Vertebral body stenting: a new method for vertebral augmentation versus kyphoplasty

Vertebroplasty and kyphoplasty are well-established minimally invasive treatment options for compression fractures of osteoporotic vertebral bodies. Possible procedural disadvantages, however, include incomplete fracture reduction or a significant loss of reduction after balloon tamp deflation, prior to cement injection. A new procedure called “vertebral body stenting” (VBS) was tested in vitro and compared to kyphoplasty. VBS uses a specially designed catheter-mounted stent which can be implanted and expanded inside the vertebral body. As much as 24 fresh frozen human cadaveric vertebral bodies (T11-L5) were utilized. After creating typical compression fractures, the vertebral bodies were reduced by kyphoplasty (n = 12) or by VBS (n = 12) and then stabilized with PMMA bone cement. Each step of the procedure was performed under fluoroscopic control and analysed quantitatively. Finally, static and dynamic biomechanical tests were performed. A complete initial reduction of the fractured vertebral body height was achieved by both systems. There was a significant loss of reduction after balloon deflation in kyphoplasty compared to VBS, and a significant total height gain by VBS (mean ± SD in %, p < 0.05, demonstrated by: anterior height loss after deflation in relation to preoperative height [kyphoplasty: 11.7 ± 6.2; VBS: 3.7 ± 3.8], and total anterior height gain [kyphoplasty: 8.0 ± 9.4; VBS: 13.3 ± 7.6]). Biomechanical tests showed no significant stiffness and failure load differences between systems. VBS is an innovative technique which allows for the possibly complete reduction of vertebral compression fractures and helps maintain the restored height by means of a stent. The height loss after balloon deflation is significantly decreased by using VBS compared to kyphoplasty, thus offering a new promising option for vertebral augmentation

Volume matters: a review of procedural details of two randomised controlled vertebroplasty trials of 2009

Two recent randomised controlled trials (RCT) published by the New England Journal of Medicine (NEJM) in 2009 comparing vertebroplasty to sham procedures have concluded that vertebroplasty is no more effective than injection of local anaesthetic at the pedicle entry point. This finding contradicts previously published clinical series on vertebroplasty which have shown clinical efficacy. The procedural details of the two RCTs are analysed specifically with regard to vertebral levels treated and injected polymethylmethacrylate (PMMA) volumes in an attempt to combine the data for assessment against the available basic science underpinning the effect of vertebral augmentation procedures. Neither investigation provides a breakdown of the vertebral levels treated in the original publication or in supplementary online material. Only one investigation provides information on fill volumes with an overall average fill volume of 2.8 ± 1.2 ml SD. The available basic science indicates a minimum fill volume of 13–16% of the vertebral body volume to be necessary for a relevant biomechanical effect on restoration of vertebral strength. The most commonly treated vertebrae of the thoracolumbar junction have an anatomical vertebral body volume of ~30 ml. An effective fill would require a minimum of ~4 ml PMMA. Anatomical volumes and required fill volumes increase towards the lower lumbar spine. According to the available basic science, only vertebrae of the upper to mid thoracic spine could reasonably have received a biomechanically effective fill with the declared average volume of 2.8 ± 1.2 ml SD. The available data of the NEJM publications strongly indicates that the treatment arm includes patients who were not treated in a reasonably effective manner. The technical information provided by the NEJM publications is insufficient to conclusively prove or disprove the clinical efficacy of vertebroplasty