Spinal stenosis is a narrowing of the canal in the spinal column that encases the spinal cord. The condition presses on the spinal nerves and can lead to pain, weakness, numbness, tightness or heaviness in the buttocks, calves or legs. The symptoms worsen when walking or standing. Sitting or leaning forward often opens up the narrowed space and eases symptoms. In severe cases, spinal stenosis can lead to loss of bladder or bowel control, sexual dysfunction or loss of feeling in one or both legs.

Researchers estimate up to 500,000 Americans have symptoms of spinal stenosis. The condition is most common in people over 50. Stenosis may be caused by an inherited abnormality or acquired disease. Inherited spinal stenosis occurs when the spinal canal is unusually small or has an abnormal curvature (scoliosis). Acquired spinal stenosis can occur through trauma, disease (like arthritis or a spinal tumor) or through degeneration of structures in the spine (like a herniated disk).

Treating Spinal Stenosis

Initially, doctors may try conservative therapy for patients experiencing symptoms of spinal stenosis. Physical therapy, anti-inflammatory medications, injections of steroid medication into the spinal canal and bracing can often reduce inflammation and relieve symptoms. But these treatments do not address the cause of the problem (i.e., the narrowing of the spine). When symptoms are severe or debilitating, surgery may be recommended.

In a laminectomy or spinal decompression, surgeons remove bone and sections of soft tissue that are pressing on the spinal nerves. Some patients also require spinal fusion to stabilize the spine. Small amounts of bone are taken from the hip and placed into the space between the two target vertebrae. Tiny screws and rods are usually implanted to hold the vertebrae in place. Over time, the bone fragments heal into a solid segment, permanently fusing the top and bottom vertebrae as a single unit.

The American Academy of Orthopaedic Surgeons estimates 325,000 spinal fusions were performed in 2005. About 162,000 of the procedures were done on the lower (lumbar) spine.

The TOPS™ System

Spinal fusion is successful in about 80 percent of patients. But the treatment prevents movement, or bending, between the two fused vertebrae. If only two vertebrae are fused, patients generally won't see any significant changes in mobility. However, recent research shows, over time, fusion can put more pressure on the vertebrae immediately above and below the fused section, leading to more disk degeneration.

Researchers are now testing a new type of device for patients with moderate to severe lumbar spinal stenosis. It's called the TOPS™ System, or Total Posterior Arthroplasty Implant.

The TOPS system is designed to stabilize the spine after decompression without the need for fusion. It consists of two titanium plates connected by a flexible core that's covered in a polycarbonate urethane sleeve. After decompression, the TOPS device is inserted into the space between the vertebrae. Four tiny screws hold it in place.

Stephen Robbins, M.D. is an Orthopaedic Surgeon at Columbia St. Mary's Hospital in Milwaukee. He says, after placement of TOPS, patients usually have immediate relief from symptoms. They are able to stand and walk as soon as they get out of recovery. They are out of the hospital in about two days.

With traditional fusion, it takes at least three months for the bones to heal and six months to a year for complete fusion. So rehabilitation is delayed. With the TOPS system, there is no need to wait for fusion to heal. Rehabilitation can begin quickly and patients get back to normal activities very quickly. In addition, the flexible core of the TOPS system enables near normal bending and range of motion in the spine. Robbins is hopeful that will take the pressure off adjacent vertebrae and reduce the risk of future deterioration of disks in upper and lower vertebrae.

TOPS is currently in a Phase III trial at 8 sites across the U.S. (A list of sites follows.) For more information, log onto http://www.clinicaltrials.gov. Then type the trial identification number in the search box: NCT00405691.

TOPS™ Study Sites

Century City Doctors Hospital, Beverly Hills, CA

Seton Medical Center, Daly City, CA

South Florida Spine Clinic, Fort Lauderdale, FL

St. Joseph Medical Center and Orthopaedic Associates, Baltimore, MD

The Boston Spine Group, Boston, MA

Buffalo Spine Group, Lockport, NY

Orthopedic Spine Care of Long Island, Melville, NY

Carolinas Medical Center Hospital - Neurosurgery and Spine Associates, Charlotte, NC

For information about the TOPS™ system:

http://www.impliant.com

For information about the TOPS clinical trial, log ontohttp://www.clinicaltrials.gov. Then type the trial identification number in the search box: NCT00405691

For general information on spinal stenosis and fusion:

American Academy of Orthopaedic Surgeons, public website

National Institute of Arthritis and Musculoskeletal and Skin Diseases

North American Spine Society