Pre-operative parameters influencing vertebral body tethering outcomes: patient's characteristics play an important role in determining the outcomes at a minimum of 2 years post-op

Associations of overweight status with spinal curve correction and complications in patients undergoing vertebral body tethering: a multicenter retrospective review

PURPOSE

Our purpose was to determine associations between body mass index (BMI) category and outcomes of vertebral body tethering (VBT), a non-fusion treatment for adolescent idiopathic scoliosis (AIS) and juvenile idiopathic scoliosis (JIS).

METHODS

Using a multicenter database, we identified patients with AIS or JIS who underwent VBT from 2012 to 2018 and had minimum 2-year follow-up (median, 3.0 [interquartile range 2.2, 3.8]). BMI percentiles were used to classify patients as overweight (≥ 85th percentile) or non-overweight (< 85th percentile). Univariate and multivariate regressions assessed associations between complication rates and curve correction between groups, controlling for sex, triradiate cartilage closure, and preoperative curve magnitude.

RESULTS

Of 271 patients, 48 (18%) were overweight. Complication rates did not differ between groups. Factors associated with less correction from preoperative to first postoperative-erect imaging were overweight (β = - 10, p < 0.001), male sex (β = - 8.8 p < 0.01), closed triradiate cartilage (β = 6.0, p = 0.01), and smaller preoperative curve (β = 0.3, p < 0.01). Factors associated with a larger curve at latest follow-up were overweight (β = 4.0, p = 0.02) and larger preoperative curve (β = 0.5, p < 0.001), but tether breakage did not differ between groups (p = 0.31).

CONCLUSION

In patients who were overweight, VBT was associated with less curve correction at first erect imaging and larger final curve. However, complications and curve correction during the modulation phase were not different from those of non-overweight patients. These findings suggest that surgeons should expect less correction with VBT in patients who are overweight but similar correction over time.

LEVEL OF EVIDENCE

Prognostic, Level III.

Coronal decompensation following thoracic vertebral body tethering in idiopathic scoliosis

PURPOSE

Post-operative coronal decompensation (CD) continues to be a challenge in the treatment of adolescent idiopathic scoliosis (AIS). CD following selective spinal fusion has been studied. However, there is currently little information regarding CD following Vertebral Body Tethering (VBT). Thus, the goal of this study is to better understand the incidence and risk factors for CD after VBT.

METHODS

Retrospective review of a prospective multicenter database was used for analysis. Inclusion criteria were patients undergoing thoracic VBT, a minimum 2-year follow-up, LIV was L1 or above, skeletally immature (Risser ≤ 1), and available preoperative and final follow-up AP and lateral upright radiographs. Radiographic parameters including major and minor Cobb angles, curve type, LIV tilt/translation, L4 tilt, and coronal balance were measured. CD was defined as the distance between C7PL and CSVL > 2 cm. Multiple logistic regression model was used to identify significant predictors of CD.

RESULTS

Out of 136 patients undergoing VBT, 94 patients (86 female and 6 male) met the inclusion criteria. The mean age at surgery was 12.1 (9-16) and mean follow-up period was 3.4 years (2-5 years). Major and minor curves, AVR, coronal balance, LIV translation, LIV tilt, L4 tilt were significantly improved after surgery. CD occurred in 11% at final follow-up. Lenke 1A-R (24%) and 1C (26%) had greater incidence of CD compared to 1A-L (4%), 2 (0%), and 3 (0%). LIV selection was not associated with CD. Multivariate logistic regression analysis yielded 1A-R and 1C curves as a predictor of CD with the odds ratio being 17.0.

CONCLUSION

CD occurred in 11% of our thoracic VBT patients. Lenke 1A-R and 1C curve types were predictors for CD in patients treated with VBT. There were no other preoperative predictors associated with CD.

Vertebral body tethering for Lenke 1A curves: the lumbar modifier predicts less optimal outcomes

INTRODUCTION

The addition of the L4 "AR" and "AL" lumbar modifier for Lenke 1A idiopathic scoliosis (IS) has been shown to direct treatment in posterior spinal fusion; however, its utility in vertebral body tethering (VBT) has yet to be evaluated.

METHODS

A review of a prospective, multicenter database for VBT in IS was performed for patients with Lenke 1A deformities and a minimum of 2 years follow-up. Patients were categorized by their lumbar modifier (AR vs AL). Less optimal VBT outcome (LOVO) was defined as a final coronal curve > 35°, lumbar adding-on, or revision surgery for deformity progression or adding-on.

RESULTS

Ninety-nine patients met inclusion criteria (81% female, mean 12.6 years), with 55.6% being AL curves. Overall, there were 23 instances of tether breakage (23.3%) and 20 instances of LOVO (20.2%). There was a higher rate of LOVO in AR curves (31.8% vs 10.9%, P = 0.01). Patients with LOVO had greater preoperative deformity, greater apical translation, larger coronal deformity on first erect radiographs, and less coronal deformity correction. Failure to correct the deformity < 30° on first erect was associated with LOVO, as was LIV selection short of the last touch vertebra (TV). Independent risk factors for LOVO included AR curves (OR 3.4; P = 0.04) and first erect curve magnitudes > 30 degrees (OR 6.0; P = 0.002).

DISCUSSION

There is a 20.2% rate of less optimal VBT following VBT for Lenke 1A curves. AR curves are independently predictive of less optimal outcomes following VBT and require close attention to LIV selection. Surgeons should consider achieving an initial coronal correction < 30 degrees and extending the LIV to at least the TV to minimize the risk of LOVO.