Preliminary mechanical evaluation of two novel veterinary angle-stable-threaded interlocking nail systems

Abstract

ABSTRACT: The interlocking nail represents an excellent option as a surgical approach to treat fractures in long bones in veterinary medicine. However, failures were reported mainly due to a slack present in the interface of the rod with the screws. The present study tested and mechanically compare axial compression loads of two novel models of stable angle interlocking nails with threaded holes. Among the two models, one was uniplanar and the other was multiplanar with orthogonally arranged distal holes. Twenty-one specimens made of polylactic acid were used for the implantation of interlocking nail´s rods, divided into three groups: conventional interlocking nail (G1), novel interlocking nail with a stable angle with holes arranged in a single plane (G2), and novel interlocking nail with a stable angle in two planes, with the penultimate hole at 90 degrees from the others (G3). Biomechanical tests were performed using axial, cyclic, and destructive compression load for comparison between them. All the specimens showed plastic deformation in the screws after destructive tests, in both proximal and distal sides, being highly intense in G1. G2 and G3 of the stable angle rods supported higher loads than G1 in all tests performed (P<0.05). The novel stems did not differ statistically from each other (P>0.05). The initial hypothesis that the novel models would provide increased stability was confirmed; however, no differences were demonstrated between them. The screw locking system on the rods allowed high resistance values in the tests performed, proving to be effective and potentially applicable in real clinical situations.