An innovative method for measuring the femoral arch

A mismatch between the femoral bow and intramedullary nails causes a series of complications. Previous investigations have sought to determine the curvature of the femur using the radius of the femoral bow. However, the radius of the curvature is affected by femur length. To eliminate the influence of femur length, we instead used an angle to indicate femoral curvatures. Forty patients with intertrochanteric fractures who underwent a surgical procedure at our institution were enrolled in this study. We conducted a lateral X-ray of the contralateral femur before operation. We drew a triangle in the X-ray images using Digimizer software. The tangent values of the acute angle were used to indicate femoral curvature. The tangent values were then compared with the dimensions of currently used nails. The average tangent value of the femurs was 0.0835 ± 0.0147, as measured from the inner cortex and 0.0798 ± 0.0150, as measured from the outer cortex. The tangent values were related to sex, with males having straighter femurs than females, and there was no obvious correlation between tangent values and age or femur length. Tangent value is a reliable method with a high intersurveyor consistency; femur curvatures were significantly greater than the curvatures of currently used nails.