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Comparison Study Of Cement Delivery Devices 2004

Watanabe, Lisa, M.D.
Georgy, Bassem, M.D.

Introduction:
Syringes, stylets, and cement delivery devices are commonly used methods of applying cement into the spine during vertebroplasty. We attempt to qualitatively measure the amount of pressure that can be generated by these devices and compare the strength of the delivery devices in terms of working time.

Methods and Materials:
Testing was performed on multiple commercial devices including those made by Cook, Arthrocare-Parallax, Cardinal Health, Spinal Specialties, and BMDI as well as with 1 cc luer lock syringes. Pressure testing was performed with a water pressure meter in psi. Cement delivery working time was measured using unchilled Stryker Howmedica methy lmethacrylate cement. The mixtures were prepared using Stryker Mix-It devices according to manufacturer’s guidelines. No additional barium or antibiotic added to the cement. The syringes and delivery devices were then attached to 11 gauge 4 cm length bone trocars and tested for length of working time.

Results:
Between 800 and 1400 psi of pressure can be generated by hand injection through 1 cc syringes. Only 300-500 psi was generated by hand injection using 3 cc syringes. Significant physical strength was required to generate the higher end pressures in all cases except for BMDI. BMDI reached its pre-set pressure limit (1300 psi) with little physical effort.

The working times of the delivery devices was between 8-12 minutes. Unscrewing and leaking of connections were the main causes of device failure at high pressures. Device bursting occurred at levels of extremely high applied force that would likely not occur within the clinical realm. The 1cc syrin ges were unusable after 6 minutes, although the cement could still be pushed through the needles using stylets. Significantly greater thermal reaction was noted in the larger volume devices compared to the smaller syringes suggesting that the setting time may be affected by the volume of cement within a dispenser.

Conclusions:
All of the methods currently used for cement application in the spine have been shown to have advantages and disadvantages. The actual working time of the cement (as used in the study) is longer with the delivery devices than with the syringes. This may be due to the continuous pressure that can be applied with the devices. The working time of the syringes and devices would be prolonged with cement chilling. Further testing with different cement preparations is in progress.