Rate of Scoliosis Correction After Anterior Spinal Growth Tethering for Idiopathic Scoliosis

Which Lenke type curve is most appropriate for vertebral body tethering in adolescent idiopathic scoliosis?

PURPOSE

Clinical trials have studied the effects of curve magnitude and flexibility, age, and skeletal immaturity on the outcomes of VBT. No studies have assessed the effect of Lenke curve type on the outcomes of VBT. This study compares outcomes in patients who underwent VBT with Lenke type 1, 3, 5, and 6 curves.

METHODS

Single center retrospective review of patients undergoing mini-open thoracoscopic-assisted two row vertebral body tethering (2RVBT) for the correction of AIS with a minimum 2-year follow-up were included. Patients were grouped by Lenke type, which yielded 4 groups; types 1, 3, 5, or 6. Analysis included preoperative demographic parameters, as well as radiographic and clinical outcome measures.

RESULTS

156 2RVBT (Lenke 1, N = 61; Lenke 3, N = 35; Lenke 5, N = 37; Lenke 6, N = 23) patients met inclusion criteria. The mean preoperative apex Cobb angle in the Lenke type 1, 3, 5, and 6 groups were 50.2 ± 9.1, 50.5 ± 10.1, 45.0 ± 8.6, and 49.0 ± 10.8, respectively. This corrected to 21.2 ± 10.2, 19.2 ± 8.5, 13.6 ± 7.2, 18.5 ± 8.3 in Lenke type 1, 3, 5, and 6 groups, respectively, demonstrating that Lenke type 5 saw greatest correction following 2RVBT. With regards to revision recommendation following tether breakage, Lenke type 3 curves were most frequently indicated for fusion, whereas Lenke type 1 curves were most frequently not indicated for revision surgery.

CONCLUSION

Lenke type 5 curves are the most amenable to correction via 2RVBT, as evident by their lower post-operative apex Cobb angles and lowest rate of recommendation for revision to posterior spinal fusion.

When is Growth the Greatest? Spine and Total Body Growth in Idiopathic Scoliosis Through Sanders Maturation Stages 2, 3A, 3B, and 4

Background

Sanders maturation stages (SMS) 2 to 4 represent periods of rapid growth and are considered ideal candidates for growth modulation surgery, such as anterior vertebral body tethering. A detailed assessment of spine growth during these stages is essential but limited. This study aimed to clarify the differences in growth rates for spine and total body height across SMS 2, 3A, 3B, and 4, as well as to assess cumulative growth until skeletal maturity for these stages.

Methods

This single-center, retrospective, case-control longitudinal study evaluated consecutive patients with idiopathic scoliosis staged SMS 2 to 4. T1-S1 spine height, total body height, and curve magnitude were measured at each visit. Monthly growth rates for spine and total body height were calculated between baseline and first follow-up visit (6-12 months). In a subset followed to skeletal maturity, cumulative spine and total body height gain were assessed. To account for height loss due to scoliosis, spine and total body height were adjusted for curve magnitude using validated formulas. Multivariate linear regression models were employed to evaluate the relationship between SMS and growth, adjusting for confounding factors.

Results

A total of 517 patients (68% female) were included. Spine height growth was highest in patients at SMS 3A, approximately 1.4 times stage 2, 1.5 times stage 3B, and 1.8 times stage 4. Total body height growth rates were comparable between SMS 2 and 3A, both significantly exceeding SMS 3B and 4. Among 314 patients followed to skeletal maturity, cumulative growth in spine and total body height was greatest in patients at SMS 2.

Conclusions

This study demonstrated that spinal growth was most pronounced in patients at SMS 3A, while total body height growth was greatest during SMS 2 and 3A. Less mature patients exhibited greater cumulative growth potential in both spine and total body height. These findings provide crucial insights for determining the optimal timing of growth modulation surgery.

Level of Evidence

Level III Case-control study. See Instructions for Authors for a complete description of levels of evidence.

