95 ± 1.75 (P < 0.05, Table 3). The treated vertebrae which developed reabsorption of the CaP had a greater progression S3I-201 in vivo of the compression after the vertebroplasty than the vertebrae which did not develop reabsorption. The predisposing factor for the progression of the compression of the vertebrae

was the reabsorption of the CaP cement. Table 2 Progression of compression of treated vertebrae   Immediate postvertebroplasty One year after vertebroplasty Two years or more after vertebroplasty Compression ratio* 68.65 ± 6.71 60.98 ± 9.52 59.03 ± 11.19 Difference of compression ratio*   7.6 ± 6.8 1.9 ± 2.9 *P < 0.05 Table 3 Relationship between reabsorption of CaP and recollapse of treated vertebrae   Patients with reabsorption of CaP Patients without reabsorption of CaP Number of patient Six of 14 patients Eight of 14 patients The mean difference of AP ratio of compressed vertebrae (P < 0.05) 16.84 ± 2.57 SIS3 4.95 ± 1.75 Although we encouraged the patients to maintain their regular osteoporosis medications, six patients were intermittently administrated medications. Eight patients maintained good compliance with their osteoporosis medications after the vertebroplasty. Six (75.0%) out of the eight patients with good compliance with their osteoporosis medications

had progression of the compression of the augmented vertebrae. There was no statistical significance. Clinical outcomes The mean preoperative VAS score was 8.4 ± 0.6, and on postoperative day 1 it was 2.9 ± 1.1. The mean VAS score was significantly decreased postoperatively (P < 0.05, Table 4). The mean VAS scores were 2.9 ± 1.2 at 6 months postoperative, 3.1 ± 1.3 at 12 months postoperative, and 3.0 ± 2.4 at the final follow-up (more than 24 months; Table 4). The mean of the VAS scores see more at 6 and 12 months postoperative was slightly higher than at day 1 after the vertebroplasty.

However, there was no statistical significance (P > 0.05). Fortunately, although serial recollapses occurred after the vertebroplasty with CaP, the mean score of the VAS of the back remained low, and there were no neurologic symptoms. However, in the cases of heterotopic ossifications with new vertebral compression fractures and fracture of injected CaP solid hump, the patients presented with high VAS scores (9 and 8 points). Table 4 The changes of VAS score of back during followed period Period Preoperative Immediate postoperative Postoperative 6 months Postoperative 12 months Final followed period VAS score 8.4 ± 0.6 2.9 ± 1.1* 2.9 ± 1.2 3.1 ± 1.3 3.0 ± 2.4 *P < 0.05 Discussion PMMA was commonly used as a filler material for vertebroplasty. However, there are complications related with PMMA [1–4,17]. Recently, several studies have reported concerns about subsequent vertebral compression fractures after vertebroplasty [18–20]. Augmentation using PMMA can alter the normal spinal biomechanics and may result in subsequent vertebral compression fractures [7,8,12,14,21].