• Ming-Yang Liu, Hai-Bo Wang, Shi-Wei Liu, Guan-Peng Zhang, Jian-Guo Liu, and Chen Yang.
• Department of Orthopaedic Surgery, The First Hospital of Jilin University, Changchun, China.
• Orthop Surg. 2020 Jun 1; 12 (3): 861-868.

ObjectiveTo introduce a three-point method combining the midpoint of the posterior cruciate ligament (PCL), the midsulcus of the tibial spines, and the midpoint of the anterior cruciate ligament (ACL) to determine appropriate tibial resection and component placing during TKA and to compare this method with Insall's 1/3 method.MethodsA consecutive series of 128 knees that underwent TKA from January 2015 to August 2018 were analyzed. In one group (64 knees), the medial 1/3 of tibial tubercle (the Insall's traditional method) was used for tibial component alignment. In the other group (64 knees), the three-point line connecting the midpoint of the PCL, the midpoint of the tibial spines, and the midpoint of the ACL was used for tibial component alignment. Both groups used the anterior tibial tendon as the distal reference for tibial resection. The coronal alignment error of the tibial component was determined by the angle between the line parallel to the tibial component platform and the tibial mechanical axis measured on postoperative radiograph. The axial rotation error of the femoral or tibial component was the intersection angle between the transepicondylar axis (TEA) and a line tangent to the posterior edge of the femoral or tibial component measured on CT. The coronal and axial alignment errors were compared between the two groups.ResultsThe average coronal alignment error of the tibial component in the three-point method group was 0.2° ± 1.4° versus - 0.9° ± 1.8°in the Insall's 1/3 method group (P < 0.001), and the mean absolute value in the three-point method group reduced by 37.3% compared to Insall's traditional method group. The average axial rotation error of the femoral component was 0.2° ± 1.2° in the three-point method group versus - 1.1° ± 1.7° in the Insall's 1/3 method group (P < 0.001), and the mean absolute value in three-point method group decreased by 43.9% compared to Insall's traditional method group. The average axial rotation error of the tibial component was 0.4° ± 1.4° versus - 1.4° ± 1.8° in the Insall's 1/3 method group (P < 0.001), and the mean absolute value in the three-point method group reduced by 35.5% compared to the Insall's traditional method group. The rates of rotation outliers were significantly lower in the three-point method group (P < 0.05).ConclusionThe line connecting the midpoint of the PCL, the midsulcus of the tibial spines, and the midpoint of the ACL could be used as the reference for the tibial resection and component placing. This method appears to be more accurate than Insall's 1/3 method. The results of this study provide a candidate method for component orientation with little error.© 2020 The Authors. Orthopaedic Surgery published by Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

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