VBT Scoliosis Surgery Candidate Criteria: Who Is a Candidate for Vertebral Body Tethering?
Vertebral Body Tethering — VBT — is a modern non-fusion surgical method for correcting idiopathic scoliosis. Unlike spinal fusion, VBT does not permanently fuse the vertebrae. The goal of the procedure is to correct the spinal curve while preserving spinal mobility and using the child’s remaining growth potential to gradually improve the deformity.
Indications for VBT Surgery
VBT was developed mainly for patients with idiopathic scoliosis who are still growing. The ideal candidate is a child or adolescent with progressive scoliosis, remaining skeletal growth, and a moderate spinal curve. The decision is always made individually after reviewing standing X-rays, bending films, MRI scans, skeletal maturity, curve flexibility, and overall health.
Age and Skeletal Immaturity
VBT is usually considered for patients from approximately 8–10 years old to around 15–16 years old, while skeletal growth is still incomplete. Doctors assess biological maturity rather than chronological age alone. Key markers include Risser grade 0–2 or Sanders stage ≤4–5, which indicate meaningful remaining growth. For example, a 14-year-old girl with Risser grade 1 may still be a candidate, while a 14-year-old with Risser grade 5 is usually no longer suitable for growth-guided correction.
Degree of Spinal Curvature
Typical indications for VBT include a Cobb angle of approximately 30° to 60–65°. For smaller curves, conservative treatment such as observation or bracing is usually preferred. When the curve is greater than around 60–65°, the effectiveness of tethering may decrease, and more severe deformities often require traditional spinal correction methods. The best candidate usually has a moderate, flexible curve, for example 40–50°, that corrects well on side-bending X-rays. Good flexibility suggests that the tether may be able to guide the spine into a better position over time.
Curve Location
VBT can be used for thoracic, lumbar, and thoracolumbar curves. For thoracic curves, the approach is usually through the chest wall using thoracoscopy or a mini-thoracotomy. For lumbar curves, the surgeon may use small abdominal or diaphragm-related approaches depending on the exact anatomy. VBT is not usually performed for multiple severe curves at the same time. In most cases, the main scoliosis curve is corrected. If there is a significant second curve, tethering may be less effective and combined treatment may be required, such as tethering of the main curve and bracing for the secondary curve.
Type of Scoliosis
The main indication for VBT is adolescent idiopathic scoliosis, also known as AIS. In congenital, syndromic, or neuromuscular scoliosis, spinal growth and curve progression are less predictable. For this reason, VBT is used much less often in these cases. For example, scoliosis associated with Marfan syndrome or cerebral palsy may carry a higher risk of complications, and many such cases are still treated with more traditional surgical methods.
Failure of Conservative Treatment
Another important criterion is progression despite conservative treatment. VBT is often considered for patients whose spinal curve continues to progress despite regular use of an orthopaedic brace, or for patients who cannot tolerate brace treatment. In other words, VBT is usually considered after conservative measures have failed, but before the deformity becomes too severe or too rigid for motion-preserving correction.
Contraindications and Limitations
VBT is not recommended for patients whose skeletal growth is already complete, because without remaining growth potential the tether cannot provide additional guided correction over time. Patients with a Cobb angle greater than approximately 65–70° are also usually not ideal candidates, especially if the curve is rigid and does not correct well on bending X-rays.
Absolute contraindications may include previous surgery on the same spinal region, because scar tissue can make implant placement more difficult, as well as severe osteopenia or other conditions that significantly reduce bone strength. In these cases, the risk of implant failure or poor fixation may be higher.
Relative contraindications may include pronounced thoracic kyphosis greater than 40°, because tethering may be less effective in kyphoscoliosis. Left-sided thoracic curves also require careful evaluation, as they may indicate an atypical cause of scoliosis and may be technically more complex because of the anatomical position of the heart and aorta. Very young age, for example under approximately 8 years old, may also be a limitation. In very young children, too much remaining growth can increase the risk of overcorrection, where the curve shifts too far in the opposite direction as the child grows. In such cases, surgeons may recommend delaying the procedure or using temporary growth-friendly systems such as growing rods.