The biomechanical significance of anterior column support in a simulated single-level spinal fusion

This study examines the biomechanical effects of interbody cages and variat ions in posterior rod diameter in a simulated single-level spinal fusion. A single-level spinal fusion model composed of polyethylene cylinders, poste rior pedicular instrumentation, and variously positioned single or dual int erbody cages was used for biomechanical testing. Constructs were tested und er compressive flexural load, with measurement of stiffness, rod strain, ca ge strain, and intracage pressure. A strong linear correlation emerged betw een the mean construct stiffness and cage positioning within the sagittal p lane that was inversely related to posterior rod strain. Two small titanium mesh cages were equivalent to one large cage. In a single-level spine mode l, the presence of and sagittal position of interbody cages significantly i nfluences overall construct stiffness. Cage strain increased with more ante rior positions and was inversely related to rod strain.