In radiographs of a hip prosthesis, which feature suggests loosening?

• A. Increased radiodensity around the bone cement.
• B. Uniform alignment and absence of radiolucencies.
• C. Progressive lucent lines around the stem or cup.
• D. Shortening of the femoral neck.

Answer: (C)

Loosening shows up on X-rays as a loss of stable bone-implant bonding at the interface. The most reliable radiographic clue is progressive radiolucent lines around the prosthetic components—the stem in the femur or the acetabular cup—that widen over time. These lucent zones reflect micromotion and bone resorption at the bone-implant interface, signaling that the implant is no longer firmly fixed.

This differs from a well-fixed prosthesis, which would maintain consistent alignment and have no new or enlarging lucent gaps. Other cues, like increased radiodensity around bone cement, aren’t typical signs of loosening, and shortening of the femoral neck usually points to fracture or malposition rather than loosening.