Achieving the Needed Correction in Vertebral Body Tethering: The Relationship Between Preoperative Flexibility, Intraoperative Correction, and First Erect Imaging

BACKGROUND

Vertebral body tethering (VBT) is a nonfusion surgical treatment for scoliosis. Recent data have shown that intraoperative correction is critical for successful curve correction over time. This study aims to evaluate the relationship between preoperative, intraoperative, and postoperative correction. We hypothesize that preoperative flexibility will match first erect imaging, intraoperative correction will overestimate postoperative correction, and correction has improved over time with increased surgeon experience.

METHODS

This study is a retrospective review of patients who underwent VBT at a single center between 2015 and 2023. Patient radiographs were reviewed preoperatively (standing and fulcrum bending), intraoperatively, and postoperatively first erect.

RESULTS

Our study included 157 patients: 127 females (81%) with a mean age of 13.2 years (range: 9 to 17) at surgery and a mean of 7.9 vertebrae instrumented (range: 5 to 12 vertebrae). Twenty-three had 2 curves instrumented (85% single curve). One hundred eight patients had thoracic curves (69%), 33 thoracolumbar (21%), and 16 lumbar (10%). Preoperative curve magnitude averaged 51 degrees (range: 36 to 72). The mean bending radiograph curve measurement was 24 degrees (53% correction). The mean intraoperative curve magnitude was 15 degrees (72% correction). Intraoperative curve magnitude and correction were significantly different between curve types, with increased correction in lumbar curves (7 degrees, 86% correction) and less correction in thoracic curves (16 degrees, 68% correction). On first erect postoperative imaging (mean 8 d post-op, range: 1 to 44), the curve magnitude was 26 degrees (49% correction). The R2 correlation of the first erect radiograph was 0.209 for preoperative bending and 0.554 for intraoperative measurements. The mean difference in first erect curve magnitude was +2 degrees from preoperative flexibility radiographs and +11 degrees from intraoperative radiographs. Pre-2020, the intraoperative curve averaged 18 degrees, and >2020 averaged 13 degrees ( P =0.001). Pre-2020, the first erect averaged 30 degrees, and >2020 improved to 24 degrees ( P <0.001), despite equivalent preoperative metrics (both 51 degrees curves, P =0.98, with 54 vs. 52% flexibility, P =0.31).

CONCLUSIONS

Our study indicates that preoperative bending films can provide a practical approximation of the correction on first erect imaging. Intraoperative correction has the strongest relationship and averages 11 degrees less than the postoperative standing curve magnitude. Further, our site's intraoperative and postoperative correction has improved over time with increased surgeon experience.

LEVEL OF EVIDENCE

Level III-retrospective cohort.

Learning Curve Associated With Thoracoscopic Anterior Vertebral Body Tether and Double Anterior Vertebral Body Tether for Idiopathic Scoliosis: Analysis of Three Independent Surgeons

BACKGROUND AND OBJECTIVES

Anterior vertebral body tether (VBT) is a fusionless approach to treat idiopathic scoliosis, and surgeons are beginning to implement the technique into current practice. This study aims to evaluate the learning curve for single and double VBT.

METHODS

A retrospective review of 3 surgeons' first 40 single and 20 double VBT was performed. Skeletally immature patients with idiopathic scoliosis who underwent thoracic (single) or thoracolumbar (double) VBT were included. Thoracic VBT was done via video-assisted thoracoscopic surgery and lumbar VBT through a mini-open retroperitoneal approach. Primary outcomes of interest were operative time, radiation exposure, and radiographic correction. Pooled and individual-surgeon analyses were performed.

RESULTS

A total of 180 patients were included: 120 single and 60 double. Mean age was 12.7 years, and 87.8% were female. Mean segments tethered was 7.8 in single and 11.0 in double. Mean preoperative thoracic scoliosis was 51.5: single 50.5° and double 53.3°. Mean lumbar scoliosis was 36.4°: single 30.0° and double 49.0°. Average operating time was 276.2 minutes; double VBT was significantly longer (217.3 vs 394.0 minutes, P < .001). Mean blood loss was 198.5 mL, and mean fluoroscopy dose was 73.0 mGy. For single VBT, there was a decrease in operative time (283.3-174.8 minutes, P < .001) and fluoroscopy dose (70.1-53.5 mGy, P = .047) over time. Every 10 cases resulted in a 31.4 minute decrease in operative time ( P < .001). There were no intraoperative complications. Single VBT resulted in 54.9% thoracic curve correction. Double VBT achieved 53.0% thoracic and 56.7% lumbar correction. There were no differences in curve correction across the learning curve.

