The Risks of Tether Breaks in Scoliosis Treatment: Why Non-Surgical Methods Are Safer and More Effective
Vertebral body tethering (VBT) is a newer, fusionless surgery for adolescent idiopathic scoliosis that uses screws and a flexible cord — the "tether" — to guide a growing spine straighter while preserving more movement than a spinal fusion. It is an appealing idea, and for carefully selected patients it can work well. But families researching VBT quickly come across one recurring concern: the tether can break. In New Zealand, families researching fusionless scoliosis surgery deserve an honest look at the trade-offs. This article explains, in plain and balanced terms, what a tether break is, how often it happens, what it means for your child, and why it is worth exploring every non-surgical option thoroughly first.
What is vertebral body tethering (VBT)?
VBT is a "growth-modulation" procedure. A surgeon places screws along the outer edge of the curved vertebrae and connects them with a strong, flexible cord. Tensioning the cord gently slows growth on one side of the spine so that, as the child keeps growing, the curve can gradually straighten. Because it avoids permanently fusing the vertebrae, VBT aims to keep more of the spine's natural flexibility — which is exactly why it has become a popular alternative to fusion for the right candidates.
What does a "tether break" actually mean?
A tether break is when the flexible cord partially or fully fails after surgery. On X-ray it is usually identified indirectly: when the angle between two adjacent screws changes by more than about 5° between follow-up visits, a break is suspected. In many cases a tether break causes no symptoms and the child feels nothing — it is found on routine imaging rather than because anything obviously goes wrong.
How often do tethers break?
This is the part families most want a straight answer to, so here is the evidence as it currently stands. Tether breakage is consistently reported as the most common complication of VBT. Systematic reviews and meta-analyses put the rate at roughly 21–22% of patients, and one longer-term study found radiographically suspected breakage in as many as 66% of patients by five years. Overall complication rates for VBT sit around 23%, with unplanned reoperations reported in roughly 16% of cases. Breakage is also more common after lumbar (lower back) tethering, although newer two-cord constructs appear to reduce it.
In fairness, the numbers need context. A broken tether does not automatically mean failure: in many patients the loss of correction afterwards is limited, and the revision rate in some series is low. The point is not that VBT is dangerous, but that tether breakage is common enough that it should be a central part of any honest conversation before surgery — not a footnote.
Why do tethers break?
The spine is under constant mechanical load. The cord is repeatedly stretched and stressed with every bend, twist and growth spurt, and like any material under cyclic load it can fatigue and fail over time. Faster-growing children, larger curves, lower (lumbar) constructs and the simple passage of years all raise the chance of a break. This is a mechanical reality of the technique rather than a sign that anything was done wrong.
Putting the risk in perspective
None of this is an argument that surgery is "bad" or that surgeons are not acting in a child's best interest — for severe, rapidly progressing curves, surgery can be the right and necessary choice, and VBT is a genuine advance for families who want to avoid fusion. What the data does support is a measured, fully informed decision: understanding that a tether may break, that follow-up imaging and possible revision are part of the journey, and that the least invasive effective path is usually worth pursuing first.
The case for maximising non-surgical care first
At ScolioLife, our consistent message is that many curves — particularly mild to moderate ones caught early — can be managed conservatively, with surgery kept as an option rather than a first step. A structured non-surgical programme looks beyond the Cobb angle to rotation, posture and muscle balance, and may include:
- Custom bracing such as the ScolioAlign® 3D brace, built from a 3D scan to support the specific curve.
- Scoliosis-specific exercises to strengthen and rebalance the muscles supporting the spine.
- Posture retraining and help with related back pain.
- Attention to nutrition and bone health, and regular monitoring so the plan adapts as your child grows.
Consistency and early intervention matter more than any single tool. A well-followed conservative programme has no tether to break, and it keeps surgical options fully open if they are ever needed.
When surgery may still be the right choice
Conservative care is not a guarantee, and it is not right for every curve. Large curves, rapid progression despite good bracing, or significant symptoms may genuinely call for surgical input, and that decision belongs with you and an experienced spine team. The goal is simply that the choice is made with a full and balanced picture — including the real, well-documented frequency of tether breaks.
Frequently asked questions
Is a broken tether an emergency?
Usually not. Many breaks cause no symptoms and are found on routine X-rays. The concern is gradual: a break can allow the curve to progress, which is why ongoing monitoring matters.
Does a tether break always need another operation?
No. In many patients the loss of correction is limited and no revision is needed. In others, the curve progresses enough that further surgery is considered. It is assessed case by case.
Can a brace prevent a tether from breaking?
Bracing and surgery are different paths. Bracing is part of non-surgical management before or instead of surgery; it does not protect a surgical tether. The relevance of bracing is that it may reduce the need to reach for surgery in the first place.
Is VBT still worth considering?
For the right candidate — typically a still-growing child with a moderate, flexible curve who wants to avoid fusion — VBT can be a reasonable option. The key is going in fully informed about complications like tether breakage.
Every spine and every family’s situation is different. If you are weighing surgery against conservative care, a personalised assessment can help clarify what the curve actually needs. Learn about our approach to non-surgical scoliosis management, see real patient results, or book a consultation — online from anywhere in New Zealand, or in person at our scoliosis clinics.