Introduction
Lumbar spinal stenosis is defined as the narrowing of either the spinal canal or neural foramina.Underlying causes for the stenosis are hypertrophy of the ligament flavum and facet joints, osteophytes, spondylolisthesis and disc protrusion and commonly a combination of these causes is present (Figure 1)1,2.As spinal stenosis is a disease that is caused by the degeneration of the spine,patients aged 50 years and older are affected.Neurogenic intermittent claudication (NIC) is the most common and most described symptom associated with lumbar spinal stenosis3. Symptoms of NIC include back pain and radiating pain to the buttocks,thighs and/or legs and numbness buttocks,thighs and/or legs. The complaints become worse on prolonged standing,and are often exacerbated with walking,activity or lumbar extension.The symptoms are relieved with sitting,lying,or lumbar flexion explaining that patient with more severe symptoms may walk and stand in a characteristic bent position to relieve the pain. Biomechanically, relief of pain by lumbar flexion is explained by the increase of dimension of the spinal canal and neural foramina during flexion which reduces the compression of theneural structures of the spine and results in relief of the pain4.After diagnosis,initial treatment will focus on nonoperative treatment and may includeanalgesics, nonsteroidal anti-inflammatory medication, epidural steroid injections,oral steroids and physical therapy. For decades decompressive surgery alone or combined with fusion was the only surgical treatment option to patients who failed to respond to the nonoperative therapies. The reported success rate of decompressive surgery is quite variable,and the procedure is associated with a relatively high complication and reoperation rate5,6,7.Turner's meta-analysis of surgery for lumbar spinal stenosis reported good to excellent results ranging from 26 to 100%8. Decompressive surgery was seen as the gold standard for patients suffering from spinal stenosis. Recently, several studies indicate that patients who underwent surgery showed more improvement than patients who were treated nonsurgically, supporting a shared decision-making approach among physicians and patients when considering treatment options for lumbar spinal stenosis7,9. Based on these studies,the fact that the indicated patient population is an older population that may not be able to undergo general anaesthesia required for a decompressive surgery and that over the past several years, the current trend in surgery has been shifted to minimal soft-tissue dissection and to preserving as many structures of the spinal segment as possible, a new treatment alternative has been developed.
Interspinous decompression system
The new alternative treatment option is commonly known as interspinous decompression system as the device is implanted between the spinous processes.The working mechanism is based on the principle of reducing the pathologic extension at the symptomatic level, while allowing flexion, bending and axial rotation. Although interspinous decompression systems ar