A thoracic spine testbed for the comparative biomechanical evaluation of spinal instrumentations

This study focuses on the design, materials selection, and fabrication of a human thoracic spine (T-3 to T-12) mechanical analog testbed and an examination of its suitability for use in the comparative evaluation of biomechanical characteristics of spinal instrumentations. In this case, two constructs involving the Texas Scottish Rite Hospital (TSRH) system (namely, a specially assembled unilateral rod and the standard dual rod scoliosis arrangements) were compared. It was found that there is no statistically significant difference between the direct axial compressive stiffnesses of the constructs using these arrangements. In addition, the von Mises stresses at three selected locations on one of the vertical rods constituting the instrumentation showed statistically significant decreases when the standard dual-rod construct was used compared to the case when the unilateral-rod construct was used. It was found that the relative change in stiffness between the constructs approximated that observed in previous cadaveric and animal studies. It is thus concluded that the testbed is suitable for the stated purpose.