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In a child or adolescent, where the bones are not fully formed as in an adult, bracing can sometimes be effective at stopping progression of the curve.
When bracing fails to work or is not an option, there are two new minimally invasive options that enable the spine surgeon to access the spine through tiny incisions near the ribs:
1. Vertebral Body Stapling uses a series of staples on one side of the vertebrae to correct scoliosis like braces on teeth. Click here to read more about Vertebral Body Stapling.
2. Vertebral Body Tethering uses a cable attached to one side of the vertebrae to correct and then control the curve. Both techniques work on one side of the curve to prevent it from worsening during the adolescent growth spurt. Sometimes it may be the only surgery needed. A second benefit of both minimally invasive techniques is that they don’t burn any bridges and more traditional corrective instrumentation can be used later on if necessary.
Vertebral Body Tethering requires a spine surgeon who specializes exclusively in scoliosis as tethering is a very specialized procedure done through very small incisions to reduce disruption to muscles and ligaments in the back. This enables the scoliosis patient to recover faster with a less painful return to activity.
Zimmer Biomet makes technology related to the tethering procedure.
As with any new procedure, there is great hope that Vertebral Body Tethering can arrest a spinal curve in the young scoliosis patient and possibly eliminate the need for a more complex and invasive spine surgery. Tethering applies mostly to adolescent spinal curves that are still in the growth spurt stage.
Vertebral Body Tethering is in fact not a new concept and has much in common with scoliosis bracing which has been used as a standard treatment for spinal curves for decades.
Both bracing and Vertebral Body Tethering involve the concept of bone growth modulation which is based off the Hueter-Volkmann principle, which states that bone under more pressure will grow slower and denser than bone not under stress. So with bracing or tethering the bone on the inside part of the curve will grow slower and denser than the bone on the outer part of the curve which in turn creates a vertebrae more wedge shaped.
The difference between bracing and tethering is that the goal with bracing is to PREVENT THE SPINAL CURVE FROM WORSENING. It is important to understand that bracing does not correct the existing curve.
Conversely, with Vertebral Body Tethering loading is applied directly to the spine with a surgical procedure, which creates bone growth modulation and attempts to provide some correction of the spinal curve — if the patient has young with more bone growth in the future.
In this sense, Vertebral Body Tethering is an early intervention option for the adolescent scoliosis patient whose bones have not fully matured, rather than someone who is now an adult.
The benefits of Vertebral Body Tethering include:
The patient must young enough to still have bone growth remaining. This could be a child 8 years old. Girls still have bone growth up to age 14 while boys can still have bone growth up to age 16.
A candidate would have idiopathic scoliosis with curve less than 65 degrees who are generally flexible and whose bone structure is large enough to accept the installation of screws and anchors into the vertebrae. This is determined with an X-ray. The young patient should also have failed traditional bracing, or cannot tolerate wearing a brace.
The Vertebral Body Tethering procedure should not be used for the following patients:
The Tethering System, developed by Zimmer Biomet Spine, was approved by the FDA in August 2019. The system is made up of anchors, bone screws, cord and set screws. The anchors, bone screws and set screws are made out of titanium alloys that are commonly used as spine implants. The cord is made of a strong flexible polymer.
During surgery, the scoliosis surgeon places the anchor and bone screw into the patient's spine on the side of the spinal curve. The polymer cord is then secured to the bone screws using set screws. The surgeon then applies tension to the cord to partially reduce the curve in the person's spine. After surgery, the cord continues to straighten the spine as the patient continues to grow.
It’s important to remember that tethering carries similar risks to any invasive surgery, including the use of general anesthesia.
With Vertebral Body Tethering the surgeon accesses the spine through the chest. During surgery, the patient's lung on that side of the chest is temporarily deflated. After the tether has been installed, the lung is then re-inflated. One of the recovery aspects is that there will be soreness and pain after surgery, making it uncomfortable to take deep breaths or cough. Ultimately the chest tube is removed and the soreness disappears.
Recovery can be fairly quick with the young patient being released to return to activity and to athletics about a month to six weeks after surgery.
Research conducted in clinical trials which resulted in FDA approval of the surgical procedure indicates that Vertebral Body Tethering can be successful in arresting a curve and in some cases eliminating the need for spinal fusion or instrumentation in the future, which makes it a viable option for the child or adolescent scoliosis patient.
FDA approval was based on clinical data from 57 patients who underwent Vertebral Body Tethering. Data after two years revealed that 43 patients had sufficient improvement in the curvature of the spine and did not require spinal fusion.