Posterior lumbar interbody cages do not augment segmental biomechanical stability.

The effect on stiffness of installing posterior threaded interbody cages at LA-L5 was evaluated using fresh human cadaveric spine specimens. The cages did not increase spine stiffness significantly in any tested range of motion. Supplemental posterior pedicular screw/rod instrumentation, however, significantly increased stiffness. The assertion that use of cages as isolated posterior implants improves stability may be invalid.