Spinal instrumentation is a method of straightening and stabilizing the spineafter spinal fusion, by surgically attaching hooks, rods, and wire to the spine in a way that redistributes the stresses on the bones and keeps them in proper alignment.
Spinal instrumentation is used to treat instability and deformity of the spine. Instability occurs when the spine no longer maintains its normal shape during movement. Such instability results in nerve damage, spinal deformities, and disabling pain. Spinal deformities may be caused by:
- Birth defects.
- Marfan syndrome.
- Neuromuscular diseases.
- Severe injuries.
Curvature of the spine (scoliosis) is usually treated with spinal fusion andspinal instrumentation. Scoliosis is a disorder of unknown origin. It causesbending and twisting of the spine that eventually results in distortion of the chest and back. About 85% of cases occur in girls between the ages of 12-15, who are experiencing adolescent growth spurt.
Spinal instrumentation serves three purposes. It provides a stable, rigid column that encourages bones to fuse after spinal-fusion surgery. Second, it redirects the stresses over a wider area. Third, it restores the spine to its proper alignment.
Different types of spinal instrumentation are used to treat different spinalproblems. Several common types of spinal instrumentation are explained below.Although the details of the insertion of rods, wires, and hooks varies, thepurpose of all spinal instrumentation is the same--to correct and stabilize the backbone.
The Harrington Rod is one of the oldest and most proven forms of spinal instrumentation. It is used to straighten and stabilize the spine when curvature is greater than 60 degrees. It is an appropriate treatment for scoliosis.
Advantages of the Harrington rod are its relative simplicity of installation,the low rate of complications, and a proven record of reducing curvature ofthe spine. The main disadvantage is that the patient must remain in a body cast for about six months, then wear a brace for another three to six months while the bone fusion solidifies.
Luque rods are custom contoured metal rods that are fixed to each segment (vertebra) in the affected part of the spine. The main advantage is that the patient may not need to wear a cast or brace after the procedure. The main disadvantage is that the risk of injury to the nerves and spinal cord is higher than with a some other forms of instrumentation. This is because wires must bethreaded through each vertebra near the spinal column, increasing the risk ofsuch damage. Luque rods are sometimes used to treat scoliosis.
Drummond instrumentation, also called Harri-Drummond instrumentation, uses aHarrington rod on the concave side of the spine and a Luque rod on the convexside. The advantage is that each vertebra segment is fixed, with the risk ofnerve injury decreased over Luque rod instrumentation. The disadvantage is that, like Harrington rod instrumentation, the patient must wear a cast and abrace after surgery.
Cotrel-Dubousset instrumentation uses hooks and rods in a cross-linked pattern to realign the spine and redistribute the biomechanical stress. The main advantage of Cotrel-Dubousset instrumentation is that, because of the extensivecross-linking, the patient may have to wear a cast or brace after surgery. The disadvantage is the complexity of the operation and the number of hooks and cross-links that may fail.
Zeilke instrumentation is similar to Cotrel-Dubousset instrumentation, but isused to treat double curvature of the spine. It requires wearing a brace formany months after surgery.
The Kaneda device is used to treat fractured thoracic or lumbar vertebrae when it is suspected that bone fragments are present in the spinal canal. Variations on the basic forms of spinal instrumentation, such as Wisconsin instrumentation, are being refined as technology improves. A physician chooses the proper type of instrumentation based on the type of disorder, the age and health of the patient, and on the physician's experience.
Since the hooks and rods of spinal instrumentation are anchored in the bonesof the back, spinal instrumentation should not be performed on people with serious osteoporosis. To overcome this limitation, techniques are being explored that help anchor instrumentation in fragile bones.
Spinal instrumentation is performed by a neuro and/or orthopedic surgical team with special experience in spinal operations. The surgery is done in a hospital under general anesthesia. It is done at the same time as spinal fusion.
The surgeon strips the muscles away from the area to be fused. The surface ofthe bone is peeled away. A piece of bone is removed from the hip and placedalong side the area to be fused. The stripping of the bone helps the bone graft to fuse.
After the fusion site is prepared, the rods, hooks, and wires are inserted. There is some variation in how this is done based on the spinal instrumentation chosen. In general, Harrington rods are the simplest instrumentation to install, and Cotrel-Dubousset instrumentation is the most complex and risky. Once the rods are in place, the incision is closed.
Spinal fusion with spinal instrumentation is major surgery. The patient willundergo many tests to determine that nature and exact location of the back problem. These tests are likely to include X-rays, magnetic resonance imaging (MRI), computed tomography scans (CT scans), and myleograms. In addition, thepatient will undergo a battery of blood and urine tests, and possibly an electrocardiogram to provide the surgeon and anesthesiologist with information that will allow the operation to be performed safely. In Harrington rod instrumentation, the patient may be placed in traction or an upper body cast to stretch contracted muscles before surgery.
After surgery, the patient will be confined to bed. A catheter is inserted sothat the patient can urinate without getting up. Vital signs are monitored,and the patient's position is changed frequently so that bedsores do not develop.
Recovery from spinal instrumentation can be a long, arduous process. Movementis severely limited for a period of time. In certain types of instrumentation, the patient is put in a cast to allow the realigned bones to stay in position until healing takes place. This can be as long as six to eight months. Many patients will need to wear a brace after the cast is removed.
During the recovery period, the patient is taught respiratory exercises to help maintain respiratory function during the time of limited mobility. Physical therapists assist the patient in learning self-care and in performing strengthening and range of motion exercises. Length of hospital stay depends on the age and health of the patient, as well as the specific problem that was corrected. The patient can expect to remain under a physician's care for many months.
Spinal instrumentation carries a significant risk of nerve damage and paralysis. The skill of the surgeon can affect the outcome of the operation, so patients should look for a hospital and surgical team that has a lot of experience doing spinal procedures.
After surgery there is a risk of infection or an inflammatory reaction due tothe presence of the foreign material in the body. Serious infection of the membranes covering the spinal cord and brain can occur. In the long-term, theinstrumentation may move or break, causing nerve damage and requiring a second surgery. Some bone grafts do not heal well, lengthening the time the patient must spend in a cast or brace, or necessitating additional surgery. Castingand wearing a brace may take an emotional toll, especially on young people.Patients who have had spinal instrumentation must avoid contact sports, and,for the rest of their lives, eliminate situations that will abnormally put stress on their spines.
Many young people with scoliosis heal with significantly improved alignment of the spine. Results of spinal instrumentation done for other conditions varywidely.