CONCLUSION

VBT is viable fusionless surgical option for scoliosis. As expected, increased experience resulted in shorter operative time; the threshold for such improvement seems to be 10 cases. Importantly, adequate and consistent curve correction can be achieved at the start of the learning curve while mitigating complications.

Matched comparison of non-fusion surgeries for adolescent idiopathic scoliosis: posterior dynamic distraction device and vertebral body tethering

PURPOSE

Two non-fusion devices for adolescent idiopathic scoliosis (AIS) received HDE approval for clinical use in 2019: posterior dynamic distraction device (PDDD) and vertebral body tethering system (VBT). Although indications are similar, there is no comparative study of these devices. We hypothesize that curve correction will be comparable, but PDDD will have better perioperative metrics.

METHODS

AIS PDDD patients were prospectively enrolled in this matched multicenter study. Inclusion criteria were Lenke 1 or 5 curves, preoperative curves 35°-60°, correction to ≤30° on bending radiographs, and kyphosis <55°. Patients were matched by age, sex, Risser, curve type and curve magnitude to a single-center cohort of VBT patients. Results were compared at 2 years.

RESULTS

20 PDDD patients were matched to 20 VBT patients. Blood loss was higher in the VBT cohort (88 vs. 36 ml, p < 0.001). Operative time and postoperative length of stay were longer in the VBT cohort, 177 vs. 115 min (p < 0.001) (2.9 vs. 1.2 days, p < 0.001). Postoperative curve measurement and correction at 6 months were better in the PDDD cohort (15° vs. 24°, p < 0.001; 68% vs. 50%, p < 0.001). At 1-year, PDDD patients had improved Cobb angles (14° vs. 21°, p = 0.001). At 2 years, a correction was improved in the PDDD cohort, with a curve measurement of 17° for PDDD and 22° for VBT (p = 0.043). At the latest follow-up, 3 PDDD patients and 1 VBT patient underwent revision surgery.

CONCLUSION

Early results show PDDD demonstrates better index correction, reduced operative time, less blood loss, and shorter length of stay but higher rates of revision compared to a matched cohort of VBT patients at two-year follow-up.

LEVEL OF EVIDENCE

Level II, prospective cohort matched comparative study.

Vertebral Body Tethering in Skeletally Immature Patients: Results of a Prospective U.S. FDA Investigational Device Exemption Study

BACKGROUND

The purpose of this study was to report on 2-year results of vertebral body tethering (VBT), performed under a Food and Drug Administration protocol, to obtain insight into outcomes and complications.

METHODS

Forty prospectively enrolled patients with adolescent idiopathic scoliosis (AIS) who had a Sanders score of ≤4 or a Risser score of ≤2 underwent VBT for curves between 40° and 70°. Surgical, radiographic, and patient-reported outcomes were reviewed at a minimum 2-year follow-up.

