A 62-year-old man undergoes uncemented total hip arthroplasty with an extensively porous-coated femoral stem. At 2-year follow-up, he is asymptomatic. Radiographs show loss of proximal femoral cortical density in the calcar region with distal cortical hypertrophy around the stem tip. The stem is well fixed with no subsidence or progressive radiolucent lines. This pattern of bone remodeling is best described as:
- A Stress shielding ✓
- B Aseptic loosening
- C Particle-induced osteolysis
- D Reactive bone formation
Correct answer: A. Stress shielding
Explanation
Stress shielding is the adaptive bone remodeling that occurs when a stiff implant bypasses physiological load to the distal femur, causing proximal bone resorption, especially the calcar, and distal cortical hypertrophy. It is distinct from particle-induced osteolysis, which involves macrophage-mediated bone resorption from wear debris and typically presents with focal radiolucent lesions rather than diffuse proximal bone loss. Aseptic loosening would show progressive radiolucent lines and/or subsidence.
Reference: Campbell's Operative Orthopaedics, 14th ed.
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