Analysis of three-dimensional spine growth for vertebral body tethering patients at 2 and 5 years post operatively

Mathieu Boulet; Jennifer Hurry; David Skaggs; Michelle Cameron Welborn; Lindsay Andras; Craig Louer; A Noelle Larson; Firoz Miyanji; Stefan Parent; PSSG; Ron El-Hawary

doi:10.1007/s43390-024-00857-4

Analysis of three-dimensional spine growth for vertebral body tethering patients at 2 and 5 years post operatively

Spine Deform. 2024 Apr 3. doi: 10.1007/s43390-024-00857-4. Online ahead of print.

Authors

Mathieu Boulet¹, Jennifer Hurry¹, David Skaggs², Michelle Cameron Welborn³, Lindsay Andras⁴, Craig Louer⁵, A Noelle Larson⁶, Firoz Miyanji⁷, Stefan Parent⁸; PSSG; Ron El-Hawary^{9

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Affiliations

¹ Department of Orthopaedic Surgery, Orthopaedic Clinic, IWK Health Centre, 5850 University Avenue, PO Box 9700, Halifax, NS, B3K 6R8, Canada.
² Cedars Sinai Spine Center, Department of Orthopaedics, Los Angeles, CA, USA.
³ Department of Spine Surgery, Shriners Hospital for Children Portland, Portland, OR, USA.
⁴ Children's Hospital Los Angeles, Children's Orthopaedic Center, Los Angeles, CA, USA.
⁵ Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, USA.
⁶ Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA.
⁷ Department of Orthopaedic Surgery, BC Children's Hospital, Vancouver, BC, Canada.
⁸ Department of Orthopaedic Surgery, CHU Sainte-Justine, Montreal, QC, Canada.
⁹ Department of Orthopaedic Surgery, Orthopaedic Clinic, IWK Health Centre, 5850 University Avenue, PO Box 9700, Halifax, NS, B3K 6R8, Canada. Ron.el-hawary@iwk.nshealth.ca.
¹⁰ Cedars Sinai Spine Center, Department of Orthopaedics, Los Angeles, CA, USA. Ron.el-hawary@iwk.nshealth.ca.
¹¹ Department of Spine Surgery, Shriners Hospital for Children Portland, Portland, OR, USA. Ron.el-hawary@iwk.nshealth.ca.
¹² Children's Hospital Los Angeles, Children's Orthopaedic Center, Los Angeles, CA, USA. Ron.el-hawary@iwk.nshealth.ca.
¹³ Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, USA. Ron.el-hawary@iwk.nshealth.ca.
¹⁴ Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA. Ron.el-hawary@iwk.nshealth.ca.
¹⁵ Department of Orthopaedic Surgery, BC Children's Hospital, Vancouver, BC, Canada. Ron.el-hawary@iwk.nshealth.ca.
¹⁶ Department of Orthopaedic Surgery, CHU Sainte-Justine, Montreal, QC, Canada. Ron.el-hawary@iwk.nshealth.ca.
¹⁷ Pediatric Spine Study Group, Pediatric Spine Foundation, Valley Forge, PA, USA. Ron.el-hawary@iwk.nshealth.ca.
¹⁸ Faculty of Medicine, Dalhousie University, Halifax, NS, Canada. Ron.el-hawary@iwk.nshealth.ca.

PMID: 38568378
DOI: 10.1007/s43390-024-00857-4

Abstract

Purpose: Scoliosis can be treated with vertebral body tethering (VBT) as a 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 validated assessment technique that accounts for the shape of the spine in both the coronal and sagittal planes. This study aimed to assess if 3D-TSL increases over a five-year period after VBT implantation in thoracic curves for idiopathic scoliosis.

Methods: Prospectively collected radiographic data from an international pediatric spine registry was analyzed. Complete radiographic data over three visits (post-operative, 2 years, and 5 years) was available for 53 patients who underwent VBT.

Results: The mean age at instrumentation of this cohort was 12.2 (9-15) years. The average number of vertebrae instrumented was 7.3 (SD 0.7). Maximum Cobb angles were 50° pre-op, which improved to 26° post-op (p < 0.001) and was maintained at 5 years (30°; p = 0.543). Instrumented Cobb angle was 22° at 5 years (p < 0.001 vs 5-year maximum Cobb angle). An accentuation was seen in global kyphosis from 29° pre-operative to 41° at 5 years (p < 0.05). The global spine length (T1-S1 3D-TSL) started at 40.6 cm; measured 42.8 cm at 2 years; and 44.0 cm at the final visit (all p < 0.05). At 5 years, patients reached an average T1-S1 length that is comparable to a normal population at maturity. Immediate mean post-operative instrumented 3D-TSL (top of UIV-top of LIV) was 13.8 cm two-year length was 14.3 cm; and five-year length was 14.6 cm (all p < 0.05). The mean growth of 0.09 cm per instrumented level at 2 years was approximately 50% of normal thoracic growth. Patients who grew more than 0.5 cm at 2 years had a significantly lower BMI (17.0 vs 19.0, p < 0.05) and smaller pre-operative scoliosis (48° vs 53°, p < 0.05). Other subgroup analyses were not significant for age, skeletal maturity, Cobb angles or number of spanned vertebras as contributing factors.

Conclusions: This series demonstrates that 3D-TSL increased significantly over the thoracic instrumented levels after VBT surgery for idiopathic scoliosis. This represented approximately 50% of expected normal thoracic growth over 2 years.

Keywords: 3D; 3D-TSL; Adolescent idiopathic scoliosis (AIS); Growth modulation; Spine growth; True spine length; Vertebral body tethering (VBT).