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

Abstract

Background 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. Questions/purposes We asked whether three techniques for determining tibial component rotation based on local anatomic landmarks are reliable deeper tibial resection levels. Patients and Methods 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. Results The posterior condylar line of the tibia is the least variable local landmark for tibial component positioning at deep resection levels. Conclusions Assuming the normal posterior condylar line of the tibia is visible at revision, setting the tibial component at 10°external rotation with respect to the posterior condylar axis of the tibia gets the tibial component within 10°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.

How Does TKA Kinematics Vary With Transverse Plane Alignment Changes in a Contemporary Implant?

“…Recently, a study by Parratte et al [15] reported an alignment outside 3°of the normal mechanical axis does not successfully predict a poor-functioning TKA in a series of patients. While mechanical alignment is important, there are multiple surgically controllable variables involved in producing a successful TKA, including coronal, transverse, and sagittal plane soft tissue stability [1,4,6,17,21]. Also, in some varus knees, there are individuals who have a large adductor moment, which predicts failures in patients receiving high tibial osteotomy [16], but there is no similar study showing where muscle forces are mapped out that predicts a higher failure rate in TKA.…”

Rotational alignment of the tibial component in total knee arthroplasty: the anterior tibial cortex is a reliable landmark

“…Unfortunately, many sagittal axes are not easily and reliably identifiable during surgery. Graw et al (19) showed high variability of several sagittal axes in relation to different tibial resection levels. Na gamine et al (20) demonstrated that a sagittal anteroposterior axis was less reliable than the PCA for use in alignment in TKA.…”

Is There a Gold Standard for TKA Tibial Component Rotational Alignment?

“…Currently, many anatomic landmarks are used to align the tibial component, including the projected femoral TEA [1,2,20,24], medial border of the tibial tubercle [17,18,22,47], medial 1/3 of the tibial tubercle [17,20,47], PCL attachment [1,2,23,47], transverse axis of the tibia [18,20,47], posterior condylar line of the tibia [18,20,23], midsulcus of the tibial spine [17], malleolar axis [1,18], patellar tendon [1,2,23,24], and axis of the second metatarsal [1]. This lack of a gold standard for tibial component alignment, combined with the difficulty in identifying anatomic landmarks during surgery and variations in anatomy between knees, may lead to variations in the surgeons' ability to locate tibial component alignment axes as large as 44°internal rotation to 46°external rotation [47].…”