الفهرس 
Historical perspectives.Only 14 pages are availabe for public view
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Abstract
Since the 1930s, the relationship between disc herniation and sciatica has been well recognized. Since that time, intraoperative tools have been developed to facilitate surgical approaches and treatment of disc disease. With the introduction of the operating microscope, Yasargil and Caspar both described the minimally invasive concept of microdiscectomy. During the same period, biochemical advances in the treatment of disc herniations were also developed. In 1964, Smith was able to dissolve the nucleus pulposus in a rabbit model via percutaneous enzymatic applications; this technique was later successfully applied in humans.
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In 1975, Hijikata described the first percutaneous discectomy, which later evolved into automated discectomies.
Since the 1990s, with the application of video imaging to standard endoscopy, minimally invasive endoscopic and thoracoscopic procedures have gained rapid use and have diversified in their clinical applications.
MED is a unique approach to the surgical management of herniated lumbar disc.It combines the standard lumbar microsurgical technique with the endoscopy.It has the same goal of conventional open discectomy: Direct decompression of the affected nerve root.
This is accomplished by applying the standard surgical technique through a small tubular retractor and under endoscopic visualization. The enhanced view associated with good illumination and magnification of the endoscope allow a very good sight of the details, and enabling the surgeons to successfully address free disc fragment pathology and lateral recess stenosis.
The minimal invasiveness of MED and its small incision could decrease operative blood loss and reduce postoperative pain.
MED also allowed earlier ambulation, shortened the duration of hospitalization, and enabled the earlier resumption of normal activities.
As the clinical results are comparable with those obtained with the conventional open discectomy or microdiscectomy, MED appears to be a useful and reliable procedure for removing herniated tissue via a posterior approach. .
When the surgical outcomes and overall experience for microendoscopic discectomy are compared with those for percutaneous techniques such as chemonucleolysis, APLD, modified nucleotomy, and transforaminal endoscopic techniques, the microsurgical approach seems to be superior in most areas. Obviously, laser discectomy has no application in cases with extruded or sequestered fragments, and none of the other techniques addresses lateral recess or foraminal stenosis, which are occasionally encountered unexpectedly.
However, there are still indications for APLD, laser disc ablation, endoscopic techniques, and nucleotomy for very carefully selected patients. Despite the relative ease of performance in some cases, however, none of these methods has found a place in the hands of the majority of surgeons, because of the paucity of long-term results, the potential and real complication rates, or the learning curve for acquisition of the required technical skills. With the tremendous advances in neuroimaging, better understanding of the pathophysiological features of disc disease, and innovations in technological development, the pursuit of new, minimally invasive methods to treat lumbar disc disease should continued.
In this study, MED was performed on 30 patients from June 2002 to February 2005 . Males were 21, females were 9, and the mean age was 34(17-54) years. In 4 patient the affected disc level was L3-L4, in 22 L4-L5, and in 4 L5-S1. Patients had persistent radiculopathy for at least 2 months ,which fail to respond to conservative treatment , and may be associated with positive tension signs and/or neurological deficits. All patients had associated relevent radiological abnormalities.
The mean post-operative hospital stay was 2 days. The mean operation time was 123 minutes. The mean blood loss was 243 ml . All patients began to walk one the same operative day.
The mean JOA score was improved from 9.7±2.6 preoperatively to 26.5±2.5 postoperatively.
The mean period before return to work or school was 21 days.
There was 2 cases of dural tear without consequences, and one case of nerve root injury.
However, the difficulties of this endoscopic procedure were evident, the limited exposure because the surgical field is limited to the 16-18 mm of the working tube and two-dimensional video display. The potential injury of dura or the nerve root ,and the prolonged surgical time remain as matters of serious concern. MED requires a considerable experience.
With the increasing popularity of the MED and METRx systems, further applications have been described. Foley et al, in 1999, had described the microendoscopic approach for far lateral lumbar disc herniation.
Issac et al, in 2003), had performed MED for recurrent lumbar disc herniation.
Adamson ,in 2001,successfully used MED system in performing endoscopic cervical foraminotomy in 100 patients.
Guiot and colleagues in 2002 described the technical feasibility of decompression of lumbar stenosis via the MED system.
In 2002, Palmer et al used the tubular retractor system in microscopic lumbar discectomy.