What design feature of the Polarstem provides improved initial proximal stabilty?

• A. Cylindrical Shell
• B. Triple Taper (8,7 and 3.2 degrees)
• C. Ceramic Coating
• D. Ribbed Surface

Answer: (B)

The main idea is that immediate mechanical grip in the proximal bone is what gives the implant its early stability. A triple taper means the stem narrows in three distinct zones as it extends into the femoral canal, creating a stepped, wedge-like interference fit. This geometry increases contact and press-fit specifically in the proximal region, so the stem resists subsidence and rotation right after surgery. In practice, those three taper angles work together to lock the implant more securely in the metaphyseal bone, distributing load proximally and reducing micromotion until the bone can begin to grow onto the surface.

Other features don’t provide the same immediate proximal grip: a cylindrical shell offers a more uniform, less secure fit; a ceramic coating helps with long-term bone integration but doesn’t by itself enhance initial mechanical stability; and a ribbed surface adds roughness for friction but doesn’t create the same concentrated proximal fixation that the tapering geometry does.