Vertebral body tethering (or spine tethering) is a surgical treatment for children with scoliosis that offers significant advantages over the traditional treatments of bracing and spinal fusion. Tethering corrects the curvature and guides the spine to grow straight, unlike bracing, which can only stop the curve from progressing. Tethering maintains flexibility and motion in the spine, whereas fusing the spine eliminates movement and can prevent a child from taking part in favorite sports or physical activities. Spinal fusion also leads to more wear and tear on the unfused areas of the spine, which over time can cause degenerative arthritis.
In vertebral body tethering, a strong, flexible cord (the tether) is attached with screws to the outward-curving side of the spine and pulled taut. As the child grows, the tether slows growth on that side of the spine, while allowing it to continue on the other side. Over time, as the child grows and the spine lengthens, the tension of the tether makes the spine straighter.
The tether is removed or exchanged only when the scoliosis is completely corrected and there is risk of the spine curving in the opposite direction or if the curve worsens, which can indicate the tether has broken. Otherwise, the screws don't need to be removed. They will remain in your child's spine, unnoticed, throughout their lifetime.
UCSF surgeons are among the country's most experienced in using this innovative technique. Dr. Mohammed Diab, vice chair of pediatric clinical operations in the Department of Orthopaedic Surgery at UCSF, helped develop the treatment, working with colleagues at select medical centers nationwide. We were one of the first hospitals to offer vertebral body tethering and helped gather evidence that led the Food and Drug Administration (FDA), which regulates medical devices, to approve the treatment in 2019.
Vertebral body tethering is an option for children who have scoliosis that isn't related to a neurological condition or an injury. The ideal candidates have a curvature of the spine that is between 40° and 70°. For under 40°, bracing or observation are the preferred treatments. Above 70°, the screw-and-tether construct may not be strong enough to correct the curve. In addition, the bigger the curve, the more growth is necessary to correct it.
Because tethering uses the growth process to straighten the spine, we can only offer the treatment to children whose bones are strong enough to withstand the pull of the tether and who are still growing. There's no set age range but, in general, there's a chance the spine could overcorrect in children younger than 10, while those over age 14 may have reached or be close to their mature height.
Your child's doctor will order several tests ahead of surgery:
X-rays of the spine: X-rays are used to measure the degree of curvature both when the patient is standing and lying down.
CT scan with angiography: For this test, we inject a harmless dye into the bloodstream to obtain detailed images of the blood vessels that supply blood to the spine. If there are any in the area where the surgery is being done, the surgeon will bypass that part of the spine to ensure the safety of the operation.
MRI: This test is used to examine the spinal cord and nerves of the spine in children younger than age 10, since scoliosis patients in this age group sometimes have abnormalities of their spinal nerves which may make them ineligible for the surgery. The child must remain completely still for the MRI. If this is difficult for your child, we may suggest sedation.
You and your child will also visit UCSF's Pre-Surgery Clinic, which is staffed by nurse practitioners and anesthesiologists. They will perform any other needed tests to make sure it's safe to go ahead with surgery. The anesthesiologist will talk to you about anesthesia and pain management for during and after the operation and answer questions so you and your child are prepared.
Patients who live far from San Francisco are asked to come to UCSF several days ahead of surgery to allow time for a full evaluation, including imaging studies and a visit to the Pre-Surgery Clinic.
Your child will be admitted to the hospital on the day of the operation. The surgery takes about six hours and your child will be asleep the entire time. You will receive periodic updates from one of the operating room nurses.
After your child is given general anesthesia, the surgeon will make small incisions in either the side of the chest or the lower back, depending on the location of the curvature, to access the spine. The doctor then places titanium screws into the convex side (the side that curves outward) of each affected vertebra, guided by X-rays taken in the operating room. The screws are coated with a special material that helps them lock into the bone.
The tether, which is made of a strong polyester, is then connected to the screws and pulled taut. A neural physiologist is present throughout the procedure to monitor the function of the nerves and spinal cord.
After the operation, your child is admitted to the intensive care unit for close monitoring. As parent or guardian, you can stay with your child at all times in the ICU.
Your child may have a chest tube, placed during surgery to prevent blood from filling the chest, as well as a catheter to drain urine. Both of these will be removed within a day or two after the surgery.
Pain medications will be delivered by IV until your child resumes eating. Then oral medications are used. Pain medications have side effects, including slowed breathing, dizziness, nausea and constipation, which can be more uncomfortable than pain. The best way to manage these side effects is to use the minimum dose necessary to make the pain manageable. It's unrealistic and unsafe to try to make the pain go away – that would require too high a dose, which would produce too many side effects. Movement can help ease side effects. The day after surgery, your child will get out of bed and start walking with the help of a physical therapist.
Most patients are discharged from the hospital two to four days after the operation. The length of stay is determined primarily by your child's pain level and how comfortable you are caring for your child at home. Before your child leaves the hospital, we will check the incision, change the dressing, remove any remaining tubes and catheters, and take X-rays to make sure the screws are stable.
Your child will return home with pain medications and, if needed, a custom brace to wear for three months. Once home, your child should be able to walk, climb stairs and perform most normal activities that don't involve excessive bending or twisting. It will be a week or so before the surgical incisions are healed enough that your child can shower.
Your child will return to UCSF a week after the operation for a follow-up visit, when Dr. Diab will check the surgical wound. After that visit, your child may shower. Three months after the operation, we will take X-rays to assess the alignment. If a brace was required, your child can stop wearing it at this point.
Most children return to school one month after surgery and to full normal activity after the three-month follow-up visit. We do not recommend restricting children with tethers from any activity, although it's important to follow the same safety and commonsense guidelines that apply for kids haven't had surgery. Your child will return for annual or more frequent check-ups (according to growth) until maturity. The goal of these visits is to monitor the curve while your child is still growing.
Patients who live far away should expect to stay in San Francisco through the first week after the operation. For long-term follow-up, we can arrange video visits and to have X-rays taken at your local health care facility uploaded into MyChart for us to review.