Abstract
Background
Recent studies reported that the kinematic alignment of an implant is more physiological than the traditional methods, and therefore results in better clinical outcomes. They found that for kinematic alignment of the implant, the femoral component should be positioned valgus 2 degrees and tibial component in varus 2 degrees without femoral rotation. Other study also claimed that kinematically aligned TKA does not cause any significant failure; rather, it restores the function of the knee. Therefore kinematic alignment was raised for further patient's functional satisfaction.
Purpose
The purpose of our study is to certify correlation between parameters of implant position and postoperative clinical outcomes after kinematic alignment of TKA.
Materials and methods
We obtained 32 patients with primary osteoarthritis who need surgical treatment. During operation we targeted tibial varus of 2 degree and femoral valgus of 2 degree on coronal plane, and neutral rotation on axial plane of the knee.
ROM (range of motion) was checked at final visit to office with radiology. Average follow up was 44.5 months (range 36–60). We used the Pearson correlation coefficient to determine any relationship between coronal deformity and PCA or TRA for the entire population and individually for each gender.
Clinical outcomes including post op active knee ROM, TRA (the angle between the perpendicular line to the TEA and Akagi's line), varus and valgus angle of the knee were also analyzed.
Results
Clinical outcomes including post op knee scoring and ROM was improved. There were negative linear relationships between the femoral component rotation (internal and external) and active and passive range of motion after kinematic alignment of TKA. And we also found a negative linear relationship between the tibial rotation of the component and active and passive range of motion. And we also found a negative linear relationship between the gamma angle and active and passive range of motion. The gamma angle is most powerful predictive parameter of postoperative range of motion of the knee.
Conclusion
The alignment of the component set into the kinematic alignment of the knee: internal rotation of femur implant with good gamma angle in sagittal plane will assure better clinical outcome; ROM and scores. Coronal alignments of component (valgus or varus) were weak predictive parameters.
