A Study of Mechanical Evaluation of Reconstruction Method After Total en Bloc Spondylectomy.

Abstract

Total en bloc spondylectomy is the most efficient surgical treatment to prevent recurrence of malignant vertebral tumors. In this surgery, a tumorous vertebra is totally removed and replaced with a titanium mesh cage filled with bone autograft, and spinal instrumentation is carried out by using pedicle screw system. Two types of reconstruction method are available in clinical use. One is the multilevel posterior instrumentation (MLP), and another is the short posterior and anterior instrumentation (SPA). MLP has posterior fixations using pedicle screws and spinal rods connecting the two vertebrae above and adjacent to the removed bone and the two below the removed. SPA has anterior and posterior fixations in left side at one level above and below the removed vertebra. It is believed that bone fusion and remodeling of the grafting depend on mechanical stress condition, although mechanical stress condition has not been sufficiently investigated. In this study, experiment and analysis of the reconstructed structure were carried out to determine its stress distribution. The main results are as follows: (i) SPA was favorable to reduce stress of posterior instruments; (ii) MLP was advantageous to promote bone fusion between bone graft and vertebra.