Abstract
Introduction: Vertebroplasty increases stiffness and partly restores normal load-sharing in the human spine following vertebral fracture. The present study investigated whether the mechanical effects of vertebroplasty are influenced by the distribution of injected cement.
Methods: Ten pairs of cadaver motion segments (58–88 yr) were loaded to induce fracture, after which one from each pair underwent vertebroplasty with polymethyl-methacrylate cement, the other with a resin (Cortoss). Various mechanical parameters were measured before fracture, after fracture and following subsequent vertebroplasty. Micro-computed tomography scans and plane radiographs (sagittal, frontal, and axial) obtained from each augmented vertebral body were analysed to determine percentage cement fill in the whole vertebral body and in selected regions. The relationship between volumetric fill obtained by micro-CT and areal fill obtained by radiography was investigated using linear regression analysis. Regression analysis also indicated whether changes in mechanical parameters following vertebroplasty were dependent upon cement distribution.
Results: Cement type had no significant influence upon regional fill patterns, so data from both cements were pooled for all subsequent analyses. Volumetric fill of the whole vertebral body was predicted best by areal fill in the sagittal plane (R2=0.366, P=0.0047). Restoration of intradiscal pressure and compressive stiffness following vertebroplasty were dependent upon volumetric cement fill both in the whole vertebral body (R2=0.304, P=0.0118 and R2=0.197, P=0.0499 respectively), and in the anterior half (R2=0.293, P=0.0137 and R2=0.358, P=0.0053).
Conclusion: Cement fill patterns can best be assessed radiographically from sagittal plane views. Placement of cement in the anterior vertebral body may help to improve mechanical outcome following vertebroplasty.
Correspondence should be addressed to SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.
