Ex Vivo Measurement of Intravertebral Pressure during Vertebroplasty

Study Design. Ex vivo biomechanical study using cadaver vertebral bodies. Objective. To measure the increase in internal vertebral body pressure from cement injection during vertebroplasty. Summary of Background Data. Theoretically, the increased force required to inject polymerizing (viscous) cement into a vertebral body during vertebroplasty could produce a concomitant increase in intravertebral pressure and cause additional damage to the vertebral body. An alternative means of reducing intravertebral pressure during injection may be needed. Methods. We placed 11-gauge cannulas bipedicularly in six vertebral bodies from each of two fresh female cadaver spines (one osteoporotic, one normal). One cannula served as the injection route; a manometer was connected to the other. After immersion of the spines in a saline bath, the vertebral bodies were injected with 10 mL of Simplex P cement by depressing the syringe plunger at a rate of 7 mm/sec using a materials testing machine. Static pressure was measured before and after injection. Peak pressure was measured during injection. Maximum pressure elevation was calculated as peak pressure minus initial static pressure. Results. Maximum pressure elevation averaged (±SD) 9.4 ± 8.5 mm Hg and 6.4 ± 5.0 mm Hg in the osteoporotic and normal spines, respectively. In all cases (9 of 12) in which the pressure measurement system remained patent (i.e., not occluded by cement), postinjection pressure returned to the initial static pressure. Conclusion. The increase in intravertebral body pressure from cement injection during vertebroplasty is minimal. Alternative means of reducing intervertebral pressure before injection may not be needed.