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Estimation of femoral neck anteversion in hip replacement - Blasi Method

 
In hip replacement surgery, femoral anteversion is a crucial factor for optimal implant positioning and function. Proper anteversion ensures a stable hip joint and a good range of motion, minimizing the risk of dislocation or impingement.
 
Anteversion femoral neck in hip replacement

 

 

 

What is Femoral Anteversion?

 

Femoral neck anteversion is the angle between the femoral neck and the femoral condyles, which are the bony prominences at the knee and are dependent on the natural torsion of the femur. In adults, the normal range is usually between 8 and 20 degrees.

Why is it Important in Hip Replacement?
  • Stability:
    Proper anteversion helps maintain hip stability by optimizing the relationship between the femoral head and the acetabulum (the hip socket). 
     
    • Range of Motion:
      Correct anteversion allows for a good range of motion in the hip joint without impingement (where the bones rub against each other). 
       
      • Reduced Risk of Dislocation:
        Improper anteversion can lead to instability and increase the risk of hip dislocation.
         
         
        Andrea Blasi MD is an Italian surgeon expert in anterior hip replacement and has developed his own system for measuring the anteversion of the femoral neck in hip replacements. This system evaluates the anteversion or retroversion through observation of the angle after placing thr lower limb in a specific position. The human eye has a margin of error of about 5 degree in these conditions, an error which however is not relevant for the purpose of performing a good combined anteversion technique, I'll explain it later.
         
        Let's start with the description of the estimation method:
         
         
        The patient is inithially in a supine position
         
        Supine patient for hip anterior replacement
         

        After performing the femoral neck osteotomy and positioning the trial prosthetic stem, we place the patient in position "4".

         

         Position at 22422

         

         

        By positioning the tibia horizontal to the floor and with the knee flexed at 90 degrees we obtain that: since de mechanical axis of the tibia is 90 degrees and is supported by the posterior condylar axis of the femur, the femur will be found with is axial plane perpendicular to the ground.

        After performing the femoral neck osteotomy and positioning the trial prosthetic stem, we place the patient in position "4".

          

        Position 4 description

         

         


        This is the diagram that allows you to visualize only the skeleton of the lower limb to understand that the axis of the new femoral neck will simply be estimated with respect to an axis perpendicular to the ground.

         

         

        Anteversion femoral neck in hip replacement

         

         

         

        This is instead what we appreciate visually, with a view from above, in this case about 10 degrees anteversion. It is not essential to recognize the 5 degrees to make a good combined anteversion with the acetabular cup, the important thing is to recognize when the deviation from normality exceeds 20 degrees (and this can be perceived well) to be able to make the appropriate adjustments in the acetabular position.

         

        Anteversion evaluation hip replacement

         

         

        On the other hand, precise measurement of the degrees of anteversion of the acetabular component and the new center of rotation is very important, and a computer-assisted measurement system is probably required for this purpose, but this is a topic that deserves much more space.

         

         

        I have been practicing hip replacement surgery for many years and believe that this assessment is very useful for interpreting personalized anatomies and making corrections to reduce the risk of dislocation and impingement.

        I hope it can be useful in your surgical practice too.

         

        Good work!

         

        Andrea Blasi MD

         

        June 20, 2025

         



 

«Blasi method»

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Ultima modifica il Sabato, 21 Giugno 2025 12:26

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