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Problem of pin breakage in equine transfixation pin casting: biomechanical ex vivo testing of four different pins


Keller, Sara; Valet, Sebastian; Martens, Ann; Weisse, Bernhard; Fürst, Anton; Kümmerle, Jan M (2019). Problem of pin breakage in equine transfixation pin casting: biomechanical ex vivo testing of four different pins. Veterinary and Comparative Orthopaedics and Traumatology, 32(03):222-233.

Abstract

Objective: The aim of this study was to evaluate cyclic fatigue behaviour of a new pin with a thread run-out design in comparison with three other types of pins commonly used for equine transfixation pin casting.
Materials and Methods: Twenty-four pairs of equine cadaveric third metacarpal bones (MC3) equipped with one transfixation pin placed horizontally in the distal metaphysis were tested using a simplified model, mimicking the biomechanical situation of equine transfixation pin casting. A 6.3/8.0-mm Imex Duraface pin with thread run-out design (ITROP) was compared with a 6.1-mm smooth Steinmann pin (SSP), a Securos 6.2-mm, positive-profile pin (SPPP) and an Imex 6.3-mm, positive-profile pin (IPPP) under cyclic loading until failure in axial compression of MC3.
Results: All pins broke at clinically relevant load levels and cycle numbers. The SSP endured significantly (p = 0.0025) more cycles before failure (mean: 48685) than the ITROP (mean 25889). No significant differences in cycles to failure were observed comparing the SPPP versus ITROP, and the IPPP versus ITROP, respectively.
Clinical Significance: A thread run-out design does not necessarily lead to higher resistance against pin breakage under cyclic loading conditions. The SSP was most resistant against cyclic failure in these testing conditions, even though it was associated with more lateromedial displacement and cortical wear-out. This could outweigh reported disadvantages of the SSP such as reduced resistance to axial extraction and pin loosening.

Abstract

Objective: The aim of this study was to evaluate cyclic fatigue behaviour of a new pin with a thread run-out design in comparison with three other types of pins commonly used for equine transfixation pin casting.
Materials and Methods: Twenty-four pairs of equine cadaveric third metacarpal bones (MC3) equipped with one transfixation pin placed horizontally in the distal metaphysis were tested using a simplified model, mimicking the biomechanical situation of equine transfixation pin casting. A 6.3/8.0-mm Imex Duraface pin with thread run-out design (ITROP) was compared with a 6.1-mm smooth Steinmann pin (SSP), a Securos 6.2-mm, positive-profile pin (SPPP) and an Imex 6.3-mm, positive-profile pin (IPPP) under cyclic loading until failure in axial compression of MC3.
Results: All pins broke at clinically relevant load levels and cycle numbers. The SSP endured significantly (p = 0.0025) more cycles before failure (mean: 48685) than the ITROP (mean 25889). No significant differences in cycles to failure were observed comparing the SPPP versus ITROP, and the IPPP versus ITROP, respectively.
Clinical Significance: A thread run-out design does not necessarily lead to higher resistance against pin breakage under cyclic loading conditions. The SSP was most resistant against cyclic failure in these testing conditions, even though it was associated with more lateromedial displacement and cortical wear-out. This could outweigh reported disadvantages of the SSP such as reduced resistance to axial extraction and pin loosening.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Veterinary Clinic > Equine Department
Dewey Decimal Classification:570 Life sciences; biology
630 Agriculture
Uncontrolled Keywords:Animal Science and Zoology, General Veterinary
Language:English
Date:1 May 2019
Deposited On:28 Jan 2020 15:54
Last Modified:28 Jan 2020 15:54
Publisher:Schattauer
ISSN:0932-0814
OA Status:Green
Publisher DOI:https://doi.org/10.1055/s-0039-1678734
PubMed ID:30847874

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