[Cementless stems of the hip. Current status].

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Implant design

Context:

• Cementless hip stems are critical for joint replacement longevity.
• Primary stability (rotational, tilting, axial) is essential for implant success.
• Factors influencing stability include anchorage, stabilizers, material, and surface properties.

Purpose:

• To review the essential elements for optimal fixation of cementless hip stems.
• To discuss the role of stem design, materials, and fixation types in achieving long-term stability.
• To present survival rates for different fixation methods.

Summary:

• Optimal fixation of cementless stems requires attention to anchorage, stabilizers (fins, ribs), material (titanium alloys), and surface treatments (corundum-blasted, plasma-sprayed).
• Stem design parameters like CCD-angle and neck-axis length influence offset, leg length, and center of rotation.
• Fixation types include epiphyseal, metaphyseal, meta-diaphyseal, and diaphyseal, with varying degrees of modularity and customization.

Impact:

• Metaphyseal and meta-diaphyseal stems show 15-year survival rates of 95-98%.
• Diaphyseal-fixed stems demonstrate mid-term survival rates between 92-99%.
• Understanding these factors is vital for improving patient outcomes and implant longevity in hip arthroplasty.