Femoral matched tibia component rotation has little effect on the tibial torsion after total knee arthroplasty

Abstract

PurposeTibiofemoral synchronization technique matches the rotational alignment of the tibial component to the femoral component during the total knee arthroplasty (TKA). The rotational axis of the proximal tibia can be changed by this technique, which affects tibial torsion postoperatively. The purpose of this study was to investigate whether the tibiofemoral synchronization technique affect the tibial torsion, and the lower limb rotation after primary TKA. It was hypothesised that the tibial torsion would change after primary TKA. MethodsNinety‐three posterior stabilised TKAs from 89 patients were included from January 2017 to December 2018. Mechanical hip–knee–ankle axis (mHKA), in plain radiographs, femoral anteversion, tibial torsion, femoral neck‐malleolar angle (FNMA), and rotational alignment of the femoral and the tibial components in pre‐ and postoperative CT scans were measured by two blinded observers. The primary outcome was a postoperative change in femoral anteversion, tibial torsion and FNMA. Clinical outcomes were evaluated using the American Knee Society Knee Score (AKSKS)/Function Score (AKSFS), and Oxford Knee Score (OKS) preoperatively and at 1 year after TKA. Patients’ perception of changes in the foot progression angle after TKA was investigated. Statistical significance was set at p < 0.05. ResultsThe mean rotational mismatch between the femoral and the tibial component was 0.6 ± 3.2°. There was a significant decrease in femoral anteversion (9.5 ± 6.7° vs. 5.2 ± 6.6°, p < 0.001), and a significant increase in the FNMA (17.6 ± 9.7° vs. 21.8 ± 10.5°, p = 0.005) after TKA, while no significant change in tibia torsion was observed (25.4 ± 8.8° vs. 24.9 ± 9.3°, p = 0.739). AKSS (37.8 ± 15.1 vs. 92.8 ± 8.8, p < 0.001), AKSFS (53.9 ± 18.1 vs. 89.9 ± 5.3, p < 0.001), and OKS (18.0 ± 7.3 vs. 39.9 ± 4.8, p < 0.001) were significantly improved at 1 year after TKA. Ten knees (11%) had changes in tibial torsion greater than ± 10° postoperatively. Four of five patients who had changes in FNMA greater than 15° perceived the external rotation of the foot progression angle after TKA. All four patients had an increase in tibial torsion larger than 10°. ConclusionOur study shows that the tibiofemoral synchronization technique less likely affects the tibial torsion after primary TKA.

Medial pivot versus (cam post) posterior stabilised total knee arthroplasty, systematic review and meta-analysis of 3837 knees

“…Modern bicondylar TKAs are often designed using a dished bearing surface or a campost mechanism as these concepts help to recreate tibiofemoral rollback and stability in the sagittal plane (6)(7)(8). Posterior stabilized (PS) TKAs utilise the cam-post mechanism whereby the cam-post articulates with the tibial post improving femoral rollback and at the same time providing sagittal stability (8)(9)(10)(11)(12). Despite this it is associated with central tibial impingement and increased bleeding intra-operatively secondary to the larger osteotomy (13).…”