The Effects of Cement Augmentation Technique and Cement Volume on Pedicle Screw Fixation in Osteopenic Bone

INTRODUCTION Cement augmentation of pedicle screws has been shown to improve screw fixation in osteopenic spines. The use of polymethylmethacrylate cement augmentation has been documented in various studies using a number of different techniques: cement injection directly into an open pilot hole, through cannulated screws, using implanted sleeves, and using kyphoplasty techniques. Complications can arise regardless of the technique employed including extravasation into the surrounding anatomy with the risk of embolization. Entry into the spinal canal and neural foramen could cause direct neurologic compression. The use of cannulated and fenestrated screws through which cement can be injected has proven effective; however, once the cement is hardened the screws require extremely high and dangerous torques for removal in revision situations. [1] To address these difficulties we have developed a novel cement delivery device and technique that, once removed, leaves a threaded tract for insertion of pedicle screws [1]. Unlike the cannulated screws mentioned above, this system is withdrawn prior to hardening. A separate, non-fenestrated screw can then be inserted. This eliminates the revision complications of the fenestrated screw system and decreases the extravasation possibility with the direct injection, while still improving overall fixation strength. In previous studies we have shown that resistance to toggling was significantly improved when compared to screws implanted without cement. In this study we compared this novel technique to open pedicle injection of cement. To further investigate the use of such a device, we used two different cement volumes, 2ml and 3ml.