Preoperative templating and biomechanics in total hip arthroplasty.

Preoperative templating is an essential ingredient of a successful hip arthroplasty. The socket template is positioned first to establish the center of rotation of the reconstruction. For femoral templating, a surgeon should not only consider the part inside the bone (the size of the component), but should also consider the part outside the bone, which determines limb length and biomechanical parameters such as theabductor muscle and joint reaction forces. Medializing the hip center of rotation and increasing the horizontal femoral offset can improve clinical outcomes and reduce polyethylene wear. Modern modular systems allow limb length adjustment and biomechanical improvement for a range of patients.