A painful hip replacement
History
72-year-old man with a right total hip replacement 5 years ago, now 6 months of thigh pain, worse on weight-bearing. CRP 18 mg/L. Radiographs show a thin lucent line along part of the femoral stem. Hip aspiration was dry. The orthopaedic surgeon asks: 'Septic or aseptic loosening?'
Step 1 · Three-phase bone scan

What can be concluded from the bone scan?