Anterior Spinal Growth Modulation in Skeletally Immature Patients with Idiopathic Scoliosis: A Comparison with Posterior Spinal Fusion at 2 to 5 Years Postoperatively

Risk of early complication following anterior vertebral body tethering for idiopathic scoliosis

PURPOSE

The purpose of this study was to determine peri-operative morbidity associated with anterior vertebral body tethering (aVBT) for idiopathic scoliosis.

METHOD

Of 175 patients treated with aVBT, 120 patients had 2 year follow up and were included in this study. Prospectively collected clinical and radiographic data was analyzed retrospectively.

RESULTS

Pre-operatively, the mean patient age was 12.6 year (8.2-15.7 year), Risser 0-3, with main thoracic scoliosis 51.2° (40-70°). Immediately post-operative, scoliosis improved to 26.9° (6-53°; p < 0.05), at 1-year post-operative was 23.0° (- 11 to 50°; p < 0.01 vs immediate post-op) and at 2-year post-operative was 27.5° (- 5 to 52; p = 0.64 vs immediate post-op). Pre-operative T5-T12 kyphosis was 16.0° (- 23 to 52°), post-operative was 16.9° (- 7 to 44°), at 1-year was 17.5° (- 14 to 61°) and at 2-year was 17.0° (- 10 to 50°; p = 0.72 vs pre-op). All patients underwent thoracoscopic approach, EBL 200 ml (20-900 ml), surgical time 215.3 min (111-472 min), anesthesia time 303.5 min (207-480 min), ICU stay of 0.2 day (0-2 days), and post-operative hospital stay 4.5 days (2-9 days). During the in-hospital peri-operative period, there were no unplanned return to the operating room (UPROR) and there was a 0.8% rate of complication: one pneumothorax requiring reinsertion of chest tube. By 90 days post-operative, there was no UPROR and a 5% rate of complication. Five additional patients developed complications after discharge: one CSF leak treated with blood patch injection in the clinic and resolved, two pleural effusions requiring chest tubes, one superficial wound infection and one pneumonia treated with outpatient antibiotics. By 1-year post-op, there was a 1.7% rate of UPROR and 8.3% rate of complication. Four additional patients developed complications beyond 90 days: two upper limb paresthesia required outpatient medical management, one CSF leak which initially treated blood patch injection in the clinic initially which then required UPROR, and one compensatory lumbar curve add on that was treated with extension of the tether. By 2-years post-op, there was a 6.7% rate of UPROR and 15.8% rate of complication. 9 additional complications developed after 1 year. One curve progression, one keloid scar, one right leg weakness, 4 cable failures and 2 curve overcorrections.

CONCLUSION

This large, multicenter series of aVBT demonstrated a 15.8% complication rate and a 6.7% UPROR rate at 2 year post-operatively. This early study during the learning curve of aVBT found higher rates of CSF leaks and overall complications than would be expected for PSFI at 1 year post-operatively and a higher rate of overall complications and of UPROR than would be expected for PSFI at 2 year post-operatively. As is common with new procedures, the complication rate may fall with further experience.

Prospective Follow-up Report on Anterior Vertebral Body Tethering for Idiopathic Scoliosis: Interim Results from an FDA IDE Study

BACKGROUND

Anterior vertebral body tethering (aVBT) has emerged as a novel treatment option for patients with idiopathic scoliosis. We present the results from the first U.S. Food and Drug Administration (FDA) Investigational Device Exemption (IDE) study on aVBT.

METHODS

In this prospective review of a retrospective data set, eligible patients underwent aVBT at a single center from August 2011 to July 2015. Inclusion criteria included skeletally immature patients with Lenke type-1A or 1B curves between 30° and 65°. Clinical and radiographic parameters were collected, with the latter measured by an independent reviewer.