RESULTS

Mean age at surgery was 13 (range, 10 to 16) years. The 40 patients were 90% female; 95% White, 2.5% other, and 2.5% unreported; and 92.5% non-Hispanic, 5% Hispanic, and 2.5% unreported. A mean of 8 (range, 5 to 12) levels were instrumented. Most patients were at Sanders 4 (65%) and Risser 0 (63%). Mean length of stay was 3 ± 1 days, estimated blood loss was 236 ± 158 (range, 25 to 740) mL, and operative time was 4.4 ± 1.4 hours. Mean correction of the major curve was 44% (range, 22% to 95%) on the 3-month standing radiograph, 49% at 1 year, and 46% (range, -10% to 93%) at 2 years. The mean major Cobb angle improved from 51° ± 8° (range, 40° to 70°) preoperatively to 27° ± 11° (range, 3° to 56°) at 2 years. Success at 2 years, defined by a Cobb angle of <35° and no reoperation, was seen in 30 patients (75%) and was associated with a mean Cobb angle of <35° on the first postoperative standing radiograph (p < 0.001). Twelve patients (30%) demonstrated improvement in the curve with growth. By 2 years, 2 (5%) of the patients underwent repeat surgery (1 release for overcorrection, 1 lumbar VBT for lumbar curve progression after thoracic VBT). The Scoliosis Research Society (SRS) satisfaction score improved 2 years following surgery (p < 0.001), but other SRS domains only remained stable over time. Beyond 2 years, 1 additional lumbar tether was required after thoracic VBT, 1 implant was removed, and 3 fusions were performed, for a 10% fusion rate and overall 20% reoperation rate at a mean of 3.8 ± 1.1 years of follow-up. The rate of cord breakage in the study population was 20%.

CONCLUSIONS

In skeletally immature patients treated in the U.S. under a prospective Investigational Device Exemption, there was a 75% rate of successful outcomes at 2 years. Most correction was obtained at the time of surgery, and inadequate intraoperative curve correction was associated with a higher Cobb angle on the first postoperative standing radiograph and failure by 2 years.

LEVEL OF EVIDENCE

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

Pediatric spinal alignment and spinal development

Background

Knowledge of the growth spurt and remaining growth is essential for managing musculoskeletal diseases in children. Accurate prediction of curve progression and timely interventions are crucial, particularly for conditions like adolescent idiopathic scoliosis (AIS).

Methods

This study conducted a comprehensive review and synthesis of existing literature on spinal growth, skeletal maturity classifications, and the evolution of sagittal alignment parameters during childhood and adolescence. Key anatomical elements involved in spinal development, natural history of spinal growth, and skeletal maturity assessment systems were analyzed.

Results

The analysis highlighted that key parameters such as Pelvic incidence (PI), Pelvic tilt (PT), and Lumbar lordosis (LL) increase significantly with growth, especially during the pubertal growth spurt. In contrast, Sacral slope (SS) remains relatively constant, and Thoracic kyphosis (TK) shows a slight increase. Additionally, there is a posterior shift in the center of gravity as children grow, reflecting progressive postural maturation. The study also reviewed and compared various maturity classification systems, noting the reliability and clinical implications of systems like the Sanders Maturity Stage (SMS) and Tanner-Whitehouse III.

Conclusions

Reliable maturity classification systems, such as the Sanders Maturity Stage (SMS) and Tanner-Whitehouse III, allow for tailored treatments to individual growth patterns. Integrating these classification systems into clinical practice enables precise prediction of curve progression and timely therapeutic interventions. This includes options from bracing to surgical techniques like growing rods or vertebral body tethering (VBT), with growth modulation being a key factor in achieving successful outcomes.

Growth modulation response in vertebral body tethering depends primarily on magnitude of concave vertebral body growth

PURPOSE

There is variability in clinical outcomes with vertebral body tethering (VBT) partly due to a limited understanding of the growth modulation (GM) response. We used the largest sample of patients with 3D spine reconstructions to characterize the vertebra and disc morphologic changes that accompany growth modulation during the first two years following VBT.

METHODS

A multicenter registry was used to identify idiopathic scoliosis patients who underwent VBT with 2 years of follow-up. Calibrated biplanar X-rays obtained at longitudinal timepoints underwent 3D reconstruction to obtain precision morphological measurements. GM was defined as change in instrumented coronal angulation from post-op to 2-years.

RESULTS

Fifty patients (mean age: 12.5 ± 1.3yrs) were analyzed over a mean of 27.7 months. GM was positively correlated with concave vertebra height growth (r = 0.57, p < 0.001), 3D spine length growth (r = 0.36, p = 0.008), and decreased convex disc height (r = - 0.42, p = 0.002). High modulators (patients experiencing GM > 10°) experienced an additional 1.6 mm (229% increase) of mean concave vertebra growth during study period compared to the Poor Modulators (GM < - 10°) group, (2.3 vs. 0.7 mm, p = 0.039), while convex vertebra height growth was similar (1.3 vs. 1.4 mm, p = 0.91).

