[Modification of form, material and modularity of threaded acetabulum cups]

Area of Science:

• Orthopedic Implants
• Biomaterials Engineering
• Surgical Technology

Background:

• Threaded cups are designed for high primary stability in orthopedic fixation.
• Early designs (first generation) showed inadequate results, necessitating design improvements.
• Surface machining and material properties are critical for implant performance.

Purpose of the Study:

• To systematically analyze and compare the geometric shapes and surface roughness of first, second, and third-generation threaded cups.
• To evaluate the impact of design modifications on implant characteristics relevant to osseointegration.

Main Methods:

• Analysis of 10 first-generation and 27 second/third-generation threaded cups.
• Shape measurement using a no-touch light section technique.
• Surface roughness measurements (Ra) using profilometry.

Main Results:

• First-generation cups (polyethylene, ceramic, cobalt-chrome) had Ra of 1.5 microns, with many being conical and taller than their radius.
• Second-generation cups (titanium alloys) showed increased roughness (4.5-5.0 microns with HA coating) and varied shapes, with height often less than radius.
• Third-generation cups offer advanced inlays and material options, maintaining optimized surface structures.

Conclusions:

• Optimized surface roughness and geometric shape are crucial for enhancing primary stability and long-term osseointegration.
• Modern threaded cups utilizing titanium alloys with corundum-blasting or hydroxyapatite (HA) coatings represent a standard for effective fixation.
• Biocompatible materials and structured surfaces are essential for successful long-term osseointegration.