Periprosthetic osteolysis around a total hip replacement results from macrophage phagocytosis of polyethylene wear debris. The final common pathway leading to bone resorption is:

• A Direct osteoblast apoptosis triggered by particle endotoxin
• B Neutrophil elastase digestion of mineralised collagen matrix
• C Macrophage release of cytokines inducing RANKL expression and osteoclast differentiation ✓
• D Complement-mediated lysis of osteocytes within lacunae

Explanation

Submicron polyethylene particles are phagocytosed by macrophages, which respond by releasing pro-inflammatory mediators including IL-1, IL-6 and TNF-alpha. These cytokines upregulate RANKL on stromal and osteoblastic cells, driving osteoclastogenesis and granulomatous membrane formation, producing the lytic lesions seen radiographically. Neutrophils dominate acute infection, not aseptic osteolysis, which is why option B describes the wrong cell lineage.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.