Study of Bone-screw Surface Fixation in Lumbar Dynamic Stabilization

• Published in: Chinese medical journal Vol. 128; no. 3; pp. 368 - 372
• Main Authors: Luo, Yun-Gang, Yu, Tao, Liu, Guo-Min, Yang, Nan
• Format: Journal Article
• Language: English
• Published: China Medknow Publications Pvt Ltd 05.02.2015; Medknow Publications and Media Pvt. Ltd; Lippincott Williams & Wilkins Ovid Technologies; Department of Stomatology, The Second Hospital of Jilin University, Changchun, Jilin 130041, China%Department of Orthopedics, The Second Hospital of Jilin University, Changchun, Jilin 130041, China%Traditional Chinese Medicine Academy of Science of Jilin Provine, Changchun, Jilin 130041, China; Medknow Publications & Media Pvt Ltd; Wolters Kluwer
• Subjects: Animals; Back pain; Biomechanics; Bone Screws; Bone-screw Interface; Dynamic Fixation; Histomorphology; Mechanical Stability; Micro-computed Tomography; Care and treatment; Chinese medicine; Experiments; Goats; Lumbar vertebrae; Lumbar Vertebrae - surgery; Medical research; Original; Orthopedic fixation devices; Orthopedic Procedures - methods; Orthopedics; Pedicle Screws; Software; Statistical analysis; Surgery; Titanium; Tomography; Transplants & implants; Vertebrae; 动态稳定; 定面; 对照组; 形态学参数; 机械稳定性; 椎弓根螺钉; 结缔组织; 腰椎; China; Micro-computed Tomography; Histomorphology; Mechanical Stability; Bone-screw Interface; Dynamic Fixation
• ISSN: 0366-6999; 2542-5641
• DOI: 10.4103/0366-6999.150107

Background： We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with sun＇ounding bone, and determine whether pedicle screws achieve good mechanical stability in the vertebrae. Methods： Twenty-four goats aged 2-3 years had Cosmic pedicle screws implanted into both sides of the L2-L5 pedicles. Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5. Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine. The side that was not implanted with fixation rods was used as a static control group. Results： In the static control group, new bone was formed around the pedicle screw and on the screw surthce. In the unilateral and bilateral dynamic fixation groups, large amounts of connective tissue formed between and around the screw threads, with no new bone formation on the screw surlhce; the pedicle screws were loose after the fixed rods were removed. The bone mineral density and morphological parameters of the region of interest （ROI） in the unilateral and bilateral dynamic fixation group were not significantly different （P 〉 0.05）, but were lower in the fixed groups than the static control group （P 〈 0.05）. This showed the description bone of the ROI in the static control group was greater than in the fixation groups. Under loading conditions, the pedicle screw maximum pull force was not significantly different between the bilateral and unilateral dynamic fixation groups （P 〉 0.05）： however the maximum pull force of the fixation groups was significantly less than the static control group （P 〈 0.01 ）. Conclusions： Fibrous connective tissue formed at the bone-screw interface tinder unilateral and bilateral pedicle dynamic fixation, and the pedicle screws lost mechanical stability in the vertebrae.