Bilateral vertebral body tethering: identifying key factors associated with successful outcomes.

PURPOSE: The treatment of operative double major pediatric spinal deformities (e.g., Lenke 3 or 6) with bilateral vertebral body tethering (VBT) can be significantly more challenging when compared to other deformity patterns (e.g., Lenke 1) or treatment with a posterior spinal fusion. We aimed to identify preoperative and perioperative characteristics that were associated with successful postoperative outcomes in patients treated with both a thoracic and thoracolumbar (e.g., bilateral) tether. METHODS: We retrospectively assessed radiographic and clinical data from patients enrolled in a large multi-center study who had a minimum postoperative follow-up of two years. Standard radiographic parameters were extracted from standing spine and left hand-wrist radiographs at various timepoints. We classified patients based on their preoperative deformity pattern (Primary Thoracic [TP] vs. Primary Thoracolumbar [TLP]) and assessed: (1) deformity balance, (2) tilt of the transitional vertebra, and (3) postoperative success. RESULTS: We analyzed data from thirty-six patients (TP: 19 and TLP: 17). We observed no relationship between deformity balance at first erect and postoperative success (p = 0.354). Patients with a horizontal transitional vertebra at first erect were significantly (p = 0.001) more likely to exhibit a successful outcome when compared to those who exhibited a tilted transitional vertebra (83% vs. 62%). Patients who had TLP were also more likely to exhibit a successful outcome when compared to patients who exhibited TP (76% vs. 50%). CONCLUSION: These data indicate that double major deformities can be successfully treated with VBT, particularly for those who exhibit TLP.

Operative differences for posterior spinal fusion after vertebral body tethering: Are we fusing more levels in the end?

PURPOSE: Little is known about the perioperative characteristics associated with a posterior spinal fusion (PSF) in adolescent idiopathic scoliosis patients previously treated with vertebral body tethering (VBT). We aimed to determine if operative time, estimated blood loss, postoperative length of stay, instrumentation type, and implant density differed in patients that received a PSF (i.e., PSF-Only) or a PSF following a failed VBT (i.e., PSF-VBT). METHODS: We retrospectively assessed matched cohort data (PSF-VBT = 22; PSF-Only = 22) from two multi-center registries. We obtained: (1) operative time, (2) estimated blood loss, (3) postoperative length of stay, (4) instrumentation type, and (5) implant density. Theoretical fusion levels prior to the index procedure were obtained for PSF-VBT and compared to the actual levels fused. RESULTS: We observed no difference in operative time, estimated blood loss, or postoperative length of stay. Instrumentation type was all-screw in PSF-Only and varied in PSF-VBT with nearly 25% of patients exhibiting a hybrid construct. There was no added benefit to removing anterior instrumentation prior to fusion; however, implant density was higher in PSF-Only (1.9 ± 0.2) than when compared to PSF-VBT (1.7 ± 0.3). An additional two levels were fused in 50% of PSF-VBT patients, most of which were added to the distal end of the construct. CONCLUSIONS: We found that operative time, estimated blood loss, and postoperative length of stay were similar in both cohorts; however, the length of the fusion construct in PSF-VBT is likely to be two levels longer when a failed VBT is converted to a PSF.

Physeal fusion status and lesion size are more important than patient age for healing of juvenile osteochodritis dessicans lesions of the distal femur.

PURPOSE: The purpose of the study was to evaluate the effect of skeletal age and lesion size, location, and grade on the success of nonoperative treatment for juvenile osteochondritis dissecans (OCD). It is hypothesized that skeletal maturity, including a combination of maturation phenotypes, correlates with nonoperative lesion healing. METHODS: The clinical and radiographic data on 52 patients aged 7-20 years treated for OCD of the distal femur between 2010 and 2019 were retrospectively reviewed. Knee radiographs were assessed for number of lesions present and lesion location, size, and stage. Assessments of skeletal maturation were performed on all antero-posterior knee radiographs using the Roche, Wainer, and Thissen (RWT) method. Patients were categorized as healed if they demonstrated no pain on clinical examination. The relationship between skeletal maturity and nonoperative lesion healing was determined using Spearman rank correlations on available variables. RESULTS: Neither chronological nor skeletal age was associated with surgical status (Rho = 0.03, n.s., and Rho = 0.13, n.s., respectively) or the healing status of nonoperatively treated OCD lesions (Rho = 0.44, n.s., and Rho = 0.03, n.s., respectively). Epiphyseal fusion status of the distal femoral physis was moderately correlated with nonoperative healing, but was not statistically significant (lateral femoral physis: Rho = 0.43, p = 0.05; medial femoral physis: Rho = 0.43, n.s.). Lesion length correlated with surgical status (Rho = - 0.38, p = 0.009). CONCLUSION: The extent of fusion of the distal femoral physis (multi-stage grading) may be more strongly correlated with nonoperative healing than other markers of skeletal maturity or chronological age. Clinicians can use this as an additional radiographic sign when considering nonoperative treatment for juvenile OCD lesions in the distal femur. OCD lesion length and physeal fusion status appear to be more important for healing than patient age.