RESULTS

Fifty-seven patients (49 girls and 8 boys), with a mean age (and standard deviation) of 12.4 ± 1.3 years (range, 10.1 to 15.0 years), were enrolled in the study. The patients had a mean of 7.5 ± 0.6 levels tethered, the mean operative time was 223 ± 79 minutes, and the mean estimated blood loss was 106 ± 86 mL. The patients were followed for an average of 55.2 ± 12.5 months and had a mean Risser grade of 4.2 ± 0.9 at the time of the latest follow-up. The main thoracic Cobb angle was a mean of 40.4° ± 6.8° preoperatively and was corrected to 18.7° ± 13.4° at the most recent follow-up. In the sagittal plane, T5-T12 kyphosis measured 15.5° ± 10.0° preoperatively, 17.0° ± 10.1° postoperatively, and 19.6° ± 12.7° at the most recent follow-up. Eighty percent of patients had curves of <30° at the most recent follow-up. The most recent Scoliosis Research Society (SRS) scores averaged 4.5 ± 0.4, and scores on the self-image questionnaire averaged 4.4 ± 0.7. No major neurologic or pulmonary complications occurred. Seven (12.3%) of 57 patients had a revision: 5 were done for overcorrection and 2, for adding-on.

CONCLUSIONS

Anterior VBT is a promising technique that has emerged as a treatment option for patients with immature idiopathic scoliosis. We present the results from the first FDA-approved IDE study on aVBT, which formed the basis for the eventual Humanitarian Device Exemption approval. The findings affirm the safety and efficacy of this technique and suggest opportunities for improvement, particularly with respect to reoperation rates.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Intra-operative forecasting of growth modulation spine surgery outcomes with spatio-temporal dynamic networks

PURPOSE

In adolescent idiopathic scoliosis (AIS), non-invasive surgical techniques such as anterior vertebral body tethering (AVBT) enable to treat patients with mild and severe degrees of deformity while maintaining lower lumbar motion by avoiding spinal fusion. However, multiple features and characteristics affect the overall patient outcome, notably the 3D spine geometry and bone maturity, but also from decisions taken intra-operatively such as the selected tethered vertebral levels, which makes it difficult to anticipate the patient response.

METHODS

We propose here a forecasting method which can be used during AVBT surgery, exploiting the spatio-temporal features extracted from a dynamic networks. The model learns the corrective effect from the spine's different segments while taking under account the time differences in the initial diagnosis and between the serial acquisitions taken before and during surgery. Clinical parameters are integrated through an attention-based decoder, allowing to associate geometrical features to patient status. Long-term relationships allow to ensure regularity in geometrical curve prediction, using a manifold-based smoothness term to regularize geometrical outputs, capturing the temporal variations of spine correction.

RESULTS

A dataset of 695 3D spine reconstructions was used to train the network, which was evaluated on a hold-out dataset of 72 scoliosis patients using the baseline 3D reconstruction obtained prior to surgery, yielding an overall reconstruction error of [Formula: see text]mm based on pre-identified landmarks on vertebral bodies. The model was also tested prospectively on a separate cohort of 15 AIS patients, demonstrating the integration within the OR theatre.

CONCLUSION

The proposed predictive network allows to intra-operatively anticipate the geometrical response of the spine to AVBT procedures using the dynamic features.

Could have tethered: predicting the proportion of scoliosis patients most appropriate for thoracic anterior spinal tethering

BACKGROUND

Posterior spinal fusion (PSF) has proven to be a safe, reliable technique to treat spinal deformities in adolescents. In recent early reports, vertebral body tethering (VBT) is showing promise as a method to modulate growth, driving scoliosis correction, while offering the potential added benefit of maintaining some flexibility in the instrumented segment. With recent FDA humanitarian device exemption (HDE) approval, VBT is poised to become more widely available as a treatment for a subset of current PSF candidates. Our aim was to use approved criteria from a recent FDA IDE to determine who could have been tethered in the years preceding approval.

METHODS

A retrospective analysis was performed of patients with idiopathic scoliosis treated with PSF or VBT at a large pediatric spine center from 1/1/2016 to 6/25/2019. Tethering indications followed the criteria outlined by an ongoing FDA IDE: age 8-16, Sanders bone age ≤ 4, primary thoracic curve between 35° and 60°, and lumbar curve < 35°. Risser sign and triradiate cartilage status were also employed to ascertain skeletal maturity in the absence of Sanders score.

RESULTS

Of the 359 patients (78.6% female) who underwent PSF or VBT for idiopathic scoliosis, 75 (20.9%) met IDE criteria for VBT (57 had PSF and 18 had VBT). 284 were not appropriate for thoracic VBT: 77 (21.4%) had a non-thoracic primary curve, 80 (22.3%) were too mature at presentation, 36 (10.0%) had a lumbar curve > 34°, 9 (2.5%) had a main thoracic curve out of range, and 1 had a proximal thoracic curve > 40°. 81 patients (22.6%) had multiple exclusionary criteria.

