3D SPINE GROWTH IS MAINTAINED FIVE YEARS POSTOPERATIVE VERTEBRAL BODY TETHERING SURGERY

Scoliosis can be treated with Vertebral Body Tethering (VBT) as a growth-friendly and motion-sparing procedure. However, the knowledge of how growth is affected by a tether spanning multiple levels is unclear in the literature. Three-dimensional true spine length (3D-TSL) is a novel assessment technique that accounts for the shape of the spine in both the coronal and sagittal planes. Previous studies1 have demonstrated that 3D-TSL is more accurate than simple coronal plane height measurements. This study aimed to assess if 3D-TSL increases over a five-year period after VBT implantation. Prospectively collected radiographic data from an international pediatric spine registry was analyzed. Complete radiographic data over three visits (post-operative, two years, and five years) was available for 60 patients who underwent VBT. The mean age of this cohort was 12.2 (9 – 15) years at instrumentation. The average number of vertebrae instrumented was 7.3 (SD 0.8). Major Cobb angles were 50.1° pre-operative; 27.3° post-operative and 34.1° at 5 years (p Immediate mean post-operative 3D-TSL of the tethered segments (top of UIV to top of LIV) was 13.74 (SE 0.23) cm; two-year length was 14.31 (SE 0.22) cm; and five-year length was 14.70 (SE 0.22) cm (p Over the instrumented levels, 40/60 (66.7%) patients had greater than 0.5 cm of 3D growth at two years and 25/60 (41.7%) patients had more than one centimeter of gain at five years. Subgroup analyses were not significant for age, Cobb angles or number of spanned vertebrae between these patients and those who had less significant growth through the follow-up. This series demonstrates that 3D-TSL can increase over the instrumented levels after VBT surgery. At five years, this average 3D growth of 0.96 cm or 0.13 cm per instrumented level lends support to the theory that VBT surgery is a growth friendly fusionless technique.