Effect of tibial plateau leveling osteotomy on mechanical tibial axis shift in dogs: two dimensional bone study in sagittal plane

Abstract

To determine the tibial axis shift (TAS), change in tibial plateau angle (TPA), and the position of the tibial articular surface after tibial plateau leveling osteotomy (TPLO) simulation in the tibiae of dogs, tibias of 91 dogs from 23 different breeds were used. The TPA, tibial length, midshaft width, medial tibial condyle length, and distances between the tibial axis (TA) and cranial-most point of the medial condyle were measured on the tibial images. After simulated TPLO, all measurements were retaken. Paired t-tests were used to compare pre- and postoperative variables. Pearson correlation analysis was conducted to assess whether the difference between pre- and postoperative TAS was related to tibial length, tibial width, medial condyle length, and/or the degree of TPA rotation. The results showed that TPLO shifted the cranial-most point of the medial condyle caudally and distally, and the caudal-most point caudally and proximally. These shifts resulted in significant differences between pre- and postoperative distances between the TA and the cranial-most point and its percentage to the medial condyle length. It is concluded that the TPLO led to caudal TAS and altered the position of the articular surface of the medial condyle with respect to the distal part of the tibia.