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Failure of constrained acetabular liner without metal ring disruption
Sathappan S Sathappan1, Daniel Ginat, Mathew Teicher
1Department of Orthopedic Surgery, Musculoskeletal Research Center, Hospital for Joint Diseases, New York, New York, USA.
Orthopedics
|March 19, 2009
Summary
This study reports a novel failure mode of a constrained acetabular liner, where dissociation occurred at the liner-bipolar head interface due to polyethylene rim deformation, not locking ring failure. This highlights a previously undocumented failure mechanism in total hip arthroplasty.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Medical Device Engineering
Background:
- Constrained acetabular liners are used in total hip arthroplasty (THA) to prevent dislocations in high-risk patients.
- These liners can fail at multiple interfaces, with recurrent dislocation being a common outcome.
- Previous failures at factory-assembled interfaces were attributed to locking ring failure.
Observation:
- A case of dissociation of a cemented Osteonics acetabular constrained liner is presented.
- The failure occurred at the constrained liner insert-bipolar head interface.
- This dissociation was caused by deformation of the polyethylene rim, not locking ring failure.
Findings:
- This represents the first reported case of a tripolar constrained liner disengaging without locking ring disruption.
- The failure mechanism involved deformation of the polyethylene rim, facilitating dissociation.
- This novel failure mode differs from previously documented issues at other interfaces.
Implications:
- This finding expands the understanding of potential failure modes for constrained acetabular liners.
- It suggests that polyethylene rim integrity is critical for the stability of factory-preassembled constrained liner systems.
- Further investigation into liner material properties and design may be warranted to prevent such dissociations.
