Which radiographic signs suggest loosening of a hip prosthesis?

• A. Progressive lucent lines around the stem or cup, subsidence or migration, varus/valgus tilt, pedestals or circumferential lucencies.
• B. Increased radiodensity around the prosthesis with no lucent lines.
• C. Uniform alignment and constant position.
• D. Shortening of the neck without lucencies.

Answer: (A)

Loosening of a hip prosthesis shows up on X-rays as signs at the bone-implant interface that indicate loss of secure fixation. The most telling are progressive lucent lines around the stem or cup, which reflect breakdown of the bond between bone and implant and tend to widen over time. Substantial subsidence or migration of the component shows the implant moving within the bone, another clear cue that fixation has failed. Varus or valgus tilt signals asymmetric loss of support and instability of the stem or cup. Pedestals, or circumferential lucencies around the prosthesis, indicate bone resorption around the implant and a lack of stable seating.

Other patterns don’t fit loosening as well. Increased radiodensity with no lucent lines can occur with sclerosis or other bone reactions but does not demonstrate the interface failure typical of loosening. Uniform alignment and constant position suggest the components remain well fixed. Shortening of the neck without lucencies doesn’t reflect loosening of the stem-bone or cup-bone interface.