IN-VITRO EVALUATION OF 4 METHODS OF ATTACHING TRANSFIXATION PINS INTOA FIBERGLASS CAST FOR USE IN HORSES

Objective - To compare the axial stability provided by 4 methods of at taching transfixation pins into a fiberglass cast. Design - Axial stab ility of 4 methods of transfixation pin attachment to a fiberglass cas t cylinder was determined in vitro. Methods of attachment included sim ple incorporation of the pins into the cast, placement of a washer and nut on the pin and incorporation into the cast, extension of pins bey ond the cast and attachment to a steel halo, and washers within the ca st and attachment to a steel halo. Population - A model was designed t o simulate a transfixation cast applied to the equine metacarpus. 8 id entical constructs were present in each of the 4 groups. 6 fiberglass cylinders were also tested to identify the contribution of the cast cy linder to the overall stability of the transfixation cast. Procedure - Load-displacement curves were recorded, and a stiffness modulus was c alculated for each treatment group and for a simple fiberglass cylinde r without transfixation pins. Result and Conclusion - There was no sig nificant difference among the 4 methods of attachment. The fiberglass cast material appears to be the major determinant of axial stability.