The effects of vertebral body tethering on sagittal parameters: evaluations from a 2-years follow-up

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.

A comparison of patients receiving vertebral body tethering for adolescent idiopathic scoliosis in the public and private hospital setting

PURPOSE

Vertebral body tethering (VBT) is a new growth-modulating surgery for adolescent idiopathic scoliosis (AIS) requiring a distinct skillset and intraoperative setup. We compared perioperative details and outcomes of VBTs performed in a public pediatric orthopedic hospital and a general private hospital setting.

METHODS

We identified all patients receiving VBT for AIS from 1/2020 to 12/2023 with ≥ 6 months post-operative follow-up, with surgeries performed by the same senior surgeons. Clinical, radiological, and surgical details were retrieved.

RESULTS

24 VBTs were performed in the private setting and 16 in the public setting. Average age at operation was 11.9 ± 1.1 at a Sanders staging of 3.8 ± 1.2 when the major curve Cobb angle was 50.5 ± 8.0°. Tethered curves were most often thoracic in location (23/40) followed by thoracolumbar/lumbar curves (10/40) and double curve tethers (7/40). Overall correction ratio of 68.0 ± 19.0% was achieved. Time from booking to operation (82.2 ± 39.2 vs 63.1 ± 34.4 days, p = 0.112) and operation time (310 ± 86.4 min vs. 289 ± 87.4 min, p = 0.054) were longer in the public and private setting respectively but failed to reach statistical significance. Time to chest drain removal (1.5 ± 0.8 vs. 3.5 ± 1.7 days, p < 0.001) and length of stay (4.3 ± 0.9 vs. 6.6 ± 1.8 days, p < 0.001) were significantly shorter in the private setting, whilst complication rates remained similar (7/24 vs. 3/16, p = 0.456).

CONCLUSION

Expertise, resource availability, and costs differ in the public and private healthcare setting. With regards to VBT, the conditions for referral and surgical outcomes remained similar. Earlier drain removal and discharge for patients managed in the private setting was not associated with an increase in complication rate.

Analysis of three-dimensional spine growth for vertebral body tethering patients at 2 and 5 years post operatively

PURPOSE

Scoliosis can be treated with vertebral body tethering (VBT) as a motion-sparing procedure. However, the knowledge of how growth is affected by a tether spanning multiple levels is unclear in the literature. Three-dimensional true spine length (3D-TSL) is a validated assessment technique that accounts for the shape of the spine in both the coronal and sagittal planes. This study aimed to assess if 3D-TSL increases over a five-year period after VBT implantation in thoracic curves for idiopathic scoliosis.

METHODS

Prospectively collected radiographic data from an international pediatric spine registry was analyzed. Complete radiographic data over three visits (post-operative, 2 years, and 5 years) was available for 53 patients who underwent VBT.

RESULTS

The mean age at instrumentation of this cohort was 12.2 (9-15) years. The average number of vertebrae instrumented was 7.3 (SD 0.7). Maximum Cobb angles were 50° pre-op, which improved to 26° post-op (p < 0.001) and was maintained at 5 years (30°; p = 0.543). Instrumented Cobb angle was 22° at 5 years (p < 0.001 vs 5-year maximum Cobb angle). An accentuation was seen in global kyphosis from 29° pre-operative to 41° at 5 years (p < 0.05). The global spine length (T1-S1 3D-TSL) started at 40.6 cm; measured 42.8 cm at 2 years; and 44.0 cm at the final visit (all p < 0.05). At 5 years, patients reached an average T1-S1 length that is comparable to a normal population at maturity. Immediate mean post-operative instrumented 3D-TSL (top of UIV-top of LIV) was 13.8 cm two-year length was 14.3 cm; and five-year length was 14.6 cm (all p < 0.05). The mean growth of 0.09 cm per instrumented level at 2 years was approximately 50% of normal thoracic growth. Patients who grew more than 0.5 cm at 2 years had a significantly lower BMI (17.0 vs 19.0, p < 0.05) and smaller pre-operative scoliosis (48° vs 53°, p < 0.05). Other subgroup analyses were not significant for age, skeletal maturity, Cobb angles or number of spanned vertebras as contributing factors.