CONCLUSIONS

After decades with a successful treatment for AIS (PSF), we are at an inflection point: VBT is conditionally approved by the FDA as an HDE device, unleashing more widespread use. Many pediatric spine surgeons will want to know what proportion of PSFs will someday be VBTs. If FDA IDE criteria are used to ensure that a VBT candidate has an appropriate maturity stage and scoliosis deformity pattern, 20.9% of our 359 surgical range patients would have qualified for thoracic VBT.

LEVEL OF EVIDENCE

Level III.

Complications, Reoperations, and Mid-Term Outcomes Following Anterior Vertebral Body Tethering Versus Posterior Spinal Fusion: A Meta-Analysis

Background

Anterior vertebral body tethering (AVBT) is a growth-modulation technique theorized to correct adolescent idiopathic scoliosis (AIS) without the postoperative stiffness imposed by posterior spinal fusion. However, data are limited to small series examining short-term outcomes. To assess AVBT's potential as a viable alternative to posterior spinal fusion (PSF), a comprehensive comparison is warranted. The purpose of this meta-analysis was to compare postoperative outcomes between patients with AIS undergoing PSF and AVBT. Our primary objective was to compare complication and reoperation rates at available follow-up times. Secondary objectives included comparing mid-term Scoliosis Research Society (SRS)-22 scores, and coronal and sagittal-plane Cobb angle corrections.

Methods

We performed a systematic review of outcome studies following AVBT and/or PSF procedures. The inclusion criteria included the following: AVBT and/or PSF procedures; Lenke 1 or 2 curves; an age of 10 to 18 years for >90% of the patient population; <10% non-AIS scoliosis etiology; and follow-up of ≥1 year. A single-arm, random-effects meta-analysis was performed. Deformity corrections, complication and reoperation rates, and postoperative SRS-22 scores were recorded.

Results

Ten AVBT studies (211 patients) and 14 PSF studies (1,069 patients) were included. The mean follow-up durations were similar for both groups. Pooled complication rates were 26% for AVBT versus 2% for PSF, and reoperation rates were 14.1% for AVBT versus 0.6% for PSF with nonoverlapping confidence intervals (CIs). The pooled reoperation rate among studies with follow-up times of ≥36 months was 24.7% in AVBT versus 1.8% in PSF. Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar.

Conclusions

Our study showed greater rates of complications and reoperations with AVBT compared with PSF. Reoperation rates were significantly greater in AVBT studies with longer follow-up (≥36 months). Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar. While a potential fusionless treatment for AIS merits excitement, clinicians should consider AVBT with caution. Future long-term randomized prospective studies are needed.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Does preoperative and intraoperative imaging for anterior vertebral body tethering predict postoperative correction?

PURPOSE

Anterior vertebral body tethering (AVBT) is an emerging approach for idiopathic scoliosis. However, overcorrection and under-correction are common causes of revision surgery, and intraoperative tensioning of the cord is one key component to achieve appropriate curve correction. We sought to determine whether preoperative flexibility radiographs or intraoperative radiographs would predict correction at first erect imaging for scoliosis patients undergoing anterior vertebral body tethering (AVBT).

METHODS

Single-center retrospective review. Fifty-one patients with a diagnosis of idiopathic scoliosis underwent anterior body tethering. Preoperative flexibility films and intraoperative radiographs were compared to first erect standing radiographs to determine if there was a correlation in Cobb angle.

RESULTS

Preoperative major Cobb angle measured 52° ± 9°. Major Cobb angle on bending films was 24° ± 8°. Intraoperative imaging showed correction to a mean of 17° ± 8°. Postoperative first erect standing radiographs showed correction to a mean of 26° ± 10°. The mean difference in major Cobb angle between intraoperative radiograph and a first erect radiograph was 10° ± 4°, whereas the mean difference from preoperative bending radiograph at first erect was 2° ± 7°. Thus, correction on preoperative flexibility films correlated with the first erect radiograph.

