**Core Concept**
Vertebroplasty is a minimally invasive procedure used to stabilize and strengthen compressed vertebral bodies in patients with osteoporotic compression fractures or vertebral body tumors. The material used in vertebroplasty is a type of bone cement that helps to alleviate back pain and prevent further vertebral collapse.

**Why the Correct Answer is Right**
The material used in vertebroplasty is a polymethylmethacrylate (PMMA) bone cement. PMMA is a biocompatible and radiopaque material that hardens after injection into the vertebral body. It provides immediate structural support and helps to stabilize the vertebral body, reducing pain and preventing further collapse. The PMMA cement is mixed with a liquid monomer that polymerizes to form a solid, rigid structure that integrates with the surrounding bone.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a correct material used in vertebroplasty. While bone grafts are used in spinal surgery, they are not typically used in vertebroplasty.
**Option B:** Hydroxyapatite is a type of bone graft material used in spinal surgery, but it is not typically used in vertebroplasty.
**Option C:** This option is not a correct material used in vertebroplasty. While bone cements are used in orthopedic surgery, the specific type used in vertebroplasty is PMMA.

**Clinical Pearl / High-Yield Fact**
It's essential to note that vertebroplasty is not suitable for all patients with vertebral compression fractures. Patients with severe osteoporosis, cancer, or other underlying conditions may not be ideal candidates for this procedure.

**Correct Answer:** C. PMMA bone cement.