The X-STOP is a minimally invasive surgical procedure designed to alleviate painful symptoms of lumbar spinal stenosis. The device is inserted in the back of the spine to prevent a patient from bending too far backward at the narrowed segment, a position that for patients with spinal stenosis can cause leg pain (sciatica) and/or low back pain.
The device is made by Kyphon, Inc., Sunnyvale, California, and was approved for use by the FDA in November 2005.
The X-STOP, which stands for "Interspinous Process Decompression System", is a titanium implant that is inserted into the back at the lumbar spine segment that has symptomatic spinal stenosis (narrowing of the boney canal which can cause crowding of the nerve roots). The X STOP implant is placed between the spinous processes in the back of the lumbar level (one or two levels) where the stenosis is present. Spinous processes are the thin projections from the back of the spinal bones to which muscle and ligaments are attached - they can usually be felt just under the skin as the boney protrusions running down the back of the spine.
The design of the X-STOP prevents the patient from hyper-extending their spine (bending too far backward) at the segments that are treated, but still allows patients to bend forward (flexion) and also rotate their lower back to a certain extent, so it maintains some of the motion in the low back. For patients who meet certain criteria, insertion of the X-STOP may be considered as an alternative to an open laminectomy surgery, or even laminectomy and spinal fusion, the current standards of care.
The device is not appropriate for all patients with symptoms of lumbar spinal stenosis. Candidates for the X-STOP must:
Have received a clinical diagnosis of lumbar spinal stenosis, confirmed by X-ray, CT or MRI scan
Suffer from leg pain and/or buttock pain and/or groin pain (neurogenic intermittent claudication), either with or without low back pain
Have moderately impaired ability to physically function, with relief from symptoms experienced when flexing forward (bending forward at the waist)
Have completed at least six months of non-surgical treatment (such as pain medication, physical therapy, epidural injections) without satisfactory pain relief
Be over 50 years old
Significant stenosis at only one or two levels of the spine
In addition, there are some patients with lumbar spinal stenosis who fit the above criteria but who nonetheless should not use the X-STOP. The device should not be used by people who have:
An allergy to titanium or titanium alloy
Spinal anatomy that would prevent implantation of the device or cause it to be unstable in the body (e.g. ankylosing spondylitis at the operative level, spinal instability such as most grades of spondylolisthesis, fracture of the spinous process or pars interarticularis, or significant scoliosis curvature)
Cauda equina syndrome, which is multiple spinal nerve compression that causes bowel or bladder dysfunction
Severe osteoporosis, because the device is adjacent to bones in the spine and cannot function if they may be weakened by osteoporosis
A blood infection or infection of the lower back where the surgery is planned
Certain types of abnormal spinal anatomy at the operative site, including previous laminectomy
Widespread stenotic changes in the lumbar spine
The approach to spine is from the back, with the patient typically lying on the side or belly on the operating table
Local anesthesia may be used so the patient remains awake, although many surgeons recommend a general anesthetic.
A 2 to 3-inch long incision in the skin of the back is made over the affected segment level
The X-STOP is inserted between the spinous processes, under the ligament at the very back of the spine, and secured in position.
The surgical procedure to insert the X-STOP is short relative to more extensive types of back surgery such as an open laminectomy, and typically ranges from about 30 minutes to one hour. There is minimal removal of bone or soft tissue as part of the procedure, and the implant is not positioned close to nerves or the spinal cord, but rather behind the spinal canal, between the bony spinous process.
Although the X-STOP procedure can be performed on an outpatient basis, meaning that the patient may go home the day of the procedure, many physicians recommend an overnight stay in the hospital for certain patients. Patients are usually encouraged get out of bed and walk the same day as the surgery.
Complications that are thought to be more relevant and common to implantation of the X-STOP device are:
Failure of the device/procedure to relieve symptoms and/or improve the patient’s ability to function in activities of daily living
The need for additional surgery, which could include removal of the implant
The risk of the implant becoming dislodged or moving out of place
The implant is not positioned correctly, which could make the pain worse
A fracture of the spinous process while inserting the X-stop, or even after the surgery
A foreign body reaction (ex. allergic reaction)
A mechanical failure of the implant, which has two parts
Patients contemplating use of the X-STOP are advised to ask their surgeon about risks, and about the complications the surgeon has seen in using the device in his or her practice, including the risk that the surgery may not alleviate the patient’s leg pain. Adverse events involving medical devices, including some related to the X-STOP, must be reported by law to the Food and Drug Administration and are documented on the FDA website.
By: Jack Zigler, MD
October 24, 2007