CONCLUSION

Preoperative bending radiographs provide a reasonable estimate of postoperative correction for patients undergoing AVBT with tensioning of the cord. Surgeons should expect the major Cobb angle to increase on first erect radiographs compared to intraoperative radiographs. These findings may guide patient selection and assist surgeons in achieving appropriate correction intraoperatively.

Anterior Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: Early Results and Future Directions

Anterior vertebral body tether (AVBT) is a nonfusion surgical procedure for correction of scoliosis in skeletally immature individuals. With US Food and Drug Administration approval in 2019, AVBT technology is spreading and early to midterm reports are being published. Early clinical reports are promising while precise indications, outcomes, complication profiles, and best practices are being established. Patients who are skeletally immature and wish to avoid a fusion surgery may benefit from this procedure. This article highlights the translational science foundation, early to midterm clinical reports, and future directions for this growing technique in pediatric spinal deformity surgery.

Cost-Utility Analysis of Anterior Vertebral Body Tethering versus Spinal Fusion in Idiopathic Scoliosis from a US Integrated Healthcare Delivery System Perspective

Purpose

Anterior vertebral body tethering (VBT) is a non-fusion, minimally invasive, growth-modulating procedure with some early positive clinical outcomes reported in pediatric patients with idiopathic scoliosis (IS). VBT offers potential health-related quality of life (HRQoL) benefits over spinal fusion in allowing patients to retain a greater range of motion after surgery. We conducted an early cost-utility analysis (CUA) to compare VBT with fusion as a first-choice surgical treatment for skeletally immature patients (age >10 years) with moderate to severe IS, who have failed nonoperative management, from a US integrated healthcare delivery system perspective.

Patients and Methods

The CUA uses a Markov state transition model, capturing a 15-year period following index surgery. Transition probabilities, including revision risk and subsequent fusion, were based on published surgical outcomes and an ongoing VBT observational study (NCT02897453). Patients were assigned utilities derived from published patient-reported outcomes (PROs; SRS-22r mapped to EQ-5D) following fusion and the above VBT study. Index and revision procedure costs were included. Probabilistic (PSA) and deterministic sensitivity analyses (DSA) were performed.

Results

VBT was associated with higher costs but also higher quality-adjusted life years (QALYs) than fusion (incremental costs: $45,546; QALYs gained: 0.54). The subsequent incremental cost-effectiveness ratio for VBT vs fusion was $84,391/QALY gained. Mean PSA results were similar to the base case, indicating that results were generally robust to uncertainty. The DSA indicated that results were most sensitive to variations in utility values.

Conclusion

This is the first CUA comparing VBT with fusion in pediatric patients with IS and suggests that VBT may be a cost-effective alternative to fusion in the US, given recommended willingness-to-pay thresholds ($100,000–$150,000). The results rely on HRQoL benefits for VBT compared with fusion. For improved model accuracy, further analyses with longer-term PROs for VBT, and comparative effectiveness studies, would be needed.

Return to sport and daily life activities after vertebral body tethering for AIS: analysis of the sport activity questionnaire

Purpose

Vertebral body tethering (VBT) is an alternative to fusion for selected scoliosis patients. As VBT does not limit spine mobility, it has been propagated that this technique allows a quicker return to physical activity than fusion. However, no data are available to support this statement. Aim of this study was to quantify how much time patients required to resume preoperative activity level and to seek possible associations between return to physical activity and demographic, radiographic and surgical data.

Methods

One year postoperatively, the validated sport activity questionnaire (SAQ) was administered to all skeletally immature patients who underwent VBT at our institution. SAQ data were analyzed and a multivariate analysis was conducted to investigate associations between SAQ and demographic, radiographic and surgical data.

Results

Thirty-one patients aged 14.5 years completed the SAQ. Within 3 months from VBT, 97% returned to school, 61% resumed physical education, 97% carried a backpack, 68% run, and 82% rode a bike; 70% bent within a month from VBT. Ninety-four percent of patients returned to their preoperative athletic level. Within 3 months, 63% of responders resumed noncontact, 61% contact and 53% collision sports. No relevant associations were observed between the SAQ and demographic, radiographic and surgical data. In particular, number of instrumented vertebrae, level of the lowest instrumented vertebra and postoperative Cobb angle did not influence patients’ return to preoperative activities.

