The human spine successfully performs the major functions of providing motion, support, and protection of the body’s neurological structures. This complex interaction is possible because of the spine’s complicated structure. The delicate balance between bone and intervertebral disc forms multiple mobile segments through which the spinal cord and its nerve roots pass. Unfortunately, in many cases degenerative changes within the spine beginning with degeneration of the disc causes narrowing or stenosis of the canal and foramina through which the spinal cord and nerves pass. Bulging discs, arthritic joints with bone spurring, and the hypertrophy or thickening of ligaments contribute to the impingement of these neurologic structures usually occurring in patients in their 5th decade of life and becoming more common with each following decade.
As spinal stenosis progresses, soft tissues structures such as the ligamentum flavum protecting the dura or lining of the neurological structures thicken in response thereby aggravating the stenosis. This compression may cause the symptoms of leg and buttock pain, tingling, numbness, and sometimes weakness with activity such as walking when nutritional demands of the nerves are higher than the nutritional demands of nerves at rest. A key component in the diagnosis of spinal stenosis is that these symptoms are relieved with rest (such as sitting down) or with positional changes (such as leaning, or flexing forward). Resting causes less nutritional demands for the nerves and leaning forward may decrease compression by preventing the ligamentum flavum from buckling which occurs when standing fully erect.
Historically, the mainstay of treatments for spinal stenosis has been conservative including physical therapy, activity modification, medications such as NSAIDS, and potentially epidural steroid injections. Fortunately, although potentially progressive, spinal stenosis is not life or limb threatening. The decision to pursue operative intervention in the presence of failed conservative treatment is a decision patients make with their physicians about the quality of their life.
If surgery is indicated after appropriate work up and failure of all non-operative management in the presence of debilitating, life-altering pain; laminectomy has historically been the gold-standard of treatment. However, depending on the location of the stenosis, decompression surgery may potentially destabilize the spine. As a result, prospective trials have supported the emerging consensus that decompression with spinal fusion offer patients the best clinical results. Unfortunately, decompression and fusion spinal surgery is not a good alternative for some patients with its associated increased operative time, blood loss, recovery, and potential neurological complications.
Because of this unfortunate reality, less invasive as well as motion sparing technologies have been developed to deal with spinal stenosis which is a condition usually occurring in an older more fragile population. The X STOP implant was introduced to limit extension at stenotic motion segments while preserving flexion, rotation, and lateral bending. The X STOP device is implanted between the spinous processes of the pathologic motion segment after minimal dissection and without disrupting the spinal canal or stability of the spine. As an interspinous process implant, the X STOP device has the added benefit of unloading the degenerative motion segment. In a cadaveric study using magnetic resonance imaging (MRI) to quantify the dimensions of the spinal canal and foramina in extension, the X STOP was shown to significantly increase all cross-sectional areas. Another similarly designed study demonstrated the X STOP to significantly decrease intervertebral disc pressure at the implanted level while maintaining normal pressure and kinematics at adjacent, uninstrumented levels. Most importantly, in a randomized study comparing 100 X STOP patients with 91 control patients, the X STOP patients had significantly improved outcomes and satisfaction rates while maintaining a very low and favorable complication rate.
The simplicity and ease of implanting the X-STOP device complements its potential to greatly enhance the quality of life of patients suffering from spinal stenosis. Besides a very low complication rate, a very short operative time, and minimal blood loss, the device and its associated technique has the added advantages of preserving the native spinal architecture, providing a completely reversible treatment, maintaining spinal motion and the normal kinematics of adjacent spinal motion segments, and allowing immediate and expedited recovery and rehabilitation. In a patient with spinal stenosis and positional, debilitating neurogenic claudication, interspinous process decompression with the X STOP device is proving to be a very good minimally invasive, safe, and efficacious option.