Scoliosis Research Society (SRS)
An International Organization Dedicated to the Education, Research and Treatment of Spinal Deformity
Our Mission is to Foster Optimal Care for All Patients with Spinal Deformities
Distraction-based procedures include expandable spinal implants that work by controlling the spinal deformity, while still allowing the spine to grow until the child reaches an appropriate size or age for a more permanent solution, like spinal fusion. There are several different types of posterior distraction systems. The rods are periodically lengthened by relatively minor procedures usually performed every 6 months.
Growing rods are a spine-based system where the curve is spanned by one or two rods under the skin to avoid damaging the growth tissues of the spine. The rods are attached to the spine above and below the curve with hooks or screws at either end of the rod (Figure 8). Limited fusion is performed at each of the hook/screw foundation sites. The curve can usually be corrected by fifty percent at the time of the first operation. After the rods are implanted, patients are prescribed a special brace to wear for several months. The child then returns every six months to have the rods "lengthened" each) until the spine is closer to maturity. This is usually an outpatient procedure performed through a small incision. When the child becomes older and the spine has grown, the doctor will remove the instrumentation and perform a formal spinal fusion operation. In the past, this procedure had a very high complication rate, most of which were related to the instrumentation (hook dislodgement, rod breakage). Newer techniques are more promising but treatment with growing rods remains a long, difficult therapy for the child.
Figure 8 - Growing rods are a spine-based system where the curve is spanned by one or two rods under the skin to avoid damaging the growth tissues of the spine. The rods are attached to the spine above and below the curve with hooks or screws at either end of the rod.
Rib Based Systems, such as Vertical Expandable Prosthetic Titanium Rib (VEPTR), are systems used for treatment of thoracic insufficiency syndrome in skeletally immature patients. Thoracic insufficiency syndrome (TIS) is usually associated with uncommon three-dimensional deformities of both the spine and rib cage. Several types of rib-based expansion thoracoplasty operations can be used for different types of deformities to gain chest volume (to allow for growth of the underlying lungs) while indirectly correcting the scoliosis without spine fusion. This surgery can be extensive; devices are placed under the scapula (shoulder blade) and are attached to the ribs near the neck and continue down to either the ribs, spine, or to the pelvis near the waist (Figure 9). This helps to stabilize the surgically expanded chest wall constriction (expansion thoracoplasty). To keep up with a patient's growth, the devices are expanded twice a year in outpatient surgery through small incisions. Currently, there are a limited number of institutions offering rib-based surgery. Your child's spine surgeon can advise whether your child's condition is appropriate for this treatment option and to provide referral information, if needed. Some centers are using the rib-based devices as a means to straighten the spine indirectly via the ribs and chest wall.
Figure 9 - Rib-based devices are placed under the scapula (shoulder blade) and are attached to the ribs near the neck and continue down to either the ribs, spine, or to the pelvis near the waist. This is an example of a rib-rib device and a rib-spine device.
This is a newer technology that uses growing rod technology. Here the ribs, not the spine, are used as the upper anchor. The fusion of the upper portion of the spine is avoided.
Growth rods are currently the most commonly used distraction-based technique and which have the advantage of not interfering with the normal spinal growth and may even have a potential for growth stimulation beyond the normal growth rate. However, the technique requires frequent surgeries for construct lengthening to keep up with normal spinal growth and to maintain scoliosis curve correction. Multiple surgeries, mostly through the same incision site, leave the skin tissue susceptible to infection and other skin problems. Implant related complications are the most common complications in growth rod surgeries. These include rod fracture, anchor failure, or prominent implant, which can cause skin breakdown and even infection. Among the implant-related complications, rod fractures are the most common problem.
The idea of non-invasive multiple lengthening without the need for anesthesia and open surgery is appealing given the direct relationship between high complications and repeated surgeries. These devises allow for lengthening to be performed in the doctor's office. It is composed of an implantable rod, an external remote controller (ERC) and accessories. The titanium rod includes a telescopic actuator portion that holds a small internal magnet. Rotation of the magnet remotely by use of the ERC causes the rod to be lengthened or shortened. The rod is implanted and secured using standard fixation components, such as hooks and/or pedicle screws as anchors. Magnet driven rods are now being used in certain centres outside the United States and preliminary results have shown to be able to reduce morbidities, cost, and decrease stress for patients and parents. They have been implanted in cases of both idiopathic (Figure 10) and neuromuscular scoliosis.
Figure 10 - Magnetically Controlled Growing Rod (MCGR) in a patient with idiopathic early onset scoliosis.