As Vertebral Body Tethering Impacts Missouri, New Technology Grows in the Right Direction.

All eleven-year-old girls want to do is play and be active like every other child her age. Yet, the ability to have a normal childhood for one of our patients became a concern when she and her parents noticed an abnormal lateral curvature in her spine, which was later diagnosed as adolescent idiopathic scoliosis. In February 2014, she presented with a 45° thoracic deformity with a high risk of progression. At that time, the gold standard for the treatment of her deformity was a posterior spinal fusion - a surgical treatment she nor her parents were interested in pursuing. After their initial appointment, her parents scoured the internet and discovered a new non-fusion surgical technique, known as vertebral body tethering, that might correct their daughter's deformity without the need for titanium rods in her spine. In April 2014, that same eleven-year-old girl underwent vertebral body tethering of her main thoracic deformity from T5 to L1 under the care and management of Dr. Daniel Hoernschemeyer, a pediatric orthopaedic surgeon, with the University of Missouri's Department of Orthopaedic Surgery. Today, she is a healthy young adult who is thinking more about prom than about her scoliosis.

Team Integrated Enhanced Recovery (TIGER) Protocol after Adolescent Idiopathic Scoliosis Correction Lowers Direct Cost and Length of Stay While Increasing Daily Contribution Margins.

Introduction: Posterior spinal fusion (PSF) is the gold standard procedure for curve correction in Adolescent Idiopathic Scoliosis (AIS). Enhanced recovery protocols (ERPs) have been found to decrease pain and hospital length of stay (LOS) resulting in decreased total hospital charges. Methods: We identified all adolescent idiopathic scoliosis patients treated with a posterior spinal fusion at our children's hospital between 2015-2019. Length of stay, pain scores, and hospital direct costs were calculated to determine the pathway's efficacy. Results: Hospital LOS was reduced by 26% and post-op pain scores did not significantly change when using the Team Integrated Enhanced Recovery (TIGER) protocol (P<0.05). Total hospital costs decreased by 7.9%, daily contribution margins increased 7.9%, and daily net income increased 10.6% after TIGER protocol implementation. Conclusion: TIGER protocol resulted in decreased hospital LOS as well as direct costs for the hospital without increasing postoperative pain scores.

A preliminary assessment of intervertebral disc health and pathoanatomy changes observed two years following anterior vertebral body tethering.

PURPOSE: Vertebral body tethering (VBT) has been reported as a safe and effective non-fusion surgical technique for the treatment of adolescent idiopathic scoliosis, but the postoperative health of the bone and soft tissues of the spine following instrumentation remains unknown. We aimed to evaluate pathoanatomy and degenerative changes of the spine in adolescent idiopathic scoliosis patients both prior to and two years following VBT. METHODS: We prospectively enrolled nine patients who underwent VBT for the treatment of progressive adolescent idiopathic scoliosis. All patients received preoperative and two-year postoperative magnetic resonance imaging of their spine; images were assessed for pathoanatomy (e.g. nucleus pulposus positioning and muscle atrophy) and degenerative changes (e.g. Schmorl nodes, endplate oedema, disc degeneration, and osteoarthritis) at each vertebral level between T1 and S1. RESULTS: Four patients (44%) exhibited a shift of the nucleus pulposus from an eccentric position at baseline towards midline at three or more levels, most of which were in the tethered region. Tethering did not affect preexisting fatty atrophy of multifidus. No patients exhibited postoperative Schmorl nodes, endplate oedema, or disc degeneration in either the tethered or untethered regions. Four patients (44%) presented with mild facet osteoarthritis in the lower lumbar spine, which did not change postoperatively. One patient developed moderate facet osteoarthritis at L5-S1. CONCLUSIONS: These preliminary data indicate that VBT may not result in significant degenerative changes in either the intervertebral discs or the posterior facets two years following instrumentation.

