While Vertebroplasty (VP) has existed for years, most studies address osteoporotic fracture due to diffuse, low energy failure of the vertical trabeculae. Neoplastic vertebral disruption promotes focal lysis of vertical and horizontal trabeculae, often with pedicle involvement. VP used for metastases increases complication rates. Restoration of axial strength in metastatic disease is not well characterized.
32 specimens were harvested from 6 cadavers (T5-S1, age 74±14, BMD 0.7±0.2). Each consisted of one full vertebra and 2 adjacent hemi-vertebrae. Lytic lesions with peripedicular cortical disruption were created and filled with adipose tissue to simulate tumor bulk. Specimens were randomly distributed between 3 groups: lesion alone (control), standard VP, and directed peripedicular augmentation. Specimens then underwent unconstrained compression using a material-testing machine and an embedded bilateral cable system passing through the approximate center of rotation. Linear and angular body collapse, PMMA injection volume and vertebral body volume were measured.
Height reduction was significantly higher in the anterior body (p=0.003). Mean height loss was least for the group with directed VP. Directed VP demonstrated the least increase in kyphosis. Average injected cement volume for the directed VP was 49% less than the standard VP (p<0.0005). Percent body fill was lower for directed than for standard VP. VP significantly increased normalized failure stress (p=0.04).
An optimum threshold cement injection volume may exist, at which vertebral body strength is improved with minimum cement volume. Fixation by directed VP can achieve similar augmentation to standard VP with an anterior fill, while requiring half the cement injection volume.
Listed In: Biomechanical Engineering, Biomechanics, Mechanical Engineering, Orthopedic Research