# Bending Moment

### From Orthoload Wiki

The resultant bending moment **M _{bend}** , acts in the middle of the femoral neck and perpendicular to the neck axis, and is calculated with the following formula:

The forces (F_{x’}, F_{y’}, F_{z’}) and moments (M_{x’}, M_{y’}, M_{z’}) are measured in the “implant coordinate system” x’, y’, z’ centered in the middle of the implant head. The force component F_{x’} acts laterally, F_{y’} anteriorly, and –F_{z’} distally along the femur axis. The measured moment components M_{x’}, M_{y’}, and M_{z’} turn right around the x’, y’, and z’ axes. N is the distance between the head center and the middle of the femoral neck and is equal to ½ L.

M_{tne} acts around the neck axis of the femur and represents the torsional loading of the neck. It is calculated by α = -45° rotation of the "bone coordinate system” around the y-axis.