This prospective study focuses on factors that influence restoration of the vertebral body height during vertebral fracture treatment, quantifying these from diagnosis to discharge. We observed that some factors favor the restoration of the vertebral body height while others affect it negatively. Furthermore, these factors act concretely at different times during patient follow-up.
Previously published studies that analyze the change in vertebral body height after vertebral augmentation have various limitations4,6,7,9,19,20. Irregularity of the vertebral fracture makes it difficult to select a reference point to carry out the measurements, there is no consensus on how to quantify changes in vertebral body height and studies take into account different factors (dynamic mobility, IVVC, vertebral augmentation technique) that are analyzed in isolation and not as a whole4,8,9, 12–14,16,19,21. This means that surgeons do not know at what point in patient follow-up these factors influence vertebral restoration.
Overall changes in vertebral body have previously been studied at two points in time: pre- and post-surgery4–6, 12,18. To provide more detailed and accurate information, we analyzed the vertebral body at different timepoints: pre-surgery, intra-operatively (pre-cementation and post-cementation), at first medical check-up (6 weeks) and at last medical check-up (17.1 ± 12 months). To our knowledge our study is the first to analyze changes intraoperatively, establishing the changes due to patient position in order to differentiate the real effect of vertebral augmentation4,6,7,9−11.
Some authors12,16 concluded that vertebral height restoration depends more on dynamic mobility than vertebral augmentation. McKiernan et al.8 observed that approximately 35% of vertebrae were mobile. In our study, we found that after vertebral augmentation there was an increase in vertebral height of + 0.3cm (13.6%). Specifically, the patient's position change (standing to prone position) led to an increase in vertebral height of + 0.1 cm (+ 4.5%) and vertebral cementation caused a further increase in the vertebral body height of + 0.2cm (+ 8.7%). These findings go against the conclusion of Chen et al.12 and Yokoyama et al.16, since mobility of the vertebra contributed to a third of the height restoration, and the cementation was the cause of the rest.
If we assess, as a whole, the factors that influence vertebral height restoration, we can see that the factors act at different times. We observed that having a severe collapse (grade III) had the greatest influence when the patient was in the prone position (Tables 2 and 3). This observation differed from the conclusions of McKiernan et al.8 or Teng et al.9 who suggested that the change in height was favored by the presence of an IVVC. However, our results show that IVVC had the greatest influence when the vertebral augmentation was performed (P = 0.018) and not as a result of the patient's position change (P = 0.250). Determining to what extent and when a factor most influences vertebral height restoration is only possible if intraoperative radiographic measurements are performed.
Thoracolumbar zone has greater mobility than thoracic or lumbar fractures8,14,15. However, they do not specify whether this factor favors or disfavors vertebral height restoration. Our results show that location in the thoracolumbar area negatively influenced vertebral height restoration (Tables 2 and 3)
Tang et al.21 and Takahashi et al.22 suggested that vertebral fracture time evolution influences clinical and radiological results. Vertebral height and vertebral kyphotic angle after kyphoplasty were better in patients treated in the first two months from onset of symptoms. Based on our results, we cannot affirm that the time since vertebral fracture influenced in vertebral body height.
Outcomes in our cohort should be interpreted with some caution due to the potential limitations of the study. We did not compare PVP with PKP. Literature shows that PKP requires more surgical time (which is harmful in elderly patients) and is more expensive, which is why several studies recommend using PVP over PKP21,23,24. Measurements were made with radiographs. We used this technique because it is easy to use, it can be performed intra-operatively and it allows us to study the vertebral body in different positions (standing and prone position). The gold-standard technique for making measurements is CT-scan. However, few hospitals can perform intraoperative CT-scan, and, in addition, it would mean exposing the patient to high doses of ionizing radiation. There may be other factors which influence the restoration of vertebral height that we have not collected. To understand factors involved in changes in the vertebral body height better, it would be interesting to make a comparison between a conservatively treated group and a surgical group. However, our present aim was to focus exclusively on vertebrae treated with vertebral augmentation.