Screw Device: 18-Month Results

Abstracts / Spine Deformity 2 (2014) 498e517 idiopathic scoliosis (www.clinicaltrials.gov Identifier: NCT01465295). The hypothesis was that disc and vertebral height symmetry in the coronal plane would increase with time at the treated levels. Methods: Six patients with progressive juvenile or early adolescent idiopathic scoliosis underwent endoscopic placement of a titanium clip/ screw device (institutional review board approved). Inclusion criteria were Lenke 1A and 1B single thoracic curves, Cobb angle 25 to 40 , age greater than 10 years, Risser 0, and open triradiate cartilages. Vertebral and disc heights were measured (Fig.) for every patient and at every instrumented level with visible intervertebral boundaries using a clinical PACS system. The 2 primary outcome variables were side-to-side height ratios, Hconcave/Hconvex, for discs and vertebrae at each time point. Ratios were used to account for any magnification factor differences between the 2 times. Statistical differences were determined using paired t tests, 1-tailed, and Bonferroni (a 5 .05/2 5 .025). Results: Vertebral height ratios at t0- and 12 months were 0.91 ( 0.014) and 0.94 ( 0.031), respectively (p ! .025). Disc height ratios at t0- and 12 months were 0.67 ( 0.049) and 0.82 ( 0.13) (p ! .020). Vertebral height increases on convex and concave sides were 4% and 7%, respectively, whereas disc height increases on convex and concave sides were 8% and 23%. Thoracic curvatures were 34 ( 3 ) at t0- and 30 ( 13 ) at 12 months. Conclusions: Vertebral and disc height symmetry increased within 1 year in a clinical trial of growth modification using a titanium clip/screw construct. The largest contributing factor was an increase in the concave side disc height. Limitations include the inability to discern most disc and vertebral heights in patient with greatest axial rotation and largest curve. Results suggest the method may help decompress the concave side disc and alter side-to-side vertebral heights in this cohort. Longer-term results are essential to determine whether local symmetry improvements are maintained.

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EJW (grants/research support from SpineForm, LLC; consulting fees from OrthoPediatric Sports, Stryker Trauma, OrthoPediatric Spine; ownership interest/shareholder of SpineForm, LLC; royalty/patent holder from SpineForm, LLC) Paper #23 Changes in Vertebral Growth Plate After Surgical Correction of Scoliosis in an Animal Model Michal Latalski, MD, PhD, Marek Fatyga, MD, PhD Introduction: The aim of this experiment was to evaluate the behavior of a growth plate subjected to asymmetric compression and then distraction, simulating the rise and correction of scoliosis. The researchers thought that results would address the possibility of a biomechanical impact on the growth of a deformed spine. Methods: The study group consisted of 24 rates aged 49 days, weighing 119 to 127 g. During the first 3 weeks, the researchers mechanically compressed 1 side of 2 adjacent vertebrae of the tail, wedging the vertebrae. For the next 3 weeks, the researchers performed distraction of growth plates from the concave side of the deformation. For the purposes of the experiment, an external fixator operating on the principle of an Ilizarov apparatus was constructed. Control group vertebrae were not included in the stabilization. The tail of each animal was subjected to radiological examination and the cartilage growth-deformed vertebrae were examined histologically (using hematoxylineeosin and methyl blue). The authors analyzed the thickness of the growth cartilage, the hypertrophic chondrocyte zone on the convex and concave sides, and the central portion of the growth plate. Results: Histological examination confirmed the supposition of inhibited growth on the side subjected to compression; hypertrophic chondrocyte layer in this region flattened and the proliferative zone lost its compactness and became irregular. The structure of the growth plate on the convex side of the curvature changed, as well: Cell distribution was random and the columns of hypertrophic and proliferative zones were arranged angular to the growth plate. However, compared with the control group, it was not activated. Changing the forces on the fixator simulated the start of correction of the deformed spine. Introducing distraction on the concave side relieved the compressed growth plate. There was a change in the behavior of cartilage. On both the concave and convex sides of the curvature the layers returned to their initial activity. The columnar arrangement of cells became more regular in shape. Conclusions: Correction of experimentally induced uniplanar scoliosis with decompression of a compressed growth plate restarted the physiological activity of the growth plate and reduced the deformation of the vertebral body. The results of the experiment may be a starting point for considering the possibility of correcting spinal deformity by appropriately manipulating the forces acting on the growth plate. Author disclosures: ML (none), MF (none)

