Topics in Spinal Cord Injury Rehabilitation 2019

Progressive Neuromuscular Scoliosis Secondary to Spinal Cord Injury in a Young Patient Treated With Nonfusion Anterior Scoliosis Correction.

Authors: Cuddihy LA, Antonacci MD, Hussain AK, Vig KS, Mulcahey MJ, Betz RR

Ninety-eight percent of skeletally immature patients with spinal cord injury (SCI) suffer from progressive neuromuscular scoliosis (NMS). Operative treatment has typically been limited to posterior spinal fusion (PSF), but a newer technique as described may be less invasive and preserve more function. A PSF of the entire spine to the pelvis is standard of care. However, maintenance of spinal flexibility, motion, and potential growth is desirable. We present a case for proof-of-concept of utilizing a surgical motion-preserving technique to treat progressive NMS in an 11year-old girl with T10 level (AIS B) paraplegia with a progressive 60° NMS of the lumbar spine. She had anterior scoliosis correction (ASC) from T11-L5 without fusion. Over 24 months, the curve growth-modulated to a residual of 12° with continued modulation to 7° at 3-year follow-up (skeletal maturity).

Citation: Cuddihy LA, Antonacci MD, Hussain AK, et al. ProgressiveNeuromuscular Scoliosis Secondary to Spinal Cord Injury in a Young Patient TreatedWith Nonfusion Anterior Scoliosis Correction. Top Spinal Cord Inj Rehabil 2019;25(2):150-156.

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Spine 2020

Thoracoscopic Vertebral Body Tethering for Adolescent IdiopathicScoliosis: Follow-up Curve Behavior According to Sanders SkeletalMaturity Staging

Authors: Alanay A , YucekulA, Abul K, ErgeneG, Senay S, Ay B,Cebeci BO,Dikmen PY,Zulemyan T, YavuzY, Yilgor C

STUDY DESIGN: Retrospective analysis of prospectively collected dataObjective. To report the follow-up curve behaviors in different Sanders staging groups. SUMMARY OF BACKGROUND DATA: Vertebral Body Tethering (VBT) is a growth modulation technique that allows gradual spontaneous follow-up curve correction as the patient grows. There is a lack of scientific evidence regarding appropriate patient selection and timing of implantation. METHODS: Patients were grouped into five as: Sanders 1, 2, 3, 4-5 and 6-7. Data were collected preoperatively, at the day before discharge, and at each follow-up. Outcome measures were pulmonary and mechanical complications, readmission and reoperation rates. Demographic, perioperative, clinical, radiographic and complication data were compared using Fisher-Freeman-Halton exact tests for categorical variables and Kruskal Wallis tests for the continuous variables. RESULTS: Thirty-one (29F, 2 M) consecutive patients with a minimum of 12 months of follow-up were included. The mean age at surgery was 12.1 (10-14). The mean follow-up was 27.1 (12-62) months. The mean preoperative main thoracic curve magnitude was 47°±7.6°. For all curves, preoperative and first erect curve magnitudes, bending flexibility and operative correction percentages were similar between groups (for all comparisons, p > 0.05). The median height gained during follow-up was different between groups (p < 0.001), which was reflected into median curve correction during follow-up. Total curve correction percentage was different between groups (p=0.009). Four (12.9%) patients had pulmonary and 6 (19.4%) had mechanical complications. One (3.2%) patient required readmission and 2 (6.5%) required reoperation. Occurrence of pulmonary complications was similar in Sanders groups (p = 0.804), while mechanical complications and overcorrection was significantly higher in Sanders 2 patients (p = 0.002 and p = 0.018). CONCLUSIONS: Follow-up curve behavior after VBT is different in patients having different Sanders stages. Sanders 2 patients experienced more overcorrection, thus timing and/or correction should be adjusted, since Sanders 3, 4 and 5 patients displayed a lesser risk of mechanical complications.

Citation: Alanay A , Yucekul A, Abul K, et al. Thoracoscopic Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: Follow-up Curve Behavior According to Sanders Skeletal Maturity Staging. Spine 2020;[Article in press].

