BCL is the most common problem in PVP/PKP for the treatment of OVCF, especially in OVCF cases with peripheral wall damage. At present, Yeom’s[12] classification of BCL is widely recognized and applied in clinical practice. It divides BCL into 3 types: type B (leakage via the basivertebral vein), type S (leakage via the segmental vein) and type C (leakage through a cortical defect). Among which type C is the most common, and can occur in any part around the vertebral body, such as intervertebral disc, paravertebral body, posterior vertebral edge, etc. Studies show that in PVP, the direct infusion of bone cement into vertebrae can generate high infusion pressure, which make the cement easy to leak, thus the incidence of BCL is as high as 19% ~ 76%, with an average of 29% [13, 14, 15]. Later, PKP is developed, in which balloon is used to form a cavity in the vertebral body and restore the height, then bone cement is injected under low pressure, and that reduce the incidence of BCL to about 8%.[16] However, for those OVCF with peripheral vertebral wall damage, the fracture can be further enlarged due to the expansion of the injured vertebral body, which increases the risk of BCL. There is a high risk of spinal cord (cauda equina) or nerve injury especially in the case with posterior wall damage.[17]
The basic principle of vesselplasty is to insert a distal detachable mesh container (Vessel-X) into the injured vertebra through a working path, inject bone cement and pressurize the container to gradually expand, in order to restore the height of the compressed vertebral body and correct kyphosis. When bone cement starts to solidify, remove the container, and keep bone cement in the vertebral body. In the whole procedure, bone cement is always wrapped in the container, instead of pouring bone cement directly into the vertebral body, so that the container can prevent BCL in the vertebral body with damaged anterior or posterior wall. Briefly, vesselplasty is performed based on mechanics and hydrodynamics. The mesh container has a dense polymer net layered structure with different capacity designed, which can significantly reduce cement leakage. Studies indicated that PVP, PKP and vesselplasty all achieved satisfactory results in pain relief, but PKP did better in restoring vertebral body height, while vesselplasty had lower incidence of BCL.[18, 19] The Vessel-X container is made up of 100 µm mesh, and the bone cement oozing from within the container can get a good grip with cancellous bone, which is very suitable for the vertebral fracture with peripheral wall damage.[18] In our study, none of the cases had BCL into spinal canal, 2 cases had paravertebral leakage which defined as type B,[12] and only 1 case leaked through puncture channel into posterior soft tissue as type C. Those patients with BCL did not have clinical symptoms, and no special treatment was given.
In PKP, bone cement won’t be injected until vertebral expansion is completed and balloon is removed. Therefore, it is easy to cause the vertebra collapsing again due to the poor mechanical properties of the cavity. In vesselplasty, bone cement is directly injected to pressurize, and the cement dispersing outside the container can help to expand the vertebral body. Thus in theory, vesselplasty can better restore vertebral body height and correct kyphosis. However, further clinical trials are needed to compare the difference between vesselplasty and PKP. Chen et al.[20] found that vesselplasty and PKP had statistical significance compared with PVP in restoring vertebral body height, while there was no difference between the former two. As for the degree of recovering of vertebral body height, the study results are different, but all have shown significant improvement compared with before operation. In addition, the compressed vertebral body can not only cause kyphosis, but also reduce the ability in load dispersing of upper and lower intervertebral disc, resulting in fracture of adjacent vertebra or re-fracture of injured vertebra. In the treatment of OVCF, it is necessary strengthening the injured vertebral body, as well as restoring its height.[21]
According to our results, the postoperative ODI and VAS scores of patients decreased obviously, indicating that their functional status and pain caused by fracture were significantly improved. Our radiographic assessment showed that vertebral body height increased and Cobb angle was corrected significantly, suggesting satisfactory improvement of spinal deformity and restoration of vertebral body height through cement injection using mesh container. Besides, there were only 3 cases of BCL, and none of them caused relevant symptoms, which indicated sound safety of vesselplasty.
The current study has several limitations. First of all is its relatively low number of patients. For that vesselplasty has not been widely popularized, there were totally 62 patients involved in the study. Larger sample population will allow for more meaningful statistical testing and smaller deviation. Another limitation is the short follow-up period. The longest period in this study was 6 months since we initially believed that longer period of follow-up would reduce patients' compliance and make data collection more difficult. However, longer period up to 1 or 2 years may Improve the reliability of evidence. Therefore, large sample, multicenter and long follow-up studies should be performed in our future clinical work to provide spine surgeons with the best evidence-based information.