[Material related aspects of surface structured endoprostheses]

Area of Science:

• Biomaterials Engineering
• Orthopedic Surgery
• Materials Science

Background:

• Cementless implantation of endoprostheses relies on porous surface structures for bone ingrowth.
• Various porous coating technologies exist, but their long-term performance and reliability require thorough evaluation.

Purpose of the Study:

• To analyze technical challenges associated with surface-structured endoprostheses for cementless implantation.
• To compare different porous coating technologies used in hip and knee endoprostheses.
• To assess the quality of bonding and fatigue strength of these coatings.

Main Methods:

• Metallographic examination of polished specimens to evaluate prosthesis-implant bonding.
• Fraction surface analysis of tension test specimens to investigate coating integrity.
• Assessment of the notch effect and fatigue strength reduction for different coating technologies and implant alloys.

Main Results:

• Four distinct porous coating technologies were compared: sintered sphere layer, cast sphere layer, "spongy-bone" cast layer, and plasma sprayed coating.
• Metallographic analysis revealed varying degrees of bonding quality between the prosthesis and porous layers.
• Fatigue strength reduction due to the notch effect differed significantly among the tested materials and technologies.

Conclusions:

• The current quality of surface-structured endoprostheses, particularly regarding bonding and fatigue performance, is deemed unsatisfactory.
• Further research and development are necessary to enhance the reliability and efficacy of porous coatings in cementless orthopedic implants.