CONCLUSIONS

This series demonstrates that 3D-TSL increased significantly over the thoracic instrumented levels after VBT surgery for idiopathic scoliosis. This represented approximately 50% of expected normal thoracic growth over 2 years.

The efficacy of anterior vertebral body tethering in lenke type 6 curves for adolescent idiopathic scoliosis

PURPOSE

Spinal fusion is the standard treatment for severe forms of adolescent idiopathic scoliosis (AIS). However, with the lowest instrumented vertebra that is usually located at L3 or L4, patients are prone to develop adjacent segment degeneration in the long term. Vertebral body tethering (VBT) as motion preserving technique has become an alternative for select patients with AIS. Several studies have presented the outcome after thoracic VBT but no study has analyzed the outcome after VBT for Lenke type 6 curves.

METHODS

This is a retrospective single center data analysis of patients who have had bilateral VBT for Lenke type 6 curves and a minimum follow up of 24 months. Radiographic analysis was performed on several time points. Suspected tether breakages were additionally analyzed with respect to location and time at occurrence.

RESULTS

25 patients were included. Immediate thoracic curve correction was 55.4% and 71.7% for TL/L curves. Loss of correction was higher for TL/L curves and resulted in a correction rate of 48.3% for thoracic curves and 48.9% for TL/L curves at 24 months post-operatively. 22 patients were suspected to have at least one segment with a tether breakage. Three patients required a re-VBT but no patient received posterior spinal fusion.

CONCLUSION

Bilateral VBT for Lenke type 6 curves is feasible and shows a significant curve correction for thoracic and TL/L curves at a minimum of 24 months post-operatively. Tether breakage rate and loss of correction remain an unfavorable observation that needs to be improved in the future.

Evidence-based Indications for Vertebral Body Tethering in Spine Deformity

Posterior spinal fusion has long been established as an effective treatment for the surgical management of spine deformity. However, interest in nonfusion options continues to grow. Vertebral body tethering is a nonfusion alternative that allows for the preservation of growth and flexibility of the spine. The purpose of this investigation is to provide a practical and relevant review of the literature on the current evidence-based indications for vertebral body tethering. Early results and short-term outcomes show promise for the first generation of this technology. At this time, patients should expect less predictable deformity correction and higher revision rates. Long-term studies are necessary to establish the durability of early results. In addition, further studies should aim to refine preoperative evaluation and patient selection as well as defining the benefits of motion preservation and its long-term effects on spine health to ensure optimal patient outcomes.

Radiographic outcome after vertebral body tethering of the lumbar spine

INTRODUCTION

Multiple studies have analyzed the outcome after thoracic Vertebral Body Tethering (VBT). The results seem reproducible with most studies reporting coronal correction rates around 50% and a tether breakage rate near 20% at two years follow-up. There is a paucity of data on lumbar VBT, and no study has yet analyzed the radiographic outcome after lumbar VBT in a double tether technique at two years follow-up, which was the aim of this study.

METHODS

This is a retrospective, single surgeons' data analysis of all consecutive immature patients who have had VBT of the lumbar spine (to L3 or L4) between January 2019 and September 2020. Primary interest focused on coronal curve correction at two years post-operatively. Suspected tether breakages were analyzed separately and defined as an angular change of more than 5° between two adjacent screws.

RESULTS

Forty-one patients were eligible for this study and 35 (85%) had complete two-year follow-up data. Average age at surgery was 14.3 years. All patients had a Sanders stage of 7 or below. Average curve correction for thoracolumbar/lumbar curves at two years follow-up was 50%. 90% of patients had at least one level with a suspected tether breakage. No patient required a revision surgery within two years from surgery but two patients were surgically revised after two years.

