Increasing numbers of patients, particularly the elderly, are undergoing surgery for lumbar stenosis. Indeed, canal stenosis is now the most common indication for lumbar spine surgery in elderly subjects. With the aging of the population the incidence of surgical decompressions will increase . Verbiest  introduced the concept of spinal stenosis and brought the condition to the attention of the medical world. Lumbar spinal stenosis refers to a pathological condition causing a compression of the contents of the canal, particularly the neural structures. If compression does not occur, the canal should be described as nar row but not stenotic . Degenerative disc disease is by far the most common cause of lumbar spinal stenosis. A bulging degenerated intervertebral disc anteriorly, combined with thickened infolding of ligamenta flava and hypertrophy of the facet joints posteriorly result in narrowing of the spinal canal. The site of compression may be central, lateral or a combination, of the two . As for many continuous characteristics, both canal size and dural sac size present a Gaussian distribution. When a canal size is too narrow for the dural sac size that it contains, stenosis occurs. An identical canal size can therefore be stenotic for one person while not being stenotic for another who happens to have a smaller dural sac size. Lumbar spinal stenosis is therefore a clinical condition and not a radio-
Fig. 1 a After a midline posterior skin and subcutaneous tissue incision, the dissection goes through the dorsolumbar fascia approximately 5 mm to the left of the midline, preserving the supraspinous ligamentous attachment to the lumbar fascia. The multifidus is detached from the left side of the spinous processes and laminar attachments. An osteotomy is performed with a curved chisel at the base of the spinous processes of the vertebrae above and below the stenotic levels. b Retractors are placed to keep the wound open and are being loosened at regular intervals to avoid damage to the retracted muscles. c The ligamentum flavum is detached with a freer elevator and then completely resected on both sides. The lower third of the upper laminae and the upper third of the lower laminae are resected using Kerrison rongeurs of varying widths and lengths. A plastic suction device, held in one hand, is also used as a retractor. With the other hand, the Kerrison rongeurs are used to remove the hypertrophic anterior portion of the facet joints and the overlying capsular tissues. The same instruments are used to partially undermine the roofs in the laminae while respecting the integrity of the laminae. The facet and lamina roof decompressions create a portal by which the neural foramina can be decompressed by means of an extralong (30-cm) Kerrison rongeur. The adequacy of decompression is checked with foraminal probes. d After removal of the retractors the supraspinous ligamentous/fascial complex with the os-teotomized spinous processes regain their initial positions by resting on the remainder of the neural arches. Both the lumbar fascia and the subcutaneous tissue and skin are closed in a standard fashion. (With permission from )
logical finding or diagnosis. In addition, a poor correlation between radiological stenosis and symptoms has been reported .
Conservative treatment of lumbar spinal stenosis comprises physiotherapy, anti-inflammatory medications, lumbar corset, and epidural infiltration, and it is generally accepted that surgery is indicated if well-conducted conservative management fails. The aim of the operation is to improve quality of life. In recent publications from the Maine lumbar spine study Atlas et al. [3, 4]report a greater improvement in patient recorded outcomes in surgically treated patients than nonsurgically treated patients both at a 1- and at 4-year evaluation. In a prospective 10-year study Amundsen et al.  found considerably better treatment results in a group of patients randomized to surgical treatment that those receiving conservative treatment. A meta-analysis of the literature in 1991 showed on average that 64% of surgically treated patients for lumbar spinal steno sis were reported to have good-to-excellent outcomes . It appears that the morbidity associated with surgical treatment of lumbar stenosis in the elderly is important as those patients often present with a number of preexisting en-docrinological, cardiovascular, or pulmonary comorbidi-ties [7, 20, 22]. An increased complication rate has also been shown to be associated with spinal fusion performed for lumbar stenosis in elderly patients . Therefore less invasive surgical approaches are of particular interest. We describe two less invasive techniques which appear interesting in the surgical handling of spinal stenosis, particularly in the elderly.
Wide decompressive laminectomy, often combined with medial facetectomy and foraminotomy, was formerly the standard treatment. In recent years, however, a growing tendency towards less invasive decompressive surgery has emerged as a logical surgical treatment alternative, sparing anatomical structures and decreasing the risk for postoperative instability. Stenosis in the elderly is due mainly to a combination of facet hypertrophy and soft tissue buckling. It is therefore logical to limit the resection to the causative structures, thus limiting damage and instability. One such procedure, laminarthrectomy, refers to a surgical decompression involving a partial laminectomy of the vertebra above and below the stenotic level combined with a partial arthrectomy at that level. Other less invasive and destructive techniques have recently been proposed. Among these are devices inserted between the spinous processes and aiming at abolishing postural lordosis at the level of the narrowed functional unit.
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