Anterior Vertebral Body Growth-Modulation Tethering in Idiopathic Scoliosis: Surgical Technique

Differential vertebral body growth is maintained after vertebral body tethering surgery for idiopathic scoliosis: 4-year follow-up on 888 peri-apical vertebrae and 592 intervertebral discs

PURPOSE

To radiographically evaluate if vertebral body tethering (VBT) can maintain differential peri-apical vertebral growth at medium-term follow-up of 4 years.

METHODS

A prospective, international, multicenter database was queried to identify idiopathic scoliosis patients treated with thoracic VBT. Concave vs. convex vertebral body height, vertebral wedging, and disc wedging of the 3 peri-apical vertebrae were measured by two independent observers at 5 timepoints (pre-operative to 4-year follow-up).

RESULTS

65 skeletally immature patients (60 female, mean 12.8 years old, 21 with open triradiate cartilages) met inclusion criteria. Mean pre-operative maximum scoliosis of 50 ± 8° decreased significantly post-operatively to 27 ± 9° (p < 0.001), which remained stable at 4-year follow-up 30 ± 17° (p = 0.38 vs. post-operative). Mean instrumented scoliosis was 21 ± 14° at 4-year follow-up, which was significantly different than 4-year maximum scoliosis (p < 0.001). Mean pre-operative kyphosis of 30 ± 12° did not significantly change post-operatively (p = 1.0) and remained stable at 4-year follow-up (35 ± 18°; p = 0.05). Mean individual convex vertebral height increased from 17.7 ± 1.9 mm to 19.8 ± 1.5 mm (p < 0.001), while mean individual concave height increased from 14.8 ± 1.9 mm to 17.6 ± 1.6 mm (p < 0.001). Summing the peri-apical heights, the difference in height from pre-operative to 4-year follow-up was greater on the concave (8.3 ± 4.7 mm) than on the convex side (6.2 ± 4.7 mm) (p < 0.001). Mean individual vertebral wedging decreased from 6 ± 2° at pre-operative to 4 ± 2° at 4-year follow-up (p < 0.001). Mean total vertebral and disc wedging started at 29 ± 7° pre-operatively, decreased to 16 ± 6° at post-operative (p < 0.001), then further decreased to 14 ± 8° at 4-year follow-up (p < 0.001). Patients with open triradiate cartilages at the time of surgery had a larger height change over the 4 years compared to those with closed triradiate cartilages (p < 0.001).

CONCLUSION

Patients with idiopathic scoliosis treated with VBT demonstrated differential vertebral growth which was maintained at minimum 4-year follow-up. This effect was more pronounced in patients whose triradiate cartilages were open at the time of surgery.

LEVEL OF EVIDENCE

III.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Prognostic, Level III.

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.

Anterior vertebral body tethering shows clinically comparable shoulder balance outcomes to posterior spinal fusion

PURPOSE

Posterior spinal fusion (PSF) is the current gold standard in surgical treatment for adolescent idiopathic scoliosis. Vertebral body tethering (VBT) is a fusionless alternative. Shoulder balance is an important metric for outcomes and patient satisfaction. Here we compare shoulder balance outcomes between PSF and VBT.

METHODS

In this retrospective review, the pre-operative and post-operative absolute radiographic shoulder height (|RSH|) of 45 PSF patients were compared to 46 VBT patients. Mean values were compared and then collapsed into discrete groups (|RSH| GROUP) and compared. Patients were propensity score matched. Regression models based on pretest-posttest designs were used to compare procedure type on post-operative outcomes.

RESULTS

Pre-operatively there were no differences in |RSH| between PSF and VBT, however, at latest post-operative follow-up PSF maintained a larger |RSH| imbalance compared to VBT (0.91 cm vs 0.63 cm, p = 0.021). In an ANCOVA regression, PSF was associated with a larger |RSH| imbalance compared to VBT, F(1, 88) = 5.76, p = 0.019. An ordinal logistic regression found that the odds ratio of being in a worse |RSH| GROUP for PSF vs VBT is 2.788 (95% CI = 1.099 to 7.075), a statistically significant effect χ2(1) = 4.658, p = 0.031. Results were similar in subgroup analyses of Lenke 1 and Lenke 2 patients, though to less statistical significance.

CONCLUSION

While PSF was found to be associated with worse |RSH| outcomes, the actual numbers (2-3 mm) are unlikely to be clinically meaningful. Thus, in this analysis, VBT can be said to show comparable shoulder balance outcomes to PSF.

