A New Look at Vertebral Body Tethering (VBT): Through the Modified Clavien-Dindo-Sink (mCDS) Classification.

INTRODUCTION: Anterior vertebral body tethering (AVBT) is increasingly popular as an option for surgical treatment of idiopathic scoliosis (IS). While the technology remains new, it is important for families and patients to be able to compare it to the current standard of care, posterior spinal fusion (PSF). The purpose of this study is to describe the complication rate of AVBT in IS using the mCDS and to compare it to the recently reported complication rate of PSF in IS.

METHODS: A multicenter pediatric spine deformity database was queried for all idiopathic scoliosis patients who underwent vertebral body tethering. There were 171 patients with a minimum 9-month follow-up included in this study. Complications were retrospectively graded by 2 attending pediatric spine surgeons using the mCDS classification system.

RESULTS: Data from 171 patients with idiopathic scoliosis was available for analysis, with 156/171 (91%) of patients being female and an average age of 12.2 years old at surgery. There were 156 thoracic tethers (1 with an LIV below L2), 5 lumbar tethers, 9 staged double tethers, and only 1 patient with same-day double tether. Fifty-five (55) (32%) patients experienced a total of 69 complications. The most common complication type for VBT by mCDS was Grade IIIb, encompassing 29/69 (42%) of complications. The second most frequent complication grade was Grade I at 23/69 (33%). Thirty-four (34) out of 69 (49%) of the VBT complications reported required either procedural/surgical intervention or admission to the ICU.

CONCLUSIONS: This is the first study to directly compare the complication profile of VBT to PSF using the mCDS. Forty-nine percent (49%) of the VBT complications reported were at least Grade III, while only 7% of complications in the control PSF cohort from the literature were Grade III or higher. The mCDS complication classification brings light to the early learning experience of a new technique compared to the widely accepted standard of PSF for IS.

LEVEL OF EVIDENCE: III - Retrospective comparative study.