What is the main difference between a megaprosthesis and a standard arthroplasty?

• A. Megaprosthesis replaces large segments of bone (often in tumor resection or massive bone loss) with modular components; standard arthroplasty replaces joint surfaces.
• B. Megaprosthesis is used only in pediatric patients; standard arthroplasty is for adults.
• C. Megaprosthesis uses non-metal components; standard uses metal.
• D. Megaprosthesis is fixed with bone cement; standard is cementless.

Answer: (A)

The central idea is that megaprostheses are built to replace large segments of bone, whereas standard arthroplasty focuses on replacing just the joint surfaces. A megaprosthesis is designed for cases with massive bone loss or after tumor resection, using modular components that span from the remaining bone to recreate function across a substantial defect. In contrast, standard arthroplasty replaces the articulating ends of the bones (the joint surfaces) while preserving most of the surrounding bone stock. Materials and fixation can vary in both, so those factors aren’t the defining difference. The other options don’t fit because megaprostheses aren’t limited to pediatric patients, they aren’t defined by using non-metal components versus metal, and they aren’t defined by cemented versus cementless fixation.