Tornier, Inc., and research funding was provided by the International Foot & Ankle Foundation for Education and Research.

    Conflict of Interest: All of the authors are affiliated with the International Foot & Ankle Foundation for Education and Research.

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