Three-dimensional vertebral shape changes confirm growth modulation after anterior vertebral body tethering for idiopathic scoliosis

PURPOSE

To evaluate three-dimensional (3D) vertebra and disk shape changes over 2 years following anterior vertebral body tether (AVBT) placement in patients with idiopathic scoliosis (IS).

METHODS

Patients with right thoracic IS treated with AVBT were retrospectively evaluated. 3D reconstructions were created from biplanar radiographs. Vertebral body and disk height (anterior, posterior, left and right) and shape (wedging angle) were recorded over the three apical segments in the local vertebral reference planes. Changes in height and wedging were measured through 2 years postoperatively. Change in patient height was correlated with changes in the spine dimensions.

RESULTS

Forty-nine patients (Risser 0-3, Sanders 2-4) were included. The mean age was 12.2 ± 1.4 years (range 8-14). The mean coronal curve was 51 ± 10° preoperatively, 31 ± 9° at first postoperative time point and 27 ± 11° at 2-year follow-up (p < 0.001). The mean patient height increased 8 cm by 2 years (p < 0.001). The left side of the spine (vertebra + disc) grew in height by 2.2 mm/level versus 0.7 mm/level on the right side (p < 0.001). This differential growth was composed of 0.5 mm/vertebral level and 1.0 mm/disk level. Evaluation of the change in disk heights showed significantly decreased height anteriorly (- 0.4 mm), posteriorly (- 0.3 mm) and on the right (- 0.5 mm) from FE to 2 years. Coronal wedging reduced 2.3°/level with 1.1°/vertebral level change and 1.2°/disk level. There was no differential growth in the sagittal plane (anterior/posterior height). Patient height change moderately correlated with 3D measures of vertebra + disk shape changes.

CONCLUSIONS

Three-dimensional analysis confirms AVBT in skeletally immature patients results in asymmetric growth of the apical spine segments. The left (untethered) side length increased more than 3 × than the right (tethered) side length with differential effects observed within the vertebral bodies and disks, each correlating with overall patient height change.

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.

Diagnostic and therapeutic strategies in early onset scoliosis: A current concept review

Substantial advances in the treatment of early onset scoliosis (EOS) over the past two to three decades have resulted in significant improvements in health-related quality of life of affected children. In addition to classifications that address the marked heterogeneity of this patient population, increasing understanding of the natural history of the disease, and new implants and treatment techniques have resulted in innovations unlike any other area of pediatric orthopedics. The growing understanding of the interaction between spinal and thoracic growth, as well as dependent lung maturation, has had a lasting impact on the treatment strategy of this potentially life-threatening disease. The previous treatment approach with early corrective fusion gave way to a growth-friendly concept. Despite the steady development of new growth-friendly surgical treatment options, whose efficacy still needs to be validated, as well as a revival of conservative growth control with serial casts and/or braces, the psychosocial burden of the long lasting and complication-prone treatments remains high. As a consequence, EOS still represents one of the greatest pediatric orthopedic challenges.

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.

Anterior Vertebral Body Tethering: A Review of the Available Evidence

Idiopathic scoliosis is a complex three-dimensional deformity of the spine with anterior overgrowth (hypokyphosis), coronal curvature, and axial rotation. Scoliosis treatment in the skeletally immature spine is therapeutically challenging because of growth and was commonly limited to observation, bracing treatment, or fusion. Fusion accomplishes powerful deformity correction at the expense of future growth and mobility of the involved segments, increasing the risk of adjacent segment degeneration and intervertebral disk disease later in life. Anterior vertebral body tethering is a motion-preserving technique that exploits the Hueter-Volkmann principle by applying compression at the anterior and convex aspects of the curve to stimulate differential vertebral growth for gradual deformity reduction without fusion. The appropriate timing, curve magnitude, tensioning, growth prediction, indications, and limitations of tethering are being refined as this technique becomes more prevalent. Early outcome studies show that growth modulation with vertebral body tethering is safe, can achieve good results, and preserve motion in select patients.

Reducing Uncertainty in Anterior Vertebral Body Tethering: Predicting Postoperative Curvature With Fulcrum Bending Radiographs

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

Mid-term Anterior Vertebral Body Tethering (AVBT) results demonstrate an acceptable degree of clinical success, yet the revision rate remains notably higher than fusion. Fulcrum-bending radiographs have previously been shown to more reliably predict radiological outcomes in Adolescent Idiopathic Scoliosis (AIS) as compared to supine-lateral bending radiographs. This study aims to discern how Fulcrum Flexibility Rate (FFR) correlates with Correction Rate (CR) and establish whether this can reliably predict residual deformity following AVBT surgery.

