Abstract
This study evaluated the influence of modern tibial baseplate designs when using the anterior tibial cortex as a primary rotational landmark for the tibial baseplate in TKA. Eighty patients undergoing TKA were randomized in two groups. Group 1 included 25 females and 15 males receiving a posterior-stabilized (PS) symmetric tibial baseplate while Group 2 included 24 females and 16 males receiving a PS anatomical tibial component. Identical surgical technique, including the use of the surgical transepicondylar femoral axis (sTEA) and the anterior tibial cortex (“Curve-on-Curve”) as rotational alignment landmarks, was used. All patients underwent CT evaluation performed with the knee in full extension. Three observers independently measured the rotational alignment of the tibial component in relation to the sTEA. The rotational alignment of the symmetric baseplate showed an average external rotation of 1.3° (minimum 5°, maximum −1°): 91% of the knees showed 0 ± 3° with respect to the surgical sTEA, being internally rotated in 20%. The rotational alignment of the anatomical baseplate showed an average external rotation of 4.1° (minimum 0.4°, maximum 8.9°): only 47.5% of the knees showed 0 ± 3°, being externally rotated in 100%. The difference between the two groups was statistically significant. This study confirms the reliability of the “Curve-on-Curve” technique as an adequate rotational alignment anatomical landmark in TKA: the use of an asymmetric tibial baseplate might lead to external rotation of the tibial component when this technique is intraoperatively chosen.
Highlights
Many studies related a total knee arthroplasty (TKA) poor functional outcome to rotational malalignment of the femoral and tibial components [1,2,3]
We demonstrated that the anterior tibial surface contour is a reliable landmark for correct tibial component rotational positioning, in TKA designs characterized by having a symmetric tibial baseplate, with respect to the “Akagi” line and the medial third of the tibial tubercle
Rossi et al, in a cadaveric study, validated the posterolateral tibial corner as a reliable reference landmark for tibial baseplate rotational alignment [13]: the identification of this landmark requires a complete exposure of the tibial plateau, which is often difficult to obtain in many knees
Summary
Many studies related a total knee arthroplasty (TKA) poor functional outcome to rotational malalignment of the femoral and tibial components [1,2,3]. The goal of tibial component rotational alignment in primary TKA is to achieve, on the coronal plane, parallelism between the femoral transepicondylar axis (TEA) and the mediolateral (ML) axis of the tibial component, avoiding errors in internal or external rotation between the two axes. This desired coronal parallelism during active range-of-motion (AROM) is hard to be achieved because the TEA has been demonstrated to be cylindrical [4] and the tibial plateau undergoes a substantial internal rotation during ROM [5]. In a previous study [14], the authors of the current study proposed
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