Effect of vertebroplasty on the compressive strength of vertebral bodies

Abstract

Background contextPercutaneous vertebroplasty has been used successfully for many years in the treatment of painful compressive vertebral fractures due to osteoporosis. PurposeTo compare the effect of vertebroplasty on the compressive strength of unfractured vertebral bodies. Study designBiomechanical study on cadaveric thoracic vertebrae. MethodsForty vertebral bodies from four cadaveric thoracic spines were used for this experiment. Before testing, each thoracic spine was submitted to bone density testing and radiographic evaluation to rule out any obvious fractures. Under image intensification, 6 mL of a mixture of polymethylmethacrylate (PMMA) with barium (8 g of barium/40 g of PMMA) was injected into every other vertebral body of each spine specimen. After vertebroplasty, all soft tissues were dissected from the spine, and the vertebral bodies were separated and potted for mechanical testing. Testing to failure was performed using a combination of axial compression and anterior flexion moments. Two pneumatic cylinders applied anterior and posterior loads at a distance ratio of 4:3 relative to the anterior vertebral body wall, whereas two additional cylinders applied lateral loads, each at a constant rate of 200 N/s. ResultsThe average failure loads for nonvertebroplasty specimens was 6724.02±3291.70 N, whereas the specimens injected with PMMA failed at an average compressive force of 5770.50±2133.72 N. No statistically significant difference in failure loads could be detected between intact specimens and those that had undergone vertebroplasty. ConclusionsUnder these specific loading conditions, no significant increase in compressive strength of the vertebral bodies could be documented. This suggests that some caution should be applied to the concept of “prophylactic” vertebroplasty in patients at risk for fracture.