Comparison of 3.5- and 4.0-mm Cortical Bone Screws for Stabilization of an Equine Navicular Bone Fracture Model

Abstract

Objective

The aim of this study was to compare the strength (load at failure) and the number of cycles to failure of 3.5- and 4.0-mm cortical screw–bone constructs for repair of navicular bone fractures in horses.

Study Design

This was an in vitro biomechanical study that used a four-point bending apparatus to determine the load at failure of 3.5- and 4.0-mm cortical screw–bone constructs subjected to static and cyclic loading.

Results

In static testing, pairwise comparison of 4.0-mm cortical screw–bone constructs demonstrated significantly greater strength (mean increase: +16%, p = 0.0135) compared with those in the 3.5-mm group. In cyclic testing, the mean number of cycles to failure for the 4.0-mm cortical screw–bone construct was not significantly different from that of the 3.5-mm cortical screw–bone construct, due to a high variability in the values.

Conclusion

A 4.0-mm cortical screw offers biomechanical advantages over a 3.5-mm cortical screw and may be an alternative implant for the treatment of navicular bone fractures in horses. Further clinical studies are needed to determine whether this screw can also be inserted without complications in vivo.

Keywords

equine - navicular bone fracture - surgical fixation - 4.0-mm cortical screw - 3.5-mm cortical screw

Authors' Contribution

G.S. contributed to the study design, acquisition of data and drafting of the article. S.V. contributed to the conception of the study and study design, acquisition and interpretation of data and drafting and revision of the article. A.F. contributed to the conception of the study and study design, interpretation of data and revision of the article. B.W. contributed to the conception of the study and study design, interpretation of data and revision of the article. M.J. contributed to the conception and study design, acquisition and analysis of data, drafting and revision of the article. All authors approved the final version of the manuscript and agreed to be publicly accountable for the appropriate portion of the content.

Publication History

Received: 27 February 2024

Accepted: 20 June 2025

Article published online:
08 July 2025

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