[Assessment of Reduction Abilities of an Expandable Stent in Treating Osteoporosis-Related Fractures of Th/L (Thoracolumbar) Spine].

PURPOSE OF THE STUDY The method of stabilising the osteoporosis-related spinal fractures using an expandable stent (vertebral body stent - VBS) and bone cement is generally accepted for its minimal invasiveness, a low risk of complications and confirmed analgesic effect. The efficiency of reduction of a compressed vertebra is, however, still discussed in the literature. Our hypothesis was that the stent expansion in the vertebral body can achieve a statistically significant reduction in the anterior, middle and posterior part of the vertebra. MATERIAL AND METHODS The patients in whom the VBS technique was used to treat an osteoporosis-related fracture of Th/L spine in the period 2010-2014 were included in the study, namely 29 patients with 31treated fractures. The following radiographic parameters were monitored - anterior, middle and posterior vertebral body height, kyphotic angle between the upper and lower endplates of the vertebral body. Also, the radiation burden, painfulness according to VAS score and occurrence of complications were monitored. The minimum follow-up was 12 months. RESULTS The mean height of the anterior part of the vertebral body before the surgery, on the 1st postoperative day and at 6 weeks, 3 months, 6 months and 12 months was 23.5/25.4/23.9/23.6/23.6 mm respectively. The mean height of the middle part of the vertebral body at the same intervals was 17.9/24.0/23.4/22.9/22.9/22.9 mm. The mean height of the posterior part of the vertebral body was 29.6/29.8/29.4/29.3/29.2/29.2 mm. The kyphotic angle between the endplates of the vertebral body was 8.6/5.3/7.4/7.9/8.0/8.0°. The mean VAS values were 8.2/2.4/2.0/1.9/1.8/1.7. The mean duration of surgery was 54.3 minutes. The mean time of fluoroscopy was 33.4 s. The mean radiation dose was 443.1 cGycm2. The observed complications comprised 2 cases of dilatation balloon rupture, one case of a failure to expand the stents in a healed fracture due to incorrect indication. In total, four cases of cement leakage outside the vertebral body were reported, always with no clinical response. DISCUSSION All the authors agree that the method brings immediate analgesic effect, comparable to kyphoplasty or vertebroplasty. In our cohort, good reduction ability of the implant in the middle part of the vertebral body was confirmed. This has been confirmed also by other authors. Nonetheless, at a longer time interval the loss of correction was observed, which was reported only by Hartmann (5). The other authors mostly did not take into account the longer-term outcomes. CONCLUSIONS The hypothesis that the stent is capable of a statistically significant reduction in the anterior, middle and posterior portion of the vertebral body was only partially confirmed. A statistically significant reduction was seen only in the middle portion of the vertebral body. In the anterior portion of the vertebral body the reduction was demonstrable only immediately after the surgery, while the later follow-up checks revealed the loss of correction. The statistically significant improvement of the kyphotic angle between the endplates of the injured vertebra was also seen only on the first postoperative radiographs and at later follow-up checks the improvement was no more significant. The change in the height of the posterior portion of the vertebral body was not statistically significant at any of the follow-up intervals. Key words:osteoporosis, vertebral fracture, vertebral body augmentation, stentoplasty, vertebral body stent.