The use of an asymmetrical tibial tray in TKA optimises tibial rotation when fitted to the posterior tibial plateau border

Abstract

Purpose The aim of this study was to evaluate the suitability of positioning an asymmetrical tibial tray relative to the posterior tibial edge and to analyse the relationship between the posterior it and tibial rotation after computer-assisted total knee arthroplasty (TKA). It was hypothesised that an asymmetrical tray would adjust to the posterior border of the tibial plateau with proper tibial rotation. Methods Ninety-three consecutive knees underwent total knee arthroplasty using a Persona ixed-bearing system (63 varus deformities and 30 valgus deformities) and a 3-month follow-up CT scan. An independent examiner measured diferent variables: the femoral angle between the clinical epicondylar axis and the posterior condylar line of the femoral component, the tibial angle between the posterior borders of the tibial tray and the tibial plateau, and the tibial rotation with respect to the femoral component. These measurements were also compared between varus and valgus subgroups. Results For the varus and valgus subgroups, the mean postoperative femoral angle was 2.1º ± 1.2º and 2.5º ± 1.0º, respectively (n.s.). The mean posterior itting angle of the tibial tray was 0.1º ± 2.4º and 1.4º ± 3.2º for the varus and valgus subgroups, respectively, with a signiicant diference between groups (p = 0.03). The tibial rotations with respect to the femoral component for the varus and valgus groups were 0.9º ± 3.3º and 2.2º ± 3.1º of external rotation, respectively (n.s.). Conclusions This study demonstrated that itting an asymmetrical tibial tray to the posterior border of the tibial plateau could optimise tibial rotation. The posterior border was considered to be a reliable and easily identiiable landmark for proper tibial rotation and coverage during a primary TKA. Level of evidence IV KeywordsTotal knee arthroplasty • Asymmetrical tibial tray • Computer-assisted surgery • Computer tomographic (CT) scan • Component placement • Tibial posterior border • Tibial rotation

The language of knee alignment

“…36,37 Alternative tibial rotation references include the posterior tibial cortical border and the anterior plane of the tibia, defined by a line connecting the centres of the circles of best fit of both medial and lateral tibial condyles. 38,39 Analysis of 15 different landmarks for tibial rotation has not shown a clear advantage of one approach over another. It is therefore advisable to confirm that both tibiofemoral kinematics and patellofemoral tracking are optimized using more than one method.…”

No significant difference in early clinical outcomes of custom versus off-the-shelf total knee arthroplasty: a systematic review and meta-analysis

“…The shapes and sizes of off‐the‐shelf (OTS) TKA components are restricted and could result in bone–implant mismatch [25], which may in turn lead to prosthetic overhang [5], altered soft tissue tensions [8, 31], and ligament imbalance [16, 50]. Although many manufacturers of OTS TKAs extended the range and variety of implant shapes and sizes [11, 38], their clinical benefits remain insignificant [10, 42], possibly due to their limited ability to represent all morphotypes in relation to sexual dimorphism [18] and racial diversity [20].…”

Considerable inter-individual variability of tibial geometric ratios renders bone–implant mismatch unavoidable using off-the-shelf total knee arthroplasty: a systematic review and meta-analysis

“…1 3 Tibial prosthetic overhang can lead to persistent pain due to soft-tissue impingement [7,39], while bone under-coverage can lead to subsidence and aseptic loosening [34]. To optimize tibial coverage, many manufacturers extended the ranges of component sizes, and introduced asymmetric tibial baseplates [12,40], which are believed to improve clinical and functional outcomes [19,35].…”