Widening the Spinal Canal to Manage Cervical MyelopathyIn this article about cervical myelopathy, a new surgical method is described and results using it without spinal fusion are reported for a select group of adults. Cervical myelopathy is a degenerative condition that occurs with aging. Adults affected most often are 50 years old and older. The term myelopathy refers to any problem that affects the spinal cord. Cervical tells us the area affected is the cervical spine (neck region).
What kind of changes are we talking about? Well, pretty much anything that can narrow the space where the spinal cord travels down through the vertebrae. This space is called the spinal canal. Narrowing of the spinal canal is referred to as spinal stenosis. The cause of the stenosis could be bone spurs, thinning of the supportive discs, thickening of the spinal ligaments, or loss of vertebral bone height.
Patients with cervical myelopathy can experience a wide range of signs and symptoms. There can be difficulty walking, using the hands, bowel and bladder function, or even wasting of the muscles of the hands. When the muscles are affected, motor function, coordination, and muscle mass can change. Sometimes there is also a loss of normal sensation with numbness and tingling of the fingers and toes.
In addition, there can be debilitating pain. It's the pain that usually drives the patient to get treatment. What's the best way to treat this problem? Well, that is still being tested, debated, and discussed. The main thing is to take pressure off the spinal cord before the signs and symptoms become permanent. Conservative (nonoperative) care can be tried first, but many patients end up having surgery.
Anterior decompression is the most common procedure performed. The surgeon enters the spine from the front of the patient and removes the discs, bone spurs, or other soft tissues affecting the spinal cord. Often the surgeon must remove part (or all) of the vertebral bone that might be pressing on the discs. If the lamina (column of bone) is removed, the procedure is called a laminectomy. If the main body of the vertebra is removed, it's called a corpectomy.
Once any of these supportive structures have been removed, the spine must be stabilized with bone graft material, rods, screws, or other types of instrumentation. This type of surgery is major and has many potential complications.
Another (alternate) approach is a multilevel oblique corpectomy (MOC). The advantage of this procedure is that it can be done without fusing the spine. That can mean fewer complications and less risk of vertebral (spinal) instability. It is used with patients who have anterior spinal cord compression. This means the pressure on the spinal cord is toward the front of the spinal canal (closest to the vertebral body).
With a multilevel oblique corpectomy (MOC), a portion of the vertebral body is removed on a diagonal. The result is to widen the spinal canal, thus giving the spinal cord more space. The surgeon uses an anterolateral approach, reaching the vertebra from the front and side. The surgery is done from the most painful side where the compression is the worst. From this angle, the surgeon can also take the pressure off any pinched nerves as they exit the spinal canal.
The surgeon uses fluoroscopy, a special real-time form of X-ray that allows accuracy and enables the surgeon to avoid cutting blood vessels or nerves. As with the classic anterior decompression, any bone spurs encountered along the way are removed. The posterior longitudinal ligament (PLL) that tends to get thick as we age, buckles, and presses on the spinal cord or spinal nerves is also removed.
Some patients in this study had the oblique corpectomy done at just one cervical level. Most of the patients had two or more levels resected (removed). In all cases, the surgeon tried to take out less than half of the bone. This is called a limited bone resection. Because all other elements of the vertebral body and two of the three supportive bony columns are left intact, this procedure can be done without fusing the spine at the level of the decompression. And it can be done at multiple levels -- all without needing fusion.
But there is concern about the effectiveness and safety of this procedure. That's where the results of this study come in. The surgeons report on the results of over 500 levels surgically treated in the cervical spines of 268 patients. They found that using multilevel oblique corpectomy without fusion for cervical myelopathy was both safe and effective. Long-term results showed that patients were able to achieve stability without the fusion portion of the procedure.
They used a couple of different ways to measure the results. They assessed each patient's neurologic function before and after surgery using the modified Japanese Orthopaedic Association Scale. Pain intensity and duration was measured using the Neck Disability Index (NDI). The NDI also measures the effects of pain on daily function. X-rays, CT scans and MRIs were taken before and after to show the diameter of the spinal canal, alignment of the vertebrae, and position of the carotid arteries.
Almost 90 per cent of the patients reported improvement of symptoms and function with canal expansion following multilevel oblique corpectomy (MOC). Patients maintained spinal stability with only a few patients getting worse instead of better.
The main complication after MOC was Horner Syndrome from damage to one of the nerves that controls eye movement. Using an anterolateral approach for the incision leaves this particular nerve at risk for damage from moving it out of the way to get to the spine. Fortunately, this was a temporary problem for most of the affected patients. Eyelid drooping on one side is the primary symptom, which went away over time (usually within three months).
The authors conclude that lower overall complications and none related to bone grafting make this procedure worth considering. It does take some additional training and careful surgical technique. But for patients with diabetes, poor bone structure limiting fusion, and for heavy smokers, it offers a safe and effective way to treat painful, disabling cervical myelopathy.
Even with multiple levels of vertebral bones partially cut out, spinal stability is still present. Patients can get up and move early after the operation and without bracing or immobilization of any kind. The key to a successful result is to choose the right patient for the procedure. There can be no spinal instability (one vertebral body slipping or sliding around). Surgeon can expect to have fewer complications over time as they become more familiar with the technique.
Salvatore Chibbaro, MD, et al. Multilevel Oblique Corpectomy Without Fusion in Managing Cervical Myelopathy: Long-Term Outcome and Stability Evaluation in 268 Patients. In Journal of Neurosurgery: Spine. May 2009. Vol. 10. No. 5. Pp. 458-465.
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