METHODS

A review of 38 consecutive AIS patients undergoing thoracic AVBT between 2015 - 2020 was performed. Preoperative (standing and fulcrum-bending) and postoperative (first-erect) radiographs were evaluated for curve magnitude using the Cobb-method. The FFR, CR and Fulcrum Bending Correction Index (FBCI) were calculated. Patients were also percentile-ranked according to their FFR and dichotomized into flexible and rigid cohorts for comparison. Student t-test, Pearson correlation and linear stepwise regression was applied.

RESULTS

AVBT resulted in a significant improvement in the major Cobb angle (Preoperative: 50.9±7.5° vs Postoperative: 19.9±9.4°; P < .0001) with a mean FBCI of 98.0%. Bivariate correlation revealed a moderate relationship between fulcrum-bending and first-erect Cobb angle (r = .5306, P = .0006). Linear regression demonstrated a predictive relationship between fulcrum-bending and first-erect Cobb using the equation 'Postoperative Cobb = 7.5 + .65(Fulcrum-bending Cobb).'

CONCLUSION

This is the first study to demonstrate the ability of fulcrum-bending radiographs to predict early radiographic outcomes following AVBT, 'timepoint-zero' for the growth modulation process.

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.

Thoracic posterior spinal instrumented fusion vs. thoracic anterior spinal tethering for adolescent idiopathic scoliosis with a minimum of 2-year follow-up: a cost comparison of index and revision operations

PURPOSE

To compare direct costs of index and revision operations of thoracic posterior spinal instrumented fusion (TPSIF) and thoracic anterior spinal tethering (TAST) for adolescent idiopathic thoracic scoliosis in children.

METHODS

Children (ages 11-18 years) who underwent TPSIF and TAST (2/2013-9/2019) were reviewed. Follow-up < 2 years and cervical instrumentation and/or instrumentation of a lumbar level at L3 or below were exclusion criteria. Patient demographics, radiographic curve magnitude, index operations and postoperative data, as well as indications for revisions/readmissions were collected. Direct costs were identified and compared for index and revision operations during follow-up.

RESULTS

One hundred and four patients were included (TPSIF: 78; TAST: 25). TAST procedures were performed in children significantly younger and for smaller curve magnitudes. They had significantly fewer levels instrumented, shorter operating room (OR) times, and less estimated blood loss (EBL). After operation, a significantly higher percentage of TAST were admitted to ICU. Hospital length of stay (LOS) was similar between groups. Index operations' average direct costs were significantly higher for TAST than TPSIF ($52,947 v. $46,641; p = 0.02). Major cost drivers for both groups were implants, OR services, post-anesthesia care unit (PACU), and room/board. Revisions following TAST were more frequent than for TPSIF (36 v. 11.5%). Majority of TPSIF revisions were for junctional deformity. Curve progression and overcorrection were most common reason for TAST revisions. Average direct costs for revisions/readmissions were similar between groups (TPSIF: $28,485 v. TAST: $27,590; p = 0.46).

CONCLUSIONS

Index operations' average direct costs were statistically similar between TPSIF and TAST for adolescent idiopathic scoliosis. Major cost drivers were implants, OR services, PACU, and room/board. TAST index operations' direct costs and associated direct costs for implants and room/board were significantly higher, while their anesthesia and OR services were significantly lower than TPSIF. TAST revisions were for overcorrection and curve progression, while TPSIF revisions were most commonly for junctional deformity. Overall average direct costs for revisions were similar despite revision rates being higher for TAST.

LEVEL OF EVIDENCE

III.

Drain options after vertebral body tethering

PURPOSE

Since the introduction of vertebral body tethering (VBT) for adolescent idiopathic scoliosis (AIS), a variety of post-operative chest drainage systems have been utilized. Most surgeons use formal chest tubes with a Pleur-evac, while others use smaller bulb suction drains (e.g., Blake drain). In addition, some centers utilize pleural closure. This multicenter study evaluates whether drain type or pleural closure impact perioperative and 90 day complication rates.

METHODS

A retrospective review was conducted from three institutions with established VBT programs. All preoperative, perioperative and 90 day postoperative data were analyzed to determine differences in outcomes between three cohorts: standard chest tube (SCT), standard chest tube with pleural closure (SCTPC) and 10 French Bulb drain (BD).

