Study Design. A Cochrane review of randomized controlled trials.
Objectives. To collate the scientific evidence on surgical management for lumbar disc prolapse and degenerative lumbar spondylosis.
Summary of Background Data. Surgical investigations and interventions account for as much as one third of the health care costs for spinal disorders, but the scientific evidence for most procedures still is unclear.
Methods. A highly sensitive search strategy identified all published randomized controlled trials. Cochrane methodology was used for meta-analysis of the results.
Results. Twenty-six randomized controlled trials of surgery for lumbar disc prolapse and 14 trials of surgery for degenerative lumbar spondylosis were identified. Methodologic weaknesses were found in many of the trials. Only one trial directly compared discectomy and conservative management. Meta-analyses showed that surgical discectomy produces better clinical outcomes than chemonucleolysis, which is better than placebo. Three trials showed no difference in clinical outcomes between microdiscectomy and standard discectomy, but in three other studies, both produced better results than percutaneous discectomy. Three trials showed that inserting an interposition membrane after discectomy does not significantly reduce scar formation or alter clinical outcomes. Five heterogeneous trials on spinal stenosis and degenerative spondylolisthesis permit very limited conclusions. There were nine trials of instrumented versus noninstrumented fusion: Meta-analysis showed that instrumentation may facilitate fusion but does not improve clinical outcomes.
Conclusions. There is now strong evidence on the relative effectiveness of surgical discectomy versus chemonucleolysis versus placebo. There is considerable evidence on the clinical effectiveness of discectomy for carefully selected patients with sciatica caused by lumbar disc prolapse that fails to resolve with conservative management. There is no scientific evidence on the effectiveness of any form of surgical decompression or fusion for degenerative lumbar spondylosis compared with natural history, placebo, or conservative management. The Co-chrane reviews will be updated continuously as other trials become available.
In all studies of lumbar spine disorders, 10% of patients account for more than 80% of the total health care and social costs, and the 1% of patients who undergo surgery are the most expensive group. Although surgical investigations and interventions account for up to one third of the health care costs, 13 the scientific evidence for most procedures is unclear. Surgical practice and any proposed new developments should have a proper scientific basis, which should include randomized controlled trials (RCTs).
This article is based on two Cochrane reviews of surgical management for lumbar disc prolapse 25 and degenerative lumbar spondylosis, 26 which address these questions: 1) What evidence exists concerning the clinical effectiveness of lumbar spine surgery? and 2) What evidence exists concerning alternative forms and techniques of lumbar spine surgery?
The primary rationale for surgery in any form for disc prolapse is to relieve nerve root irritation or compression caused by herniated disc material. It is important to define the optimal management for specific types of prolapse. For example, different surgical procedures are probably appropriate if disc material is sequestrated rather than contained by the outer layers of the anulus fibrosus.
Chemonucleolysis using chymopapain was advocated at one point for contained lumbar disc prolapse (i. e., when there was no sequestration of fragment[s] into the spinal canal), 59 but the trial by Schwetschenau et al 58 instigated a moratorium by the Food and Drug Administration, and the drug was not released again for general use until 1982. Now, 17 years later, the role and effectiveness of chemonucleolysis still is disputed by spinal surgeons, making a systematic review of all available evidence especially valuable.
Several nonsystematic reviews consider the relative merits of microdiscectomy and automated percutaneous discectomy. In both treatments, smaller wounds are said to promote faster patient recovery with earlier hospital discharge, 36,52 but there still is no clear evidence about the clinical outcomes of these procedures. In the first clinical series of 420 patients who had laser discectomy, a 78% good or fair result was reported, but there was no control group, and outcome assessment was not blinded. 11 Subsequent studies have shown quite variable results.
There are two published meta-analyses on the surgical management of spinal stenosis 50,68 and one on the surgical management of degenerative spondylolisthesis. 42 These reviews suggest that decompression alone is the safest procedure and may give better results for patients with spinal stenosis, those with less than 8 years of clinical history, and elderly unfit patients. These studies also suggest that decompression combined with instrumented fusion may have some place for patients with degenerative spondylolisthesis, or for those with more than 15 years of history, but that there is a higher complication rate. However, these reviews were based mainly on uncontrolled, retrospective case series that reported widely varying results, and thus do not permit firm conclusions.
After more than 80 years, there still is considerable dispute as to whether lumbar fusion is an appropriate and effective method of managing back pain in patients who have degenerative lumbar spondylosis with no nerve root or cauda equina compression. Surgical technique varies widely. The nature and role of instability is poorly defined, and the clinical indications for surgery uncertain. 62 Indeed, when reported satisfactory clinical outcomes range from 16% to 95%, 67 it is particularly apposite to perform meta-analysis of the available evidence.
In recent years, there has been an explosion of surgical and commercial interest in widely varying methods of instrumented fusion in both Europe and the United States. The aforementioned meta-analysis of published case series of degenerative spondylolisthesis 42 suggested that fusion with pedicle screws produced a higher fusion rate (93% vs. 86%) than fusion without instrumentation, although the difference was not statistically significant and produced no difference in clinical outcomes (86% vs. 90%). Randomized controlled trials of fusion with instrumentation have appeared only in the past 6 years, and the results have not yet been collated. There is even less available scientific information about other methods of fusion, whether anterior or posterior.