Optimizing femur symmetry judgment using three-dimensional data correction scheme in fractures of the proximal femur

The application of the 3D printing mirror image model is based on the symmetry of the limbs. Different from image fusion to judge the similarity, based on the commonality of the limb morphology of the same organism and the isotropic of the long bone cross-section, the symmetry of the femur has been determined by calculating the dimension difference of the corresponding cross-section of the non-fractured area. However, the previous version used equidistant cross-sections for measurement and two-dimensional data correction, and there were problems with insufficient reliability and data failure. The purpose of this study is to achieve a more accurate and universal symmetry verification scheme for bilateral tubular bones through an improved method.

Forty-five imaging data of proximal femoral fracture and osteopathy were selected from October 2015 to September 2017. 10%, 30%, and 50% of the full-length of the bilateral femur is sliced to judge the similarity between paired femurs. Long and short axes of the bilateral femoral cross-sections on the two-dimensional slices were measured and compared. A stylized trigonometric were used to correct the measured axes lengths such that they more closely match with measurements taken from slices perpendicular to femoral shaft axis.

540 valid data items from the long axis and short axis of the bilateral side of the distal femur were obtained, and 192 of these were corrected. There were no significant differences between the left and right of the long and short axis of each cross-section in paired cases (P>0.05).

This study have demonstrated symmetricity of the left and right femurs. The availability of CT data at any position of the patient's lower limbs is realized through replacing the previous "two-dimensional data correction" with "three-dimensional data correction".