Introduction: Triple tibial osteotomy (TTO) has been reported to provide stability to the canine cranial cruciate ligament (CrCL) deficient stifle in clinical studies. While other proximal tibial osteotomies addressing CrCL deficient stifles, tibial tuberosity advancement (TTA) and tibial plateau leveling osteotomy (TPLO), have been biomechanically evaluated (Kipfer et al. (2008), Apelt et al. (2007), Butler et al. (2011), Pozzi et al. (2006) and Rey et al. (2014)), experimental studies on TTO are lacking. The aim of this study was to evaluate the effect of TTO on cadaveric stifle stability at multiple joint angles and under constant quadriceps and gastrocnemius loads.

Materials and methods: TTO was performed on nine right stifles from a previous study following CrCL transection and medial meniscal release (MMR), to mimic the clinical situation of preexisting medial meniscal damage or prophylactic MMR in combination with TTO. Procedure planning and calculations were performed based on radiographs of the intact stifle and carried out as described by Bruce et al. (2007). Extended limb mediolateral radiographs were obtained for postoperative PTA and tibial plateau angle (TPA) measurement. Limbs were mounted on a custom-made frame, which permitted controlled movement of the tibia relative to the femur, and extended from full flexion whilst recording the stifle region fluoroscopically. Metal markers placed at the CrCL attachment sites were used to monitor cranial tibial subluxation (CTS), and joint angle and PTA were measured from the recordings.

Results: Pre-TTO, CTS occurred at a joint angle of 65° corresponding to an intact PTA of 86°. Following TTO, CTS was significantly reduced at all joint angles compared to the CrCL deficient stifle with MMR.At joint angles between 105-140°, stifle stability was not statistically different to the intact joint. However, the stifle was significantly over-corrected through joint angles 65° to 100° (negative CTS), and under-corrected at joint angles >145°. The maximum CTS due to under-correction in the TTO stabilized stifle was 16.4% of the intact marker distance, corresponding to a mean of 3 mm.Pre-TTA radiographic PTA was 118° (± 2°) at a mean stifle angle of 146.5° (± 4°) and TPA was 29° (± 2°). The mean calculated wedge angle for TTO was 20° (± 1°).Following TTO, the mean TPA was 12° (± 2°) and the mean PTA was 100° (± 4°) at a mean stifle angle of 141° (± 8.5°). Two different complications were observed during TTO. These were fracture of the caudal tibial cortex and fracture of the distal tibial tuberosity. The complication rate was respectively 100% and 44%.

Conclusion: TTO significantly reduced CTS in this CrCl and medial meniscus deficient stifle model throughout a full range of motion, supporting clinical reports of successful treatment. Slight under-correction was observed during late extension, which could be due to the technical failure to reduce radiographic PTA to 90° in the extended stifle. The under-correction found may be of questionable clinical significance, due to the limited amount of CTS observed.