Issue link: https://viewer.e-digitaledition.com/i/1439655
Between 2% and 3% of the U.S. population — 6 to 9 million people — have scoliosis. Most children affected experience the onset of the condition between ages 10 and 15. Although both males and females are equally affected, females are eight times more likely to progress to a severe curvature that requires bracing or surgery. Dr. Lonner worked with Zimmer Biomet Spine to create The Tether. "Twenty-fi ve years ago, I was one of the handful of surgeons in the United States performing scoliosis fusion through the side, like we're doing now for tether," Dr. Lonner says. "So the approach was very similar, and that provided a lot of insights for me. ... It was less muscle dissection, and there was some benefi t to that." DRAWBACKS TO VBT Dr. Lonner is careful to emphasize that his results showing a similar curve correction from VBT compared with spinal fusion are just from his own patients — all carefully selected as candidates — and the results are only two years out. "We really need fi ve-year, 10-year and 20-yea r follow-ups a nd compa risons to fusion to determine the best route," Dr. Lonner says. Research conducted in Canada in the years following surgery (using a diž erent tether than the Zimmer Biomet version) showed a higher than expected rate — 15.8% — of post-surgery complications. " W hat we found is that ever y time point — from the fi rst being in hospital, to 30 days, to one year, to two years — the complication rates and the risk of re-operation increased, at every one of those time points," says Ron El-Hawary, MD, MSc, FRCS(C), Chief of Orthopaedics at the IWK Health Centre and Professor in the Department of Surgery at Dalhousie University. "That's pretty common for a lot of surgical procedures, but you hope that things plateau over the long term. That's why a two-year followup is usually a good benchmark for orthopedic study, because if an implant survives for two years, that's usually good for the much longer term. What's diž erent with ver- tebral body tethering is that as time goes on, we suspect that there might be more complications that arise." Dr. El-Hawa r y a lso ha s fou nd, i n research to be published in 2022, that a patient's weight can impact the ež ec- tiveness of VBT. "If patients have a BMI greater than the 85th percentile for their age ... the VBT doesn't seem to work as well over time," Dr. El-Hawary says. "You can get a good correction in the OR , but that growth modulation where you hope the scoliosis continues to get better over time — it doesn't seem to work as well if you're overweight." CAN VBT USE BECOME WIDESPREAD? The more familiar risks of spinal fusion, combined with its wide availability, are likely to ensure it remains the most com- mon surgical treatment for scoliosis in the near future. "It's very predictable in terms of what happens over the short term, you get a great correction of the scoliosis, and it's a pretty safe operation," Dr. El-Hawary says. "But the downside is that you lose some mobility of the spine and can end up with vertebral degeneration 20, 30, 40 years later. So that's why we are thinking about fusion ty pe surger y, as it might decrease those longer term issues." Ongoing resea rch to track patients f ive a nd 10 yea rs out f rom V BT may prov ide more a n s wer s t o ques t ion s i n c lu d i n g h o w m a n y p a t i e n t s a r e brea king the cord, how ma ny patients a re ex per ienci n g overcor rec t ion i n their cur vature a nd how ma ny patients ultimately need spina l fusion. " We're fol low i ng our patients a nd seeing where the sweet spot is for the pr op er i nd ic a t ion s a nd t he pr op er t e ch n ique for apply i n g t he t et her," Dr. Lonner says. "So getting more data is going to be impor ta nt for t he nex t generation of surgeons. A nd tra ining more surgeons is pa r t of t he process of increa sing ava ilabilit y for patients a nd their fa milies." Advanced robotics may a lso be able to improve accuracy a nd e¨ ciency of placement of the screws, lowering com- plications. However, fi nding the correct window of growth for VBT surgery may be the most important path forward. " I do t hin k t his w i l l become more w i d e l y u t i l i z e d a n d a v a i l a b l e f o r patients," Dr. Lonner says. ■ M D N E W S . C O M /// M D N E W S C E N T R A l N E W Y O R K n 2 0 2 2 1 3