Paper #24 Prospective FDA IDE Clinical Safety Trial of a Scoliosis Growth Modulation Clip/Screw Device: 18-Month Results Eric J. Wall, MD, Joseph E. Reynolds, Jain V. Jain, MD, Donita I. Bylski-Austrow, PhD, George H. Thompson, MD, Paul Samuels, MD, Sean J. Barnett, Alvin H. Crawford, MD

Author disclosures: DIB (grants/research support from SpineForm, LLC; Royalty/patent holder from SpineForm, LLC); NAE (none); DLG (none); JER (grants/research support from SpineForm, LLC; consulting fees from SpineForm, LLC; ownership interest shareholder of SpineForm, LLC; salary from SpineForm, LLC; royalty/patent holder from SpineForm, LLC);

Introduction: The purpose of this study was to determine 18-month results of a prospective, first human use, Food and Drug Administration Investigational Device Exemption clinical safety trial of a titanium clip/ screw device in children with late juvenile and early adolescent idiopathic scoliosis (www.clinicaltrials.gov Identifier: NCT01465295). Methods: Six patients with progressive idiopathic scoliosis underwent endoscopic placement of a titanium clip/screw device (institutional review board approved). Inclusion criteria were Lenke 1A and 1B single thoracic

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Abstracts / Spine Deformity 2 (2014) 498e517 



curves, Cobb angle 25 to 40 between T3 and L1, age greater than 10 years, open triradiate cartilages, Risser stage 0, and thoracic kyphosis less than 40 . Criteria were chosen to include only patients at very high risk for progression to greater than 50 . Results: Complications included a procedure-related mucous plug resulting from single lung ventilation in 1 patient, which resolved after bedside bronchoscopy. A chylous effusion in 1 resolved with a pigtail catheter and nonfat diet. There was no device misplacement into the spinal canal or disc space, no neuromonitoring changes or neurological deficits, and no device breakage. Mean postoperative hospital stay was less than 4 days. Mean surgical implantation time was 90 minutes (range, 57e124 minutes). Mean blood loss was less than 75 mL. Mean major curve was 34 ( 3 ) preoperatively and 36 ( 15 ) at 18 months (p O .8). One patient increased from 35 to 55 and subsequently required posterior spinal fusion and segmental spinal instrumentation. The best result was in a patient who improved from 36 to 13 in 18 months and has continued to correct to date (Fig.). Losses in correction were primarily due to blade migration in vertebrae. Scoliosis Research Societye22 scores were 4.36 ( 0.46) at screening and 4.31 ( 0.29) at 18 months (p O .6). Food and Drug Administration Investigational Device Exemption approval was granted for the next 30 subjects. Conclusions: At 18 months, mean curves did not increase significantly from baseline after implantation of a titanium clip/screw implant in a small prospective cohort of very immature patients at extremely high risk of progression. In this initial safety study, blood loss was minimal, surgical times were low, and no device misplacement occurred. Curve changes were highly variable, including 1 conversion to posterior spinal fusione segmental spinal instrumentation to date, yet also continuing proof of concept of growth modification in humans by this method.

