Markus Windolf¹, Michael Leitner¹, Karsten Schwieger¹, Simon Pearce¹, Erich Schneider¹, Kenneth Johnson².
¹AO-Foundation, Davos, Switzerland, ²The Ohio State University, Columbus, Ohio, United States

ACVS Abstract 2007 

The purpose of the study was to compare the achieved tibial plateau rotation after TPLO procedure to the radiographically planed rotation. Moreover, the translational and rotational movements of the tibial plateau fragment were determined in order to investigate which movement is most influential upon the biomechanical stability under cyclic loading. Titanium pins were inserted into the tibial plateau and the proximal metaphysis of 18 cadaveric canine tibiae 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 TPLO plate with either three conventional (n=10) or three locking screws (n=8) in the proximal fragment. CT-scans were performed at three stages: 1) pre-osteotomy (intact bone), 2) post-osteotomy and tibial plateau rotation (temporarily affixed) and 3) post-stabilization with plate and screws. The bones were cyclically loaded in axial compression with a constant peak-load of 1000N for 30,000 cycles. Although deviations up to 28.4% were observed, the radiographically planned tibial plateau rotation correlated significantly with the actual achieved rotation (r=0.558, P=0.016).

A significant correlation between the amount of rotation about the sawing axis of the proximal fragment (CT-scan 1 to 3) and the plastic deformation of the construct after 30,000 testing cycles could be found (r=0.539, P=0.026). Furthermore, fracture reduction related significantly with biomechanical stability of the construct. This study shows that lower degree of rotation about the sawing axis and careful fracture reduction are beneficial for biomechanical stability.