Reducing Uncertainty in Anterior Vertebral Body Tethering: Predicting Postoperative Curvature With Fulcrum Bending Radiographs

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

Mid-term Anterior Vertebral Body Tethering (AVBT) results demonstrate an acceptable degree of clinical success, yet the revision rate remains notably higher than fusion. Fulcrum-bending radiographs have previously been shown to more reliably predict radiological outcomes in Adolescent Idiopathic Scoliosis (AIS) as compared to supine-lateral bending radiographs. This study aims to discern how Fulcrum Flexibility Rate (FFR) correlates with Correction Rate (CR) and establish whether this can reliably predict residual deformity following AVBT surgery.

METHODS

A review of 38 consecutive AIS patients undergoing thoracic AVBT between 2015 - 2020 was performed. Preoperative (standing and fulcrum-bending) and postoperative (first-erect) radiographs were evaluated for curve magnitude using the Cobb-method. The FFR, CR and Fulcrum Bending Correction Index (FBCI) were calculated. Patients were also percentile-ranked according to their FFR and dichotomized into flexible and rigid cohorts for comparison. Student t-test, Pearson correlation and linear stepwise regression was applied.

RESULTS

AVBT resulted in a significant improvement in the major Cobb angle (Preoperative: 50.9±7.5° vs Postoperative: 19.9±9.4°; P < .0001) with a mean FBCI of 98.0%. Bivariate correlation revealed a moderate relationship between fulcrum-bending and first-erect Cobb angle (r = .5306, P = .0006). Linear regression demonstrated a predictive relationship between fulcrum-bending and first-erect Cobb using the equation 'Postoperative Cobb = 7.5 + .65(Fulcrum-bending Cobb).'

CONCLUSION

This is the first study to demonstrate the ability of fulcrum-bending radiographs to predict early radiographic outcomes following AVBT, 'timepoint-zero' for the growth modulation process.

Patient series

BACKGROUND

Anterior vertebral body tethering (AVBT) and posterior spinal fusion (PSF) are options for patients with idiopathic scoliosis. Combining both procedures in patients with double curves, a procedure in which PSF is performed for the thoracic curve and AVBT for the lumbar curve, provides maximal correction of the thoracic curve with a theoretical maintenance of motion in the lumbar spine.

OBSERVATIONS

The authors retrospectively reviewed 20 skeletally immature patients diagnosed with idiopathic scoliosis at a single institution with an average age of 12.7 ± 1.6 years and who had undergone hybrid treatment with an average follow-up of 8 months. The PSF procedures averaged 276 ± 63 minutes with 442.8 ± 295 mL of blood loss, and the AVBT averaged 275 ± 54 minutes with 118.3 ± 80 mL of blood loss. Following the hybrid correction, the thoracic and lumbar coronal curve angles improved from 67.6° to 21.6° and from 65.2° to 24°, respectively. The three-dimensional kyphosis improved from 3.3° to 24°.

LESSONS

A combined approach of PSF and AVBT is safe and effective for idiopathic scoliosis. This approach combines the gold standard of thoracic fusion with the motion preservation benefits of AVBT in the lumbar spine. This study will continue to refine indications for AVBT.

Anterior Vertebral Body Tethering for Skeletally Immature Patients with AIS: Indication for Spinal Fusion at Skeletal Maturity Is Not Obviated in 60% of Cases

The role of anterior vertebral body tethering (aVBT) in obviating the need for spinal fusion in patients with AIS remains unclear, and a large amount of variation exists in the data among different studies. The present study aims to investigate and analyze what factors have a potential influence on aVBT outcome. Skeletally immature patients with AIS who underwent aVBT for scoliosis correction were followed up until skeletal maturity. The mean age at the time of surgery was 13.4 ± 1.1, and the mean follow-up time was 2.5 ± 0.5 years. The Cobb angle of the main curve was 46.6 ± 9° at the time of surgery and was significantly corrected to 17.7 ± 10.4° (p < 0.001) immediately postoperatively. A significant loss of correction was observed during the latest follow-up (Cobb angle 33.8 ± 18.7°; p < 0.001). An indication for spinal fusion at skeletal maturity was not obviated in 60% of the patients. The factors identified as having an influence on the outcome were preoperative bone age and the magnitude of the major curve. Patients with advanced bone age and larger curves were more likely to reach an indication for spinal fusion at skeletal maturity. In conclusion, no general recommendation for aVBT can be made for AIS patients. The method can be discussed as a treatment option in skeletally very immature preadolescent patients (Sanders Stadium ≤ 2) with a moderate Cobb angle (≤50°) who failed previous brace therapy.

