A 72-year-old woman presents 8 years after total hip replacement with groin pain and a serum metal ion level showing cobalt 8 µg/L and chromium 9 µg/L. MRI reveals a large pseudotumor adjacent to the acetabular component. The most likely bearing surface combination responsible for this presentation is:

• A Ceramic-on-ceramic
• B Metal-on-polyethylene
• C Metal-on-metal ✓
• D Ceramic-on-polyethylene

Explanation

Metal-on-metal (MoM) hip resurfacing and large-head MoM total hip arthroplasty produce metallic debris through wear and corrosion at the taper junction, leading to adverse local tissue reactions (ALTR) including pseudotumors and ARMD (adverse reaction to metal debris). Elevated cobalt and chromium ions above 7 µg/L are the diagnostic threshold per MHRA/FDA guidance. Ceramic and polyethylene bearings do not generate such ion levels.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.