Preclinical evaluation of a novel anterior non-fusion fixation device for atlantoaxial instability: an in vivo comparison study in a canine model

  • Xuan Cai
  • Xiaoqing Yi
  • Haopeng Li
  • Xijing HeEmail author
Original Article



The Anterior Atlantoaxial Non-Fusion Fixation System (AANFS) was a novel motion preservation device for atlantoaxial instability to replace traditional fusion techniques. The purpose of this in vivo study was to evaluate the clinical features and biomechanical properties of this new device in a canine model by comparing it with a conventional method.


Eighteen adult male canines were randomly divided into group 1, which received the AANFS replacement, group 2 which received the Harms rigid fixation procedures, and group 3, which served as the control group. Routine follow-up evaluations were performed postoperatively. Specimens were harvested 12 weeks after the operation. Biomechanical tests were conducted to obtain the range of motion (ROM) and neutral zone (NZ) at C1–C2 segment in different groups.


The canines successfully tolerated the entire experimental procedure. No significant differences were found in surgery time, blood loss and recovery time between the AANFS group and the Harms rigid fixation group. Radiological examinations revealed that the position of the implant was good. Biomechanical results showed that, compared with the intact group, the mean ROM and NZ in flexion, extension, lateral bending and rotation were significantly reduced after rigid fixation. However, after the AANFS implantation, ROM and NZ in all directions were similar to those of the intact state.


This study for the first time provides an animal model for studying non-fusion strategies of upper cervical spine. The AANFS was able to maintain movement function of the atlantoaxial joint and may be an alternative to traditional fusion techniques.

Graphical abstract

These slides can be retrieved under Electronic Supplementary Material.


In vivo Canine model Atlantoaxial instability Non-fusion Biomechanics 



This study was sponsored by National Natural Science Youth Funds of China (Program No.: 81601955) ( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no competing interests.

Ethics statement

This study was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by the Committee of the Second Affiliated Hospital of Xi’an Jiaotong University (Permit Number: 2016-20). All surgery was performed under sodium pentobarbital anesthesia, and all efforts were made to minimize suffering.

Data availability

All data generated or analyzed during this study are included in this article.

Supplementary material

586_2019_5916_MOESM1_ESM.pptx (7.3 mb)
Supplementary material 1 (PPTX 7507 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Orthopaedic SurgerySecond Affiliated Hospital of Xi’an Jiaotong UniversityXi’anPeople’s Republic of China
  2. 2.Department of PediatricsSecond Affiliated Hospital of Xi’an Jiaotong UniversityXi’anPeople’s Republic of China

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