[Lumbar interbody fusion. Biomechanical significance for the spine]

The authors discuss the significance of interbody fusion for early and long term stability of the lumbar spine. They stress that the aim of the modern spinal instrumentation is to promote bone healing and not to replace fusion. Without fusion every stabilization device will fail in fatigue. The biomechanics of different types of spinal fusion and biomechanical conditions at fusion site are discussed. A history of lumbar interbody fusion including threaded implants (cages) is presented. Interbody cages combine positive properties of tricortical bone graft: the strength of cortical to the bone with improved incorporation properties of cancellous bone. In contrast bone graft their biomechanical performance is far better: they increase strength and stability of osteosynthesis, do not go collapse and resorption, prevent from decrease in disc space height and kyphotic angulation of the fused motion segment, require less bone to achieve fusion. They can be used solely without support of any stabilization system. Preliminary experience in fusion with interbody threaded implants suggest significant efficacy of this method.