VBT, or Vertebral Body Tethering (sometimes just called "tethering"), is a surgical treatment for children with idiopathic scoliosis and sufficient growth remaining as determined by your surgeon. Screws are placed in the side of vertebral bodies and a polyethylene-braided flexible rope is placed between the screws and is then tensioned to immediately correct part of the spinal curve. The remaining spinal curve will continue to correct as the child grows. As opposed to a spinal fusion, the child will maintain some motion throughout the instrumented portion of the spine.
Who is a candidate for VBT?
Children who meet all of the following conditions may be a candidate for VBT:
- Idiopathic scoliosis
- Scoliosis curves between 40-65 degrees
- Vertebral bodies of sufficient size to accommodate screws
- At least 10 years old and generally younger than 16 years old
- Have significant growth remaining
- Your child would otherwise require a spinal fusion
- Sanders score of 2-5 or Risser 0-3, according to your child's doctor
If your child meets any of the following, they are not a candidate for VBT.
- Skeletal maturity has been reached
- Previous spinal surgery
- Poor bone quality/Metabolic Bone Disease
- Curves >65 degrees
- Kyphosis >50 degrees
- Prior Thoracic Surgery
- Underlying cardiac or pulmonary disease
What to expect for this procedure:
The surgery is typically performed by a spinal surgeon who may choose to work in conjunction with a general surgeon. Neuromonitoring is utilized to monitor spinal cord function throughout the surgery and ensure the highest level of safety for your child. The surgery is typically performed using a minimally invasive approach either thoracoscopically or through a mini-open incision, resulting in minimal blood loss. Screws are then placed in the pre-selected vertebral bodies on the convex (outer) side of the curve. Once the screws have been placed, a polyethylene-braided rope is seated in the screws under tension to partially correct the spinal curve as the child grows. Typically, a chest tube or drain is then placed at the conclusion of the procedure and remains with the patient during their hospital stay.
What is the desired outcome?
The goal is to have the vertebral bodies remodel or reshape over time, which is what will sustain the correction of your scoliosis curve, rather than relying on the poly-ethylene rope to hold your curve in place. This rope will likely break over time, however it should not negatively affect your child's curve as long as the spine has remodeled as expected. We also hope to achieve a curve that is less than 30 degrees at skeletal maturity.
What are possible outcomes?
- Some patients will have near complete correction of their curve
- Some patients may have some spinal curve remaining if they do not have enough remaining growth or if their tether ruptures too soon.
- Many of these patients will have dramatic improvement of their curve and will need no further procedures
- Some of these patients may require a second procedure, either a revision tether or possibly a fusion procedure depending on how much growth they have left and the size of their curve
- Some patients may overcorrect (the spine will begin to curve in the other direction)
- Many of these patients will have mild overcorrection and no symptoms
- Some of these patients may have more significant overcorrection or have significant remaining growth and they may need to have their tether released.
Common Complications
- Tether breakage: This may occur at any time but most commonly occurs between 1.5 - 3 years after surgery. This may result in recurrence of some deformity depending on how much the vertebra have remodeled.
- Failure of Spine Remodeling or Growth Modulation: In patients that do not have significant remaining growth their vertebra may not have the ability to reshape prior to the tether breakage. If the tether breaks, there can be recurrence of the spinal curve.
Less Common Complications
The following complications are much less common, but have been reported and are important for you to understand.
- Injury to nearby structures including the ureters, aorta, vena cava, heart, or lungs
- Bleeding which may require blood transfusion
- Injury to the spinal cord which may result in numbness, weakness or both and may be temporary or permanent
- This can also include a dural tear which is a tear of the outermost membrane of the spinal cord and result in a leak of spinal fluid.
- Pulmonary complications which may include:
- Residual air around the lungs or pneumothorax which may require a chest tube to drain or may resolve on its own
- Residual fluid around the lungs which may require a chest tube to drain or may resolve on its own
- Persistent atelectasis which may cause lower oxygen saturation and a longer hospital stay or in rare cases pneumonia
- Delayed (2-6 weeks) build of fluid around the lung that may require a chest tube
- Surgical Site Infection that may require antibiotics or surgical debridement
- Screw pullout or migration which is where the screw changes position over time. In some cases, this may be observed and may need the screw to be revised
- Over-correction of the spinal deformity can occur in patients with too much growth. In some patients this may be observed, but in some patients this may require release or removal of the tether
- Irritation of the diaphragm or psoas muscles may be temporary or permanent. For those patients where it does not resolve it may require removal of the tether.