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Spine Deformity 2020

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

Authors: Baroncini A, David Trobisch D, Migliorini F

Study design: Retrospective study. Objectives: Vertebral body tethering (VBT) is raising interest for the treatment of adolescent idiopathic scoliosis (AIS), but many scoliosis surgeons have not been trained in anterior surgical approaches. We analyzed data of our first patients to define the learning curve for VBT. Summary of background data: VBT has shown encouraging results in the treatment of growing AIS patients, but there is a paucity of data and long-term results are not yet available. To our best knowledge, there is no published data regarding the learning curve for VBT. Methods: A retrospective analysis was performed, of all consecutive patients who underwent VBT at our Institution. Outcomes of interest were intubation time, surgical duration and estimated blood loss per screw and hospitalization length. For the statistical analysis, we referred to a linear model regression diagnostic and we used the Pearson product-moment correlation (r) for pairwise correlation. The final effect ranked between + 1 and − 1. Results: Data of 90 patients were analyzed, age 14.6 ± 1.8 years. On average, 9.4 ± 2.6 levels were instrumented. Per screw, mean intubation time was 33.1 ± 7.6 min (r = − 0.57; p > 0.0001), mean surgical duration 21.3 ± 5.7 min (r = − 0.55; p > 0.0001), mean estimated blood loss 21.3 ± 18.2 ml (r = − 0.66; p > 0.0001). Mean hospitalization length was 8.3 ± 3.1 days (r = − 0.32; p = 0.002). No intraoperative complications were reported. Conclusion: VBT has a rapid learning curve: the estimated blood loss per screw is expected to decrease by 60%, intubation time and surgical duration by over 50%, and hospitalization length by 32% for each treated patient. Level of evidence: III.

Citation: Baroncini A, David Trobisch D, Migliorini F. Learning curve for vertebral body tethering: analysis on 90 consecutive patients. Spine Deform 2020;[Epub ahead of print].

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Dartmouth Orthopaedic Journal 2014

Comparison of Two Fusionless Scoliosis Surgery Methods in the Treatment of Progressive Adolescent Idiopathic Scoliosis: A Preliminary Study

Authors: Braun JT

Summary: Initial correction and subsequent control of progression were evaluated in 9 adolescent idiopathic scoliosis (AIS) patients treated with one of two methods of fusionless scoliosis surgery (FSS): vertebral stapling versus ligament tethering. Ligament tethering demonstrated significantly greater initial correction and subsequent control of curve progression than stapling. Ligament tethering, unlike bracing or fusion surgery, allows significant scoliosis correction without sacrificing growth, motion and function of the spine. Introduction: Fusionless scoliosis surgery (FSS) is a novel treatment option for AIS patients not amenable to brace treatment and at high risk (>90%) for progression to fusion surgery. Though two FSS methods, vertebral stapling and ligament tethering, have demonstrated effectiveness in controlling AIS progression, these have never been compared clinically in well matched groups with similar indications. Methods: Retrospective study of 9 consecutive AIS patients (average age 12+11) treated with stapling versus tethering for thoracic curves >30° (average 35.6°) in the setting of skeletal immaturity (average Risser 0 to 1). Risk of progression was assessed using 3 methods (Lonstein, Sanders, ScoliScore). All patients had >90% risk of progression to fusion surgery by at least 2 of the 3 methods. Cobb angles pre-op, post-op and final were compared. Results: Nine well matched female patients with 14 curves underwent endoscopic FSS: 4 had stapling of 6 curves and 5 had tethering of 8 curves. Stapled curves were initially corrected from 34.5° pre-op to 31.3° post-op but subsequent curve control was poor with progression over 22 months to 44.5°. Tethered curves initially corrected from 36.6° pre-op to 21.4° post-op with good control over 14.4 months with additional correction to 17.8°. Ligament tethering demonstrated significantly greater initial correction (p=.001) and subsequent control of curve progression (p=.002) when compared to vertebral stapling. No significant complications were encountered; however, 1 stapled patient required fusion for a progressive curve to 55°. Conclusion Both initial correction and subsequent control of curve progression are important in the fusionless treatment of AIS. In this preliminary study, it appears that ligament tethering provides greater initial correction and subsequent control of AIS curve progression than vertebral stapling

Citation: Braun JT. Comparison of Two Fusionless Scoliosis Surgery Methods in the Treatment of Progressive Adolescent Idiopathic Scoliosis: A Preliminary Study. Darthmouth Orthop J 2014.

