Seating of ceramic liners in the uncemented trident acetabular shell: is there really a problem?

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Medical Device Auditing

Background:

• Concerns exist regarding incomplete seating of metal-backed ceramic liners in the Trident acetabular system.
• This audit investigated the incidence of incomplete liner seating in total hip arthroplasties (THAs).

Purpose of the Study:

• To retrospectively review primary and revision THAs using the Trident acetabular system to assess the rate of incomplete liner seating.
• To identify potential contributing factors and inform procedural adjustments.

Main Methods:

• Retrospective review of 68 patients (78 THAs) between 2003 and 2007.
• Radiographic analysis (anteroposterior and lateral) by three specialist surgeons to detect incomplete liner seating.
• Categorization of cases into primary and revision arthroplasties.

Main Results:

• Six liners (8% overall) were incompletely seated.
• All incomplete seating events occurred in primary THAs (10% risk in primary group), with 0% risk in revision THAs.
• The incidence in the primary group was comparable to published data (16.4%).

Conclusions:

• Incomplete seating of metal-backed ceramic liners is a notable risk, particularly in primary THAs.
• Shell deformation is suspected as a contributing factor to malseating.
• Adjusting the underreaming technique (e.g., to 0.8 mm) may reduce the rate of malseating, especially in sclerotic bone.