Experimental study Cross-link is a risk factor for rod fracture at pedicle subtraction osteotomy site: A finite element study Tae Hyun Park a,b,h , Su Heon Woo a , Sung Jae Lee b , Dong Min Sohn b , Chun Kee Chung c,d,e,f , Yongjung Jay Kim g , Seil Sohn h,⇑ a R&D Center, Medyssey Co, Ltd, Jechon, Republic of Korea b Department of Biomedical Engineering, College of Biomedical Science& Engineering, Inje University, Gyeongnam, Republic of Korea c Department of Neurosurgery, Seoul National University College of Medicine, Republic of Korea d Neuroscience Research Institute, Seoul National University Medical Research Center, Republic of Korea e Clinical Research Institute, Seoul National University Hospital, Republic of Korea f Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Republic of Korea g Department of Orthopedics, Columbia University, College of Physicians and Surgeons, New York, NY, USA h Department of Neurosurgery, CHA University, CHA Bundang Medical Center, Republic of Korea article info Article history: Received 15 March 2019 Accepted 29 April 2019 Available online xxxx Keywords: Cross-link Rod fracture PSO Spine Finite element analysis abstract Background: We aim to investigate using finite element model (FEM) whether the use of a cross-link is a risk factor for rod fracture at the pedicle subtraction osteotomy (PSO) site. Methods: The geometry and dimensions of the FEM were obtained from a high-resolution computed tomography scan data of a 65 years old female patient with spinal sagittal imbalance. The intact model was modified to place PSO on the L4 spine. A cross-link was placed at the PSO site. A multisegment spinal fusion model from L1 to the pelvis was used to compare and analyze the peak von Mises stress (PVMS) values of the implants. A compressive follower load of 400 N was added to the validated intact lumbar spinal model in the follower load path direction. Results: After PSO surgery, the PVMS of the rod was significantly increased during flexion and extension at the PSO site. With the cross-link at the PSO site, the PVMS of the rod was further significantly increased during flexion and extension. Conclusion: The cross-link at the PSO site increased the risk of rod facture, especially during flexion and extension stress. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction The normal lumbar lordosis (LL) relieves the load on the spine and allows the spinal muscles to work effectively. Over the last years, osteotomy procedures, especially pedicle subtraction osteot- omy (PSO), have been refined and improved to better address sev- ere sagittal imbalance of the spine [1]. PSO is widely considered as a powerful technique allowing a correction up to 30–35 degrees through three columns without lengthening the anterior column [2,3]. Although several studies have reported satisfactory clinical and radiological results after PSO even at long term follow-up [4], overall complication rates remain considerably high, ranging from 37 to 59% [5,6]. According to a previous study, PSO has been clearly associated with high rates of implant failure/pseudoarthrosis. Smith et al. found that rod fracture occurred in 22% of PSO patient with a min- imum one year follow-up [7]. Rod fracture can negatively affect clinical outcome by producing pain and loss of deformity correc- tion. In order to reduce the risk of rod fracture, there have been several efforts, including the use of a satellite rod and a cobalt chrome rod [8]. Knowledge about risk factors of rod fracture can be important clinically. It has been reported that the use of a cross-link improves struc- tural stability and inhibits the lateral shift of instrumentation. The cross-link also creates higher stiffness of the overall fixation sys- tem [9]. However, Barton et al. insisted that a cross-link may cause rod fracture [10]. Several biomechanical studies have evaluated rod strain at PSO sites [8,11–14]. However, few biomechanical studies have investigated whether a cross-link at the lumbar PSO site was a risk factor for rod fracture. https://doi.org/10.1016/j.jocn.2019.04.036 0967-5868/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Neurosurgery, CHA University College of Medicine, 59, Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13496, Republic of Korea. E-mail address: sisohn@cha.ac.kr (S. Sohn). Journal of Clinical Neuroscience xxx (xxxx) xxx Contents lists available at ScienceDirect Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn Please cite this article as: T. H. Park, S. H. Woo, S. J. Lee et al., Cross-link is a risk factor for rod fracture at pedicle subtraction osteotomy site: A finite ele- ment study, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.04.036