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Journal of Bone and Joint Surgery 2010

Growth Modulation by Means of Anterior Tethering Resulting in Progressive Correction of Juvenile Idiopathic Scoliosis: A Case Report

Authors: Crawford CH & Lenke LG

In the present report, we describe the case of a young boy with juvenile scoliosis in whom anterior tethering resulted in gradual correction over four years. We are not aware of any previous such report in the literature. The patient and his family were informed that data concerning the case would be submitted for publication, and they consented.

Citation: Crawford CH & Lenke LG. Growth Modulation by Means of Anterior Tethering Resulting in Progressive Correction of Juvenile Idiopathic Scoliosis: A Case Report. J Bone Joint Surg 2010;92:202-209.

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The Spine Journal 2015

Spinal growth modulation with posterior unilateral elastic tether in immature swine model

Authors: Liu J., Li Z., Shen J., Xue X

Background context Fusionless scoliosis surgery is frequently performed in children. Many studies have analyzed the effects of spinal growth modulation by tethering the anterior and anterolateral aspects of the spine in animal models. However, few studies have reported the disc health and spinal motion in spines with posterior unilateral elastic tethering. Purpose To analyze the regional radiography, biochemistry, and histology of spinal motion segments fixed by posterior unilateral elastic tethering. Study design A randomized controlled trial. Outcome measures Preoperative and postoperative radiographs of the spines were taken. After an 8-week recovery period, the spines were harvested en bloc and underwent radiographic, biochemical, and histologic analyses. Methods Fifteen 3-monthold swine were randomly divided into three groups. Instrumentation was performed posteriorly in the swine. In the elastic fixation (EF) group, five swine were instrumented on the left side of the lumbar vertebrae from L1 to L5 with pedicle screws that were connected with a unilateral elastic tether with tension to produce a curve on the spine. The same surgery was performed in the five animals of the metal rod fixation (MF) group, in which the screws were connected with metal rods and curves were established. In the control group, five animals were instrumented with five screws with no connecting cable. Results Scoliosis and lordosis were created in the coronal and sagittal planes in both the EF and MF groups. On average, the Cobb angles were 12.16°±1.37° and 9.10°±2.02°(p=.023) in the coronal plane and 17.44°±11.29° and 5.32°±3.06°(p=.049) in the sagittal plane in the two groups, respectively. The vertebrae and discs wedged on the tethered side in the two groups showed no significant differences (p>.05). The thickness of end-plate epiphysis on the fixed side was significantly decreased in the two groups (p=.032 and p=.024). No apparent change was found in the gross morphology of the discs in the two groups. The distribution of collagen types I and II decreased and that of matrix metalloprotease-3 (MMP-3) increased in both the EF and MF groups. Additionally, the proteoglycan synthesis decreased in the two groups. Conclusions Unilateral elastic tethering resulted in vertebral wedging and scoliosis. Although changes in collagen and MMP-3 distribution, proteoglycan synthesis, end-plate epiphysis, and disc thickness were observed, the tethered discs and end plates did not demonstrate gross morphologic signs of degeneration.

Citation: Liu J, Li Z, Shen J, et al. Spinal growth modulation with posterior unilateral elastic tether in immature swine model. Spine J 2015;15(1):138-145.

