Michael Leitner¹, Simon Pearce¹, Markus Windolf¹, Stefan Zeiter¹, Peter Schawalder², Kenneth Johnson³.
¹AO-Foundation, Davos, Switzerland, ²University of Bern, Department of Veterinary Clinical Medicine, Bern, Switzerland, ³The Ohio State University, Department of Vetrinary Clinical Science, Columbus, Ohio, United States

ACVS Abstract 2007

The purpose of this study was to investigate deviation from the ideal tibial plateau position and the fixation stability after TPLO procedure using plates with either locking or conventional screws in the proximal fragment. Eight pairs of cadaveric canine tibiae were assigned pair-wise to either the conventional screw group or the locking screw group. Titanium pins were inserted into the tibial plateau and the proximal metaphysis of each tibia as reference objects to track the fragment movements by means of CT-imaging.

TPLO procedures were performed using the Slocum technique and a 6 hole Synthes plate with conventional or locking screws. CT-imaging was performed at three stages to determine rotation and translation of the proximal fragment: 1) post-osteotomy and tibial plateau rotation, 2) post stabilization with the implants and 3) after 30,000 cycles of axial compression testing. After 30,000 cycles, mechanical testing was continued with monotonically increasing load until failure of the construct, defined as 6mm of crosshead displacement. A paired nonparametric test was used for statistical comparison between groups. Based on the CT data, rotational movements about any of the three axes were not significantly different.

Translational movement of the proximal fragment towards the plate was significantly greater in the conventional screw group (P¼0.006). However, there were no significant differences between groups in stiffness or number of cycles to failure. This study showed superior maintenance of tibial plateau position in the locking screw group. However, screw type had no effect on the fixation stability of the construct under cyclic loading.