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Vet Comp Orthop Traumatol 2022; 35(01): 033-046
DOI: 10.1055/s-0041-1735551
Original Research

Influence of Screw-Hole Defect Size on the Biomechanical Properties of Feline Femora in an Ex Vivo Model

QiCai Jason Hoon 
1   Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
,
Tian Wang
2   Surgical and Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW Sydney, Randwick, New South Wales, Australia
,
Evelyn Hall
1   Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
,
William R. Walsh 
2   Surgical and Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW Sydney, Randwick, New South Wales, Australia
,
Kenneth A. Johnson 
1   Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
› Author Affiliations
Funding This work was supported by the Sydney University clinical residency research programme.
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Abstract

Objective The study aims to evaluate the biomechanical properties of feline femora with craniocaudal screw-hole defects of increasing diameter, subjected to three-point bending and torsion to failure at two different loading rates.

Study Design Eighty femoral pairs were harvested from adult cat cadavers. For each bending and torsional experiment, there were five groups (n = 8 pairs) of increasing craniocaudal screw-hole defects (intact, 1.5 mm, 2.0 mm, 2.4 mm, 2.7mm). Mid-diaphyseal bicortical defects were created with an appropriate pilot drill-hole and tapped accordingly. Left and right femora of each pair were randomly assigned to a destructive loading protocol at low (10 mm/min; 0.5 degrees/s) or high rates (3,000 mm/min; 90 degrees/s) respectively. Stiffness, load/torque-to-failure, energy-to-failure and fracture morphology were recorded.

Results Defect size to bone diameter ratio was significantly different between defect groups within bending and torsional experiments respectively (intact [0%; 0%], 1.5 mm [17.8%; 17.1%], 2.0 mm [22.8%; 23.5%], 2.4 mm [27.8%; 27.6%], 2.7 mm [31.1%; 32.4%]) (p < 0.001). No significant differences in stiffness and load/torque-to-failure were noted with increasing deficit sizes in all loading conditions. Screw-hole (2.7 mm) defects up to 33% bone diameter had a maximum of 20% reduction in bending and torsional strength compared with intact bone at both loading rates. Stiffness and load/torque-to-failure in both bending and torsion were increased in bones subjected to higher loading rates (p < 0.001).

Conclusion Screw-hole defects up to 2.7 mm did not significantly reduce feline bone failure properties in this ex vivo femoral study. These findings support current screw-size selection guidelines of up to 33% bone diameter as appropriate for use in feline fracture osteosynthesis.

Keywords

screw-hole - feline femora - defect size - torsion - three-point bending

Note

The study has been presented as a scientific abstract at the European College of Veterinary Surgeons Virtual Resident's Forum 2020: Small Animal Orthopaedics.


Authors' Contribution

Q.J.H. and T.W. contributed to the study conception, study design, acquisition of data and data analysis and interpretation. E.H. contributed to the statistical data analysis and interpretation. K.J. and W.W. contributed to the study conception, study design, data analysis and interpretation. All authors drafted, revised and approved the manuscript prior to submission.




Publication History

Received: 10 November 2020

Accepted: 27 July 2021

Article published online:
06 September 2021

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