Polarstem

The major cause of our failures with dual mobility cups was the design of femoral stems After the Polarcup we created the Polarstem in 2002 which is a self-locking straight cement less stem with a double coating titanium + Hap

They have further improved the fixation, but especially tried to restore the offset of the hip, facilitate the mini-approach, the DDA and the implementation in narrow femoral diaphyses with thick cortical It will be a synthesis: From the fully coated straight stem of Corail And the self locking stem of Muller

What was the problems ?

One of our major worries with this stem design was the offset. As you can see here medialisation is important
Another problem that we sometimes met, was the need to ream narrow diaphysisotherwise the stem could not be fully seated.
We have also observed radiolucent line on the greater trochanter Maybe indirect sign of the stress shielding?
Evenif the stress shielding has become rare, it is not exceptional, as here with a Corail stem on a femur with narrow diaphysis that needs to be reamed.

Due to those problems we changed to a new design

The standard Polarstem is 4mm more lateralized than the Corail stem
The differents neck shaft angles and offset ratio, keeping stem body unchanged
With these three versions we can now adapt the polarstem for all cases. It‘salso interessant for those who use navigation and are looking for a millimeter precision.
We have increased the Muller’s Self locking primary fixation.

To avoid distal blocking the proximal part was got wider (about 1 mm)

Triple Taper

The shape of the stem, has no discontinuity, in order to avoid any conflict with cup or bone, And we have a rounded polished neck to optimize with a DM cup
The distal part is thinner but also shorter especially well adapted to the morphology of young patients, even with thick cortical bone and curved femoral shafts. And also very useful, for minimal invasive approaches,spacially for Direct Anterior Approach.
The HA coating,  provides immediate primary fixation,

and the projected titanium layer, has a better porosity for secondary anchorage,