The More the Merrier: Integrating Multiple Models of Skeletal Maturity Improves the Accuracy of Growth Prediction.

BACKGROUND: Multiple systems using radiographic skeletal markers to measure development have been described, including the Greulich and Pyle Atlas (GP), the Fels Method (Fels), and the Sanders Hand Classification (Sanders). The purpose of this study was to quantitatively assess whether the integration of skeletal maturity assessment methods and demographic variables improves the accuracy of pediatric growth predictions over the use of skeletal markers or chronologic age alone. METHODS: The Brush Inquiry contains prospectively collected longitudinal data on children who lived in Cleveland, Ohio between 1926 and 1942. A total of 16 boys and 29 girls were selected for study. All had age, height, and an anteroposterior radiograph of the hand at each of 3 visits. Those visits occurred at 85%, 90%, and 95% of final height. We determined the growth completed at each visit by dividing the height observed by the final height at skeletal maturity. Boys and girls were analyzed separately using chronologic age, height, GP, Fels, and Sanders. The residual difference between the height predicted and actual height, as well as the SD of the prediction error of the cohort at each time point was calculated. To account for multiple visits from each subject, all linear models were produced using the generalized estimating equations (GEEs) procedure. RESULTS: For boys, age, GP, and Fels performed similarly in predicting growth remaining at all 3 time points. For girls, age, GP, and Fels performed similarly in predicting growth remaining at the 85% and 95% time points; however, the Fels Method demonstrated improved performance at the 90% time point compared with chronologic age (P = 0.0076) and GP alone (P = 0.0155). For both boys and girls, the most accurate multivariate GEE model with the lowest SD of prediction error integrated Fels, age, GP, Sanders, and height. CONCLUSIONS: The most accurate multivariate GEE model of growth prediction for both boys and girls integrated Fels, age, GP, Sanders, and height. When calculating the amount of growth remaining, it is prudent to integrate multiple systems for greater predictive accuracy. LEVEL OF EVIDENCE: Level III.

Estimating peak height velocity in individuals: a comparison of statistical methods.

BACKGROUND: Estimates pertaining to the timing of the adolescent growth spurt (e.g. peak height velocity; PHV), including age at peak height velocity (aPHV), play a critical role in the diagnosis, treatment, and management of skeletal growth and/or developmental disorders. Yet, distinct statistical methodologies often result in large estimate discrepancies. AIM: The aim of the present study was to assess the advantages and disadvantages of three modelling methodologies for height as well as to determine how estimates derived from these methodologies may differ, particularly those that may be useful in paediatric clinical practice. SUBJECTS AND METHODS: Height data from 686 individuals of the Fels Longitudinal Study were modelled using 5th order polynomials, natural cubic splines, and SuperImposition by Translation and Rotation (SITAR) to determine aPHV and PHV for all individuals together (i.e. population average) by sex and separately for each individual. Estimates within and between methodologies were calculated and compared. RESULTS: In general, mean aPHV was earlier, and PHV was greater for individuals when compared to estimates from population average models. Significant differences between mean aPHV and PHV for individuals were observed in all three methodologies, with SITAR exhibiting the latest aPHV and largest PHV estimates. CONCLUSION: Each statistical methodology has a number of advantages when used for specific purposes. For modelling growth in individuals, as one would in paediatric clinical practice, we recommend the use of the 5th order polynomial methodology due to its parameter flexibility.

Early Maturity as the New Normal: A Century-long Study of Bone Age.

