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Stiffness of bipolar hip prostheses.
1Departemt of Orthopaedic Surgery, Pontefract General Infirmary, Yorkshire, UK.
Injury
|September 1, 1989
Summary
Stiff bipolar hip arthroplasty bearings may result from high-density polyethylene (HDP) debris. This debris causes wear and distortion, leading to increased friction and stiffness, even with lubrication.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Materials Science
Background:
- Bipolar hip arthroplasty is used for hip fractures.
- Inner bearing stiffness is a complication observed post-surgery.
- High-density polyethylene (HDP) wear debris is implicated.
Purpose of the Study:
- To investigate the cause of inner bearing stiffness in bipolar hip arthroplasty.
- To test the hypothesis that lack of lubrication causes stiffness.
- To analyze the role of HDP debris in wear and stiffness.
Main Methods:
- Mechanical modeling of a hip joint with a Hastings bipolar arthroplasty.
- Analysis of retrieved Bateman bipolar hip arthroplasty components.
- Evaluation of dynamic frictional forces at the inner bearing with and without lubrication.
Main Results:
- High-density polyethylene (HDP) debris, wear, and distortion were found in a stiffened inner bearing.
- Lubrication with synovial or serosanguinous fluid did not significantly reduce dynamic frictional forces.
- Reduced initial movement due to debris concentrates loads, increasing shear forces and HDP distortion.
Conclusions:
- Inner bearing stiffness in bipolar hip arthroplasty is likely caused by HDP debris.
- Debris leads to mechanical failure modes including wear, creep, and distortion.
- Concentrated loading exacerbates HDP component damage, contributing to stiffness.