Corrosion at the modular head-neck taper (trunnion) of a total hip replacement generates metal debris causing adverse local tissue reaction even with a metal-on-polyethylene bearing. This failure mode is best described as:

• A Pitting corrosion initiated by chloride ions in joint fluid alone
• B Galvanic corrosion between the cement mantle and the titanium stem
• C Stress corrosion cracking of the femoral stem
• D Fretting and mechanically assisted crevice corrosion at the taper junction ✓

Explanation

Trunnionosis results from micromotion (fretting) at the modular taper combined with crevice corrosion in the confined fluid-filled gap; mechanical disruption of the passive oxide layer drives metal ion release. This occurs independently of the bearing surface, which is why cobalt ions can rise even with ceramic or metal heads on polyethylene. Galvanic and stress corrosion mechanisms do not explain the localised taper damage.

Reference: Miller's Review of Orthopaedics, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.