Evaluation of Interbody Cage Insertion in Treatment of Lumbar Disc Prolapse

Discectomy for lumbar disc herniation is one of the most common operation performed worldwide for lumbar-related symptoms. The basic principle of the various techniques is to relieve the nerve root compression induced by the herniation. Over the past 30 years, many technical improvements have decreased operative trauma by reducing incision size, thereby reducing postoperative pain and hospital stay and time off work, while improving clinical outcome. Magnification and illumination systems by microscope and endoscope have been introduced to enable minimally invasive techniques. Lumbar interbody fusion using cages has gained momentum in the recent years after approval of the cages by the FDA (United States Federal Drug Administration) for lumbar interbody insertion. The indications for this procedure remain controversial and include mechanical low back pain, degenerative disc disease, recurrent disc herniation, spondylolisthesis (grade I). In degenerative disc disease or following surgical discectomy, segmental stenosis occurs due to a combination of disc herniation, posterior osteophyte formation, facet overriding and hypertrophy and ligamentum flavum hypertrophy. All these factors combine to compromise the nerve root as it exits through the intervertebral foramen resulting in recurrent radiculopathy. In such cases, Lumbar inter body fusion using cages can open up the intervertebral foramen by maintaining or restoring disc height. On the other hand, there is considerable controversy surrounding the effectiveness of lumbar fusion for the treatment of low back pain. Among the different surgical approaches available, with or without instrumentation, none can be considered the "gold standard". The technique and results of inter body fusion were first reported by Cloward. It did not, however, gain widespread acceptance due to technical difficulties. Insertion of a rectangular bone graft makes it difficult to avoid nerve root trauma resulting in radicular deficit or irritation and dural tears. Non-union or bone graft extrusion were reported as well as bone graft collapse with subsequent segmental stenosis.In the past few years, rigid cages housing autogenous bone have become increasingly popular for the purpose of interbody fusion. Their ease of insertion has decreased the technical difficulties of the earlier Cloward approach and makes the procedure more reproducible. The rigidity of the cages also allows for the preservation of the disc space. Cages are available in a wide variety of shapes and designs, the most common being the cylindrical and rectangular wedge shaped cages.