[Role of surgery in spinal degenerative disease. Analysis of systematic reviews on surgical and conservative treatments from an evidence-based approach].

INTRODUCTION: The lifetime prevalence of invalidating back pain in general population caused by Spinal Degenerative Disease (SDD) is about 70-80%. Global costs related to this disease are enormous (1-2% gross domestic product). From an Evidence-based point of view, there is a striking discrepancy between the use of many available surgical techniques (especially for spinal fusion) and the lack of scientific support.

METHODS: The authors carefully reviewed all published metaanalysis on SDD therapies up to December 2003. Treatment recommendations were classified according to levels of evidence (strong, moderate, mild or lack of evidence) for both surgical and conservative measures.

RESULTS: Forty-four metaanalysis were selected (nine on lumbar surgery, three on cervical surgery and thirty-two on other therapies). Relating surgery, there is strong evidence favouring early laminectomy in cauda equina syndrome secondary to lumbar disc herniation; discectomy or microdiscectomy are superior to chemo-nucleolysis in lumbar prolapse and spondylosis; and fusion surgery (probably noninstrumented) in adult isthmic spondylolysthesis or degenerative spondylolysthesis with spinal stenosis. In cervical spondylosis and radiculomyelopathy, discectomy seems as effective as discectomy plus fusion, which does not seem to be better than untreated SDD beyond 24 months. Preoperative antibiotics seem to prevent infection in spinal surgery. No benefit of surgery is demonstrated in discogenic pain. None of conservative therapies are supported by strong evidence. Antidepressants improve pain perception but do not influence the functional status.

DISCUSSION: Although lumbar instrumented surgery has nearly doubled over two decades and the annual growth is about 20%, clinical results do not seem to have improved, not even global fusion rates. The increasing use of fusion surgery for cases other than spinal deformities, spondylolysthesis or spinal stenosis plus lysthesis may be related to multiple technical and clinical-epidemiological factors where huge financial and commercial interests must be considered. It is crucial to differentiate subsets of patients prone to benefit from surgery. It is discussed whether randomized trials incorporating sham operations are ethically justifiable, because of the lack of sound evidence for many spinal procedures. The efficacy of most conservative treatments is mild or moderate (mainly transient) and they should be probably used in combination. CONCLUSIONS. There is no strong evidence favouring most of surgical procedures for SDD from an evidence-based approach. It seems necessary that scientific organizations studying SDD create clinical guidelines relating its multidisciplinary and integral management, recognizing that, up to now, few interventions positively modify in the long-term the natural history of the disease.