Impact of Axial Component Alignment in Total Knee Arthroplasty on Lower Limb Rotational Alignment: An In Vitro Study

Abstract

Correct rotational implant alignment is associated with increased postoperative function and implant survival in total knee arthroplasty (TKA). Due to conformity between tibial and femoral implants, particularly in full extension, we assumed a mutual interference of femoral and tibial component rotations. We, therefore, hypothesized that different rotational alignments of the tibial or femoral components change the rotational postures between the tibia and femur after TKA. In 10 healthy knees of whole body cadavers, TKA was performed. Both femoral and tibial components were implanted in different internal (6 degrees) and external (3 and 6 degrees) rotational alignments. Consequential osseous rotational changes between the tibia and the femur were measured in full extension using a commercial computer navigation device. External rotation of the femoral component resulted in significant external rotation of the tibia, while external rotation of the tibial component caused a significant internal rotation of the tibia. The opposite applied to femoral and tibial component internal rotations. Therefore, largest changes of the osseous tibiofemoral rotational postures were found by the combination of 6 degrees femoral component internal and 6 degrees tibial component external rotations (mean 11.2 degrees, standard deviation 5.0, < 0.001), as both cause tibial internal rotation. In conclusion, the present results suggest that axial component alignment significantly affects lower limb rotational alignment. However, its clinical impact on forefoot progression, Q-angle, the patella, collateral, and cruciate ligaments, and surrounding soft tissues has to be clarified in further clinical and biomechanical studies.

Influence of Component Rotation in Total Knee Arthroplasty on Tibiofemoral Kinematics—A Cadaveric Investigation

“…As a consequence, internal rotation of the femoral component causes a relative internal rotation of the lower thigh in comparison to the femoral bone and vice versa. In contrast, internal rotation of the tibial component causes, owing to tibio-femoral conformity, a compensatory external rotation of the lower thigh and vice versa [46]. These circumstances explain the initial contradictory results concerning combinations of different component rotations: If the femoral component is internally rotated, tibial internal rotation is increased.…”

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

“…The lower limb rotation can be affected by external or internal rotation of the tibial component in combination with a 3–5° external rotation of the femoral component—a combination often used in TKA [9, 19]. If both components are rotated externally, the lower limb rotational change would be small because the external rotation of the tibial component would decrease tibial torsion (compensatory effect of both components on lower limb rotation).…”

“…Tibial component internal rotation relative to native anteroposterior axis of the proximal tibia causes the external torsion of the tibia, increasing the external rotation of the foot progression angle and Q‐angle, and vice versa. A previous study investigated the effect of the rotational alignment of the femur and the tibia on lower limb rotational alignment using cadavers [19]. However, in vivo data are lacking.…”

“…As a result, the rotational axis of the proximal tibia after TKA may be changed according to the tibia component rotation. Postoperative changes in the rotational axis of the proximal tibia cause compensatory inverse tibial rotation in TKA with a fixed‐bearing design [19], which affects the foot progression angle distally and the patellofemoral alignment proximally. Tibial component internal rotation relative to native anteroposterior axis of the proximal tibia causes the external torsion of the tibia, increasing the external rotation of the foot progression angle and Q‐angle, and vice versa.…”

Medial-lateral translational malalignment of the prosthesis on tibial stress distribution in total knee arthroplasty: A finite element analysis

“…The 3D model of the right tibia and the tibial plateau prosthesis (Ai Kang A3)were prepared as STL format files, and the simulated surgery was performed in Magics (v21.0, Materialise, Leuven, Belgium). The posterior slope was set to 5 °, and the tibial model was resected in the traditional surgical fashion (Indelli et al, 2016;Maderbacher et al, 2017), by removing the tibia 6 mm below the medial tibial articular surface, perpendicular to the mechanical axis. The application of this study focused on the stress distribution during the interaction of the proximal bone with the platform prosthesis, so the distal tibia was separated from the system to reduce the calculation time.…”