CONCLUSION

VBT in the lumbar spine resulted in 50% coronal curve correction two years post-operatively despite a tether breakage in 90% of patients.

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.

The different applications of Vertebral Body Tethering - Narrative review and clinical experience

Background

Vertebral body tethering (VBT) has been originally developed as a growth modulation technique for the surgical management of skeletally immature patients with adolescent idiopathic scoliosis (AIS). Given the positive results obtained in this setting, the use of VBT is gradually expanding to other patient categories, such as those with no or limited remaining growth or with non-idiopathic scoliosis. Aim of this manuscript is to offer an overview over the current applications of VBT, along with imaging and comments derived from the clinical experience. The work was based on a literature search conducted in January 2023 on Pubmed, Scopus and Web of Science databases. Following keywords were used for the search: vertebral body tethering, adolescent idiopathic scoliosis, early onset scoliosis, neuromuscular scoliosis, syndromic scoliosis.

Results

Three patient categories in which VBT has been applied have been highlighted: VBT for growth modulation in AIS, VBT as anterior scoliosis correction in AIS and VBT for non-idiopathic curves or early-onset scoliosis.

Conclusion

While growth modulation in AIS still represents the most widespread use of VBT, the use of this technique has yielded positive results in different settings as well, such as scoliosis correction in AIS or temporary or definitive curve management in non-AIS curves. While long-term results are lacking, patient selection seems to play a central role to reduce the complication rate and ensure predictable and stable results.

Perioperative Outcomes of Open Anterior Vertebral Body Tethering and Instrumented Posterior Spinal Fusion for Skeletally Immature Patients With Idiopathic Scoliosis

BACKGROUND

Correcting adolescent idiopathic scoliosis (AIS) without fusion can be achieved with anterior vertebral body tethering (AVBT). However, little is known about the perioperative outcomes, pain control, and clinical outcomes in patients undergoing AVBT compared with instrumented posterior spinal fusion (IPSF).

METHODS

In this retrospective cohort study, we compared pediatric patients with AIS who underwent either AVBT or IPSF. Inclusion criteria were based on the AVBT group, which included primary thoracic idiopathic scoliosis, Risser ≤1, curve magnitude 40 to 70 degrees, age 9 to 15, no prior spine surgery, index surgery between 2014 and 2019, and minimum 2-year follow-up. Patient demographics, perioperative metrics, pain visual analog scale scores, opiate morphine equivalent usage, cost data, and radiographic outcomes were compared.

RESULTS

We identified 23 patients who underwent AVBT and 24 matched patients in the IPSF group based on inclusion criteria. Patients undergoing AVBT and PSF were similar in age (12±1 y vs. 13±1 y, P =0.132) and average follow-up time (3.8±1.6 y vs. 3.3±1.4 y, P =0.210). There were 23 female patients (87%) in the AVBT group and 24 female (92%) patients in the IPSF group. Intraoperatively, estimated blood loss (498±290 vs. 120±47 mL, P <0.001) and procedure duration (419±95 vs. 331±83 min, P =0.001) was significantly greater in the IPSF group compared with AVBT. Length of stay was lower in the AVBT group compared with PSF (4±1 vs. 5±2 d, P =0.04). PSF patients had significantly greater total postoperative opiate morphine equivalent use compared with AVBT (2.2±1.9 vs. 5.6±3.4 mg/kg, P <0.001). Overall direct costs following PSF and AVBT were similar ($47,655+$12,028 vs. $50,891±$24,531, P =0.58). Preoperative radiographic parameters were similar between both the groups, with a major thoracic curve at 51±10 degrees for AVBT and 54±9 degrees for IPSF ( P =0.214). At the most recent follow-up, IPSF patients had greater curve reduction to a mean major thoracic curve of 11±7 degrees (79%) compared with 19±10 degrees (63%) in AVBT patients ( P =0.002). Nine patients (39%) required revision surgery following AVBT compared with 4 patients(17%) following IPSF ( P =0.09).

