Copyright by Stryker



Pre-operation planning
Femoral Templating
Pre-operative planning is essential and should be conducted using templates which are placed on a frontal radiograph of the femur and then checked against the magnification noted on the template (available in magnification of 10%, 15% and 20%). To calculate the level of magnification a small centimetre ruler is placed in the plane of the greater trochanter.
 
The pre-operative planning of modular stem necessitates three steps:

1.   Determine the center of rotation of the acetabulum

2.   Determine the metaphyseal position and size of the femoral component

3.   Determine the proper modular neck in term of leg length and offset
 
 

The choice of the femoral component is made according to 3 reference points c, d and e, as shown below:


  1. Implant sizing is determined during templating. The chosen implant should fill the metaphysis whilst preserving the femoral calcar.
  2. Height is determined by the digital point D indicated on the template. The shoulder of the implant must be level with the lower part of the digital fossa d.
  3. The inferior-lateral or trochanteric-diaphyseal point E. The lower, lateral part of the prosthesis must come to lean against the infero-lateral part of the greater trochanter e marked on the radiograph, ensuring a thickness of cancellous bone that will be at least 3mm.
  4. At the diaphyseal level, the implant drawn on the template must be centered in the shaft of the femoral diaphysis, to avoid either varus or valgus positioning.

 

 

  
 
Adjustment of the femoral neck osteotomy
 
         

 

 
The cervical point C can be found on the template and the line of the femoral neck osteotomy (cervical osteotomy) drawn by linking the digital point D to the cervical point C. This makes an angle of approximatly 60° with the axis of the diaphysis.