animals were euthanized at 17 weeks. Radiographs and true axial computed tomographic images of the spine were obtained. The parameters of the rib cage deformity including the rib hump, rib vertebral angle difference, apical rib spread difference, apical vertebral bodyerib ratio, and rib length difference were measured. The spinal deformity including the Cobb, sagittal kyphosis, and apical vertebral rotation were measured. Histological examination of the intercostal muscle was performed. Results: An average 53.0 right thoracic scoliosis with a mean e3.6 apical hypokyphosis was created in the right thoracic nerve neurotomy groups at 17 weeks’ follow-up. Apical vertebral rotation (mean, 32.8 ) occurred toward the right side. The rib hump (mean, 10.5 mm), rib vertebral angle difference (mean, 27.5 ), apical rib spread difference (mean, 13.8 mm), apical vertebral bodyerib ratio (mean, 3.0), and rib length difference (mean, 15.8 mm) measurements demonstrated rib cage torsion to the convex side. Histological examination of the right intercostal muscle showed denervation. In the bilateral thoracic nerve neurotomy group, no scoliosis or thoracic torsion was seen, but an average thoracic lordosis of e32.3 was created. Conclusions: Unilateral thoracic nerve neurotomy induced rib cage torsion toward the operative side, resulting in idiopathic-like thoracic hypokyphotic scoliosis in an immature pig model. Neurogenic thorax imbalance may be the initiating cause of idiopathic scoliosis.

Author disclosures: XW (none); HZ (grants/research support from Scoliosis Research Society); DS (none) Author disclosures: EJW (grants/research support from SpineForm, LLC; consulting fees from OrthoPediatric Sports, Stryker Trauma, OrthoPediatric Spine; ownership interest/shareholder of SpineForm, LLC; royalty/ patent holder of SpineForm, LLC); JER (grants/research support from SpineForm, LLC; consulting fees from SpineForm, LLC; ownership interest/shareholder of SpineForm, LLC; salary from SpineForm, LLC; royalty/ patent holder of SpineForm, LLC); JVJ (consulting fees from Medtronic); DIB (grants/research support from SpineForm, LLC; nonfinancial research support; royalty/patent holder of SpineForm, LLC); GHT (consulting fees from Shrine Medical Advisory Board; salary from Co-Editor, Journal of Pediatric Orthopaedics); PS (none); SJB (consulting fees from Surgical Innovations, Nucleus Medical; salary from Kaleidoscope); AHC (none) Paper #25 Unilateral Thoracic Nerve Neurotomy Causes Rib Cage Torsion and Idiopathic-like Thoracic Scoliosis Xiaobin Wang, MD, PhD, Hong Zhang, MD, Dan Sucato, MD, MS Introduction: The initiating factor of idiopathic scoliosis is unknown. The current study was performed to test whether neurogenic thorax imbalance can initially cause scoliosis in an immature pig model. Method: Seventeen 1-month-old pigs were assigned to 3 groups: Group 1 (n 5 6), in which the right thoracic nerve root was cut from T7 to T14 with bilateral paraspinal muscle stripping; Group 2 (n 5 5), treated in the same way except the left paraspinal muscle was intact; and Group 3 (n 5 6), in which the thoracic nerve root was bilaterally cut from T7 to T14. All

Paper #26 Anterior Vertebral Body Tethering for Immature Adolescent Idiopathic Scoliosis: 1-Year Results on the First 32 Patients Amer Samdani, Robert J. Ames, BA, Jeff S. Kimball, BS, Joshua M. Pahys, MD, Harsh Grewal, MD, Glenn J. Pelletier, MD, Randal R. Betz, MD Introduction: Anterior vertebral body tethering (VBT) offers a fusionless treatment option for skeletally immature patients with adolescent idiopathic scoliosis. It is a growth-modulation technique that uses patients’ growth to attain progressive scoliosis correction. Numerous animal models support its promise; however, clinical data remain sparse. The authors conducted a retrospective chart review to evaluate the clinical and radiographic outcomes of anterior VBT. Methods: Clinical and radiographic data were retrospectively analyzed. The researchers reviewed 32 patients who underwent thoracic VBT with a minimum 1-year follow-up. Pertinent clinical and radiographic data were collected. Analysis of variance, Student t test, and Fisher exact test were used to compare different time points. Results: A total of 32 patients with thoracic idiopathic scoliosis (72% female) with a minimum 1-year follow-up were identified; mean age at surgery was 12 years. All patients were considered skeletally immature preoperatively: mean Risser score of 0.42 and mean Sanders score of 3.2. Patients underwent tethering of an average of 7.7 levels (range, 7e11 levels). Median blood loss was 100 mL. Mean preoperative thoracic curve magnitude was 42.8  8.0 , which corrected to 21.0  8.5 on first erect