CONCLUSION

When successful, VBT enables asymmetric vertebra body growth, leading to continued postoperative coronal angulation correction (GM). A strong GM response is correlated with concave vertebral body height growth and overall instrumented spine growth. A poor GM response is associated with an increase in convex disc height (suspected tether rupture). Future studies will investigate the patient and technique-specific factors that influence increased growth remodeling.

Subclassification of Sanders Maturation Stage 3 Demonstrates Differences in Spine and Total Height Velocity Between 3A and 3B in Patients With Idiopathic Scoliosis

STUDY DESIGN

A single-center retrospective case-control study.

OBJECTIVE

To compare the spine and total height velocity between Sanders maturation stage (SMS) 3A and 3B.

SUMMARY OF BACKGROUND DATA

Identifying SMS 3 is critical for treating growing children because it represents the early phase of rapid adolescent growth. However, there is limited literature available that clearly describes the growth differences between 3A and 3B.

MATERIALS AND METHODS

The current study included consecutive patients with idiopathic scoliosis staged SMS 3 from January 2012 to December 2021. T1-S1 spine height, total body height, and curve magnitude were measured at the initial and follow-up visits. In addition to the spine and total height velocity calculated per month, corrected height velocity was estimated for curve magnitude using a validated formula. Mann-Whitney U test was used to compare SMS 3A and 3B outcomes, followed by a multiple linear regression model to evaluate the association of the SMS subclassifications to growth velocity adjusted for confounding factors.

RESULTS

A total of 204 patients (66% girls, mean age: 12.3±1.3 y) met the inclusion criteria. Patients staged SMS 3A had higher spine height velocity (mm/month) in both girls (2.3 vs. 1.5, P <0.001) and boys (2.6 vs. 1.7, P <0.001), as well as total height velocity [mm/month; (5.8 vs. 4.3, P <0.001 for girls; 6.6 vs. 4.5, P <0.001 for boys]. Corrected velocity showed similar results with greater spine and total height velocity in SMS 3A. Multivariate analysis indicated a significant association of the SMS subclassification to the spine and total height velocity. The scoliosis curve progression was comparable between SMS 3A and 3B.

CONCLUSIONS

SMS 3A and 3B had differential growth velocity in the spine and total body height. These results indicate the importance of the SMS 3 subclassification for managing scoliosis treatment, including observation, bracing, and surgical interventions with fusion and growth modulation.

LEVEL OF EVIDENCE

Level III-case-control study.

Thoracoscopic Anterior Vertebral Body Tethering in Lenke Type-1 Right Adolescent Idiopathic Scoliosis

Background

Vertebral body tethering (VBT) is indicated for skeletally immature patients with progressive adolescent idiopathic scoliosis (AIS) who have failed or are intolerant of bracing and who have a major coronal curve of 40° to 65°. The vertebral body must be structurally and dimensionally adequate to accommodate screw fixation, as determined radiographically. The best indication for VBT is a flexible single major thoracic curve with nonstructural compensating lumbar and proximal thoracic curves (Lenke 1A or 1B). VBT allows for progressive correction of the deformity without spinal fusion by utilizing a minimally invasive fluoroscopic technique.

Description

The procedure for a right thoracic curve is performed with use of a right thoracoscopic approach with the patient in the left lateral decubitus position. The thoracoscope is introduced through a portal at the apex of the curvature in the posterior axillary line. Instrument portals are created lateral to each vertebral body in the mid-axillary line. Screws are inserted into each vertebral body under biplanar fluoroscopic control and with intraoperative neuromonitoring. An electroconductivity probing device, while not mandatory, is routinely utilized at our practice. The tether is attached to the most proximal screw of the construct, and then reduction is obtained sequentially by tensioning the tether from one vertebral screw to the next.

Alternatives

Bracing is the gold-standard treatment for progressive AIS involving the immature spine. The most commonly utilized surgical treatment is posterior spinal fusion (PSF), which should be considered when the major coronal curve exceeds 45°.