RESULTS

104 patients were identified for the study. 57 SCT, 25 SCTPC and 22 BD. All data are listed in order: SCT, SCTPC, BD. Length of stay (3.7, 4.3, 3.0 days) was less in the BD group (p = 0.009); post-operative drainage (460, 761, 485 cc) was less in the SCT and BD groups (p < 0.001); intra-operative estimated blood loss (EBL) 146, 382, 64 cc was less in the BD group (p < 0.001). No significant difference in number of days (3.2, 3.2, and 2.8 days) drainage was in place, groups (p = 0.311). Complication profile was similar with 2 chest tube reinsertions in the SCT and one hemothorax that resolved spontaneously in BD group.

CONCLUSIONS

In this series of 104 patients, SCT, SCTPC and BD all had a similar safety profile. All three methods were safe and effective in managing post-operative chest drainage after thoracic VBT. In the series, BD group had significantly shorter LOS than both groups that used chest tubes.

LEVEL OF EVIDENCE

Level III, Retrospective cohort study.

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.

Reliability of radiographic assessment of growth modulation from anterior vertebral body tethering surgery in pediatric scoliosis

PURPOSE

To assess the reliability of vertebral height and angular measurements for anterior vertebral body tethering (AVBT).

METHODS

Eight observers measured PA radiographs of 15 idiopathic scoliosis patients treated with AVBT, pre-operative and 4-year follow-up. Vertebral wedging, disc wedging, convex vertebral body heights, and concave vertebral body heights of the 3 apical vertebrae were measured. For each observer, there were a total of 90 measurements for vertebral body height and 75 measurements for all wedging types At least 14 days elapsed between first and second round measurements.

RESULTS

From the pre-operative to the 4-year follow-up time-point, the total wedging angle over the 3 peri-apical levels fell from 30 ± 7° to 16 ± 6° (p < 0.001) and the difference between the convex and concave vertebral heights decreased from 9 ± 4 to 6 ± 3 mm (p < 0.001). Interobserver agreement for pre-operative vertebral body heights was good [ICC = 0.80; 95% CI (0.74-0.85)]. At 4-year follow-up there was a moderate agreement [ICC = 0.67 (0.59-0.74)]. There was a poor interobserver agreement for pre-operative wedging angle measurements [ICC = 0.41 (0.32-0.52)] and 4-year follow-up [ICC = 0.45 (0.36-0.56)]. The Limits of Agreement with the Mean (LOAM) for pre-op heights was ± 2.4 mm, similar to the follow-up ± 2.6 mm. When raters are averaged in random groups of two the agreement limits decrease to ± 1.8 mm pre-op and ± 1.6 mm at follow-up. Similarly for wedging angles, LOAM values among the 8 observers of ± 4.6° pre-op and ± 4.2° dropped to ± 2.7° for both pre-op and follow-up when random groups of two raters were averaged together. Intraobserver agreement ranged from good to excellent per individual (ICC = 0.84-0.94) for pre-operative vertebral body heights, but this decreased at 4-year follow-up (ICC = 0.52-0.88). Intraobserver agreement was low overall for wedging (pre-operative ICC = 0.41-0.71; 4-year follow-up ICC = 0.41-0.76).

CONCLUSION

Based on 8 individual observers, interobserver agreement ranged from good (pre-operative vertebral body heights) to moderate (4-year follow-up vertebral body heights) to poor (all wedging angles). To improve the reliability of the measurement of wedging angles, we recommend averaging the measurements of at least two observers.

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.

Meta-analysis on the efficacy and safety of anterior vertebral body tethering in adolescent idiopathic scoliosis

PURPOSE

In this meta-analysis, we analyzed the efficacy and safety of anterior vertebral body tethering in patients with adolescent idiopathic scoliosis.

METHODS

We performed a literature search and analyzed the following data: baseline characteristics, efficacy measures (corrections of the main thoracic curve, proximal thoracic curve, and thoracolumbar curve, thoracic kyphosis, lumbosacral lordosis, rib hump, lumbar prominence and SRS-22 scores, and complications. Analyses were performed with Cochrane's Review Manager version 5.4.

RESULTS

Twelve studies met the inclusion criteria. Significant corrections of the main thoracic (MD 22.51, 95% CI 12.93 to 32.09) proximal thoracic (MD 10.14°, 95% CI 7.25° to 13.02°), and thoracolumbar curve (MD 12.16, 95% CI 9.14 to 15.18) were found. No statistically significant corrections were observed on the sagittal plane assessed by thoracic kyphosis (MD - 0.60°, 95% CI - 2.45 to 1.26; participants = 622; studies = 4; I2 = 36%) and lumbosacral lordosis (MD 0.19°, 95% CI - 2.16° to 2.54°). Significant corrections were identified for rib hump (MD 5.26°, 95% CI 4.19° to 6.32°) and lumbar prominence (MD 1.20°, 95% CI 0.27° to 2.13°) at final follow-up. Significant improvements of total SRS-22 score (MD - 0.96, 95% CI - 1.10 to - 0.83) were achieved at final follow-up. The most common complication was overcorrection (8.0%) and tether breakage (5.9%), with a reoperation rate of 10.1%.

