What chemical compound, abbreviated PMMA, is used as bone cement in total joint arthroplasties?

• A. Polymethyacrylate
• B. Polyethylene
• C. Calcium phosphate
• D. Titanium

Answer: (A)

PMMA stands for polymethyl methacrylate, an acrylic polymer used as bone cement in total joint arthroplasties. It is prepared by mixing a liquid monomer with a polymer powder, then polymerizes to form a solid cement that bonds the prosthesis to the prepared bone surface. This cement fills gaps, distributes load, and provides immediate fixation of the implant while the bone heals. It is radiopaque, so it can be seen on imaging. The other materials listed aren’t bone cement in this context: polyethylene is used for the bearing surface between mating components, calcium phosphate is a bone graft substitute, and titanium is a metal implant material.