Kinematic alignment in total knee replacement successfully restores the native knee phenotype in the short term

The goal of kinematic alignment (KA) in total knee arthroplasty (TKA) is to bring back the natural knee phenotypes. This study compared postoperative functional phenotypes in KA-TKAs against native phenotypes of healthy young Iranians, addressing the need for population-specific alignment targets.

The study analysed 300 KA-TKAs and 150 native phenotypes of healthy young Iranians. Full-limb radiographs were used to measure alignment parameters and classify phenotypes. Patient-reported outcomes were collected to assess functional recovery. The research focused on phenotype restoration, gender differences and ethnic variations in constitutional alignment.

KA-TKA successfully restored constitutional knee phenotypes in 91.7% of patients. The top five phenotypes showed similar proportions in both TKA (52.7%) and control (54.2%) groups. Females demonstrated higher phenotype restoration rates, particularly for valgus-dominant phenotypes. The Forgotten Joint Scores at 3 months showed a significant improvement of 18% when comparing phenotype-matched patients to outliers. KA-TKA cases that failed to match the control phenotype distribution amounted to 8.3%, and these cases showed significant preoperative deformities as well as high body mass index. The research demonstrated important differences in ethnic populations since 53.7% of Iranians showed constitutional varus compared to 28.3% of Swiss individuals.

The study demonstrates that KA-TKA successfully restores native knee phenotypes to most Iranian patients. The alignment targets require customization for population-specific standards together with attention to gender-specific variations.

Level III.