Influence of surgical technique on femoral sagittal alignment in total knee arthroplasty: a comparative radiographic study

BACKGROUND: Femoral component alignment has important implications for implant longevity and favorable outcomes following total knee arthroplasty (TKA). However, the effect of surgical technique on sagittal alignment parameters is not well understood. This study aimed to understand how surgical technique in TKA affects femoral flexion and condylar offset in the sagittal plane. METHODS: A retrospective review was performed of 699 postoperative radiographs from TKAs performed using a single implant system. Three cohorts were analyzed: rigid intramedullary rod, flexible intramedullary rod, and robotic-assisted TKA. Radiographic measurements included femoral flexion angle, anterior and posterior condylar offset, and mechanical femoral flexion angle. Femoral flexion measured on the mechanical axis was greater than when measured on the distal anatomic axis in the rigid rod and robotic-assisted groups. Robotic-assisted TKA had the highest posterior condylar offset, but this difference was not observed when normalized for radiographic magnification. CONCLUSION: Instrumentation technique in TKA may result in significant differences in sagittal alignment, specifically in femoral flexion. Clinical implications of sagittal alignment variability have yet to be fully described.