Biomechanical effect of anterior grafting devices on the rotational stability of spinal constructs

In the thoracolumbar spine, frequently strut grafting is used to restore th e anterior and middle column defects. Biomechanical stability of the surgic al construct may be altered significantly depending on the type of anterior grafting devices. In this study, a biomechanical flexibility lest was cond ucted to compare the stabilizing role of various types of anterior grafting devices, such as a polymethylmethacrylate block, tricortical iliac crest b one graft, one large Harms cage, and two small Harms cages using a calf lum bar corpectomy model. The Harms cage, especially one large cage, improved t he axial rotational stability significantly in both anterior and posterior fixation groups as compared with the iliac bone or polymethylmethacrylate. No significant difference in the stabilizing role was found among different grafting devices in lateral bending, flexion, and extension. These results suggest that a more rigid spinal construct can be obtained by using a meta l cage with improved friction at the cage-bone interface.