Original Article DOI 10.3349/ymj.2010.51.5.753 pISSN: 0513-5796, eISSN: 1976-2437 Yonsei Med J 51(5):753-760, 2010 Video-Assisted Thoracoscopic Surgery for Correction of Adolescent Idiopatic Scoliosis: Comparison of 4.5 mm versus 5.5 mm Rod Constructs Hak Sun Kim,1 Jin Oh Park,1 Ankur Nanda,1 Phillip Anthony Kho,1 Jin Young Kim,1 Hwan Mo Lee,1 Seong Hwan Moon,1 Jung Won Ha,2 Eun Kyoung Ahn,3 Dong Eun Shin,4 Sung Jun Kim,5 and Eun Su Moon1 Departments of 1Orthopaedic Surgery and 5Radiology, Yonsei University College of Medicine, Seoul; Departments of 2Orthopaedic Surgery, 3Anesthesiology and Pain Medicine, National Health Insurance Corporation Ilsan Hospital, Goyang; 4Department of Orthopaedic Surgery, CHA University, Pocheon, Korea. Received: April 2, 2009 Revised: November 19, 2009 Accepted: November 25, 2009 Corresponding author: Dr. Eun Su Moon, Department of Orthopaedic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, 712 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea. Tel: 82-2-2019-3418, Fax: 82-2-573-5393 E-mail: mes1007@yuhs.ac ∙The authors have no financial conflicts of interest. © Copyright: Yonsei University College of Medicine 2010 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non- Commercial License (http://creativecommons.org/ licenses/by-nc/3.0) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose: The purpose of this study is to report the comparative results of thoracoscopic correction achieved via cantilever technique using a 4.5 mm thin rod and the poly-axial reduction screw technique using a 5.5 mm thick rod in Lenke type 1 adolescent idiopathic scoliosis (AIS). Materials and Methods: Radiographic data, Scoliosis Research Society (SRS) patient-based outcome ques- tionnaires, and operative records were reviewed for forty-nine patients undergoing surgical treatment of scoliosis. The study group was divided into a 4.5 mm thin rod group (n = 24) and a 5.5 mm thick rod group (n = 25). The radiographic para- meters that were analyzed included coronal curve correction, the most caudal instrumented vertebra tilt angle correction, coronal balance, and thoracic kyphosis. Results: The major curve was corrected from 49.8O and 47.2O pre-operatively to 24.5O and 18.8O at the final follow-up for the thin and thick rod groups, respecti- vely (50.8% vs. 60.2% correction). There were no significant differences between the two groups in terms of kyphosis, coronal balance, or tilt angle at the time of the final follow-up. The mean number of levels fused was 6.2 in the thin rod group, compared with 5.9 levels in the thick rod group. There were no major intraopera- tive complications in either group. Conclusion: Significant correction loss was observed in the thin rod system at the final follow-up though both groups had comparable correction immediately post-operative. Therefore, the thick rod with poly axial screw system helps to maintain post-operative correction. Key Words: Instrumentation, rod, scoliosis, thoracoscopic surgery INTRODUCTION Video-assisted thoracoscopic surgery (VATS) is fast becoming the standard means of approaching the anterior thoracic spine in patients with spinal deformity.1-6 Previously published clinical reports of VATS have suggested an efficacy which is Yonsei Med J http://www.eymj.org Volume 51 Number 5 September 2010 753