Interbody cage devices, used to assist interbody fusion, are rapidly gaining popularity in the surgical management of chronic low back pain. This update provides a structural classification of commonly used devices and assesses them against a set of clearly defined surgical goals, including ability to correct the existing mechanical deformation, ability to provide mechanical stability, ability to provide a suitable environment for arthrodesis, and ability to limit "built-in" morbidity. In addition, the materials used in the devices are examined regarding their biomechanical, biologic, and radiographic characteristics.
