الفهرس 
IntroductionOnly 14 pages are availabe for public view
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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
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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