[Discogenic low back pain and degenerative lumbar spinal stenosis - how appropriate is surgical treatment?].

Surgery in acute and/or chronic low back pain is still a matter of intensive and controversial discussions. A vast number of minimally invasive or so called semi-invasive procedures have been published in the last 3 decades, but evidence-based data on efficacy and benefit of most of these techniques are still lacking. However, empirical data suggest good or at least satisfactory clinical results for a limited number of procedures if they are applied under restrictive indication criteria. Discogenic low back pain and lumbar spinal stenosis belong to the most frequent diagnoses associated with low back pain. This article gives a survey on definitions, indication criteria and modern surgical or semi- invasive techniques used for the treatment of these two pathologic entities. Discogenic low back pain: This clinical and morphological entity is defined as low back pain arising mainly from disc degeneration. Pain generators are usually nociceptors in the cartilaginous endplates, in the outer anulus fibrosus as well as in the periosteum of the vertebral bodies. Clinical symptoms correlate with morphologic changes detected with MR-imaging (modic type I) or with contained disc protrusions mainly without neurological symptoms. Surgery is rarely indicated, spontaneous remissions occur in more than 60% of all cases. Spinal fusion has been the only surgical option in cases which did not respond to conservative therapy. Recently, electro-thermal modulation of the posterior anulus fibrosus has been published as a semi- invasive technique to relieve low back pain generated by fissures in the outer anulus and ingrowing nociceptors (intradiscal electro-thermal therapy, IDET(TM)). First results are promising, however, prospective randomised studies comparing this technique with conservative therapy are still lacking. The same is true for artificial nucleus pulposus replacement using hydrogel cushions implanted in the intervertebral space after removal of the nucleus pulposus from posterior or through an anterior approach (PDN, prosthetic disc nucleus(TM)). In cases with severe disc degeneration total disc replacement is another innovative option (ProDisc(TM)). Two metal endplates with titanium surface coating are implanted through a minimal invasive anterior approach (mini-laparotomy). A polyethylene inlay anchored in the caudal endplate holds the distance between the endplates and preserves the physiological range of motion between the two vertebral bodies. Degenerative lumbar spinal stenosis: Narrowing of the spinal canal due to degenerative changes of the disc, the facet joints and thickening of the yellow ligament is a geriatric disease which is diagnosed in increasing numbers within the last 10 years. More than 80% of the patients present with low back pain in association with neurogenic claudication. Neurological symptoms at rest are less frequently found. The spontaneous course shows progressive symptoms in more than 50% of all patients. More than 35% of the patients have associated diseases which might influence the perioperative course, complication rates and outcomes of surgery. Surgery is indicated in patients with progressive neurological symptoms, unacceptable decrease of quality of life or progressive intractable pain. In patients with mainly "leg symptoms" microsurgical mono- or multisegmental decompression is the procedure of choice. If low back pain is predominant and associated with degenerative instability such as degenerative spondylolisthesis or lumbar scoliosis, decompression must be combined with instrumented spinal fusion. In general a restrictive indication for surgery must be recommended especially for spinal fusion procedures. Non-fusion techniques such as intradiscal electro thermal therapy or spine arthroplasty with replacement of nucleus pulposus or total disc show promising early results; however, little is known about the long-term effect. It should be a principle to apply surgery in the least invasive way.