Cystic Adverse Local Tissue Reactions in Asymptomatic Modular Metal-on-Metal Total Hips May Decrease Over Time.

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Radiology

Background:

• Pain is not always an indicator of bearing-related problems in hip implants.
• Adverse local tissue reactions (ALTRs) can occur in asymptomatic patients with modular metal-on-metal total hip arthroplasties.
• The natural history of ALTRs in asymptomatic individuals requires further investigation.

Purpose of the Study:

• To determine the natural history of ALTRs in asymptomatic patients with modular metal-on-metal total hip arthroplasties.
• To evaluate changes in ALTR lesions over a one-year period.
• To correlate imaging findings with serum metal ion levels.

Main Methods:

• Eighty-three asymptomatic patients with hip implants underwent metal ion testing and Metal Artifact Reduction Sequence MRI (MARS MRI).
• ALTR lesions were identified and classified using the MRI Classification System of Hart et al.
• Follow-up MARS MRI was performed after one year for patients with identified lesions.

Main Results:

• Thirty-one percent (26/83) of asymptomatic patients showed ALTR lesions on initial MRI.
• Of 19 patients available for follow-up, most ALTRs decreased in size (79%).
• Three patients became symptomatic and required revision surgery; serum cobalt and chromium levels remained below 7 ppb for all patients.

Conclusions:

• Most ALTRs in asymptomatic patients with these hip implants tend to decrease in size.
• Despite the tendency for regression, clinical vigilance is necessary due to the potential for symptomatic progression.
• Regular monitoring may be warranted for asymptomatic patients with identified ALTRs.