A 68-year-old woman with a cemented total hip replacement performed 12 years ago presents with groin pain and periprosthetic osteolysis on X-ray without loosening of the acetabular component. The most likely mechanism of osteolysis in this scenario is:
- A Macrophage-mediated foreign body reaction to polyethylene wear particles ✓
- B Cement disease from methacrylate monomer leaching
- C Stress shielding leading to cortical thinning
- D Infection-mediated osteoclast activation
Explanation
Periprosthetic osteolysis is primarily driven by ultra-high-molecular-weight polyethylene (UHMWPE) wear particles that trigger macrophage activation, releasing pro-inflammatory cytokines (IL-1, TNF-α, IL-6) that stimulate osteoclastogenesis via the RANK-RANKL pathway. This particle disease mechanism is distinct from cement disease (which describes early loosening) and stress shielding (which causes cortical thinning proximal to a well-fixed femoral stem, not focal osteolysis). Infection would typically cause diffuse bone loss with systemic signs. Elevated inflammatory markers would suggest infection whereas normal CRP/ESR with focal lytic lesions is characteristic of particle disease.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.