Rationale

PSF has proven to be a dependable technique to correct scoliotic deformities. It has a low complication rate and good long-term outcomes. However, concerns exist regarding the stiffness conferred by PSF and the long-term effects of adjacent segment disease. Thus, interest had developed in non-fusion solutions for AIS correction. VBT utilizes the Hueter-Volkmann principle to guide growth and correct deformity. Compressive forces applied to the convexity of the deformity by a polyethylene tether allow the patient's growth to realign the spine. Intraoperative correction triggers growth modulation, and most of the modulation seems to occur during the first 12 months postoperatively. The best results have been seen with a short Lenke type-1A curve in a patient with closed triradiate cartilage, a Risser 3 or lower (ideally Risser 0) iliac apophysis, and a flexible curve characterized by a 50% reduction of the major coronal curve angle on side-bending radiographs.

Expected Outcomes

In 57 immature patients with a Lenke type-1A or 1B curve (i.e., a 30° to 65° preoperative Cobb angle), Samdani et al.3 found a main thoracic Cobb angle reduction from 40° ± 7° preoperatively to 19° ± 13° at 2 years after VBT. In the sagittal plane, the T5-T12 kyphosis measured 15° ± 10° preoperatively, 17° ± 10° postoperatively, and 20° ± 13° at 2 years. No major neurologic or pulmonary complications occurred. A total of 7 (12.3%) of the 57 patients underwent surgical revision, including 5 for overcorrection and 2 to span additional vertebrae. In a study of 21 skeletally mature patients, Pehlivanoglu et al.4 found that the Cobb angle was reduced from 48° preoperatively to 16° on the first-erect postoperative radiograph and finally to 10° at the latest follow-up (mean, 27.4 months). The 2 main complications of VBT reported in the literature are overcorrection and tether breakage. Both may require revision, which explains the higher rate of revision observed for VBT compared with PSF.

Important Tips

Good patient selection is important. VBT is most appropriate in cases of a flexible Lenke type-1A or 1B curve in an immature child before Risser stage 3 and after triradiate cartilage closure.Always monitor and control screw positioning in both anteroposterior and lateral planes fluoroscopically.The screws should be placed parallel to the vertebral end plates or, even better, be angled inferiorly for the upper vertebrae and angled superiorly for the lower vertebrae to decrease the risk of pull-out when tensioning the device and during growth modulation. Less tension on the uppermost and lowermost instrumented vertebrae than at the apex, as controlled by the tensioning device, can also help to limit pull-out.

Acronyms and Abbreviations

VBT = vertebral body tetheringAIS = adolescent idiopathic scoliosisIONM = intraoperative neuromonitoringPSF = posterior spinal fusionUIV = upper instrumented vertebraLIV = lower instrumented vertebraAP = anteroposteriorK-wire = Kirschner wire.

Posterior Vertebral Pedicular Tethering for the Treatment of Idiopathic Adolescent Scoliosis

Over the last decade, there has been a new wave of interest in non-fusion techniques for the treatment of adolescent idiopathic scoliosis. These are not new techniques, as they were first published and presented in the late 1950s, using compression of the convexity or distraction of the concavity of the main curvature. More recently, anterior vertebral body tethering has raised great interest, as although it is a major procedure through the child's chest, it seems appropriate for the thoracic curves. The main objective of this article is to describe Posterior Vertebral Pedicular Tethering (PVPT) as a "new" technique performed as a less invasive spinal procedure for the treatment of certain thoracolumbar and lumbar scoliosis in growing adolescents. It is an alternative growth modulation technique appropriate for thoracolumbar and lumbar curvatures where we observe reduction of the three plane deformity of idiopathic scoliosis in adolescents.

Vertebral body tethering: An alternative to posterior spinal fusion in idiopathic scoliosis?

INTRODUCTION

Skeletally immature patient with adolescent idiopathic scoliosis (AIS) whose curves continue to progress despite bracing should be treated surgically. Vertebral body tethering (VBT) is a non-fusion, compression-based, growth preserving alternative to posterior spinal fusion (PSF) based on the concept of 'growth modulation' to prevent possible functional complications secondary to fusion while correcting scoliotic deformity. This review aims to shed light on the indications of VBT, short- and medium-term outcomes, describe the surgical technique and associated complications, and to compare its efficacy to that of PSF.