CONCLUSIONS

Anterior vertebral body tethering is effective to reduce the curve in the coronal plane and clinical deformity. Maximum correction is achieved at one year. The method should, however, be optimized to reduce the rate of complications.

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.

Spontaneous Lumbar Curve Correction Following Vertebral Body Tethering of Main Thoracic Curves

BACKGROUND

Growth modulation through anterior vertebral body tethering (AVBT) has emerged as a fusionless option for the treatment of progressive scoliosis. When tethering the main thoracic curve, the compensatory thoracolumbar/lumbar curve must correct indirectly as a result. The present study evaluated the response of these lumbar curves following AVBT of the main thoracic curves.

METHODS

Patients who underwent thoracic AVBT and who had a minimum follow-up of 2 years were included. Magnitudes of the thoracic and lumbar curves were recorded preoperatively and at the first-erect and 2-year postoperative visits. Lumbar curves were further stratified according to their lumbar modifier (A, B, or C). Analysis of variance (ANOVA) and repeated-measures ANOVA were performed to compare correction rates, and the Pearson coefficient was utilized to determine the correlation between the tethered thoracic curve and uninstrumented lumbar curve magnitudes.

RESULTS

A total of 218 patients were included. Thoracic curve correction was 40% at the first-erect visit and 43% at 2 years (p = 0.012). Lumbar correction was 30%, 26%, and 18% at the first-erect visit (p < 0.001 for all compared with preoperatively) and minimally changed at 31%, 26%, and 24% at 2 years for lumbar modifiers A, B, and C, respectively. A total of 118 patients (54%) showed thoracic curve improvement between the first-erect and 2-year visits. In a subgroup analysis, these patients had a correction in lumbar curve magnitude from preoperatively to the first-erect visit of 30%, 22%, and 16% for lumbar modifiers A, B, C, respectively, that increased to 42%, 34%, and 31% at 2 years, with strong correlation to thoracic correction at 2-year follow-up (r = 0.557, p < 0.001).

CONCLUSIONS

Although there was immediate lumbar correction following AVBT of a main thoracic curve, further improvement following initial correction was only observed among patients with growth modulation of the thoracic curve. Considering all patients, the uninstrumented lumbar curve corrected 30% at 2 years and the instrumented thoracic curve corrected 40%. As indications for AVBT are refined, these data will provide insight into the response of the uninstrumented lumbar curve.

LEVEL OF EVIDENCE

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

3D Radiological Outcomes and Quality of Life of Patients With Moderate Idiopathic Scoliosis Treated With Anterior Vertebral Growth Modulation Versus Bracing: Two-Year Follow-up

STUDY DESIGN

Observational cohort study.

OBJECTIVE

To test the hypothesis that anterior vertebral body growth modulation (AVBGM) achieves 3D deformity correction after 2-year follow-up while brace treatment limits curve progression for moderate idiopathic scoliosis (30-50°).

SUMMARY OF BACKGROUND DATA

For idiopathic scoliosis, bracing and AVBGM have overlapping indications in skeletally immature patients with moderate scoliosis curve angles, creating a grey zone in clinical practice between them. The relative 3D deformity control performance over a 2-year period between these fusionless treatments is still uncertain.

METHODS

A retrospective review of a prospective idiopathic scoliosis patients database, recruited between 2013 and 2018 was performed. Inclusion criteria were skeletally immature patients (Risser 0-2), with Cobb angles between 30° and 50° and a 2-year follow-up after bracing or AVBGM. 3D radiological parameters and health related quality of life (HRQoL) scores were evaluated. Unpaired t test was used.

RESULTS

Thirty nine patients (12.7 ± 1.3 y.o.) with Cobb angles more than or equal to 30° treated with brace and 41 patients (11.8 ± 1.2 y.o.) with presenting Cobb angles less than or equal to 50° who received AVBGM were reviewed. The statistical analysis of 3D deformity measurements showed that at 2-year follow-up, only the 3D spine length and both sides apical vertebral heights changed significantly with brace treatment. While AVBGM treatment achieved statistically significant correction differences in thoracic and lumbar Cobb angles, TrueKyphosis, 3D spine length, and selective left apical vertebral height ( P < 0.05). 35% of brace patients had a curve progression of more than 5° at final follow-up while it was 0% for AVBGM. HRQoL assessment showed no statistically significant differences between pre and post SRS-22 total scores for each group ( P > 0.05).