Video-Assisted Thoracoscopy for Vertebral Body Tethering of Juvenile and Adolescent Idiopathic Scoliosis: Tips and Tricks of Surgical Multidisciplinary Management

VATS (video assisted thoracoscopic surgery) is routinely and successfully performed in minor and major complex thoracic procedures. This technique has been recently introduced for the treatment of severe forms of idiopathic scoliosis (IS) with the aim to repair the deformity, reduce morbidity and to prevent its progression in patients with skeletal immaturity. This study aims to present VATS in anterior vertebral body tethering (AVBT) approach to support the pediatric orthopedic surgeons during vertebral body fixation. Surgical and anesthesiologic tips and tricks are reported to assure a safe procedure. The study includes preadolescents with IS and a grade of scoliosis >40° that had a high probability of deterioration due to remaining growth (December 2018 to April 2021). Skeletal immaturity of enrolled patients was assessed by Sanders classification and Risser sign. Patients had a Risser score between 0 and 1 and a Sanders score >2 and <5. AVBT technique using VATS was performed by a senior pediatric surgeon assisting the pediatric orthopedic surgeon. Twenty-three patients have been submitted to VATS AVBT in the period of study (age range 9–14 years). The patients had a classified deformity Lenke 1A or B convex right and all types of curves were treated. In all patients, the vertebrae submitted to tethering surgery ranged from D5 to D12; mean curve correction was 43%. Three postoperative complications occurred: one late postoperative bleeding requiring a chest tube positioning on 12th postoperative day; one screw dislodged and needed to be removed; one child showed worsening of the scoliosis and needed a posterior arthrodesis. Initial results of VATS AVBT in growing patients with spinal deformities are encouraging. An appropriate selection of patients and a pediatric dedicated multidisciplinary surgical approach decrease intraoperative complications, time of operation and postoperative sequelae and guarantee an optimal outcome.

Efficacy of Anterior Vertebral Body Tethering in Skeletally Mature Children with Adolescent Idiopathic Scoliosis: A Preliminary Report

BACKGROUND

Anterior vertebral body tethering (AVBT) offers a dynamic fusionless correction option for children with adolescent idiopathic scoliosis (AIS). Few existing clinical studies evaluating novel AVBT in skeletally immature children have questioned the midterm efficacy with concerns of overcorrection and curve progression with remaining growth. The current study investigates the effect of this technique in skeletally mature children (Risser ≥ 4 and Sanders ≥ 7) with AIS with limited remaining growth potential.

METHODS

We evaluated skeletally mature children with AIS who underwent the AVBT technique for a single structural major curve between 40° and 80° with ≥50% flexibility on dynamic radiographs and a minimum of 1 year of follow-up. Pertinent clinical and radiographic data collected include skeletal maturity, curve type, Cobb angle, sagittal parameters, and a patient-reported outcome measure Scoliosis Research Society-22 (SRS-22) questionnaire.

RESULTS

All 10 children were female with a mean age of 14.9 ± 2.7 years at the time of surgery. The mean follow-up was 24.1 ± 3.6 months. The mean Risser and Sanders scores were 4.2 ± 0.6 and 7.2 ± 0.6, respectively. Three patients had major thoracic curves, and 7 patients had thoracolumbar/lumbar curves. Cranial and caudal instrumented levels were T5 and L4. Mean preoperative Cobb's angle was 52.0° ± 11.6° and was corrected to 15.9° ± 6.8° on the first erect postoperative radiograph, with stabilization of corrected curve at the 1-year follow-up (mean Cobb's angle of 15.3° ± 8.7°). Mean preoperative and postoperative SRS-22 scores were 78.0 ± 3.2 and 92.5 ± 3.1, respectively (P < .01). No complications were noted until the last follow-up.

CONCLUSION

Our preliminary experience with this novel AVBT as an alternative technique to fusion to stabilize progressive idiopathic scoliosis in skeletally mature children is promising.

LEVEL OF EVIDENCE

4.