A 72-year-old woman presents 8 years after total hip replacement with progressive groin pain. ESR is 28 mm/hr, CRP 6 mg/L. Hip aspiration shows 1,800 WBC/μL with 65% neutrophils. Plain radiograph shows lucency at the cement-bone interface around the acetabular cup. The most likely diagnosis is:

• A Periprosthetic joint infection (PJI)
• B Transient synovitis of the hip
• C Aseptic loosening with particle disease ✓
• D Stress fracture of the acetabulum

Explanation

Aseptic loosening due to polyethylene particle-induced osteolysis classically presents years after implantation with pain and radiolucent lines at the implant-bone interface. The synovial fluid WBC <2,000/μL and relatively low CRP do not meet the Musculoskeletal Infection Society criteria for PJI (which requires >3,000 WBC/μL or >80% neutrophils or elevated serum markers). Chronic particle disease (osteolysis) is the most common late cause of aseptic loosening after THR.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.