CONCLUSION

Even though these two cohorts are not fully comparable, bracing seems to control progression for a significant portion of patients with moderate scoliosis curves, while AVBGM significantly corrected and maintained 3D deformity parameters at 2-year follow-up.

Intervertebral Disk Health Following Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: A Preliminary Study

BACKGROUND

Interest in vertebral body tethering (VBT) as an alternative to posterior spinal fusion for adolescent idiopathic scoliosis (AIS) continues to grow. The purpose of this study was to prospectively assess intervertebral disk health on magnetic resonance imaging (MRI) at 1 year following VBT in AIS patients.

METHODS

AIS patients were enrolled in a prospective surgeon-sponsored Food and Drug Administration (FDA) Investigational Device Exemption (IDE) Study and underwent MRI at 1-year following VBT. All spanned disks and the untethered disks immediately adjacent to the upper instrumented vertebra and lowest instrumented vertebra levels were evaluated according to Pfirrmann grading criteria. Associations between patient factors and preoperative and postoperative disk health and patient-reported outcomes were evaluated.

RESULTS

Twenty-two patients were enrolled with a postoperative MRI (25 curves, 188 disks), and 7 patients (7 curves) had both preoperative and postoperative MRIs (67 disks). The mean age was 12.7 years. Most were Risser 0 (65%) and either Sanders Skeletal Maturity Score 3 (35%) or 4 (53%). In the 7 patients with preoperative and postoperative MRI, the mean Pfirrmann grade of the disks spanned by the tether was 1.88 preoperatively and 2.31 postoperatively ( P =0.0075). No statistically significant differences in preoperative versus postoperative Pfirrmann grade were identified in the disks adjacent to the upper or lower instrumented vertebrae. No association was found between patient-reported outcomes and Pfirrmann grade.

CONCLUSION

At 1 year postoperatively, increased degenerative changes in disks spanned by the tether was identifiable on MRI without evidence of adjacent segment disk disease. These changes were not associated with patient-reported outcomes.

LEVEL OF EVIDENCE

Level III.

Pulmonary Complications after Vertebral Body Tethering: Incidence, Treatment, Outcomes and Risk Factor Analysis

Introduction: Vertebral body tethering (VBT) is gaining popularity for the management of selected AIS patients. The most frequent non-mechanical complications after VBT are pulmonary complications, with a reported incidence of up to 8% for recurrent pleural effusion. However, only trace data have been published on this topic. We aimed to analyze the incidence, timing, treatment, outcomes and risk factors of pulmonary complications after VBT. Materials and Methods: All patients who underwent VBT between September 2018 and September 2022 were retrospectively reviewed. The rate of pulmonary complications was analyzed and the symptoms, timing of onset, treatment and outcomes were recorded. An analysis of demographic, radiographic, surgical and pulmonary function data was conducted to explore possible risk factors for pulmonary complications. Results: Data from 140 patients were available: 14 experienced a pulmonary complication 1 day to 6 weeks after VBT, with 9 presenting a recurrent pleural effusion. A total of 13 patients required invasive treatment. All recovered without sequelae. The risk factor analysis did not result in any significant observations. However, 11/14 patients had had a diaphragm split. Conclusion: Pulmonary complications were observed in 10% of patients. The timing, symptoms and required treatment were heterogeneous. Pleural effusion seems to be more common after diaphragm crossing, but evidence is not yet conclusive.

Anterior vertebral body tethering for idiopathic scoliosis in growing children: A systematic review

BACKGROUND

The management of idiopathic scoliosis (IS) in skeletally immature patients should aim at three-dimensional deformity correction, without compromising spinal and chest growth. In 2019, the US Food and Drug Administration approved the first instrumentation system for anterior vertebral body tethering (AVBT), under a Humanitarian Device Exception, for skeletally immature patients with curves having a Cobb angle between 35° and 65°.

AIM

To summarize current evidence about the efficacy and safety of AVBT in the management of IS in skeletally immature patients.

METHODS

From January 2014 to January 2021, Ovid Medline, Embase, Cochrane Library, Scopus, Web of Science, Google Scholar and PubMed were searched to identify relevant studies. The methodological quality of the studies was evaluated and relevant data were extracted.

