Anterior vertebral body tethering is a surgical option for growing adolescents with idiopathic scoliosis, a sideways curvature of the spine. This treatment corrects the curve while the individual is still growing, serving as an alternative to traditional spinal fusion surgery. The procedure uses the body’s growth to guide the spine into a straighter alignment. This technique preserves spinal motion, which is a departure from the rigid fixation of fusion.
How Vertebral Body Tethering Works
Vertebral body tethering operates on the principle of growth modulation, guiding the spine’s development over time. The concept is similar to how a trellis guides a growing plant. Surgeons place bone screws into the vertebral bodies on the convex, or outer, side of the curve. These screws anchor a strong, flexible cord, or tether, which is pulled taut.
The tension on the convex side of the spine slows its bone growth, allowing the concave, or inner, side to grow faster. As the child grows taller, this differential growth progressively straightens the spine. This corrects the scoliosis deformity over time.
Patient Candidacy for the Procedure
Patient candidacy for anterior vertebral body tethering (AVBT) depends on growth potential and the characteristics of the spinal curve. A primary factor is skeletal immaturity, meaning the patient has significant growth remaining. Surgeons assess this using indicators like the Risser sign from a pelvic X-ray or a Sanders score from a hand X-ray. Ideal candidates are between the ages of 10 and 16.
AVBT is designed for thoracic or thoracolumbar curves, located in the upper or middle-to-lower parts of the back. The curve’s magnitude must be between 35 and 65 degrees. Curves less severe may be managed with bracing, while more severe curves might not be effectively corrected by the tether alone.
The flexibility of the spine is also assessed through bending X-rays. This indicates the spine is not too rigid and can be guided by the tether’s tension. Patients who have failed or are intolerant to bracing are also considered for this option.
The Surgical Process
The surgery is a minimally invasive procedure performed using a thoracoscopic approach. The surgeon operates through small incisions on the side of the chest, guided by a camera called a thoracoscope, which avoids the large incision of open-back surgery. The patient is positioned on their side, and the lung on that side is temporarily deflated to create a clear working space.
Through these ports, the surgeon places titanium screws into the front of the vertebral bodies along the outer edge of the curve. Once the screws are securely in place, the flexible polymer cord—the tether—is threaded through the heads of the screws.
The surgeon applies a calculated amount of tension to the tether, providing some immediate partial correction of the curve. This tension guides the spine’s growth over the following months and years. After the tether is secured, the lung is re-inflated, and the incisions are closed.
Post-Surgery Recovery and Outcomes
Following surgery, patients remain in the hospital for a few days for monitoring and pain management. Most can walk soon after the procedure and return to school within two to four weeks. Initial restrictions on activities include limiting bending, lifting, and twisting for several weeks to allow the body to heal.
A gradual return to activities, including sports, is possible within six weeks to three months post-operation. Long-term success depends on the tether guiding the spine’s continued growth. Regular follow-up appointments with X-rays are necessary to monitor the curve’s correction.
While outcomes are positive, with curve correction and preservation of spinal motion, potential complications exist. These include tether breakage, which may not require intervention if sufficient correction has occurred, or overcorrection, where the spine curves in the opposite direction. In some cases, a revision surgery may be needed to address these issues or convert to a spinal fusion if the desired result is not achieved.
Comparison with Spinal Fusion
The primary distinction between AVBT and spinal fusion is the approach to correction. Spinal fusion permanently joins vertebrae, creating an immobile segment of bone that stops the curve’s progression and halts growth in that part of the spine. In contrast, AVBT is a growth modulation technique that uses the patient’s growth to correct the curve while preserving spinal motion and flexibility. This preservation of movement is an advantage, potentially reducing the risk of adjacent segment disease, which is extra wear on discs near the fused area.
The surgical procedures also differ. AVBT is performed through small, minimally invasive incisions, while spinal fusion requires a larger, open incision down the back. This leads to a shorter hospital stay and a faster recovery for AVBT patients, who may return to full activity in about three months, compared to six months or more for fusion patients.
The choice between the two involves trade-offs. Spinal fusion provides a more predictable, one-time correction. AVBT’s outcomes can be less predictable and depend on the patient’s remaining growth. It also carries unique risks, like tether breakage or overcorrection, which may require a second surgery. Fusion is a long-established procedure with decades of data, while AVBT is newer and its long-term results are still being studied.