Femoral version: Comparison among advanced imaging methods.

Accurate assessment of femoral version is essential to the surgical treatment of lower extremity deformities, yet the ideal modality and technique to measure femoral version is controversial. This study explored two hypotheses: First, there is no difference in the accuracy of femoral version measurement from 2D CT, 2D MRI, and 3D biplanar radiography reconstructions compared to a 3D model created from CT. Second, there is a difference between the measured version from traditional axial sections of the proximal femur compared to femoral neck oblique sections for CT and MRI. Eight adult cadaver lower extremities underwent CT, MRI, and biplanar radiography. Femoral version measurements from the CT and MRI axial and oblique sections, as well as biplanar radiography reconstructions, were compared to 3D reconstructed models from CT. All five techniques underestimated femoral version compared to the 3D model, but none were statistically significantly different. Regarding the first hypothesis, all five techniques had excellent correlation (r > 0.81, p ≤ 0.01) with the 3D model. Concerning the second hypothesis, the CT and MRI version measurements in femoral neck oblique sections were greater by 5.4° and 1.4°compared to traditional axial sections, respectively. All five techniques across three modalities provided accurate assessment of femoral version, suggesting that the treating physician's choice of modality can be determined per individual patient, not on measurement accuracy. CLINICAL SIGNIFICANCE: In choosing a modality to determine femoral version, consider the advantages and disadvantages of each modality for the individual patient, using femoral neck oblique slices for CT and MRI when available.