TKA sagittal alignment with navigation systems and conventional techniques vary only a few degrees

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering

Background:

• Total knee arthroplasty (TKA) aims for reliable prosthetic alignment.
• Sagittal plane component alignment in TKA is less reliable than coronal plane alignment, even with navigation systems.

Purpose of the Study:

• To compare sagittal prosthetic alignment in TKAs using conventional techniques versus three navigation systems.
• To evaluate the accuracy and consistency of sagittal plane alignment achieved by navigation-assisted TKA.

Main Methods:

• Radiographs of the entire lower extremity were used to measure and compare sagittal alignments.
• Sagittal alignments were simulated using the conventional technique and three navigation approaches.
• Reference frames were established to analyze component alignment in the sagittal plane.

Main Results:

• Sagittal alignments differed by 2-4 degrees between conventional and navigation techniques.
• Navigation systems resulted in 1-4 degrees of hyperextension, while conventional techniques yielded 1 degree of flexion.
• Variations in reference points on the distal femur caused up to 3 degrees of sagittal plane alignment difference with navigation systems.

Conclusions:

• Navigation systems for TKA demonstrate variability in sagittal plane alignment.
• Surgeons and technicians must be aware of potential hyperextension risks with navigation systems.
• Sagittal plane malalignment may be linked to osteolysis and anterior post-cam impingement.