RESULTS

Seven clinical trials recruiting 163 patients were included in the present review. Five studies out of seven were classified as high quality, whereas the remaining two studies were classified as moderate quality. A total of 151 of 163 AVBT procedures were performed in the thoracic spine, and the remaining 12 tethering in the lumbar spine. Only 117 of 163 (71.8%) patients had a nonprogressive curve at skeletal maturity. Twenty-three of 163 (14.11%) patients required unplanned revision surgery within the follow-up period. Conversion to posterior spinal fusion (PSF) was performed in 18 of 163 (11%) patients.

CONCLUSION

AVBT is a promising growth-friendly technique for treatment of IS in growing patients. However, it has moderate success and perioperative complications, revision and conversion to PSF.

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.

The Role of Vertebral Body Tethering in Treating Skeletally Immature Scoliosis

This is a critical analysis of a study by Hoernschemeyer et al, "Anterior Vertebral Body Tethering for Adolescent Scoliosis with Growth Remaining: A Retrospective Review of 2 to 5-Year Postoperative Results" (J Bone Joint Surg Am, 2020;102[13]:1169-1176), that assessed the clinical and radiographic outcomes of vertebral body tethering (VBT) in the treatment of adolescent scoliosis. The authors demonstrated successful treatment in 74% of patients, based on radiographic outcomes and avoidance of subsequent posterior spinal fusion. Nearly a quarter of patients required revision surgery. Almost half suffered a broken tether, although the effects of such complications are not fully understood. The study provided valuable information for determining which patients are reasonable candidates for VBT and emphasizes several questions surrounding this novel technology that remain unanswered. This analysis discusses the study's strengths and weaknesses, suggests potential directions of future research, and examines the potential indications for VBT.

Dual modality of vertebral body tethering : anterior scoliosis correction versus growth modulation with mean follow-up of five years

Aims

Vertebral body tethering (VBT) is a non-fusion technique to correct scoliosis. It allows correction of scoliosis through growth modulation (GM) by tethering the convex side to allow concave unrestricted growth similar to the hemiepiphysiodesis concept. The other modality is anterior scoliosis correction (ASC) where the tether is able to perform most of the correction immediately where limited growth is expected.

Methods

We conducted a retrospective analysis of clinical and radiological data of 20 patients aged between 9 and 17 years old, (with a 19 female: 1 male ratio) between January 2014 to December 2016 with a mean five-year follow-up (4 to 7).

Results

There were ten patients in each group with a total of 23 curves operated on. VBT-GM mean age was 12.5 years (9 to 14) with a mean Risser classification of 0.63 (0 to 2) and VBT-ASC was 14.9 years (13 to 17) with a mean Risser classification of 3.66 (3 to 5). Mean preoperative VBT-GM Cobb was 47.4° (40° to 58°) with a Fulcrum unbend of 17.4 (1° to 41°), compared to VBT-ASC 56.5° (40° to 79°) with 30.6 (2° to 69°)unbend. Postoperative VBT-GM was 20.3° and VBT-ASC Cobb angle was 11.2°. The early postoperative correction rate was 54.3% versus 81% whereas Fulcrum Bending Correction Index (FBCI) was 93.1% vs 146.6%. The last Cobb angle on radiograph at mean five years’ follow-up was 19.4° (VBT-GM) and 16.5° (VBT-ASC). Patients with open triradiate cartilage (TRC) had three over-corrections. Overall, 5% of patients required fusion. This one patient alone had a over-correction, a second-stage tether release, and final conversion to fusion.

Conclusion

We show a high success rate (95%) in helping children avoid fusion at five years post-surgery. VBT is a safe technique for correction of scoliosis in the skeletally immature patient. This is the first report at five years that shows two methods of VBT can be employed depending on the skeletal maturity of the patient: GM and ASC.

Cite this article: Bone Jt Open 2022;3(2):123–129.

Video-Assisted Thoracoscopy for Vertebral Body Tethering of Juvenile and Adolescent Idiopathic Scoliosis: Tips and Tricks of Surgical Multidisciplinary Management

