Do CAS measurements correlate with EOS 3D alignment measurements in primary TKA?

Area of Science:

• Orthopedic surgery
• Medical imaging technology
• Biomechanical analysis

Background:

• Accurate coronal alignment is crucial for successful total knee arthroplasty (TKA).
• Computer-assisted surgery (CAS) is increasingly used for intraoperative guidance.
• EOS 3D reconstructions offer a precise method for preoperative and postoperative alignment assessment.

Purpose of the Study:

• To compare intraoperative CAS alignment measurements with pre- and postoperative EOS 3D coronal alignment measurements in TKA.
• To evaluate the accuracy and reliability of CAS systems in TKA procedures.

Main Methods:

• A prospective study involving 56 TKAs using imageless CAS.
• Coronal alignment measurements taken intraoperatively with CAS (pre-bone cut and post-implantation).
• Pre- and postoperative alignment measured using EOS 3D reconstructions, eliminating acquisition errors.

Main Results:

• Significant differences observed in varus/valgus (VV) angles between CAS and EOS measurements.
• Preoperative mechanical lateral distal femoral angle (mLDFA) showed no significant difference.
• CAS measured significantly more valgus for mechanical medial proximal tibial angle (mMPTA) preoperatively compared to EOS.

Conclusions:

• Discrepancies between CAS and EOS measurements are attributed to weight-bearing differences and potential CAS validity/reliability issues.
• EOS 3D may overestimate VV angle in cases with significant mechanical axis deviation.
• CAS tends to measure more valgus than EOS for minor axis deviations and mMPTA, impacting clinical relevance and raising concerns about CAS system reliability in TKA.