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Vet Comp Orthop Traumatol 2013; 26(03): 177-185
DOI: 10.3415/VCOT-12-05-0061
Original Research
Schattauer GmbH

Ex vivo evaluation of the biomechanical effect of varying monocortical screw numbers on a plate-rod canine femoral gap model

P. J. Delisser
1   School of Veterinary Science, University of Bristol, Langford House, Langford Bristol, UK
,
G. P. McCombe
2   Department of Engineering, University of Bristol, Advanced Composites Centre for Innovation in Science, Queen's Building, Bristol, UK
,
R. S. Trask
2   Department of Engineering, University of Bristol, Advanced Composites Centre for Innovation in Science, Queen's Building, Bristol, UK
,
J. A. Etches
2   Department of Engineering, University of Bristol, Advanced Composites Centre for Innovation in Science, Queen's Building, Bristol, UK
,
A. J. German
3   Department of Obesity and Endocrinology, The University of Liverpool, Leahurst Campus, Chester High Road, Neston, UK
,
S. L. Holden
3   Department of Obesity and Endocrinology, The University of Liverpool, Leahurst Campus, Chester High Road, Neston, UK
,
A. M. Wallace
1   School of Veterinary Science, University of Bristol, Langford House, Langford Bristol, UK
,
N. J. Burton
1   School of Veterinary Science, University of Bristol, Langford House, Langford Bristol, UK
› Author Affiliations
Further Information

Publication History

Received 05 May 2012

Accepted 23 March 2012

Publication Date:
19 December 2017 (online)

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Summary

Objective: To compare the biomechanical behaviour of plate-rod constructs with varying numbers of monocortical screws applied to an ex vivo canine femoral-gap ostectomy model.

Sample population: Twenty Greyhound dog cadaveric femurs.

Methods: Bone mineral density (BMD) was assessed with dual x-ray absorptiometry. Bones were assigned to four groups. Bones had a 12-hole 3.5 mm locking compression plate with one bicortical non-locking cortical screw in the most proximal and distal plate holes and an intramedullary Steinmann pin applied across a 20 mm mid-diaphyseal ostectomy. Additionally, one to four monocortical non-locking cortical screws were then placed (Groups 1–4 respectively) in the proximal and distal fragments. Stiffness and axial collapse were determined before and after cyclic axial loading (6000 cycles at 20%, 40%, and 60% of mean bodyweight [total: 18000 cycles]). Constructs subsequently underwent an additional 45000 cycles at 60% of bodyweight (total: 63000 cycles). Loading to failure was then performed and ultimate load and mode of failure recorded.

Results: The BMD did not differ significantly between groups. Construct stiffness for group 1 was significantly less than group 4 (p = 0.008). Stiffness showed a linear increase with an increasing number of monocortical screws (p = 0.001). All constructs survived fatigue loading. Load-to-failure was not significantly different between groups. Mean load- to-failure of all groups was >1350N.

Clinical relevance: Ex vivo canine large-breed femurs showed adequate stability biomechanically and gradually increasing stiffness with increasing monocortical screw numbers.

Keywords

fracture - biomechanics - stiffness - comminuted - screw number
 

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