Financial support provided by a grant from the Fund for Companion Animal Health, Department of Clinical Sciences, Cummings School of Veterinary Medicine at Tufts University.
Nonlinear Stiffness Profiles of External Fixators Constructed with Composite Rods
Version of Record online: 11 DEC 2006
Volume 35, Issue 8, pages 700–704, December 2006
How to Cite
CARLSON, K. R., KRAUS, K. H. and KOWALESKI, M. P. (2006), Nonlinear Stiffness Profiles of External Fixators Constructed with Composite Rods. Veterinary Surgery, 35: 700–704. doi: 10.1111/j.1532-950X.2006.00213.x
- Issue online: 11 DEC 2006
- Version of Record online: 11 DEC 2006
- Submitted April 2006; Accepted June 2006
Objective— To determine if composite connecting rods confer nonlinear stiffness characteristics on unilateral and bilateral external skeletal fixators (ESF) in cranial–caudal bending and axial loading.
Study Design— Mechanical testing performed on models.
Sample Population— Six models of 6-pin ESF constructs composed of birch dowels, a commercial ESF system, and composite connecting rods.
Methods— Unilateral and bilateral ESF configurations were assembled using either specially designed composite titanium and silicone (composite group) or solid titanium (solid group) connecting rods. Mechanical testing was performed in axial loading and 4-point cranial–caudal bending. Stiffness was determined at a low and high-load range, and was considered increasing and nonlinear if the stiffness at high loads was greater than at low loads.
Results— The stiffness of the solid group was linear in all testing modes and configurations. Bilateral composite fixators had a nonlinear increasing stiffness in axial loading and cranial–caudal bending. Unilateral composite fixators had a nonlinear increasing stiffness in axial loading, but not cranial–caudal bending. Solid connecting rods conferred a higher stiffness in all testing modes and configurations.
Conclusions— Composite connecting rods resulted in nonlinear increasing axial and bending stiffness in bilateral fixators, and in axial load in unilateral fixators.
Clinical Relevance— Conventional ESF can be constructed so that the stiffness increases as load increases. This provides the surgeon with additional options to control the local mechanical environment of a healing fracture, which may be used to enhance fracture healing.