- To support the fusion of the vertebrae, the surgeon uses a steel rod, extending from the bottom to the top of the curve. (More than one rod may be used depending on the type of curve, and whether outward curvature of the spine is present.)
- The rod is attached by hooks that are suspended from pegs inserted into the bone.
- Similar to changing a tire, the steel rod is jacked up and then locked into place to support the spine securely. The surgeon is then ready to fuse the vertebrae together.
- After this operation, patients must wear a full body cast and lie in bed for 3 - 6 months until fusion is complete enough to stabilize the spine.
- After 1 - 2 years, the steel rod is not really necessary, but it is almost always left in place unless infection or other complications occur.
The Harrington procedure is very difficult to undergo, particularly for young people, and although the operation can achieve a 50% correction of the curve, studies have reported a 10 - 25% loss in this correction over time. The procedure does not correct the rotation of the spine and, therefore, does not improve an existing rib hump that was caused by the rotation. The operation does not interfere with normal pregnancies and deliveries later in life.
Certain complications may occur from this procedure:
- About 40% of Harrington patients have a condition called the flat back syndrome, because the procedure eliminates normal lordosis (the inward curving of the lower back). Flat back syndrome from the Harrington procedure does not cause any immediate pain. In later years, however, the disks may collapse below the fusion, making it difficult to stand erect, and the condition can cause significant pain and emotional distress.
- Studies have reported that 5 - 7 years after their surgery, between a fifth and a third of patients who had the Harrington procedure experienced low back pain. In such cases, however, the pain was not severe enough to interfere with normal activities and did not require additional surgery.
- Children younger than age 11 whose skeleton is immature and who have the Harrington procedure have a fairly high risk for a specific curve progression called the crankshaft phenomenon. This condition occurs when the front of the fused spine continues to grow after the procedure. The spine cannot grow longer, so it twists and develops a curvature. However, in one study that followed patients for 5 - 16 years, crankshaft curve progression was moderate, with the Cobb angle averaging 9 degrees and rotation averaging 7 degrees.
Cotrel-Dubousset Procedure. The Cotrel-Dubousset procedure corrects not only the curve but also possibly rotation, and it does not cause flat back syndrome.
With this procedure, a surgeon cross links parallel rods for better stability in holding the fused vertebrae. Patients often go home in 5 days and may be back in school in 3 weeks.
The Texas Scottish-Rite Hospital (TSRH) Instrumentation. The Texas Scottish-Rite Hospital (TSRH) instrumentation is similar to the Cotrel-Dubousset procedure in that it uses parallel rods and other devices that reverse rotation as well as improve curvature. TSRH, however, uses smooth rods and hooks that are designed to make removal or adjustment easier later on if complications arise. Complications are similar to the Cotrel-Dubousset procedure.
Additional Forms of Instrumentation. Other instrumentation procedures have refined the hardware used in the Harrington and Cotrel-Dubousset operations. Some, but not all, are listed below:
- Luque instrumentation is used primarily in people whose scoliosis is due to problems of nerves and muscles, such as in children with cerebral palsy. After surgeons developed Luque instrumentation to help maintain normal lordosis, experts hoped that bracing would not be needed. Several studies showed, however, that without braces, correction was lost after this operation, and the procedure may have a higher risk for spinal cord injury than other standard procedures.
- Wisconsin segmental spine instrumentation (WSSI) is as safe as the Harrington rod and nearly as strong as the Luque instrumentation.
Instrumentation for Anterior Approach. The anterior approach, in which the surgeon performs the operation by opening the chest wall, requires specific hardware. Halm-Zielke instrumentation, for example, uses TSRH instrumentation with bone grafts constructed from ribs to prop open the spaces between the disks. It allows true three-dimensional curve correction. However, it does not solve specific problems -- higher risks for kyphosis (an outward curve) and pseudoarthrosis (a false joint at the fusion site). Variants using two rod systems, fusion cages, or other instruments appear to improve this procedure.
Approaching the Spine
Posterior Approach (Through the Back). Many surgeons use a posterior approach for scoliosis, which reaches the surgical area by opening the back of the patient. It has been the gold standard for decades and is generally used with Harrington instrumentation. The posterior approach has advantages and disadvantages:
- Advantages. Surgeons are familiar with it, so fusion rates are excellent, curve correction is good, and it has few complications.
- Disadvantages. Preadolescent children are at risk for the crankshaft phenomenon (a worsening of the curve) later on. (Newer posterior instrumentation, such as the Isola instrumentation, may prevent this occurrence.) The posterior approach also does not always correct hypokyphosis (the loss of normal outward curvature) in the thoracic (upper) spine. The procedure is not always effective for curves in the thoracolumbar region (where the upper and lower spine meet) and may cause spinal abnormalities there.
Anterior Approach (Through the Front). Increasingly, surgeons are using the anterior approach, in which the surgeon performs the operation through the chest wall (called a thoracotomy). With the anterior approach, the surgeon makes an incision in the chest, deflates the lung, and removes a rib in order to reach the spine. This rib can be used during the operation as a strut to support the spine. It also may be repositioned within the patient until it is used for bone grafting during fusion.
The anterior approach also has its advantages and disadvantages:
- Advantages. Because the frontal approach allows the procedure to be performed higher up in the spine than with standard procedures, the patient may have a lower risk for lower-back injury later on. In addition, transfusion rates are much lower with the anterior approach. With increasing experience, the anterior approach is as effective as the posterior approach.
- Disadvantages. It is a newer procedure than the posterior approach, and, among inexperienced surgeons, carries a higher risk for complications than in the more standard posterior approach. Poorer lung function after surgery has been noted, possibly because the wide chest incision impairs the chest muscles, which can affect lung function afterward. Hardware failure rates may also be higher in the anterior approach than in the posterior approach. Increasing experience and newer hardware designs are reducing many of these problems.
Previous Section
Review Date: 04/06/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
