All dual mobility cups are not the same

Area of Science:

• Orthopedic surgery
• Biomaterials engineering
• Medical device design

Background:

• Dual mobility cups have been a significant advancement in hip arthroplasty for over two decades.
• Despite their long history, a single company dominated the market due to industrial ownership, limiting broader adoption.
• The concept has gained traction, with numerous variations available, necessitating a clear classification system.

Purpose of the Study:

• To propose a comprehensive classification system for dual mobility cups.
• To differentiate between conventional cup characteristics and those specific to dual mobility implants.
• To analyze the diverse designs, materials, and fixation methods within the dual mobility cup market.

Main Methods:

• Comparative analysis of dual mobility cups against standard metal-back cups.
• Examination of the additional interface responsible for polyethylene insert mobility within the acetabular cup.
• Review of published literature focusing on cup design, materials, fixation, and insert characteristics.

Main Results:

• Complications such as intraprosthetic dislocation and fixation failures have historically hindered the widespread adoption of dual mobility implants.
• Despite being a 40-year-old concept, over 95% of publications on dual mobility cups have emerged in the last decade, indicating recent surge in interest and research.
• Significant variations exist in dual mobility cup designs, materials, and fixation methods.

Conclusions:

• The latest generation of dual mobility cups integrates advanced features for enhanced performance.
• These implants utilize cast chrome-cobalt alloy cups with porous titanium and hydroxyapatite coatings for press-fit fixation.
• New insert designs aim to eliminate intraprosthetic dislocation risks while preserving polyethylene's elasticity, demonstrating effectiveness in preventing instability.