A 68-year-old patient with a DePuy ASR metal-on-metal hip resurfacing implant presents with groin pain, a 'soft tissue mass' around the hip, and serum cobalt level of 14 µg/L (normal <2 µg/L). MRI shows a large fluid collection with local soft-tissue destruction. What is the DIAGNOSIS and recommended management?
- A Acute periprosthetic infection; DAIR with component retention
- B Adverse reaction to metal debris (ARMD/ALVAL); revision to non-metal-on-metal bearing ✓
- C Aseptic loosening; revision to a larger diameter metal-on-metal head
- D Iliopsoas bursitis; aspiration and corticosteroid injection
Explanation
Adverse reaction to metal debris (ARMD) — also termed aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) — is a specific complication of metal-on-metal (MoM) hip bearings. Cobalt and chromium ions from the bearing couple cause a local pseudo-tumour (fluid-filled mass), soft-tissue necrosis, and systemic metal toxicity. Serum cobalt >7 µg/L with symptoms mandates urgent revision to a non-MoM bearing (ceramic-on-polyethylene or ceramic-on-ceramic). The ASR (DePuy Articular Surface Replacement) was recalled in 2010 due to high failure rates from ARMD. Further MoM bearings are contraindicated in revision.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.