A 72-year-old woman presents 8 years after a cemented total hip replacement with progressive groin pain and a serum metal ion level of cobalt 9 µg/L. CT of the hip shows a large pseudotumor with soft tissue destruction around the acetabular component. The bearing surface most likely responsible for this pattern of failure is:

• A Ceramic-on-polyethylene articulation
• B Highly cross-linked polyethylene-on-metal articulation
• C Metal-on-metal (MoM) articulation ✓
• D Ceramic-on-ceramic articulation

Explanation

Adverse local tissue reaction (ALTR) with pseudotumor formation is the hallmark complication of metal-on-metal bearings, caused by corrosion products (cobalt and chromium ions and particles) triggering a hypersensitivity reaction. Elevated serum cobalt >7 µg/L prompts urgent cross-sectional imaging. Ceramic-on-ceramic and ceramic-on-polyethylene bearings do not release metallic ions and are not associated with this entity.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.