2.1 Hip Arthroplasty Templating

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  The first step is to evaluate your patient completely and consider medical comorbidities, such as age, sex, preoperative diagnosis, level of activity, mental status, arthritic involvement of other joints, and patient expectations.

  
  
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  Certain patient groups have a higher risk of dislocation—including patients with neuromuscular problems, substance abuse, and dementia.

  
  
  
  
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    In these patients, consider a larger femoral head and try to avoid a posterior approach. You can use a constrained cup as last resort.

  
  
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  Assess preoperative limb length discrepancy—perceived versus actual.

  
  
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  Obtained standardized radiograph series (AP pelvis, AP, and cross-table lateral of the hip) with known magnification marker.

  
  
  
  
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    Position hip in 10 to 15 degree internal rotation to counteract femoral neck anteversion.

    
    
    
    
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      This allows visualization of entire femoral neck, leading to accurate offset measurement.

    
    
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    Evaluate the lumbar spine as a cause of fixed pelvic obliquity.

    
    
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    Evaluate Dorr type of proximal femoral bone (A, B, or C).

    
    
    
    
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      It helps determine if you will you need to ream, for example, Dorr A bone.

    
    
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    Note osteophytes, protrusio acetabuli, coxa profunda, or hip dysplasia as they will affect your cup position.

  
  
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  Template in the order of surgery. Start with the acetabulum first, then progress to femur. ²

  
  
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  Steps

  
  
  
  
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    Draw a horizontal reference line through base of the acetabular teardrops.

    
    
    
    
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      Teardrops are close to the center of hip rotation and reproducible landmarks.

    
    
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    Mark ilioischial line and superolateral margin of acetabulum (sourcil).

    
    
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    Acetabulum templating

    
    
    
    
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      Cup size should be such that medial border approximates ilioischial line with adequate superolateral coverage, when abducted 40 to 50 degrees, and minimal subchondral bone removal.

      
      
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      Bottom of cup level with inferior teardrop. However, some surgeons think this is too much bone removal.

      
      
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      After cup positioning, mark the center of rotation for the cup. Measure the distance of this point to the horizontal reference line compared to the other side. Those distances should be equal.

    
    
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    Femoral templating

    
    
    
    
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      Its goals are to restore offset, fill the canal, and optimize limb length.

      
      
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      Measure limb length discrepancy (distance between proximal aspect of lesser trochanter and the horizontal reference line).

      
      
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      Draw a line perpendicular to femoral shaft at level of greater troch to find center of rotation for the femoral head.

      
      
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      Measure amount of desired limb length change (the vertical distance between femoral center of rotation and acetabulum center of rotation).

      
      
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      Choose stem size—fills metaphysis or diaphysis depending on design.

      
      
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      Template a mid-range neck length to allow for correction with head size/offset intraoperatively.

      
      
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      Record sizes of cup, head, and stem. There are various templating software programs which contain implant shaped templates in appropriate sizes.

      
      
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      Use your template as an operative guide but be prepared to make adjustments intraoperatively.