Evaluation of biomechanical and histological features of vertebrae following vertebroplasty using hydroxyapatite blocks.

Vertebroplasty was performed using hydroxyapatite blocks to examine the course of compressive strength and histological features in a dog model. The vertebral fracture model was prepared by punching a hole in the center of the vertebra and at 4 sites around the vertebra (5 holes in total) from the front side of the vertebra using an air drill and hollowing the holes. Measurements were made on healthy vertebrae, vertebrae from the vertebral fracture model, vertebrae removed from animals immediately after vertebroplasty, vertebrae collected 1 and 2 months after vertebroplasty, and vertebrae untreated for 1 month after vertebral fracture. Histological examinations were also performed 1 and 2 weeks and 1 and 2 months after vertebroplasty with hydroxyapatite blocks. The strength of vertebrae in the fracture model immediately after vertebroplasty was significantly higher than that in the untreated fracture, and the strength of vertebrae 1 month after the procedure was equivalent to that of healthy vertebrae. Histologically, new bone formation was found around hydroxyapatite blocks 2 weeks after the procedure, and strong crosslinking between neighboring hydroxyapatite blocks was found after 1 month.These results suggest that hydroxyapatite blocks may be effective as filling material for vertebral fracture from both biomechanical and histological perspectives.