Cup loosening after cemented Metasul® total hip replacement: a retrieval analysis

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Pathology

Background:

• Small-diameter cemented Metasul® cups are associated with early loosening.
• The specific histological features contributing to this failure mode require elucidation.

Purpose of the Study:

• To investigate the histological characteristics of periprosthetic tissues from aseptically loose cemented Metasul® cups.
• To determine if a specific tissue reaction is linked to the failure of these implants.

Main Methods:

• Histological analysis of periprosthetic tissues from two revised cemented Metasul® cups.
• Microscopic examination for metallosis, wear debris, and inflammatory cell infiltration.

Main Results:

• All samples exhibited metallosis with metallic wear debris in tissues and macrophages.
• Perivascular lymphocyte and plasma cell infiltration, consistent with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL), was observed.
• Tissue reaction occurred despite wear levels being within reported normal limits.

Conclusions:

• A hypersensitivity-like reaction (ALVAL) is present in aseptically loose Metasul® cups.
• Continuous release of metallic ions may trigger ALVAL, potentially contributing to acetabular component failure.
• While ALVAL may be involved, high mechanical stress could also initiate acetabular loosening.