This image is an annotated X-ray of a total hip arthroplasty (THA) showing common postoperative radiographic findings and complications around the prosthesis. Here's a clear breakdown of each labeled term:
🔶 Heterotopic Ossification:
Definition: Bone formation in soft tissues where bone normally does not exist.
Radiographic finding: Irregular ossification around the joint, usually periarticular.
Clinical note: Common after hip surgery; may restrict motion.
🔶 Stress Shielding:
Definition: Localized bone loss (osteopenia) due to altered load distribution — the metal prosthesis bears more stress than the bone.
Radiographic finding: Thinning of the proximal femoral cortex, especially in the calcar region.
🔶 Aseptic Loosening:
Definition: Failure of the bond between bone and prosthesis without infection.
Radiographic finding: Periprosthetic lucent zones (>2 mm), often progressive, around the stem or cup.
Mechanism: Micromotion and fibrous tissue interface formation.
🔶 Septic Loosening:
Definition: Loosening due to infection.
Radiographic finding: Rapidly progressive lucency with periosteal reaction or bone destruction.
Key distinction: Infection causes aggressive and irregular bone changes compared to aseptic loosening.
🔶 Spot Welding:
Definition: Endosteal bone formation in direct contact with the prosthesis.
Radiographic finding: Localized areas where bone density increases along the stem — indicates good osseointegration (favorable sign).
🔶 Fibrous Membrane:
Definition: Thin fibrous interface (< 2 mm) between bone and prosthesis.
Radiographic finding: Narrow radiolucent line with a thin sclerotic border — often stable and non-progressive.
🔶 Periprosthetic Fracture:
Definition: Fracture of the bone surrounding the prosthesis, usually due to trauma or stress.
Radiographic finding: Commonly occurs near the tip of the femoral stem.
Classification: Often described by the Vancouver classification (location and implant stability).