In vitro evaluation of four methods of attaching transfixation pins into a fiberglass cast for use in horses

Abstract

Objective - To compare the axial stability provided by 4 methods of attaching transfixation pins into a fiberglass cast. Design - Axial stability of 4 methods of transfixation pin attachment to a fiberglass cast cylinder was determined in vitro. Methods of attachment included simple incorporation of the pins into the cast, placement of a washer and nut on the pin and incorporation into the cast, extension of pins beyond the cast and attachment to a steel halo, and washers within the cast and attachment to a steel halo. Population - A model was designed to simulate a transfixation cast applied to the equine metacarpus. 8 identical constructs were present in each of the 4 groups. 6 fiberglass cylinders were also tested to identify the contribution of the cast cylinder to the overall stability of the transfixation cast. Procedure - Load-displacement curves were recorded, and a stiffness modulus was calculated for each treatment group and for a simple fiberglass cylinder without transfixation pins. Result and Conclusion - There was no significant difference among the 4 methods of attachment. The fiber-glass cast material appears to be the major determinant of axial stability.