CONCLUSIONS

In a select cohort of patients, AVBT offers decreased surgical time, blood loss, length of stay, and postoperative opiate usage compared with IPSF. Although IPSF resulted in greater deformity correction at 2-year follow-up, the majority of patients who underwent AVBT had ≤35 major curves and avoided fusion. There is optimism for AVBT as a treatment option for select AIS patients, but long-term complications are still being understood, and the risk for revision surgeries remains high.

LEVEL OF EVIDENCE

Level III.

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.

The preliminary outcomes of vertebral body tethering in treating adolescent idiopathic scoliosis: a systematic review

PURPOSE

VBT is a novel alternative to spinal fusion surgery to treat skeletally immature AIS and was approved to correct idiopathic scoliosis in August 2019 by US Federal Drug Administration (FDA). To systemically review the preliminary outcomes of vertebral body tethering (VBT) in treating adolescent idiopathic scoliosis.

METHODS

The electronic databases PubMed, EMBASE, and Web of Science were queried up to January 2022 for articles regarding VBT. Basic characteristics of patients, changes of radiographic parameters in coronal and sagittal planes, and clinical outcomes of surgical treatment of VBT including complication and revision rates were summarized.

RESULTS

Twenty five studies met the inclusion criteria. Most studies (23/25) included patients with only skeletal immaturity. The average % correction of the main/tethered curve at final follow-up, and % correction of thoracic kyphosis at final follow-up were reported to be 15.6-106.5% and - 31.8 to 20.0%, respectively. The most common complications for VBT were tether breakage (n = 145;21.3%), pulmonary complications (n = 49; 6.9%), and overcorrection (n = 30; 4.2%). The revision rate was 13.1%.

CONCLUSION

VBT could effectively and safely correct spinal deformity in skeletally immature patients with AIS and preserve the motion and growth of the spine. However, VBT has a relatively high complication and revision rates. Therefore, surgeons should cautiously consider VBT for treating AIS. Future research efforts are needed to lower the complication and revision rates. Whatever, VBT is still in its infancy and may have a promising future as a non-fusion solution for AIS.

The timing of tether breakage influences clinical results after VBT

INTRODUCTION

Tether breakage is a frequent mechanical complications after vertebral body tethering (VBT), but not all patients with a breakage show loss of correction. The reason of this clinical finding has not yet been clarified. We hypothesized that the integrity of the tether is relevant only in the early stages after VBT, when it drives growth modulation and tissue remodelling. After these mechanisms have taken place, the tether loses its function and a breakage will not alter the new shape of the spine. Thus, tether breakage would have a greater clinical relevance when occurring shortly after surgery.

METHODS

All consecutive patients who underwent VBT and had a min. 2-year follow-up were included. The difference in curve magnitude between the 1st standing x-ray and the last follow-up was calculated (ΔCobb). For each curve, the presence and timing of tether breakage were recorded. The curves were grouped according to if and when the breakage was observed (no breakage, breakage at 0-6 months, 6-12 months, > 12 months). The ΔCobb was compared among these groups with the analysis of variance (ANOVA).

RESULTS

Data from 152 curves were available: 68 with no breakage, 12 with a breakage at 0-6 months, 37 at 6-12 months and 35 > 12 months. The ANOVA found significant difference in the ΔCobb among the groups (Sum of square 2553.59; degree of freedom 3; mean of square 851.1; Fisher test 13.8; P < 0.0001). Patients with no breakage or breakage at > 12 months had similar ΔCobb (mean 4.8° and 7.8°, respectively, P = 0.3), smaller than the 0-6 or 6-12 groups (15.8° and 13.8°, respectively).

CONCLUSION

Tether breakage leads to a consistent loss of correction when occurring within the first 12 months, while it has limited clinical relevance when occurring later on.

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.