Study of transpedicular screw fixation on spine development in a piglet model

Shi et al. Journal of Orthopaedic Surgery and Research (2016) 11:8 DOI 10.1186/s13018-015-0302-9 RESEARCH ARTICLE Open Access Study of transpedicular screw fixation on spine development in a piglet model Ya-min Shi1*, Fang-zheng Zhu2, Xing Wei1 and Bing-yao Chen1 Abstract Background: Transpedicular screws may cause damage to the cartilage in the neural arch of the vertebra, and give continuous pressure to the skeleton besides the vertebral body. The aim of this study is to examine the morphological change of the vertebral body at fixation sites and development of the vertebral body after fixation. Methods: A piglet model was used to study the influence of transpedicular screw fixation on spine development. Transpedicular screw fixation was adjusted to meet specific requirements of surgery on piglet. The screws and plates were placed at L1–L3 vertebral plates via routine surgical approach. Scoliosis and kyphosis Cobb angles were measured. Results: Anatomical characteristics of 6-week-old piglets fit the transpedicular screw system, and can meet the requirements of related studies. Transpedicular screw fixation system has no significant influence on the development of canalis vertebralis. Fixation did not cause developmental stenosis of canalis vertebralis and damage to spinal cord or nerve root. However, transpedicular screw fixation significantly impacted the development of the spine: it shortened the spine by curtailing the length of the vertebral body and intervertebral space. Our results also suggested that slow growth of epiphyseal plate may contribute to the shortening of the vertebral body. Conclusion: Transpedicular screw fixation system is beneficial for fixation of the developing spine. It may not cause scoliosis but could lead to change of cervical curvature. Keywords: Transpedicular screw fixation, Spine development, A piglet model, Canalis vertebralis Background Transpedicular screw fixation was developed by RoyCamille in the 1970s [1], and had been used to treat unstable thoracolumbar junction fractures. Since then, transpedicular screw fixation was widely used for spinal fracture, deformity, tumor, and degenerative diseases, boosting the development of spinal surgery [2–4]. Spinal deformity is a common disease with high frequency in adolescences [5]. As the understanding of spinal deformity increases, the importance of early treatment for spinal deformity had been noticed [6]. The processus spinosus and vertebral plate of children were frail, and the pedicle and vertebral body cannot form firm synostosis. Therefore, a planted instrument may not successfully fix and correct the deformity due to its weak stability. For * Correspondence: Ya-min Shi and Fang-Zheng Zhu are the first co-author 1 Department of Orthopaedic Surgery, The First Affiliated Hospital of PLA General Hospital, NO. 51, Fu-chen road, Beijing 100037, China Full list of author information is available at the end of the article children with spinal diseases such as spinal fraction, tumor, hemilaminectomy, or scoliosis correction, transpedicular screw fixation is the sole method to provide strong fixation [7]. This method had been widely used to treat spinal diseases of children under the age of 10 years. Since spines of children are still in development, transpedicular screw fixation may slightly impact the development of spines. Jeszenszky et al. [8] demonstrated that after transpedicular screw fixation at L2, compared with L3, the diameter of the vertebral canal decreased by 5.4 %, and sagittal diameter decreased by 9.5 % in 6 months. Akin Cil et al. [9] also reported that after lateral transpedicular screw fixation, disorder of pedicle development and canales spinalis stenosis was found. However, these studies were limited to the analysis of a single screw on the neurocentral cartilage (NCC), and they did not include effects on spine development. In this study, a piglet model was used to study the influence of transpedicular screw fixation on spine © 2016 Shi et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Shi et al. Journal of Orthopaedic Surgery and Research (2016) 11:8 development. Transpedicular screw fixation was adjusted to meet specific requirements of operating on piglet. Animals were examined by CT and X-ray before and after surgery. The screws and plates were placed at L1–L3 vertebral plates through routine surgical approach. Data from this study suggested that transpedicular screw fixation system may be beneficial for fixation of developing spine, while not causing scoliosis. Materials and methods Animals The use of piglets in this study is reviewed and approved by the ethical committee of General Hospital of People’s Liberty Army. Piglets (6-week-old, 9 males and 14 females, 8.5 ± 1.7 kg, 51 ± 4 cm in spine length) were used in this study. All animals passed the investigation by National Animal Quarantine Center, and the possibility of tumor and deformity of spine were ruled out by spiral computed tomography (CT) and X-ray. Page 2 of 11 Operation procedure: Skins at the incision site were sterilized with iodophor, and incised at the center of the back. The incision started from T14 to L4. Skins and subcutaneous tissues were cut layer by layer. Subperiosteal dissection was conducted bilaterally, and paravertebral muscles were pulled aside. The sides of L1–L3 were revealed to the exterior side of zygopophysis, and the root of processus transversus were exposed. Group B: After revelation, the incision sites were washed, sterilized with 70 % ethanol (volume/volume), and the wound was sutured. During the operation, approximately 15 mL of blood flowed out. The average time for surgery is about 1.5 h. Group C: After revelation, a total of six screws were bilaterally placed into L1–L3. The average sagittal angle of L1–L3 pedicle and vertebral body is 42.5°. Thus, the screw sites were the central point on the root of processus transversus, with a separation angle of 40° between screws and vertical plane of spine (be perpendicular to vertebral lamina). After fixation, the incision sites were washed, placed with drainage strip, sterilized with Group assignment A cohort of 23 piglets were randomized into four groups: group A included three subjects as control, without any treatment; group B included three subjects as control, with vertebral lamina revelation (L1–L3); group C included five subjects as control, with six screws bilaterally (...truncated)