Effect of tibial subluxation on the measurements for tibial tuberosity advancement in dogs with cranial cruciate ligament deficiency. An ex vivo study.

Objectives: The main objectives were to evaluate the impact of femorotibial subluxation on the preoperative measurements for tibial tuberosity advancement (TTA) by defining radiographic landmarks and testing the repeatability for assessing cranial tibial subluxation (CTS). Also, we aimed at developing a formula to calculate the necessary adjustment in measurement of TTA in stifles with CTS.

Methods: Forty stifles were used to examine the influence of CTS on preoperative TTA measurements before and after transection of the cranial cruciate ligament. Mediolateral radiographs were obtained and measurements performed by three investigators. The observed variabilities were assessed by inter- and intra-observer differences.

Results: Measurements of CTS and preoperative TTA showed a good to excellent inter- and intra-observer correlation. We found a significant influence of CTS on TTA measurements and developed a formula to calculate the necessary adjustment in measurement of TTA in stifles with CTS.

Conclusion: We found a correlation between the tibial subluxation and the measurements for TTA, with the latter decreasing with increasing subluxation. This has to be taken into account when measuring the advancement in stifles with complete rupture of the cranial cruciate ligament. We provided a formula to calculate the necessary addition to the measured advancement.