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Journal of Bone and Joint Surgery 2018

Anterior Spinal Growth Tethering for Skeletally Immature Patients with Scoliosis: A Retrospective Look Two to Four Years Postoperatively

Authors: Newton PO, Kluck DG, Saito W, Yaszay B, Bartley CE, Bastrom TP

BACKGROUND: Anterior spinal growth tethering (ASGT) has been shown to alter spinal growth with the potential to correct scoliosis while maintaining spine flexibility. The purpose of this study was to report the 2 to 4-year outcomes of ASGT in skeletally immature patients with thoracic scoliosis. METHODS: We conducted a retrospective review of patients with thoracic scoliosis who underwent ASGT with a minimum of 2 years of follow-up. Patient demographics, perioperative data, and radiographic outcomes are reported. A "successful" clinical outcome was defined as a residual curve of <35 degrees and no posterior spinal fusion indicated or performed at latest follow-up. RESULTS: Seventeen patients met the inclusion criteria. The etiology was idiopathic for 14 and syndromic for 3. The mean follow-up was 2.5 years (range, 2 to 4 years). Preoperatively, all patients were at Risserstage 0, with a mean age at surgery of 11 +/- 2 years (range, 9 to 14 years). There was an average of 6.8 +/- 0.5 vertebrae tethered per patient. The average thoracic curve magnitude was 52 degrees +/- 10 degrees (range, 40 degrees to 67 degrees ) preoperatively, 31 degrees +/- 10 degrees immediately postoperatively, 24 degrees +/- 17 degrees at 18 months postoperatively, and 27 degrees +/- 20 degrees at latest follow-up (51% correction; range, 5% to 118%). Revision surgery was performed in 7 patients: 4 tether removals due to complete correction or overcorrection, 1 lumbar tether added, 1 tether replaced due to breakage, and 1 revised to a posterior spinal fusion. In 3 additional patients, posterior spinal fusion was indicated due to progression. Eight (47%) of the patients had a suspected broken tether. Ten (59%) of the 17 were considered clinically successful. CONCLUSIONS: Despite most patients having some remaining skeletal growth at the time of review, the results of the current study demonstrate that at mid-term follow-up, ASGT showed a powerful, but variable, ability to modulate spinal growth and did so with little perioperative and early postoperative risk. Fusion was avoided for 13 of the 17 patients. The overall success rate was 59%, with a 41% revision rate. Understanding the parameters leading to success or failure will be critical in advancing a reliable definitive nonfusion treatment for progressive scoliosis in the future. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Citation: Newton PO, Kluck DG, Saito W, et al. Anterior Spinal Growth Tethering for Skeletally Immature Patients with Scoliosis: A Retrospective Look Two to Four Years Postoperatively. J Bone Joint Surg Am 2018;100(19):1691-1697

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Spine 2017

Risk of implant loosening after cyclic loading of fusionless growth modulation techniques: nitinol staples vs flexible tether

Authors: Yaszay B., Doan J.D., Parvaresh K.C., Farnsworth C.L.

Study Design. Biomechanical evaluation using porcine spines. Objective. Compare the fixation strength of two currently used fusionless adolescent idiopathic scoliosis correction techniques following cyclic loading using porcine spines. Summary of Background Data. The ability of fusionless implants to control or correct scoliosis in a growing patient requires such implants to maintain spinal fixation. Because they cross the disc, motion may weaken fixation over time. Methods. Eight pig spines were divided into cycled segments (T10-T13) and uncycled segments (T7-T8, L2-L3). Initial range of motion (ROM) was determined in torsion, flexion-extension, and lateral bending (0.58/s to 1.75 Nm). Staple group (n ¼ 4): 6 mm parallel staples were inserted on the right anterolateral spine across each intervertebral disc. Cycled segments received six staples (three adjacent discs) and uncycled segments received four staples (two separate discs). Tether group (n ¼ 4): 5.35 35 mm right anterolateral vertebral body screws were placed into each vertebra. Cycled segments received four screws and uncycled segments received four screws. Screws in cycled segments were connected with a flexible tether tensioned to straight alignment. ROM of instrumented cycled segments was measured, and then segments were loaded to the measured ROM in flexionextension (2000 cycles), lateral bending (1000 cycles), and axial rotation (2000 cycles). Implants were axially loaded to failure. Parametric tests compared pre- to postimplant ROM; nonparametric tests compared staple to screw pullout strength; P < 0.05 was significant. Results. There were no differences in ROM before instrumentation between groups. ROM was not changed except tethers decreased left lateral bending (–6.28). Although staple pullout was less than screw pullout for cycled and uncycled segments (P < 0.05 and P ¼ 0.057, respectively), there was no difference in pullout strength with and without cyclic loading for either group (P ¼ 0.4). Conclusion. Tethers decreased lateral bending away from the tether. Screws had almost five times greater load to failure than staples. Five thousand cycles did not result in loosening of either staple or tether screws. Key words: anterolateral spinal implant cyclic loading, anterolateral spinal staples, anterolateral spinal tether, anterolateral spinal tether pull-put, anterolateral vertebral staple pull-out, fusionless scoliosis correction, fusionless spinal implant biomechanics, SMA staples, spinal growth modulation, staple spine range of motion, tether spine range of motion.

