Effect of tibial plateau leveling on cranial and caudal tibial thrusts in canine cranial cruciate-deficient stifles: An in vitro experimental study

Objectives-To investigate the effect of tibial plateau leveling (TPL) on ti bial subluxation and tibial axial rotation; to determine the minimal tibial plateau rotation (MinTPR) angle that provides stifle stability; and to eva luate caudal cruciate ligament (CaCL) strain following tibial platt au rota tion in cranial cruciate ligament (CrCL)-deficient stifles. Animals-Fifteen canine cadaver hind limbs. Methods-Tibial subluxation was measured from lateral radiographs in intact, loaded stifles and after sequential CrCL transection, MinTPR, TPL, and CaC L transection. The MinTPR angle was determined using a custom-made hinge pl ate and compared with the TPL angle. Tibial axial rotation was evaluated in CrCL-deficient stifles before and after TPL. Finally, CaCL strain was reco rded in intact, loaded stifles, and following MinTPR, TPL, and tibial plate au over-rotation (MaxTPR) using a force probe. Results-Cranial tibial subluxation in CrCL-deficient stifles was eliminated with TPL. Tibial plateau rotation, however, induced caudal tibial subluxat ion, which significantly increased from MinTPR to TPL before and after CaCL transection. The MinTPR angle was 6.5 degrees +/- 0.9 degrees less than th e TPL angle (P < .05). Tibial internal rotation decreased significantly aft er TPL in CrCL-deficient stifles. Finally, CaCL strain increased with incre asing tibial plateau rotation. Conclusions-This study suggests that, during stance phase, TPL transforms c ranial tibial thrust into caudal tibial thrust, thereby stabilizing the sti fle in the cranio-caudal plane via the constraint of the CaCL. The increase in CaCL stress, which results from tibial platt au rotation, could predisp ose the CaCL to fatigue failure and therefore would caution against tibial platt au over-rotation. (C) Copyright 2001 by The American College of Veter inary Surgeons.