Abstract Adolescent idiopathic scoliosis affects children aged 11–18 years. Severe disease may necessitate spinal fusion. Vertebral body tethering gradually corrects scoliosis as the patients grow. The application of video-assisted thoracic surgery to the thoracic spine is a new area for further development. Scoliosis, Video-assisted thoracic surgery, Spine INTRODUCTION Adolescent idiopathic scoliosis can be treated using external braces for early disease or spinal fusion for more severe deformity. Video-assisted thoracic surgery (VATS) tethering allows for smaller incisions and, thus, potentially faster recovery, avoiding the morbidity associated with fusion. The ideal age range for tethering is between 11 and 18 years, and there should be no evidence of growth plate closure as continued growth after tethering allows for gradual curve correction. Bone age can be assessed radiologically by the epiphyseal status of the hand (the modified Tanner–Whitehouse system) or from pelvis ossification (the Risser sign). The Cobb angle is the angle of the most tilted vertebra from the apex (mid-point) of the curve (Fig. 1). The indications for tethering are an angle of 40–70 degrees and a Risser stage of ≤2 or a modified Tanner–Whitehouse score of ≤4. Figure 1: View largeDownload slide A preoperative (A) and postoperative (B) X-ray (arrow) showing the Cobb angle. Figure 1: View largeDownload slide A preoperative (A) and postoperative (B) X-ray (arrow) showing the Cobb angle. TECHNIQUE The preoperative setup requires standard VATS equipment, double-lumen tube intubation, neuromuscular monitoring of motor-evoked and somatosensory-evoked potentials, and intraoperative computed tomography and guided instrument navigation (O-arm® and Stealth®, Medtronic). Patients are placed in a lateral decubitus position with the apex of the curve facing up. Total intravenous anaesthesia without muscle relaxation is employed to allow reliable motor-evoked potentials. The lamina of the spinous process at the apex of the curve is dissected through a longitudinal incision. A reference frame is then clamped to facilitate computed tomography navigation during vertebral instrumentation. A 2-cm muscle-sparing access port is made in the 4th intercostal space using no rib retraction. A figure-of-eight stich is placed on the posteromedial dome of the diaphragm. It is retracted anterolaterally through a 1-cm thoracoport, which is later used as the chest drain site. This exposes the lowest thoracic vertebrae. The energy device is used to dissect the pleura off the lateral surface of the vertebral bodies and to ligate crossing segmental or intercostal arteries, which may cause spinal cord ischaemia. Spinal cord function is monitored using motor-evoked potentials. Additional ports are placed as needed to facilitate screw placement. The navigated probe is used to identify the target vertebra, entry site and trajectory needed for instrumentation. A navigated awl is used to start the entry hole followed by a stabilizing staple tapped into place. A navigated tap is used to ensure that both cortices of the vertebral body have been breached. A ball-tipped feeler is then used to assess the depth of the hole to confirm that the vertebral canal has not been breached. A hydroxyapatite-coated titanium screw is then fixed in place. This process is repeated for each vertebra included in the tether. The tethering cord is then introduced and seated into the screws. Tension is applied to the cord along with direct manual compression on the chest wall. This process is repeated as the cord is secured at each level using a set screw. Excess cord is trimmed to 2 cm proximally and distally. The duration of the operation is approximately 4–6 h. Intraoperative complications include spinal cord ischaemia, misplacement of vertebral screws and injury to nearby structures. A chest drain is placed prior to closure, and a chest X-ray is performed immediately postoperatively and again after the removal of chest drain (Video 1). Mobilization is allowed on the 1st postoperative day and discharge usually by the 4th postoperative day. The patients are advised not to engage in sports for 3 months to allow for bone ingrowth into the screws. Follow-up is performed for every 6 months until skeletal maturity is achieved. Correction is assessed clinically and radiologically. DISCUSSION Adolescent idiopathic scoliosis presents in up to 5% of children younger than 18 years . Bracing is utilized to correct curves less than 40° . Fusion is an option for advanced curves but has associated morbidity and reduced mobility. Tethering leads to gradual curve correction by changing the shape of the vertebra while preserving spine mobility (Fig. 2). The application of VATS leads to reduced pain, blood loss and length of stay . Video 1 Operative preparation and technique are explained. Video 1 Operative preparation and technique are explained. Close Figure 2: View largeDownload slide Location of video-assisted thoracic surgery ports (A) and curve correction over time (B). Figure 2: View largeDownload slide Location of video-assisted thoracic surgery ports (A) and curve correction over time (B). Spinal tethering was first reported by Crawford and Lenke [4, 5], and 2-year results were reported in Samdani’s series. They have reported good outcomes in a majority of patients experiencing curve correction with an associated reduction in the Cobb angle and minimal complications. Potential complications include either over-deformity or under-deformity correction, progression of scoliosis, gradual screw migration, cord rupture and nerve injury. Spinal fusion or redo tethering may be necessary in such cases. The application of VATS to disorders of the thoracic spine is a new area for further development. Our joint practice with orthopaedic surgeons will allow skills from both disciplines to be employed. Conflict of interest: none declared. REFERENCES 1 Konieczny MR , Senyurt H , Krauspe R. Epidemiology of adolescent idiopathic scoliosis . J Child Orthop 2013 ; 7 : 3 – 9 . Google Scholar CrossRef Search ADS PubMed 2 Weinstein SL , Dolan LA , Wright JG. Effects of bracing in adolescents with idiopathic scoliosis . N Engl J Med 2013 ; 369 : 1512 – 21 . Google Scholar CrossRef Search ADS PubMed 3 Shah RD , D’Amico TA. Modern impact of video assisted thoracic surgery . J Thorac Dis 2014 ; 6(Suppl 6) : 631 – 6 . 4 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 Am 2010 ; 92 : 202 – 9 . Google Scholar CrossRef Search ADS PubMed 5 Samdani AF , Ames RJ , Kimball JS , Pahys JM , Grewal H , Pelletier GJ et al. Anterior vertebral body tethering for immature adolescent idiopathic scoliosis: one-year results on the first 32 patients . Eur Spine J 2015 ; 24 : 1533 – 9 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)
European Journal of Cardio-Thoracic Surgery – Oxford University Press
Published: May 17, 2018
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