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Abstract One primary goal of spinal fusion is to remove pain generating tissues and to alleviate the patient’s pain by stabilization of one or more motion segments. Posterior lumbar interbody fusion is widely used as a treatment method for chronic degenerative spondylosis. The PLIF procedure maintains decompression of neural elements and stabilizes fusion segments through anterior column fusion after disc removal. Various types of intervertebral cages have been developed to maintain the stability of fusion segments during the healing process. Introduction of these cages prevents the disc space from collapsing and maintains stability until the fusion mass has healed. Therefore, the primary purpose of intervertebral cage placement is to create a proper biomechanical environment through successful fusion. In order to accomplish this, it is necessary for the fusion segment to be built up as a stiff post operative structure through the intervertebral cage. Interbody fusion, or fusion across the disc space, can be performed by using several surgical approaches. Posterior lumbar interbody fusion, anterior lumbar interbody fusion, and transformational lumbar interbody fusion have unique advantages and potential complications associated with each approach. Each technique can stand alone or can be accompanied by supplemental segmental posterior instrumentation (posterior rods and pedicle screws most commonly). The purpose of all interbody fusion devices is to restore and maintain disc space height and normal sagittal contours (lordosis) and to increase the stability of the operated segment or segments. Stability and lordosis are obtained by stretching the annulus and supporting ligaments via distraction of the disc space. This stretching of the motion segment is termed “ligamentotaxis” and provides a biomechanically stable construct that will limit motion and permit fusion to develop. Distraction of the disc space also results in indirect decompression of the foramina. Posterior lumbar interbody fusion is used most often when decompression of a nerve root is required. For each approach, an annular window is created and a total discectomy performed to achieve clean bleeding Summary 47 endplates. This clean bone surface provides an optimal environment for fusion to occur. A posterior lumbar interbody fusion typically requires resection of a major portion of the posterior lumbar laminae and, frequently, near total facetectomies for levels above L5–S1. To obtain access to the disk space, the surgeon must retract the thecal sac and nerve roots medially. Through this approach, it is often difficult to place sufficiently large devices to gain stability and provide ligamentotaxis without injuring the nerve roots. Because of the increased risk of nerve root complications and relatively poor results with stand-alone posterior lumbar interbody fusion constructs, most posterior lumbar interbody fusion operations today use supplemental posterior instrumentation. Posterior instrumentation allows smaller stabilization devices to be placed within the disk space, which has the secondary effect of limiting nerve root injuries. Many of the posterior lumbar interbody fusion procedures are accompanied by posterolateral inter transverse process fusion. The literature investigated the effects of geometric properties, loading conditions and cage bone interface mechanics on the characteristics of several interbody cages. The biomechanical benefit of a stand alone two part cage is promising in spinal surgery to avoid surgical morbidities in damaged posterior muscles and facet joints caused by posterior instrumentation. This device addresses the stability required for interbody fusion, and supports the necessity of clinical trials using this alternative to the circumferential fixations. However, in the osteoporotic spine, supplementation with posterior fixation is recommended under various loading conditi |