Effect of Cranial Tibial Closing Wedge Angle on Tibial Subluxation: An Ex Vivo Study

Abstract

To evaluate the effect of cranial tibial wedge osteotomy (CTWO) angle on cranial tibial subluxation (CTS) and postoperative tibial plateau angle (TPA). Ex vivo biomechanical study. Canine pelvic limbs (n=6). 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). 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. 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. 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.