Comparison of Femoral Rotation in Total Knee Arthroplasty with Measured Resection Technique and Balanced Flexion Gap Technique

Purpose: Avoiding femoral malrotation has always been a technical challenge for orthopaedic surgeons in total knee arthroplasty. While modern surgical techniques have made the surgeon’s task easier, nevertheless it remains unclear which of the two most common techniquesthe measured resection or balanced flexion gap techniquesmore accurately restores femoral component rotation. This study aimed to compare the femoral rotation produced by these two surgical techniques and the relationship between the femoral rotation and coronal tibial alignments.This retrospective cohort study compared 20 posterior stabilized Anatomic Modular Knee (AMK), aligned using a measured resection technique to 20 mobile bearing Low Contact Stress knee (LCS) aligned using a balanced flexion gap referencing system. Long leg standing x-rays and CT scans of knees were used to measure rotation of the femoral component in the axial plane and tibial alignment in the coronal plane. Results: Average femoral component rotations were 2.98 (SD 3.21) degrees and 2.26 (SD 1.20) degrees for the AMK and LCS, respectively. Tibial component alignments were 0.66 (SD 1.94) degrees valgus and 0.4 (SD 1.09) degrees valgus for the AMK and LCS, respectively. These differences were not statistically significant. Conclusion: There were no statistically significant differences in femoral rotation between the two referencing systems. However, the balanced flexion gap method had a narrower range of implant rotational position. No statistically significant relationship was found between femoral rotation and tibial alignment in either system.