BACKGROUND: Epiphyseal fusion (EF) marks the completion of longitudinal bone growth, a critical milestone monitored during treatment of skeletal growth and/or developmental disorders. Recently, a trend toward accelerated skeletal maturation in children has been documented. Because current methods for assessing skeletal maturation include children in their reference populations born as early as the 1930s, the timing of EF events in contemporary patients may differ substantially from those standards. QUESTIONS/PURPOSES: (1) Do children today initiate the process of EF in the hand and wrist earlier than past generations on which maturity standards are based? (2) Do children today complete EF in the hand and wrist earlier than past generations on which maturity standards are based? METHODS: A total of 1292 children (665 males, 627 females) participating in the Fels Longitudinal Study, born between 1915 and 2006, were included in this retrospective, observational study. Each participant had between one and 39 serial left hand-wrist radiographs during childhood obtained specifically for research purposes. Main outcomes were the chronological age at the first sign of EF initiation (EF-I) and the first chronological age when EF was complete (EF-C) in the radius and ulna, and metacarpals and phalanges of the first, third, and fifth rays according to criteria of the Fels method. EF is a reliable metric with an average κ agreement statistic of 0.91. Penalized B-splines were used to model the changes in EF-I and EF-C ages and to identify changes across continuous birth years with major comparisons between children born in 1935 and 1995. RESULTS: Approximately half of the epiphyses of the hand and wrist examined exhibited earlier EF-I and/or earlier EF-C in children born in 1995 compared with those born in 1935. The age at each milestone (EF-I and EF-C) decreased by as much as 6.7 and 6.8 months in males and 9.8 and 9.7 months in females, respectively. This change occurred gradually over the past century. The more proximal traits (EF of the distal radius, distal ulna, and metacarpals) were more likely to experience a shift in timing, whereas timing of EF in the phalanges remained relatively stable across birth years. CONCLUSIONS: A trend has occurred over the past century in the timing of EF, in both initiation and completion of the process, for many of the bones of the hand and wrist. Earlier EF reflects modern population advances in both skeletal and sexual maturation. Shifts in the timing of EF have the potential to influence treatment strategies for skeletal growth and/or developmental disorders such as scoliosis or leg length inequality, moving treatment windows to earlier ages. Earlier EF-I and EF-C identified in this study signals a need to reevaluate the timing of maturational milestones and current standards for skeletal assessment. LEVEL OF EVIDENCE: Level II, prognostic study.

Automated extraction of biplanar stereo-radiographic image measurements: Mizzou 3D SPinE.

PURPOSE: Although several studies have reported on the application of biplanar stereo-radiographic technology in pediatric clinical practice, few have performed large-scale analyses. The manual extraction of these types of data is time-consuming, which often precludes physicians and scientists from effectively utilizing these valuable measurements. To fill the critical gap between clinical assessments and large-scale evidence-based research, we have addressed one of the primary hurdles in using data derived from these types of imaging modalities in pediatric clinical practice by developing an application to automatically transcribe and aggregate three-dimensional measurements in a manner that facilitates statistical analyses. METHODS: Mizzou 3D SPinE was developed using R software; the application, instructions, and process were beta tested with four separate testers. We compared 1309 manually compiled three-dimensional deformity measurements derived from thirty-five biplanar three-dimensional reconstructions (image sets) from ten pediatric patients to those derived from Mizzou 3D SPinE. We assessed the difference between manually entered values and extracted values using a Fisher's exact test. RESULTS: Mizzou 3D SPinE significantly reduced the duration of data entry (95.8%) while retaining 100% accuracy. Manually compiled data resulted in an error rate of 1.58%, however, the magnitude of errors ranged from 5.97 to 2681.82% significantly increased the transcription accuracy (p value < 0.0001) while also significantly reducing transcription time (0.33 vs. 8.08 min). CONCLUSION: Mizzou 3D SPinE is an essential component in improving evidence-based patient care by allowing clinicians and scientists to quickly compile three-dimensional data at regular intervals in an automated, efficient manner without transcription errors.

Anterior Vertebral Body Tethering: A Single-Center Cohort with 4.3 to 7.4 Years of Follow-up.

BACKGROUND: Vertebral body tethering (VBT) is a well-recognized, non-fusion alternative for idiopathic scoliosis in children with growth remaining. To date, there have been almost no published outcome studies with postoperative follow-up of >2 years. We aimed to fill this gap by evaluating mid-term outcomes in our first 31 consecutive patients. METHODS: We retrospectively assessed additional clinical and radiographic data (mean, 5.7 ± 0.7 years) from our first 31 consecutive patients. Assessments included standard deformity measures, skeletal maturity status, and any additional complications (e.g., suspected broken tethers or surgical revisions). Using the same definition of success (i.e., all residual deformities, instrumented or uninstrumented, ≤30° at maturity; no posterior spinal fusion), we revisited the success rate, revision rate, and suspected broken tether rate. RESULTS: Of our first 31 patients treated with VBT, 29 (of whom 28 were non-Hispanic White and 1 was non-Hispanic Asian; 27 were female and 2 were male) returned for additional follow-up. The success rate dropped to 64% with longer follow-up as deformity measures increased, and the revision rate increased to 24% following 2 additional surgical revisions. Four additional suspected broken tethers were identified, for a rate of 55%, with only 1 occurring beyond 4 years. No additional patients had conversion to a posterior spinal fusion. We observed a mean increase of 4° (range, 2° to 8°) in main thoracic deformity measures and 8° (range, 6° to 12°) in thoracolumbar deformity measures. CONCLUSIONS: With >5 years of follow-up, we observed a decrease in postoperative success, as progression of the deformity was observed in most subgroups, and an increase in the revision and suspected broken tether rates. No additional patients had conversion to a posterior spinal fusion, which may indicate long-term survivorship. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Double major curvature treated with vertebral body tethering of both curves: how do outcomes compare to posterior spinal fusion?

