A biomechanical analysis of intravertebral pressures during vertebroplasty of cadaveric spines with and without simulated metastases

Study Design. A biomechanical cadaveric study of thoracic and lumbar vertebrae with simulated metastases quantifying intravertebral pressures during transpedicular vertebroplasty. Objective. To compare intravertebral pressure during percutaneous vertebroplasty in vertebrae with and without simulated lytic metastases. Summary of Background Data. Percutaneous vertebroplasty is designed to proved stability to vertebrae weakened by osteoporosis or metastatic disease. The complication rate is higher when the procedure is used for the treatment of lytic vertebral lesions. The major complications reported are radiculopathy, spinal cord compression, and embolic phenomena. Methods. Ten fresh-frozen cadaveric vertebrae were tested intact (7 lumbar, 3 thoracic) and 7 were tested with simulated lytic defects (4 lumbar, 3 thoracic). Defects were created by replacing a core of cancellous bone with soft tumor tissue in the center of the vertebral body. Simplex P (Howmedica Osteonics, Mahwah, NJ) cement was injected into each vertebra through a unipedicular approach at a constant rate of 3 mL per minute. Cement volume, injection force, and intravertebral pressures at the posterior vertebral body wall were recorded. Following the procedure, the vertebrae were sectioned to visualize cement and tumor disbursement. Results. There was no significant difference between the two groups for age, size, trabecular density, and cement volume. Vertebrae with simulated metastases generated an average maximum pressure of 39.66 kPa during cement injection versus 6.83 kPa in intact vertebrae (P<0.05). Higher pressures were also generated in smaller vertebrae based on a power relationship (r(2)=0.71 intact, r(2)=0.43 tumor). Conclusions. Percutaneous vertebroplasty produces higher intravertebral pressures in vertebrae containing a simulated lytic metastasis than in intact vertebrae. Pressures generated in the tumor specimens are sufficiently elevated to cause embolic phenomena.