Highly Cross-linked Polyethylene Liner Dissociation from a Cement-less Modular Acetabular Shell: Two Case Reports

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Medical Device Engineering

Background:

• Total hip arthroplasty (THA) is a common procedure for hip joint issues.
• Polyethylene liner dissociation from cementless acetabular sockets is a rare but serious complication.
• Understanding the failure mechanisms of THA components is crucial for improving patient outcomes.

Purpose of the Study:

• To report and analyze two cases of polyethylene liner dissociation from a cementless acetabular socket.
• To investigate the potential causes of liner dissociation in the context of specific implant models.
• To contribute to the understanding of rare complications in THA to inform future implant design.

Main Methods:

• Retrospective review of two cases of polyethylene liner dissociation following THA.
• Analysis of patient demographics, surgical history, and implant details (26 mm femoral head, CPE liner, acetabular inclination).
• Examination of the explanted polyethylene liners for signs of damage, including partial rim damage and scratches.

Main Results:

• Two cases (0.04%) of cross-linked polyethylene liner dissociation from AMS-HA shells occurred approximately 10 years post-THA.
• No implant loosening was observed in either case.
• Explanted liners showed partial damage to the elevated rim and scratches on the back, suggesting a mechanical failure related to the fixation mechanism.

Conclusions:

• The observed liner dissociation is likely attributed to a design flaw in the push-in type liner fixation of the specific acetabular socket model.
• This complication, though rare, highlights the importance of evaluating liner fixation integrity in cementless THA.
• Further investigation into liner locking mechanisms is recommended to prevent such rare adverse events.