Experimental Study On Femoral Neck-shaft Projectional Angle Measured By X-ray Estimates Femoral Neck Anteversion And Its Clinical Application

Objective: To attempt to establish a skeletal model by femoral specimens with changes in femoral neck anteversion angle caused by the changes in neck-shaft projectional angle, the preliminary study on the quantitative relationship between changes in femoral neck anteversion and neck-shaft projectional angle, with statistical methods for analysis, sought to summary the relationship between them, and make preliminary validation using clinical case,may be applied to evaluate the developmental dislocation of the hip patients with the quantitative relationship.Methods: We utilized six children's femoral specimens of different ages, made the specimens with femoral subtrochanteric osteotomy, and changed the femoral neck anteversion angle randomly from 0 ~ 90 degrees, then took the femur with standard anteroposterior X-ray, and measured neck-shaft projectional angle, with statistical methods for data analysis, summarized the dependent relationship between neck-shaft projectional angle and femoral neck anteversion angle. Verified the equation with a retrospective analysis of clinical cases and assessed its practical value.Results: We obtained the relationship between neck-shaft projectional angle Y and femoral neck anteversion angle X by analyzing the measured data with SAS9.13 statistical analysis software, coinciding exponential curve, the mathematical expression is: Y=e(4.908+0.0031X), it follows that the equation is X = (lnY-4.908) / 0.0031. And the neck-shaft projectional angle and anteversion angle correlation coefficient R=0.9835, the relationship between them is close. With the same degree's change in FNA , through comparing two sets of data, the left and right side neck-shaft projectional angle, there was no significant difference (P>0.05).When the FNA is 0 degree, the neck-shaft projectional angle equals the true neck-shaft angle, regardless of the size of the ture neck-shaft angle, as long as the FNA increases to 90 degree, the neck-shaft projectional angle totally increased to 180 degree. When the true neck-shaft angle is constant, the neck-shaft projectional angle will increase gradually with the FNA.Conclusions: According to the established skeletal model, when the true neck-shaft angle is constant, the relationship between neck-shaft projectional angle and femoral neck anteversion angle meets exponential curve, and they are validated by the clinical cases, the clinical cases basically match the equation. It can provide guidance for clinical treatment and follow-up of children with developmental dislocation of the hip. Through measuring the neck-shaft projectional angle estimate the FNA, control the rotation osteotomy to correct femoral anteversion angle in clinical practice, direct femoral head and acetabulum concentric reduction. It can quantitatively measure the effect of postoperative follow-up of children with DDH.