Centre of rotation of angulation (CORA)-based levelling osteotomy (CBLO) is a recent addition to surgical procedures for stabilization of the cranial cruciate ligament-deficient canine stifle joint. Careful identification of the CORA location preoperatively and use of this location intraoperatively are required to ensure accurate correction of the tibial plateau angle. Limited data are available regarding the magnitude and source of potential errors during planning and execution of CBLO. A geometric model enabling isolation of various error sources is described.

Landmarks were derived from tibial radiographs (n = 50) by 5 observers and used to define proximal and distal anatomical axes for simulation of CBLO. Observer-specific CORA locations with mean landmark data were used to assess planning errors, and simulated malpositioning of the CORA at 10 mm from the ideal location was used to assess surgical errors.

Planning errors result mainly from tibial plateau misidentification, with CORA locations dispersed up to ±10 mm proximodistally from ideal (95% confidence). Malpositioning of the CORA during surgery causes equal and opposite changes in tibial plateau angle (TPA) and anatomical-mechanical axis angles, and varying degrees of translation and limb length changes. The magnitude of these changes is dependent on initial TPA and limb length, with smaller dogs and steeper tibial plateaus resulting in larger errors.

Optimal planning and execution are required to achieve the planned outcome of CBLO. The main source of error in our simulation is identification of the tibial plateau. While both pre- and intraoperative errors influenced TPA, based on our geometric model the effect in larger dogs may not be clinically significant. If distalisation of the CORA is required during surgery, compensation of the CORA angle to maintain the target TPA is possible.

基于旋转角中心（CORA）的水平截骨术（CBLO）是稳定颅骨十字韧带缺损犬窒息关节的外科手术中的一项最新举措。术前仔细确定CORA位置，并在术中使用该位置，以确保准确校正胫骨平台角度。有关CBLO计划和执行期间潜在错误的严重程度和来源的可用数据有限。描述了能够隔离各种错误源的几何模型。

地标 由5位观察者从胫骨X线片（n = 50）得出，用于定义近端和远端解剖轴，以模拟CBLO。具有平均地标数据的特定于观察者的CORA位置用于评估计划错误，并且距理想位置10 mm处的CORA模拟错位用于评估手术错误。

计划错误主要是由于胫骨平台识别不正确造成的，CORA位置与理想位置（95％置信度）的距离最大为±10 mm。手术期间CORA的位置不当会导致胫骨平台角（TPA）和解剖机械轴角的变化相等且相反，并且平移度和肢体长度的变化也不同。这些变化的幅度取决于初始TPA和肢体长度，较小的狗和较陡峭的胫骨平台会导致较大的误差。

要实现CBLO的计划成果，需要进行最佳计划和执行。在我们的模拟中，误差的主要来源是胫骨平台的识别。虽然术前和术中错误均会影响TPA，但根据我们的几何模型，对大型犬的影响可能并不具有临床意义。如果在手术期间需要对CORA进行远端治疗，则可以补偿CORA角度以维持目标TPA。