Spinal Tethering Device Revolutionizes Scoliosis Treatment

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An innovative scoliosis treatment was recently created by John T. Braun, MD, an orthopedic spine and scoliosis surgeon in the Pediatric Orthopaedics Service at MassGeneral Hospital for Children. The treatment uses the Anterior Vertebral Tethering System, which is a spinal growth modulation device that offers a minimally invasive, fusionless treatment option for adolescent idiopathic scoliosis and received FDA approval in 2019.

With this treatment, patients experience immediate active correction and ongoing passive modulation powered by their own skeletal growth. Issues associated with spinal fusion, including loss of spine function and adjacent segment damage, are minimized or eliminated. The device will transform the treatment experience for adolescents around the world, including many of the 25,000 in the United States who face surgery each year.

"The FDA approval is wonderful news for patients," Dr. Braun says. "It is a single definitive intervention that allows children with scoliosis to treat their condition and enter adulthood with a strong, healthy spine."

Limitations of Fusion Surgery for Scoliosis

Scoliosis affects 2%–4% of the overall population, primarily females. The irregular vertebral growth that characterizes the condition usually arises during puberty, and it can range in severity from a single, mild, slowly developing curve to a severe double curvature.

Physicians define the severity of spinal curvature using the Cobb angle, a radiographic and manual measure. Curves of less than 25° are considered mild, those between 25° and 40° are moderate, and measures over 40° are severe.

Current scoliosis treatment focuses on curve correction and preservation of growth, motion and function. Approximately 90% of patients—those with mild curves—are monitored with no other treatment. Most of the rest are treated nonsurgically with therapy or bracing.

The roughly 1% of scoliosis patients who require surgery have historically faced a growth- and function-limiting option in the form of fusion surgery. The fusion procedure requires a spinal incision of 8–14 inches followed by significant dissection, decortication and cauterization. Bone grafts fuse sections of the spine together, creating inflexible pillars.

Fusion surgery's long-term effects on the spine can be significant. Patients who have surgery in early adolescence may face decades of pain and additional surgeries. A study of adult women, conducted by the Minnesota Spine Foundation and published in Spine, showed their ability to side flex was reduced by 20%–60% after fusion. Adjacent segment damage is another long-term risk, as detailed in a study conducted at the Katharina Schroth Spinal Deformities Rehabilitation Centre and published in Scoliosis. While fusion may correct sections of the spine, the vertebrae above and below are at risk of stress and damage, resulting in pain and future surgeries.

"Early in my career, I treated many patients who were experiencing these types of complications," Dr. Braun says. "One individual had been fine for 30 years. She presented with severe pain and ultimately had over 40 surgeries that were directly related to fusion complications. This experience drove me to find a better solution."

Harnessing Growth to Correct Scoliosis

The tethering procedure uses a patient's natural growth as the correction mechanism. The surgeon laterally places anchors and screws into the vertebral body on the convex side of the curvature. A polyethylene terephthalate (PET) tensioning cord is secured to the vertebral body screws and connects the levels of the spine to be corrected.

This lateral tension band across the convex side of the spine allows the surgeon to immediately create pressure to partially correct the curvature. During the remaining spinal growth period, the tension band either halts or continues to adjust the curve.

"Tethering allows us to modulate scoliosis curvature while preserving the spine as a spine," Dr. Braun says. "It allows us to retain growth, motion and function while seeing many other benefits."

Tethering's fusionless curve correction has the additional benefit of reducing surgical risk. In contrast to fusion, tethering surgery is limited to several 1.5-2-centimeter incisions and minimal tissue destruction—primarily skin and a small amount of muscle between the ribs.

Dr. Braun performed the first successful tethering procedure in 2010, and ongoing research has demonstrated its benefits. Dr. Braun conducted clinical studies establishing a two-year post-surgical Cobb angle of 40° or less as a success measure for his spinal tethering technique. His patients saw shifts from a mean 46.8° Cobb angle to a mean 21.3° angle in the two years following surgery.

A retrospective study of medical records suggests several additional positive outcomes. Tether patients had an in-hospital opioid consumption of 70 morphine milligram equivalents versus 193.4 for fusion. Surgical blood loss is significantly reduced, and tethering patients are discharged after 4.4 days versus 6.2 for fusion patients.

The Tether has been approved for patients diagnosed with progressive idiopathic scoliosis who:

• Are skeletally immature
• Require surgical treatment to obtain or maintain a proper curve
• Have a major Cobb angle of 30°-65°
• Have an osseous structure dimensionally adequate to accommodate screw fixation
• Are intolerant to brace wear or have failed bracing

Continuing Scoliosis Treatment Innovations

Dr. Braun and his team foresee an opportunity to create a patient registry and monitor the long-term benefits of tethering.

"Going forward, we can reach more patients and provide data to support general and specific aspects of treatment," says Dr. Braun. "We plan to explore questions such as the range of correction possible and ideal growth status. We can also assess more mature patients. My colleagues and I are poised to take tethering to the next level."

Learn more about pediatric orthopedics at Mass General

Refer a patient to Department of Orthopaedics at Mass General