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Influence of material characteristics on fill volumes in vertebroplasty: observations in a prospective randomized study comparing Cortoss and PMMA 2008

Interventional Spine

H. Paul Hatten, MD

Scientific Paper

Purpose

Cortoss is a self-setting, bioactive composite, which was developed specifically for use in vertebral augmentation. Its material charateristics and method of delivery differ significantly from those of PMMA. One difference is that Cortoss is hydrophylic and PMMA hydrophobic. Both materials are being compared in a prospective randomized IDE study designed to evaluate the safety and effectiveness of Cortoss in pts. with osteoporotic vertebral compression fractures. This presentation focuses on the difference in volumes of material used in the study.

Methods & Materials

In our institution, 57 of the total of 256 pts. included in the study were treated and followed. Thirty-six (36) were randomized to Cortoss, and 21 to PMMA. In all pts. material was injected until one of the following was observed on lateral fluoroscopy: 1) material leaking outside the contour of the fractured vertebra, either through the fracture line in the endplate or through a (paravertebral) vein; 2) the material in the AP direction flowed closer to the posterior wall than approx. one third of the total AP distance. After the injection was stopped, an AP view was taken; if the material had not yet crossed the midline, some more material was injected; for PMMA with material that had increased in thickness; for Cortoss with freshly prepared material. Pts. are followed for 24 months with regards to pain (Visual Analogue Scale), function (Oswestry), radiological evolution and complications.

Results

Follow up at time of writing is complete for 80% of pts. at 6-, 55% at 12-, and 11% at 24-months. With regard to pian, function, frequency of leaks and complications we observed no significant differences in our series so far. The appearance of Cortoss in fresh fractures differed from that of PMMA, in that Cortoss showed a more speckled trabecular pattern as opposed to the more homogeneous appearance of PMMA. This difference was reflected in the average volumes injected: 1.9 cc of Cortoss pre level in 50 levels, and 3.5 cc per level for PMMA in 28 levels, i.e. 80% more.

Conclusion

Because of its hydrophylicity, the use of Cortoss in vertebroplasty allows the injection of a significantly lower volume of material thnan necessary with PMMA, while achieving the same clinical benefits. The literature suggests that there may be a correlation between the volume of material used and the risk of emboli*. The use of Cortoss instead of PMMA thus could lead to a lower risk of embolic complications, and might allow the safe treatment of more than two levels in one setting.

References

*ANJR 2007:28 567-69
H. Paul Hatten, MD, consultant to Orthovita Inc.