A disadvantage to using extramedullary alignment guides of the tibia for total knee arthroplasty (TKA) is difficulty in correctly identifying the ankle center. The anterior border of the tibia is easily palpable, as it is not covered by muscles and its shape is convex anteriorly. We hypothesized that appropriate points exist along the anterior border that can be used as landmarks for extramedullary guides. Prior to TKA, computed tomographic images of the entire tibia were obtained from 101 osteoarthritic knees with varus deformities. The relationship between the lines connecting two points on the anterior border and the mechanical axis was evaluated using 3D imaging software. The mean angles between each of 10 determined axes and the mechanical axis varied from 3.2° varus to 2.1° valgus in the coronal plane. In the sagittal plane, all axes referencing the anterior border of the tibia showed anterior inclination to the mechanical axis. The line connecting the medial one-third of the patellar tendon attachment and the distal one-fourth of the anterior border, however, was highly consistent and parallel to the mechanical axis in the coronal plane. This axis can be effectively used as a landmark for extramedullary guides during TKA.
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