Which Asymmetric Tibial Component Is Optimally Designed for Calipered Kinematically Aligned Total Knee Arthroplasty?

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Medical Device Design

Background:

• Kinematically aligned (KA) total knee arthroplasty (TKA) aims to restore prearthritic joint lines.
• Tibial component rotation in KA TKA is set relative to the flexion-extension plane, differing from mechanical alignment (MA) targets.
• Asymmetric tibial components offer potential for improved fit and function in TKA.

Purpose of the Study:

• To determine the optimal asymmetric tibial component for calipered KA TKA.
• To compare femoral component (FC) target and tibial tubercle (TT) target asymmetric tibial components.
• To evaluate component alignment, tibial resection coverage, and cortical overhang.

Main Methods:

• Bilateral calipered KA TKA performed on 40 patients using different asymmetric tibial components.
• Tibial component placement guided by a kinematic tibial template parallel to the knee's flexion-extension plane.
• Computer tomography analysis to assess internal-external deviation, resection coverage, and cortical overhang; patient outcomes assessed via FJS and OKS.

Main Results:

• The FC-target component had a mean 2° external deviation, while the TT-target had a mean -8° internal deviation (p < 0.001).
• Baseplate and insert coverage was greater with the FC-target component (88%/84%) versus TT-target (84%/79%) (p < 0.001).
• The FC-target insert provided 3mm more posterolateral coverage (p < 0.001); cortical overhang incidence was low (2.5%) for both.

Conclusions:

• The asymmetric tibial component with an FC target is more optimal for calipered KA TKA.
• This component demonstrates reduced deviation from the MA target and superior tibial resection coverage.
• No significant differences in patient-reported outcomes (FJS, OKS) were observed between the components.