This study is an opportunity to provide continued reasonable assurance of the safety and probable benefit of The Tether HUD. The study will collect long term safety and efficacy information from patients who have had their idiopathic scoliosis treated via anterior vertebral body tethering (AVBT) with The Tether.

While spinal fusion remains the standard surgical treatment for progressive idiopathic scoliosis, concerns about the long-term effects of spinal fusion have led to the investigation of growth-modulation techniques. Anterior Vertebral Body Tethering (AVBT) is one such technique that utilizes growth modulation to remodel the shape of the vertebra and straighten scoliotic curves in skeletally immature individuals. In this technique, screws are inserted at each vertebral level for the length of the convex side of the curve. A strong cord is connected through the screw tulip heads and used to initially straighten the curve as each level is fixed with a set screw. Following surgery and during the growth period the spine begins to remodel according to the Hueter-Volkmann Law, bone growth is relatively inhibited in areas of increased pressure (convex or tethered side) and relatively stimulated in areas of decreased pressure or tension (concave side). Following this principle, AVBT has been shown to alter spinal growth with the potential to correct scoliosis while maintaining spine flexibility.

The objective of the study is to assess the ongoing safety and probable benefit of The Tether HUD which was approved by the FDA under an HDE. Subject enrollment and data collection will be managed by the Harms Study Group (HSG) and Setting Scoliosis Straight Foundation (SSSF) Registry. Institutions that are HSG members or affiliates, with Investigators/surgeons that are trained and approved to perform surgeries with The Tether, will participate in the registry. Ten sites from this group will be identified as study sites specific to this Tether post-approval study (PAS). Consecutive subjects from these sites, that meet the eligibility criteria of this study, will be flagged in the registry as the PAS cohort and the study endpoints will be assessed across this population.

Inclusion Criteria:

• Diagnosis of progressive idiopathic scoliosis
• Skeletally immature, based on both Risser (<5) and Sanders (<8) assessments
• Major Cobb angle ≥30° and ≤65°
• Osseous structure dimensionally adequate to accommodate screw fixation, as determined by radiographic imaging
• Failed or intolerant to bracing

Exclusion Criteria:

• Presence of any systemic infection, local infection, or skin compromise at the surgical site
• Prior spinal surgery at the level(s) to be treated
• Documented poor bone quality, defined as a T-score -1.5 or less
• Any other medical or surgical condition which would preclude the potential benefit of spinal surgery, such as coagulation disorders, allergies to the implant materials, and patient's unwillingness or inability to cooperate with post-operative care instructions
• Unwillingness, inability, or living situation (e.g. custody arrangements, homelessness, detention) that would preclude ability to return to the study site for follow-up visits as described in protocol and Informed Consent
• Unwillingness to sign Informed Consent Form and participate in study procedures

The Tether™ - Vertebral Body Tethering System is indicated for skeletally immature patients that require surgical treatment to obtain and maintain correction of progressive idiopathic scoliosis, with a major Cobb angle of 30 to 65 degrees whose osseous structure is dimensionally adequate to accommodate screw fixation, as determined by radiographic imaging. Patients should have failed bracing and/or be intolerant to brace wear.