Citation: Yaszay B, Doan JD, Parvaresh KC, et al. Risk of implant loosening after cyclic loading of fusionless growth modulation techniques: nitinol staples vs flexible tether. Spine 2017;42(7):443–449.

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Journal of Bone & Joint Surgery 2020

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

Authors: Hoernschemeyer DG, Boeyer ME, Robertson ME, Loftis CM, Worley JR, Tweedy NM, Gupta SU, Duren DL, Holzhauser CM, Ramachandran VM

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

Citation: Hoernschemeyer DG, Boeyer ME, Robertson ME, 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 A 2020 Jul 1;102(13):1169-1176

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Spine 2014

Anterior vertebral body tethering foridiopathic scoliosis: two-year results.

Authors: Samdani AF, Ames RJ, Kimball JS, Pahys JM, Grewal H, Pelletier GJ, Betz RR

STUDY DESIGN: Retrospective review. OBJECTIVE: To report the 2-year results of the initial cohort undergoing anterior vertebral body tethering (VBT). SUMMARY OF BACKGROUND DATA: Anterior VBT is a promising new technique with abundant preclinical studies but very few clinical results. It is a growth modulation technique, which utilizes patients' growth to attain progressive correction of their scoliosis. We report 2-year results of the initial cohort undergoing this procedure. METHODS: After obtaining institutional review board approval, we retrospectively reviewed our first 11 consecutive patients who underwent anterior VBT with 2-year follow-up. We collected pertinent preoperative, intraoperative, and most recent clinical and radiographical data. Student t test and Fisher exacttest were utilized to compare different time points. RESULTS: Eleven patients with thoracic idiopathic scoliosis (8 females) were identified, with a mean age of 12.3 ± 1.6 years. Preoperatively, all were skeletally immature (Sanders mean = 3.4 ± 1.1; Risser mean = 0.6 ± 1.1). All underwent tethering of an average of 7.8 ± 0.9 (range: 7-9) levels, with the most proximal being T5 and the most distal L2. Preoperative thoracic Cobb angle averaged 44.2 ± 9.0° and corrected to 20.3 ± 11.0° on first erect, with progressive improvement at 2 years (Cobb angle = 13.5 ± 11.6°, % correction = 70%; P < 0.00002). Similarly, the preoperative lumbar curve of 25.1 ± 8.7° demonstrated progressive correction (first erect = 14.9 ± 4.9°, 2 yr = 7.2 ± 5.1°, % correction = 71%; P < 0.0002). Thoracic axial rotation as measured by a scoliometer went from 12.4 ± 3.3° preoperatively to 6.9 ± 3.4° at the most recent measurement (P < 0.01). No major complications were observed. As anticipated, 2 patients returned to the operating room at 2 years postoperatively for loosening of the tether to prevent

Citation: Samdani AF, Ames RJ, Kimball JS, et al. Anterior vertebral body tethering for idiopathic scoliosis: two-year results. Spine 2014;39(20):1688-1693.

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