Torsional Moment
The torsional moment Mtpr relative to the hip stem reflects the contact load situation between the stem and the bone. Mtpr is derived from forces measured in the implant coordinate system:
where Fypr (in N) is the force in the anterior–posterior directions, Mzpr (in Nm) is moment in the mediolateral direction, and Lxp (in m) is the implant-specific head offset.