PURPOSE: Vertebral body tethering (VBT) is a non-fusion alternative to posterior spinal fusion (PSF). There have been few reports on VBT of two curvatures. We aim to compare the radiographic outcomes between VBT and PSF in patients with double curvatures in which both curves were instrumented. METHODS: 29 AIS patients matched by Lenke, age (± 2 years), triradiate cartilage closure status, major Cobb angle (± 8°), and T5-T12 kyphosis (± 10°). Variables were compared using Wilcoxon rank-sum tests, Student's t tests, and chi-Square. Clinical success was defined as major curve < 35°. RESULTS: Group baseline demographics were similar. Major thoracic (T) curve types had significantly better major (VBT 51.5 ± 7.9° to 31.6 ± 12.0° [40%] vs. PSF 54.3 ± 7.4° to 17.4 ± 6.5° [68%]; p = 0.0002) and secondary curve correction in the PSF group. 71% of major T VBT patients were clinically successful versus 100% of PSF. Major thoracolumbar (TL) curve types experienced comparable major (VBT 52.3 ± 7.0° to 18.3 ± 11.4° (65%) vs. PSF 53.0 ± 5.2° to 23.8 ± 10.9° (56%); p = 0.2397) and secondary curve correction. 92% of major TL VBT patients were clinically successful versus 75% in the PSF group. There was no difference in T5-12 kyphosis or lumbar lordosis between groups for any curve type. There were 4 patients (13.8%) with major complications in the VBT group compared to 0 (0%) in the PSF. CONCLUSION: Patients with double major AIS who underwent VBT with major T curve types had less correction than PSF; however, those with major TL curves experienced similar radiographic outcomes regardless of procedure. Complications were greater for VBT.

Outcomes of vertebral body tethering in the lumbar spine.

PURPOSE: The use of vertebral body tethering (VBT) for the treatment of main thoracic deformities in adolescent idiopathic scoliosis patients is becoming increasingly more common, but limited data exist on its safety and efficacy in thoracolumbar deformities. We aimed to evaluate the postoperative outcomes of patients with thoracolumbar (TL) deformities that were treated with VBT. METHODS: We assessed clinical and radiographic data from twenty-eight consecutive patients that were surgically managed with VBT, all of whom exhibited a TL deformity with at least two years (mean: 44.7 ± 14.5 months) of postoperative follow-up. Standard radiographic parameters were extracted from left hand wrist and standing posterior-anterior and lateral spine radiographs at various timepoints. Outcome variables were assessed based on preoperative Lenke Classification and included: deformity measures, complications, surgical revisions, and postoperative success. RESULTS: The mean age at the time of instrumentation was 13.4 ± 1.3 years, with an average preoperative Sanders Stage of 4.6 ± 1.4. A significant reduction in preoperative deformities was observed at most postoperative timepoints. A perioperative complication was observed in three patients and surgical revision was required in another four patients. A suspected broken tether was observed in sixteen patients, most of which occurred at the apex of the lumbar deformity. Only one patient required surgical revision due to a suspected broken tether. We observed an overall success rate of 57%, regardless of Lenke Classification. CONCLUSIONS: These data indicate that VBT can successfully correct TL deformity patterns in 57% of patients without an increase in the rate of perioperative complications, suspected broken tethers, or surgical revisions.

When successful, anterior vertebral body tethering (VBT) induces differential segmental growth of vertebrae: an in vivo study of 51 patients and 764 vertebrae.

