Vertebral Body Tethering Outcomes for Pediatric Idiopathic Scoliosis

Scoliosis is a condition in which the spine is deformed by a curvature in the coronal plane. It is generally associated with a twisting (axial plane) deformity as well. It can have a variety of underlying etiologies and the etiology is used to classify the types of scoliosis. Idiopathic scoliosis is sub-classified in two ways: by age of onset and by magnitude of deformity. Curves between 10 and 25 degrees are considered mild. Curves between 25 and 50 degrees are classified as moderate. Curves greater than 50 degrees are termed severe. The current standard of care for moderate scoliosis in patients with remaining growth is to utilize a thoracolumbosacral orthosis (TLSO brace) to prevent progression of deformity. The scientific evidence has supported the efficacy of this intervention in avoiding progression of the Cobb angle to 50 degrees or more.

If treated with a TLSO brace, many idiopathic scoliosis patients would conceivably be subjected to years of brace wear and the cost and psychological factors inherent therein. Additional downsides of brace treatment include the potentially negative psychosocial impact of wearing an external sign of deformity during adolescence, a key period of emotional development. Prior research has identified negative psychosocial effects related to wearing a brace in children.

Recent evidence has suggested that certain curve patterns will likely progress to 50 degrees or more, despite treatment with a TLSO brace. Sanders, et al. demonstrated a correlation of Cobb angle (greater than 35 degrees) and skeletal maturity (bone age 4 or less) to the risk of progression to 50 degrees or more, despite TLSO bracing. The evidence supports that the current practice of TLSO bracing is not an effective treatment to avoid progression to 50 degrees in these patients. It is on this population (thoracic Cobb angle greater than 35 degrees, bone age of 4 or less) that we intend to test the safety and feasibility of Anterior Vertebral Body Tethering to avoid curve progression to 50 degrees.

The study intervention is surgical orthopedic implantation of the Anterior Vertebral Tether Device, by way of thoracoscopic surgery under general anesthesia. The primary outcome measures include assessments of safety of the insertion procedure and of the device, as well as the secondary measure of feasibility by determining the ability to successfully implant the investigational device.

Inclusion criteria

• Males or females age 8 to 16 years old at time of enrollment (inclusive)
• Diagnosis of idiopathic scoliosis
• Sanders bone age of less than or equal to 4
• Thoracic curve of greater than or equal to 35 degrees and less than or equal to 60 degrees
• Lumbar curve less than 35 degrees
• Patient has already been identified for and recommended to have surgical intervention
• Spina bifida occulta is permitted
• Spondylolysis or Spondylolisthesis is permitted, as long as it is non-operative, the subject has not had any previous surgery for this, and no surgery is planned in the future

Exclusion criteria

• Pregnancy (current)
• Prior spinal or chest surgery
• MRI abnormalities (including syrinx greater than 4mm, Chiari malformation, or tethered cord)
• Neuromuscular, thoracogenic, cardiogenic scoliosis, or any other non-idiopathic scoliosis
• Associated syndrome, including Marfan syndrome or neurofibromatosis
• Sanders bone age greater than 4
• Thoracic curve less than 35 degrees or greater than 60 degrees
• Lumbar curve greater than or equal to 35 degrees
• Unable or unwilling to firmly commit to returning for required follow-up visits
• Investigator judgement that the subject/family may not be a candidate for the intervention