- Persistent back or chest pain after surgery. This is most common in patients with preoperative pain, but can occur in any patient. Frequently it will respond to physical therapy but may persist in some patients.
FAQs
What is VBT?
Vertebral Body Tethering is a type of surgical treatment for children with idiopathic scoliosis and sufficient growth remaining as determined by your surgeon. Screws are placed in the vertebral bodies and a poly-ethylene braided rope is placed between the screws and is then tensioned to correct part of the spinal curve. The remaining spinal curve will continue to correct as the child continues to grow. As opposed to a spinal fusion, the child will maintain some motion throughout the instrumented portion of the spine.
How is the procedure performed?
The surgery is typically performed by a spinal surgeon who may or may not work in conjunction with a general surgeon. Neuromonitoring is utilized to monitor spinal cord function throughout the surgery. The surgery is typically performed using a minimally invasive approach either thoracoscopically or through a mini-open incision. This allows for limited blood loss. Screws are then placed in the pre-selected vertebral bodies on the convex side of the curve. Once the screws have been placed, a poly-ethylene braided rope is seated in the screws under tension to partially correct the spinal curve. Typically, a chest tube or drain is then placed at the conclusion of the procedure, which will temporarily remain in the patient.
Should a disc excision (disk removal) be performed during VBT?
At this time, a disc excision is consistent with a spinal fusion. It is believed that by violating the disc you damage it and although in the short term patients may continue to observe relative motion, the discs will ultimately degenerate and auto-fuse over time.
How often should my child follow-up?
Follow-up can vary based upon surgeon preference. Generally, patients are followed every 6-12 months until the child has completed growth. This allows the surgeon to monitor curve correction and also evaluate for complications.
What is recovery like?
Recovery is similar to that of a posterior spinal fusion except for a few differences. Patients typically will have a chest tube or drain after a thoracic VBT that can remain in place for 2-4 days. The hospital stay is between 2-5 days and similar pain medications are used as with a posterior spinal fusion. VBT patients can often begin returning to sports and activities approximately 4-6 weeks after surgery.
Case Studies
Each child's journey with scoliosis is different and will depend on a lot of factors. Things like curve size, previous treatment, flexibility, and growth remaining will impact what your surgeon believes is the best choice of treatment.
The following case examples describe three patients who were treated with vertebral body tethering. A variety of timepoints are included to help you better understand what might be expected should your child undergo this type of surgery and treatment plan.
Case #1
12-year-old female who presented with adolescent idiopathic scoliosis and a flexible curve of 58 degrees bending out to 22 degrees. She did not have any previous treatment and underwent VBT surgery at age 13. Her curve corrected to 34 degrees immediately after surgery and at 5 years post-surgery, she had developed a second curve below the tethered portion of her spine.
Case #2
14-year-old female who presented with adolescent idiopathic scoliosis and a flexible curve of 49 degrees bending out to 13 degrees. She was previously treated with a brace and underwent VBT surgery. Immediately after surgery, her curve corrected to 33 degrees and at her most recent follow-up one year after surgery, her curve corrected to 29 degrees.
Case #3
10-year old female with adolescent idiopathic scoliosis and a flexible curve of 48 degrees bending out to 5 degrees. She was previously treated with a brace and underwent VBT surgery at age 11. Her curve corrected to 25 degrees immediately after surgery. There was curve progression at 2.3 years after the index surgery, her spinal curve over-corrected and she required tether removal 2 months later. At 10 months post-revision surgery, her curve is 35 degrees.
Case #4
12-year-old female who presented with adolescent idiopathic scoliosis and a flexible thoracolumbar curve of 47 degrees, bending out to 18 degrees in the thoracolumbar spine. Immediately after surgery the curve corrected to 11 degrees in the thoracolumbar spine. At >2 year follow-up the curve is <10 degrees.
Case #5
12-year-old female who presented with adolescent idiopathic scoliosis and a flexible double major curve of 50 degrees in the thoracic and 50 degrees in the thoracolumbar spine, bending out to 37 degrees. Immediately after surgery the curve corrected to 15 degrees in the thoracic spine and less than 10 degrees in the thoracolumbar spine. At >2 year follow-up both curves are <10 degrees.