Measuring femoral and rotational alignment: EOS system versus computed tomography

Area of Science:

• Orthopedics
• Radiology
• Medical Imaging

Background:

• Computed tomography (CT) is the standard for measuring femoral and tibial rotational alignment.
• The EOS System offers 3D lower-limb modeling with automated torsion measurements using low-dose biplanar radiography.

Purpose of the Study:

• To determine if the EOS System provides equivalent femoral and tibial torsion measurements compared to CT.
• To assess the interobserver reproducibility of the EOS System for torsion measurements.

Main Methods:

• Retrospective analysis of 43 lower limbs in 30 patients.
• Comparison of femoral and tibial torsion measurements between CT and EOS imaging.
• Assessment of agreement using Pearson's correlation coefficient and interobserver reproducibility using the intraclass correlation coefficient (ICC).

Main Results:

• EOS and CT measurements for femoral torsion (13.4° vs. 13.7°) and tibial torsion (30.8° vs. 30.3°) showed strong associations (P=0.93 and P=0.89, respectively).
• Interobserver reproducibility was high for both systems, with ICCs for EOS: 0.93 (femoral) and 0.86 (tibial); CT: 0.90 (femoral) and 0.92 (tibial).

Conclusions:

• The EOS system is a valid and reliable alternative to CT for measuring lower-limb torsion.
• EOS imaging provides comprehensive 3D evaluation with significantly reduced radiation exposure for patients.