Objective: To evaluate the effect of cranial tibial wedge osteotomy (CTWO) angle on cranial tibial subluxation (CTS) and postoperative tibial plateau angle (TPA).
Study design: Ex vivo biomechanical study.
Sample population: Canine pelvic limbs (n=6).
Methods: TPA determined from a lateral radiographic projection. CTS under 30% body weight load was measured from radiographs in the intact limb and after transection of the cranial cruciate ligament. A CTWO equal to TPA+10 degrees was performed at the distal extent of the tibial crest, and was stabilized with a custom designed hinge plate and external skeletal fixator. TPA and CTS in the loaded limb was determined from radiographs at 4 CTWO angles: TPA-5 degrees, TPA, TPA+5 degrees, and TPA+7.5 degrees. Comparison of CTS between the intact limb and the 4 CTWO angle groups was performed using 1-way repeated-measures ANOVA and a Dunnett multiple comparison test (significance at P<.05).
Results: CTS was significantly greater than that of the intact limb in the TPA-5 degrees and TPA groups. CTS was not significantly different from the intact limb in the TPA+5 degrees or TPA+7.5 degrees groups with corresponding TPAs of 5.9 degrees and 3.8 degrees, respectively.
Conclusion: Using this model, CTS was neutralized at a TPA of approximately 4-6 degrees with a CTWO angle between TPA+5 degrees and TPA+7.5 degrees.
Clinical relevance: A CTWO angle between TPA+5 degrees and TPA+7.5 degrees is necessary to neutralize CTS and achieve a postoperative TPA of 4-6 degrees if the CTWO is performed at the distal extent of the tibial crest and the caudal cortices are aligned.