In vitro comparison of a novel external fixator and traditional full-limb transfixation pin cast in horses.
OBJECTIVE
To compare the mechanical properties and failure modes of a standardized short oblique distal radial metaphyseal osteotomy stabilized using either a transfixation pin cast (TPC), a modular-sidebar external skeletal fixator (ESF), or a solid-sidebar ESF (modular- or solid-ESF, respectively) using static or cyclic axial loading to failure.


METHODS
In vitro study.


METHODS
Equine cadaver forelimbs.


METHODS
A 30 degrees oblique distal radial osteotomy was created and stabilized using 1 of the 3 fixation methods: (1) TPC, (2) modular-ESF, or (3) solid-ESF. Limbs were tested using static (TPC, modular-ESF, and solid-ESF) or cyclic (TPC and solid-ESF) axial loading to failure. The stiffness, yield load, yield displacement, failure load, and failure displacement for static loading and the cycles to failure for cyclic loading at 75% failure load were obtained. Data were analyzed using a Kruskal-Wallis test. Level of significance was P<.05.


RESULTS
The solid-ESF had a greater stiffness, higher yield and failure load and a lower yield and failure displacement than the TPC (P=.01) and the modular-ESF (P=.02). TPC had a higher yield load, failure load, and yield displacement than the modular-ESF (P=.01). Mean cycles to failure for TPC was 2996+/-657 at a load of 16,000 N and for solid-ESF 6560+/-90 cycles at a load of 25,000 N.


CONCLUSIONS
The solid-ESF was stiffer and stronger than the TPC and modular-ESF and failed at a greater number of cycles in axial loading compared with the TPC.


CONCLUSIONS
This study is an initial step in evaluating the solid-ESF. Further testing needs to be performed, but this fixation may offer a viable alternative to the traditional TPC for stabilization of long bone fractures in adult horses.
Nutt
James N
JN
Richard S. Reynolds, Jr. Comparative Orthopedic Research Laboratory, Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, USA.
Southwood
Louise L
LL
Elce
Yvonne A
YA
Nunamaker
David M
DM
D000818:Animals; D001696:Biomechanical Phenomena; D016267:External Fixators / Q000662:veterinary*; D006736:Horses / Q000601:surgery*; D066298:In Vitro Techniques; D010027:Osteotomy / Q000379:methods / Q000662:veterinary*; D011884:Radius / Q000601:surgery*; D011885:Radius Fractures / Q000601:surgery / Q000662:veterinary; D016474:Weight-Bearing