Bending over to pick up things and turning over in bed in daily life can lead to fractures in patients with osteoporosis to a great extent. According to statistics, there are 1000 brittle fractures caused by osteoporosis every second in the world, of which about half occur in the vertebral body. It’s a frequent occurrence in China, one of the world’s Cradle of civilization. It has been reported in Hong Kong that about 30% of the elderly have osteoporotic fragile fractures. Since minimally invasive surgery was first reported in 1987, infusions of cement, a bone adhesive, into fractured vertebrae have resulted in effective treatment for the vast majority of patients with OVCFs. Since the beginning of this century, PKP has been one of the most commonly used minimally invasive procedures for the treatment of Osteoporotic Vertebral Compression Fractures due to its advantages of minimal trauma and rapid improvement of symptoms. Therefore, all patients in our medical institution are treated with PKP.
When basic data were collected, it was suggestive that the volume of cement in a single vertebral body is less and the procedure time and bleeding are more in patients with sandwich vertebra. Only one vertebral body in all patients with ordinary adjacent vertebra received cement augmentation, however, patients with sandwich vertebra had at least two fractured vertebrae that had received cement augmentation. Therefore, we injected cement bilaterally through the pedicle for a single fractured vertebral body, and unilaterally through the pedicle for two or more fractured vertebral bodies. As a result, the volume of cement in a single vertebral body in sandwich vertebrae was smaller than that in ordinary adjacent vertebral body patients. It is consistent with the conclusion of several meta-analyses that the volume of cement used in unilateral Percutaneous kyphoplasty is less than that of conventional bilateral Percutaneous kyphoplasty-. The operation time of unilateral Percutaneous kyphoplasty is less than that of bilateral Percutaneous kyphoplasty, but the operation time of unilateral PKP for two or more fractured vertebral bodies is significantly higher than that of bilateral PKP for one vertebral body. The number of fractured vertebral bodies in sandwich vertebral body patients is more than that in ordinary adjacent vertebral body patients, resulting in an increase in the probability of provoking paravertebral and internal vertebral vessels during operation, and a significant increase in the amount of bleeding. These differences, however, did not affect our findings.
We performed a retrospective analysis of all patients treated with PKP, including significant clinical data, because the patients who came to our medical institution for help were prompted by low back pain. However, this important data was not recorded in the recent study of Ping-Yeh C et al. As we recorded the preoperative data, although the number of vertebral fractures was high in the sandwich vertebral bodies, the preoperative average VAS score of the 10 patients with the sandwich vertebral bodies was 7.80±0.63, with no difference from the preoperative average of 7.47±0.80 in the ordinary adjacent vertebral bodies. After the minimally invasive procedure, all patients reported reduced pain. The postoperative VAS score of 10 patients with sandwich vertebral bodies was 2.60±0.70 and that of ordinary adjacent vertebral bodies was 3.09±1.08. Although there was no identified difference between the two groups, they were statistically less than that before operation. The same findings were identified when the ODI score was collated. There was no significant difference between the preoperative ODI score of 74.80±4.34 in the 10 patients with sandwich vertebra and 72.40±4.73 in patients with the ordinary adjacent vertebra. Patients who received PKP showed significant improvement in mobility because of the rapid relief of postoperative low back pain. There was no detectable difference in the ODI score, the postoperative ODI score of 10 patients with sandwich vertebral bodies was 28.30±6.80 and that of ordinary adjacent vertebral bodies was 30.14±3.40. But they were significantly smaller than those before operation. It is consistent with the report of Zhou X’s. That the original discomfort disappeared after cement injection into the fractured vertebral body of OVCFs patients. This further confirmed the feasibility of cement strengthening of the fractured vertebral body, as the heat released by cement solidification was sufficient to destroy the nerves causing the patient’s low back pain.
Theoretically, the sandwich vertebral body receives double load transmission from the upper and lower vertebral bodies, which is more prone to endplate collapse. But our research has overturned this theory. During the follow-up period, a total of 8 patients had fractures near the cement reinforced vertebral body, 1 (10.00%) occurred in the sandwich vertebral body, that is, the sandwich vertebral body fracture, and the other 7 (3.26%) had ordinary adjacent vertebral fractures. It should be noted that the incidence of sandwich vertebral fractures was 10.00% , which was not statistically higher than 3.26% for ordinary adjacent vertebral fractures. This is consistent with the conclusion of Ping-Yeh C et al23. Although the incidence of sandwich vertebral body and ordinary adjacent vertebral body fractures in this study is less than 21.3% and 16.4% in Ping-Yeh C’s study24. However, the results are very different from the long-term studies conducted by Liu J et al . Liu J et al26 reported that the incidence of sandwich vertebral fracture was 12.9%, which was statistically higher than that of ordinary adjacent vertebral fracture of 6.2%. and they considered that 85% of sandwich vertebral fractures occurred 5 years after operation. The average follow-up time of sandwich vertebral body patients and ordinary adjacent vertebral body patients was 31.30 ± 18.04 months and 25.85 ± 7.96 months, the follow-up time was short, which may be the reason why it is very different from the research conclusions of Liu J et al27.
All OVCFs patients treated with PKP in our medical institution were in the early stage of the main complaint of low back pain. Therefore, cement may have less of an acceleration of adjacent vertebral degeneration, since the callus has not largely formed and the cement intersects with the surrounding fractured trabeculae. In addition, it may be that the strong stress of the cement-augmented vertebral body on the adjacent vertebrae is partially counteracted by the surrounding soft tissue, making osteoporosis, the patient’s underlying disease, a major factor in new vertebral fractures. Finally, our medical practitioners do not strive for a perfect cement-to-bone contact between the upper and lower endplates of fractured vertebrae. This reduces the stress changes in the spinal unit and reduces the risk of recurrent fracture.
The fractured sandwich vertebral body is located in L2, which is around the maximum range of motion of the vertebral body. Faced with a high fracture rate of 10.00% of the sandwich vertebrae, we felt it was necessary to take measures to reduce the risk of refracture. At the beginning of this century, some researchers injected cement into adjacent intact vertebral body after the fractured vertebral body was strengthened with cement, it was found that the subsequent fracture rate of adjacent vertebral bodies was significantly reduced and satisfactory results were achieved. Recently, when Jia P et al injected cement into the fractured vertebral body, they also injected cement into the sandwich vertebral body, which is a special adjacent vertebral body. Surprisingly, none of the sandwich vertebrae patients who underwent prophylactic cement injections during follow-up were found to have new fractures. Therefore, we suggest that the sandwich vertebral body can be injected with cement as appropriate in order to reduce the incidence of subsequent fractures.
This study makes it clear that the incidence of sandwich vertebral fracture is not higher than that of ordinary adjacent vertebral body. But some study limitations still exist in our study. To start with, this was a single-center retrospective study with a small number of cases and a short-term follow-up. Secondly, patients received standardized anti-osteoporosis treatment after operation, which may affect our statistics of fracture incidence in different patients.