Tibial component positioning in total knee arthroplasty: bone coverage and extensor apparatus alignment

Abstract

IntroductionThe implantation of a total knee arthroplasty (TKA) requires, among other considerations, correct positioning of the tibial component to provide the best long-term stability of the prosthesis [12]. Lotke and Ecker [19] insist upon adequately setting the tibial component in the frontal plane, while other authors identify mispositions of the tibial tray in the transverse plane [8] as another possible source of failure. Indeed, malrotating the tibial component with respect to the femoral one [4,18,23] can lead to premature tibial polyethylene wear, one of the most common causes of revision in TKA [5].Concerning the position of the prosthetic tibial tray in the transverse plane, the surgeon should basically integrate two factors simultaneously when implanting it. Both an 'optimal' bone coverage ensuring thorough stability and a satisfactory extensor apparatus alignment providing a harmonious patellofemoral tracking should be supplied by the tibial component.Optimal bone coverage is achieved when the tibial component covers most of the underlying tibial plateau [9,12,16] or, more precisely, when it provides a maximal Abstract Correct positioning of the tibial component in total knee arthroplasty (TKA) must take into account both an optimal bone coverage (defined by a maximal cortical bearing with posteromedial and anterolateral support) and satisfactory patellofemoral tracking. Consequently, a compromise position must be found by the surgeon during the operation to simultaneously meet these two requirements. Moreover, tibial tray positioning depends upon the tibial torsion, which has been shown to act mainly in the proximal quarter of the tibia. Therefore, the correct application of the tibial tray is also theoretically related to the level of bone resection. In this study, we first quantified the torsional profile given by an optimal bone coverage for a symmetrical tibial tray design and for an asymmetrical one. Then, for the two types of tibial trays, we measured the angle difference between optimal bone coverage and an alignment on the middle of the tibial tubercule. Results showed that the values of the torsional profile given by the symmetrical tray were more scattered than those from the asymmetrical one. However, determination of the mean differential angle between the position providing optimal bone coverage and the one providing the best patellofemoral tracking indicated that the symmetrical prosthetic tray offered the best compromise between these two requirements. Although the tibiofemoral joint is known to be asymmetric in both shape and dimension, the asymmetrical tray chosen in this study was found to fulfill this compromise with more difficulty.

What is the optimal alignment of the tibial and femoral components in knee arthroplasty?

“…The goal of tibial component positioning is to maximize coverage to prevent settling (Lemaire et al 1997), and to achieve a neutral tibial alignment. The latter is achieved by a proximal tibial cut 90º to the mechanical axis (Ritter et al 1996).…”

Influence of landmark and surgical variability on virtual assessment of total knee arthroplasty

“…Such analyses could include direct assessment of morphological parameters (component fit, overhang, malrotation, etc.) that have been correlated with clinical outcomes of TKA (Bindelglass et al 1991;Lemaire et al 1997;Berger et al 1998;Dennis 2004;Chau et al 2009;Nicoll and Rowley 2010), in which variations of several millimetres in key dimensions can result in component upsizing or downsizing relative to resections using nominal surgical parameters. Analyses could also entail more mechanistic evaluations of devices appropriate for predictions of, for example, subsidence, stability and kinematics.…”

The position and orientation of total knee replacement components

“…Rotational malalignment leads to patellar maltracking, anterior knee pain, femorotibial flexion instability, decreased movement and increased polyethylene wear. [25][26][27][28][29][30][31] Higher revision rates have been found in patients with malaligned femoral or tibial components, 1,2,4,6,32,33 and so identifying malalignment is crucial for optimal management of patients with a painful TKR.…”