Navigation systems have been developed to achieve more reliable prosthetic alignment in TKAs. However, the component alignment
in the sagittal plane is reportedly less reliable than in the coronal plane even with navigation systems. We measured and
compared sagittal prosthetic alignments for TKAs with the conventional technique and three navigation approaches to establish
reference frames, using radiographs of the entire lower extremity while standing. The sagittal alignments simulated on the
radiographs with the conventional technique and navigation systems differed by a mean of 2° to 4°. Use of navigation systems
resulted in a mean of 1° to 4° hyperextension between the femoral and tibial components and use of the conventional technique
resulted in a mean of 1° flexion. Use of different reference points on the distal femoral condyle for the navigation systems
resulted in differences of as much as 3° alignment in the sagittal plane. Although optimal prosthetic alignment for TKA in
the sagittal plane is unknown, surgeons and technicians using navigation systems should be aware of this difference in the
sagittal plane and the risk of hyperextension between the femoral and tibial components, which might be associated with osteolysis
and anterior post-cam impingement.
Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest,
patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations
were conducted in conformity with ethical principles of research, and that informed consent for participation in the study
was obtained.