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Acetabular cup malalignment after total hip resurfacing arthroplasty: a case for elective revision?
Matthew C Mai1, Joseph C Milbrandt, John Hulsen
1Division of Orthopedics and Rehabilitation, Southern Illinois University School of Medicine, Springfield, Illinois 62794-9679, USA.
Orthopedics
|November 12, 2009
Summary
A resurfacing hip implant with poor positioning led to significantly elevated metal ion levels, indicating a need for revision surgery. Early intervention is crucial for malpositioned implants to prevent failure, even if the patient is clinically well.
Area of Science:
- Orthopedic surgery
- Biomaterials science
- Toxicology
Background:
- Resurfacing hip arthroplasty offers an alternative to traditional total hip replacement.
- Acetabular cup positioning is critical for implant longevity and patient outcomes.
- Metal-on-metal bearings can lead to elevated serum metal ion levels.
Observation:
- A patient with a resurfacing implant in a malpositioned acetabular cup experienced substantial clinical improvement initially.
- Progressively elevated serum cobalt (Co) and chromium (Cr) ion levels were detected over time.
- The acetabular component eventually failed after 4.5 years, necessitating revision to total hip arthroplasty.
Findings:
- A strong correlation exists between increased cup inclination and elevated serum Co/Cr levels.
- This patient's metal ion levels were significantly higher than typically observed, exceeding 400 times the expected range.
- Acetabular malalignment was identified as a contributing factor to the high metal ion concentrations.
Implications:
- Early revision should be strongly considered for resurfacing implants with component malpositioning.
- Abnormally elevated metal ion concentrations warrant revision regardless of the patient's clinical status.
- The findings highlight the risks associated with malpositioned metal-on-metal bearings in hip implants.