Evaluation of the External Rotation of femur component in functionally aligned Robotic Assisted Total Knee Arthroplasty

Background: The conventional total knee arthroplasty (TKA) for grade 4 knee arthritis lacks individualized strategies for determining femur component rotation, contributing to suboptimal clinical outcomes and heightened patient dissatisfaction. Methods: A retrospective assessment of 100 consecutive active robotic assisted TKA (RA-TKA) patients was performed. Patients with grade 4 knee arthritis receiving RA-TKA were included, whereas prior knee surgery patients were excluded. The functionally aligned TKA (FTKA) trans-epicondylar axis (TEA), posterior condylar axis (PCA), and posterior femoral axis (FAA) were evaluated. The relation between FAA, TEA, and PCA were examined. Negative value denotes internal rotation of the femur component. The study's null hypothesis was that there would not be a statistically significant difference between FAA and the standard 3 degrees of external rotation applied during conventional TKA (C-TKA). The student's t-test was used to compare the mean rotation values (between FTKA and C-TKA) with p-value of less than 0.05 deemed significant. Results: Total 100 patients (Male: Female – 11:89) were studied. The FAA was externally rotated in relation to TEA (mean 1.451° SD 1.023°, p value <0.0001). As regards the PCA, the FAA was externally rotated (mean 2.36° SD 2.221°, p value 0.0002). Conclusion: Functional alignment TKA technique resulted in external rotation of the femur component in respect to TEA and PCA. This negates the null hypothesis indicating statistically significant difference amongst the femur component rotation implanted according to FTKA concept with robotic assisted technology and C-TKA.