Conclusion

VBT allows patients to quickly return to their preoperative activity level, irrespectively of the postoperative Cobb angle or type of instrumentation.

Learning curve for vertebral body tethering: analysis on 90 consecutive patients

STUDY DESIGN

Retrospective study.

OBJECTIVES

Vertebral body tethering (VBT) is raising interest for the treatment of adolescent idiopathic scoliosis (AIS), but many scoliosis surgeons have not been trained in anterior surgical approaches. We analyzed data of our first patients to define the learning curve for VBT. VBT has shown encouraging results in the treatment of growing AIS patients, but there is a paucity of data and long-term results are not yet available. To our best knowledge, there is no published data regarding the learning curve for VBT.

METHODS

A retrospective analysis was performed, of all consecutive patients who underwent VBT at our Institution. Outcomes of interest were intubation time, surgical duration and estimated blood loss per screw and hospitalization length. For the statistical analysis, we referred to a linear model regression diagnostic and we used the Pearson product-moment correlation (r) for pairwise correlation. The final effect ranked between + 1 and - 1.

RESULTS

Data of 90 patients were analyzed, age 14.6 ± 1.8 years. On average, 9.4 ± 2.6 levels were instrumented. Per screw, mean intubation time was 33.1 ± 7.6 min (r = - 0.57; p > 0.0001), mean surgical duration 21.3 ± 5.7 min (r = - 0.55; p > 0.0001), mean estimated blood loss 21.3 ± 18.2 ml (r = - 0.66; p > 0.0001). Mean hospitalization length was 8.3 ± 3.1 days (r = - 0.32; p = 0.002). No intraoperative complications were reported.

CONCLUSION

VBT has a rapid learning curve: the estimated blood loss per screw is expected to decrease by 60%, intubation time and surgical duration by over 50%, and hospitalization length by 32% for each treated patient.

LEVEL OF EVIDENCE

III.

Safety and efficacy of anterior vertebral body tethering in the treatment of idiopathic scoliosis

AIMS

Spinal fusion remains the gold standard in the treatment of idiopathic scoliosis. However, anterior vertebral body tethering (AVBT) is gaining widespread interest, despite the limited data on its efficacy. The aim of our study was to determine the clinical efficacy of AVBT in skeletally immature patients with idiopathic scoliosis.

METHODS

All consecutive skeletally immature patients with idiopathic scoliosis treated with AVBT enrolled in a longitudinal, multicentre, prospective database between 2013 and 2016 were analyzed. All patients were treated by one of two surgeons working at two independent centres. Data were collected prospectively in a multicentre database and supplemented retrospectively where necessary. Patients with a minimum follow-up of two years were included in the analysis. Clinical success was set a priori as a major coronal Cobb angle of < 35° at the most recent follow-up.

RESULTS

A total of 57 patients were included in the study. Their mean age was 12.7 years (SD 1.5; 8.2 to 16.7), with 95% being female. The mean preoperative Sanders score and Risser grade was 3.3 (SD 1.2), and 0.05 (0 to 3), respectively. The majority were thoracic tethers (96.5%) and the mean follow-up was 40.4 months (SD 9.3). The mean preoperative major curve of 51° (SD 10.9°; 31° to 81°) was significantly improved to a mean of 24.6° (SD 11.8°; 0° to 57°) at the first postoperative visit (45.6% (SD 17.6%; 7% to 107%); p < 0.001)) with further significant correction to a mean of 16.3° (SD 12.8°; -12 to 55; p < 0.001) at one year and a significant correction to a mean of 23° (SD 15.4°; -18° to 57°) at the final follow-up (42.9% (-16% to 147%); p < 0.001). Clinical success was achieved in 44 patients (77%). Most patients reached skeletal maturity, with a mean Risser score of 4.3 (SD 1.02), at final follow-up. The complication rate was 28.1% with a 15.8% rate of unplanned revision procedures.

CONCLUSION

AVBT is associated with satisfactory correction of deformity and an acceptable complication rate when used in skeletally immature patients with idiopathic scoliosis. Improved patient selection and better implant technology may improve the 15.8% rate of revision surgery in these patients. Further scrutiny of the true effectiveness and long-term risks of this technique remains critical. Cite this article: Bone Joint J 2020;102-B(12):1703-1708.