METHODS

A review of peer-reviewed literature on VBT as a surgical technique, its indications, outcomes, complications, and comparison with other surgical interventions to correct AIS was conducted in December 2022.

RESULTS

Indications remain controversial and mainly include stage of skeletal maturity based on radiographic markers, curve location, magnitude and flexibility, and presence of secondary curve. Assessment of VBT clinical success should not be restricted to improvement in radiographic parameters but should include functional results and patient-centered outcomes, improved body image and pain, and durability of outcomes. In contrast to fusion, VBT seems to be associated with preserved spinal growth, shorter recovery, potentially better functional outcomes, less motion loss but possibly less curve correction.

DISCUSSION

Yet still, with VBT there exists a risk of overcorrection, construct breakage or failure of procedure which require revision and at times conversion to PSF. Patient and family preferences must be accounted for acknowledging gaps in knowledge, attributes and drawbacks of each intervention.

Vertebral Body Tethering in AIS Management-A Preliminary Report

Vertebral Body Tethering (VBT) is a recently developed surgical technique for the treatment of progressive and severe scoliosis in patients with significant growth potential. It has been used since the first exploratory series, which showed encouraging results on the progressive correction of the major curves. This study reports on a retrospective series of 85 patients extracted from a French cohort, with a follow-up at a minimum of two years after a VBT with recent screws-and-tether constructs. The major and compensatory curves were measured pre-operatively, at the 1st standing X-ray, at 1 year, and at the last available follow-up. The complications were also analyzed. A significant improvement was observed in the curve magnitude after surgery. Thanks to growth modulation, both the main and the secondary curves continued to progress over time. Both the thoracic kyphosis and lumbar lordosis remained stable over time. Overcorrection occurred in 11% of the cases. Tether breakage was observed in 2% of the cases and pulmonary complications in 3% of the cases. VBT is an effective technique for the management of adolescent idiopathic scoliosis patients with residual growth potential. VBT opens an era of a more subtle and patient-specific surgical management of AIS that considers parameters such as flexibility and growth.

Minimum 3-year experience with vertebral body tethering for treating scoliosis: A systematic review and single-arm meta-analysis

PURPOSE

Over the past 12 years, vertebral body tethering (VBT) has been gradually promoted for treating scoliosis, but there are few published studies, with only short-term follow-up. This study aimed to systematically review VBT efficacy and safety for treating scoliosis.

METHODS

PubMed, Web of Science, Embase, and the Cochrane Library were searched for studies on VBT treatment of scoliosis published up to November 2021. Two researchers independently screened the literature, extracted data, and assessed the risk of bias in included studies. Data on clinical efficacy, unplanned reoperations, and complications were extracted. The meta-analysis was performed with R 4.1.0.

RESULTS

Twenty-six studies involving 1045 patients were included in the meta-analysis. The correction rate of major curve immediately post-operation was 46.6% ± 13.8% (16%-69%) and that at final follow-up was 53.2% ± 17.9% (16%-79%). The single-arm meta-analysis results of all included studies showed that VBT was effective in general. The overall clinical success rate was 73.02% (95% confidence interval [CI]: 68.31%-78.05%). The pooled overall unplanned reoperation rate was 8.66% (95% CI: 5.53%-13.31%). The overall incidence rate of complications was 36.8% (95% CI: 23.9%-49.7%). The subgroup analysis based on follow-up time indicated that patients with follow-up time >36 months had increased clinical success rate, unplanned reoperation rate, and incidence rate of complications compared with those with <36 months' follow-up time. The preliminary results showed that after 36 months of follow-up, only 7.17% (95% CI: 4.81%-10.55%) of patients required posterior spinal fusion (PSF) surgery and nearly 93% of patients avoided spinal fusion surgeries.

