Is The Tibia Mechanical Axis The Correct Landmark To Minimize Risk Of Tibia Loosening?

Description

The presentation discusses the findings of a study on kinematic alignment in total knee arthroplasty (TKA), conducted by employees of Smith and Nephew. The researchers introduce their disclosures and explain the rising popularity of kinematic alignment among surgeons, emphasizing the quest to enhance patient outcomes by accurately reproducing natural anatomy during knee procedures.



They address the hesitancies surrounding kinematic alignment, particularly the concern of deviating from traditional alignment parameters, which may increase tibial loosening due to heightened shear loads. The study hypothesizes that cuts made perpendicular to the load-bearing axis of the tibia could reduce shear forces during activities, specifically in varus and valgus alignments.



Using a computational model, the researchers simulated knee flexion and engaged different alignment scenarios to analyze tibial shear loads with two different knee implant designs: asymmetric and symmetric. The results demonstrated that aligning tibial cuts to the leg mechanical axis rather than the tibial axis yielded varying tibial shear loads based on the alignment. In varus knees, aligning to the leg axis proved beneficial in reducing shear loads compared to the tibial axis. Conversely, in valgus knees, greater shear loads resulted from aligning to the leg axis due to the lateral pull from the quadriceps, suggesting that a cased approach could minimize complications and improve outcomes.



Additionally, the implications of joint line orientation were explored, showing that it aligns more closely with constitutional varus and valgus populations when the appropriate alignment strategy is employed. The conclusion asserts that it is indeed feasible to achieve kinematic alignment effectively while mitigating shear loads, thereby addressing concerns of tibial loosening.



The overall findings of the study support the advancement of kinematic alignment in TKA, with promising results indicating that proper alignment can restore native joint orientation and improve clinical outcomes.

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