PURPOSE: This study aimed to determine (1) does vertebral body tethering (VBT) produce differential growth modulation in individual vertebrae in patients with idiopathic scoliosis, (2) does VBT change disc shape, and (3) does VBT affect total spine length? METHODS: Patients with idiopathic scoliosis treated with VBT of the main thoracic curve and minimum 2-year follow-up were included. Vertebrae and discs were categorized as uninstrumented proximal thoracic, instrumented main thoracic, or uninstrumented thoracolumbar-lumbar. The left- and right-sided heights of each vertebra and disc were measured on subsequent radiographs to assess for differential growth. T1-T12 thoracic and T1-S1 thoracolumbar growth velocities were compared with standardized reference data. RESULTS: Fifty-one patients (764 vertebrae and 807 discs) were analyzed. The average major curve magnitude improved from 46° ± 11° to 17° ± 11° at 2-year follow-up. Differential growth was observed in MT vertebrae, in which the left/concave side grew 2.0 ± 2.2 mm compared with 1.5 ± 2.3 mm on the right/convex (tethered) side (p < 0.001). Differential height changes were observed for all discs, but were most pronounced in instrumented MT discs, in which the right/convex sides decreased by an average of 1.2 mm each, compared with no significant height change on the left/concave side. Total spinal growth velocities were not significantly different from standard reference data. CONCLUSION: Vertebral body tethering limits convex spinal growth as designed while permitting concave growth. Curve correction results from differential vertebral growth and decreased convex disc height. Overall spinal growth continues at the expected rate. LEVEL OF EVIDENCE: Level IV case series.

Evidence of the non-linear nature of skeletal maturation.

OBJECTIVE: The aim of this study was to assess longitudinal trajectories of skeletal maturation to determine if children exhibit periods of rapid maturation during normal childhood and adolescence. DESIGN: Retrospective longitudinal study. PATIENTS: 345 participants, with an average of 25 assessments per participant, between 3 and 20 years of age from the Fels Longitudinal Study. MAIN OUTCOME MEASURE: s : Chronological age (ie, timing) and rate (ie, tempo) of skeletal maturation, as assessed by the Fels Method, at each maturational milestone, as well as the duration of time spent between any two milestones, were calculated for each participant-specific maturational trajectory and compared between three unique, non-linear maturational trajectory types. RESULTS: More than 81% of participants exhibited a rapid period of skeletal maturation during childhood and/or adolescence, most of whom were characterised by a single maturational spurt during adolescence. Participants with only a single adolescent spurt in skeletal maturation reach adolescent onset and peak approximately 2.8 and 4.2 years earlier, respectively, in boys (p<0.001) and girls (p<0.001), than when compared with participants with both childhood and adolescent spurts. Differences in the timing and tempo of maturational milestones were driven primarily by trajectory type. CONCLUSIONS: Rapid changes in skeletal maturation occur during normal childhood and/or adolescence, indicating the presence of a maturational spurt: a developmental phenomenon that has remained largely uncharacterised. This work highlights patterned changes in the timing, tempo and duration of longitudinal skeletal maturation while simultaneously shifting the paradigm that skeletal maturation progresses linearly.

Anterior Vertebral Body Tethering for Adolescent Scoliosis with Growth Remaining: A Retrospective Review of 2 to 5-Year Postoperative Results.

BACKGROUND: Anterior vertebral body tethering (VBT) is an early treatment option for progressive scoliosis in pediatric patients, allowing for continued deformity correction during normal growth. We report postoperative radiographic and clinical outcomes for patients treated with VBT. METHODS: This clinical and radiographic retrospective review of 31 consecutive patients included an analysis of preoperative, perioperative, and postoperative details, including the Lenke classification; Cobb angle measurements of the proximal thoracic, main thoracic, and lumbar curves; the sagittal profile; and skeletal maturity. Successful outcomes were defined by a residual curve of ≤30° in skeletally mature patients who did not undergo a posterior spinal fusion (PSF). RESULTS: Of the 31 patients treated, 29 met the inclusion criteria, and 2 were lost to follow-up. The mean patient age (and standard deviation) at the time of the surgical procedure was 12.7 ± 1.5 years (range, 10.2 to 16.7 years), with most patients classified as Risser grade 0 or 1 (52%) and Sanders stage 3 (32%). A mean of 7.2 ± 1.4 vertebral levels were instrumented, with a minimum preoperative Cobb angle of 42°. At the latest follow-up, 27 patients had reached skeletal maturity (Sanders stage ≥7) and 20 patients exhibited a curve magnitude ≤30°, for a success rate of 74%. A suspected broken tether occurred at ≥1 level in 14 patients (48%). Two patients underwent PSF and 4 had tether revision. The overall revision rate was 21% (6 of 29). CONCLUSIONS: This study shows the success and revision rates as well as the impact of a suspected broken tether on the procedural success of VBT. Despite our patient population being slightly more mature at the time of the surgical procedure compared with previous studies, we had a higher success rate and a lower revision rate. A PSF was avoided in 93% of patients, indicating that VBT may be a reliable treatment option for adolescent scoliosis in skeletally immature individuals. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.