Rotational References for Total Knee Arthroplasty Tibial Components Change with Level of Resection

Various landmarks can guide tibial component rotational alignment in routine TKA, but with the deeper tibial resection levels common in complex primary and revision TKAs, it is unknown whether these landmarks remain reliable. We asked whether three techniques for determining tibial component rotation based on local anatomic landmarks are reliable deeper tibial resection levels. The femoral transepicondylar axis was identified by three independent reviewers on MR images of knees from 24 men and 24 women and transposed at a traditional tibial resection level and at the level of the proximal, middle, and distal parts of the proximal tibiofibular joint. Three axes were drawn on axial slices at these levels: the geometric center of the tibial plateau to the medial 1/3 of the tubercle, the posterior condylar line of the tibia, and the largest mediolateral dimension of the tibia. These lines were compared with the transposed femoral epicondylar axis line. The posterior condylar line of the tibia is the least variable local landmark for tibial component positioning at deep resection levels. Assuming the normal posterior condylar line of the tibia is visible at revision, setting the tibial component at 10A degrees external rotation with respect to the posterior condylar axis of the tibia gets the tibial component within 10A degrees of proper rotation in 86% to 98% of patients, even to the distal part of the proximal tibiofibular joint. The experienced surgeon then can adjust this position based on cues from an assortment of other axes.