CONCLUSIONS

The current evidence from at least 3-year follow-up in different countries indicates that VBT is an effective surgical approach for treating scoliosis, with 73.88% of patients achieving clinical success. Nevertheless, about one in seven patients (15.8%) required unplanned reoperations, but only 7.17% required PSF. About half (52.17%) of the patients experienced complications. Due to the limitation of the study number and quality, our conclusion may be biased and requires verification by further studies with longer follow-up times.

To tether or fuse? Significant equipoise remains in treatment recommendations for idiopathic scoliosis

PURPOSE

Vertebral body tethering (VBT) continues to grow in interest from both a patient and surgeon perspective for the treatment of scoliosis. However, the data are limited when it comes to surgeon selection of both procedure type and instrumented levels. This study sought to assess surgeon variability in treatment recommendation and level selection for VBT versus posterior spinal fusion (PSF) for the management of scoliosis.

METHODS

Surgeon members of the Pediatric Spine Study Group and Harms Study Group were queried for treatment recommendations and proposed upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV) selection for PSF and VBT based on 17 detailed clinical vignettes. Responses were subdivided in each clinical vignette according to surgeon experience and treatment recommendations with assessment of intra-rater reliability. Binomial distribution tests were used to establish equipoise, selecting p < 0.10 to indicate the presence of a treatment choice with consensus set > 70% agreement. For treatment choice, responses were assessed first for consensus on the decision to proceed with PSF or VBT.

RESULTS

Thirty-five surgeons with varied experience completed the survey with 26 surgeons (74%) completing the second follow-up survey. Overall, VBT was the recommended treatment by 47% of surgeons, ranging by clinical vignette. Consensus in treatment recommendation was present for 6 clinical vignettes including 3 for VBT and 3 for PSF, with equipoise present for the remaining 11. Of the 17 vignettes, 12 demonstrated moderate intra-observer reliability including the 3 consensus vignettes for VBT. Sanders stage ≤ 3 and smaller curve magnitude were related with VBT recommendation but neither age nor curve flexibility significantly influenced the decision to recommend VBT. Surgeons with high VBT volume, ≥ 11 VBT cases/year, were more likely to recommend VBT than those with low volumes (0-10 cases per year (p < 0.0001)). High VBT volume surgeons demonstrated consensus in VBT recommendation for Lenke 5/6 curves (75% mean recommendation). High VBT volume surgeons had a significantly higher VBT recommendation rate for Lenke 1A, 2A curves (71.8% vs 48.0%, p = 0.012), and Lenke 3 curves (62% vs 26.9%, p = 0.023). Equipoise was present for all vignettes in low volume surgeons. In addition, high VBT volume surgeons trended toward including more instrumented levels than low VBT volume surgeons (7.17 vs 6.69 levels).

CONCLUSION

Significant equipoise is present among pediatric spine surgeons for treatment recommendations regarding VBT and PSF. Surgeon-, patient-, and curve-specific variables were identified to influence treatment recommendations, including surgeon experience, curve subtype, deformity magnitude, and skeletal maturity. This study highlights the need for continued research in identifying the optimal indications for VBT and PSF in the treatment of pediatric spinal deformity.

Vertebral Body Tethering: Indications, Surgical Technique, and a Systematic Review of Published Results

Vertebral body tethering (VBT) represents a new surgical technique to correct idiopathic scoliosis using an anterior approach, spinal instrumentation with vertebral body screws, and a cable compressing the convexity of the curve. According to the Hueter-Volkmann principle, compression reduces and distraction increases growth on the growth plates. VBT was designed to modulate spinal growth of vertebral bodies and hence, the term ‘growth modulation’ has also been used. This review describes the indications and surgical technique of VBT. Further, a systematic review of published studies was conducted to critically evaluate the results and complications of this technique. In a total of 23 included studies on 843 patients, the preoperative main thoracic curve corrected from 49 to 23 degrees in a minimum 2 year follow-up. The complication rate of VBT was 18%. The results showed that 15% of VBT patients required reoperations for pulmonary or tether-related issues (10%) and less than 5% required conversion to spinal fusion. While the reported median-term results of VBT appear promising, long-term results of this technique are currently lacking.