THE EFFECT OF HOLE DIAMETER ON THE TORSIONAL MECHANICAL-PROPERTIES OFTHE EQUINE 3RD METACARPAL BONE

The torsional monotonic structural material properties of equine metac arpi with or without, either a 5/16 inch or 3/8 inch diameter bicortic al lateromedial middiaphyseal hole were assessed to determine the effe ct of a hole on metacarpal strength. Torsional stiffness was not signi ficantly effected by the presence of a bicortical hole, whereas yield and failure angles, torques and energies of metacarpi with a hole were 51% to 97% of those of intact bones. Significant differences were not apparent for yield and failure mechanical properties between metacarp i with a 5/16 inch diameter hole and metacarpi with a 3/8 inch diamete r hole; however, postyield mechanical properties were lower for metaca rpi with a 3/8 inch hole. Whereas some metacarpi with a 5/16 inch hole were capable of plastic deformation before failure, metacarpi with a 3/8 inch diameter hole appeared to have sufficient stress concentratio n to propagate complete fracture on structural yield. (C) Copyright 19 96 by The American College of Veterinary Surgeons