Abstract
Objective: The tibial crest and fibula are used as a landmark for extramedullary tibial alignment in total knee arthroplasty. We studied the accuracy of using this landmark for extramedullary alignment in total knee arthroplasty.
Methods: We evaluated 60 knees in 47 patients. Computed tomography-based simulation software was used to perform evaluations using preoperative TKA planning (ZedKnee, LEXI, Tokyo, Japan). We defined the mechanical axis of the tibia as a straight line from the center of the tibial tray to the center of the tibial distal plafond. The proximal tibial crest line was taken as the line connecting the two points at 10 cm and 15 cm distal to the knee joint line. The fibular axis was defined as a straight line from the center of the fibular head to the center of the lateral maleolli. The angles between the proximal tibial crest line and the mechanical axis in the coronal and sagittal planes and the angle between the fibular axis and the sagittal mechanical axis were measured.
Results: The mean angles between the mechanical axis and the proximal tibial crest line were 0.3°±2.5° (range -4.9° to 6.8°) of varus in the coronal plane and 3.1°±1.1° (range 1° to 5.6°) of anterior slope in the sagittal plane. Forty-seven tibias (78.3%) were within 3 in the coronal plane and 41 tibias (68.3%) were from 2° to 4° of anterior slope in the sagittal plane. In patients with more than 3° of varus or more than 4° of anterior slope, tibial lengths were significantly shorter (p＜0.01 in the coronal plane and p＜0.05 in the sagittal plane). The angle between the mechanical axis and the proximal tibial crest line was significantly correlated with tibial length (r=0.63, p＜0.01 in the coronal plane). The mean angle between the fibular axis and the sagittal mechanical axis was 1.5°±0.8° (range -0.7° to 3.1°) of posterior slope and was highly consistent.
Conclusion: Although surgeons have to be careful, and in patients with short or long tibia, reference to other landmarks is mandatory, the proximal tibial crest is a useful landmark in total knee arthroplasty; we rediscovered that the fibula is a reliable landmark in the sagittal plane.