VATS (video assisted thoracoscopic surgery) is routinely and successfully performed in minor and major complex thoracic procedures. This technique has been recently introduced for the treatment of severe forms of idiopathic scoliosis (IS) with the aim to repair the deformity, reduce morbidity and to prevent its progression in patients with skeletal immaturity. This study aims to present VATS in anterior vertebral body tethering (AVBT) approach to support the pediatric orthopedic surgeons during vertebral body fixation. Surgical and anesthesiologic tips and tricks are reported to assure a safe procedure. The study includes preadolescents with IS and a grade of scoliosis >40° that had a high probability of deterioration due to remaining growth (December 2018 to April 2021). Skeletal immaturity of enrolled patients was assessed by Sanders classification and Risser sign. Patients had a Risser score between 0 and 1 and a Sanders score >2 and <5. AVBT technique using VATS was performed by a senior pediatric surgeon assisting the pediatric orthopedic surgeon. Twenty-three patients have been submitted to VATS AVBT in the period of study (age range 9–14 years). The patients had a classified deformity Lenke 1A or B convex right and all types of curves were treated. In all patients, the vertebrae submitted to tethering surgery ranged from D5 to D12; mean curve correction was 43%. Three postoperative complications occurred: one late postoperative bleeding requiring a chest tube positioning on 12th postoperative day; one screw dislodged and needed to be removed; one child showed worsening of the scoliosis and needed a posterior arthrodesis. Initial results of VATS AVBT in growing patients with spinal deformities are encouraging. An appropriate selection of patients and a pediatric dedicated multidisciplinary surgical approach decrease intraoperative complications, time of operation and postoperative sequelae and guarantee an optimal outcome.

Iatrogenic dural tear after growth modulation in AIS: an unusual complication and its management

PURPOSE

To report a case of iatrogenic durotomy with symptomatic Chiari-like deformity in a patient after undergoing anterior vertebral body growth modulation (AVBGM) in skeletally immature patients with adolescent idiopathic scoliosis (AIS). There have not been reports of iatrogenic durotomy in the literature and its management after AVBGM.

METHODS

A 13-year-old skeletally immature girl underwent successful AVBGM for thoracic AIS from T6 to T12. Despite uneventful post-operative hospitalization, the patient suffered from recurrent and persistent bouts of headaches that were mostly orthostatic. At 3 months post-op, an MRI was performed on the suspicion of a cerebrospinal fluid (CSF) leak due to an iatrogenic durotomy. On MRI, decreased volume of CSF and a decrease in the dural sac diameter were observed. Furthermore, a pseudo-meningocele was seen at the last level of instrumentation.

RESULTS

After an unsuccessfully trial of epidural blood patch combined with 5 days of supine immobilization, the patient was consented to screw revision as well as a lumbar drain. The lumbar drain was installed to redirect the CSF leak to allow the durotomy to heal. After 11 days, the drain was removed based on the favorable clinical evolution.

CONCLUSION

Iatrogenic durotomy is a rare complication in AVBGM. This is the first report of such a case that involves a Chiari-like deformity on initial MRI investigation. We suggest that an MRI is performed for all patients presenting with symptoms of CSF leak after AVBGM.

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.

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.

Congenital Kyphosis: Progressive Correction With an Instrumented Posterior Epiphysiodesis: A Preliminary Report

PURPOSE

Congenital kyphosis is a rare condition. In this case series we sought to identify the outcomes and complications of posterior instrumented fusion and the resultant epiphysiodesis effect in uniplanar congenital kyphosis in pediatric patients.

METHOD

Pediatric patients were included if treated for a uniplanar congenital kyphotic deformity treated with posterior instrumented spinal fusion between October 2006 and August 2017, with a minimum of 2 years of follow-up. Patients were excluded if a coronal deformity >10 degrees was present.

RESULTS

Six patients met the inclusion criteria. Mean age at surgery was 3.6 years. The mean kyphotic deformity before surgery was 49.7 degrees. All patients underwent posterior instrumented fusion with autogenous iliac crest graft and a cast or brace postoperatively. One patient showed a loss of motor evoked potential on prone positioning which returned to normal on supine positioning. No patient showed any postoperative neurological deficits. One patient was diagnosed with a wound infection which was successfully treated with oral antibiotics.By a follow-up of 5.4 years (range, 2.2 to 10.9 y) there was no failure of instrumentation. An epiphysiodesis effect (a difference of ≥5 degrees in the kyphotic deformity measured between the immediate postoperative and final follow-up lateral whole spine XR) of 16.2 degrees (range, 7.2 to 30.9 degrees) was seen in 5 patients. The mean annual epiphysiodesis effect was 2.7 degrees (95% confidence interval, 1.4-4.1 degrees). No kyphosis proximal to the instrumentation was observed for the duration of follow-up.

CONCLUSION

Posterior instrumented fusion and epiphysiodesis is safe and effective. The epiphysiodesis effect occurs in 5/6 of cases, and our data suggests that the procedure is associated with an acceptable blood loss and a low incidence of neurological complications.