Canine Atlantoaxial Ventral Stabilization: Computed Tomography Analysis of Optimal Safe Implantation Corridors and Comparison of the Technical Outcome and Biomechanical Properties of 3 Surgical Techniques

Abstract

Canine atlantoaxial instability is a severely debilitating condition most commonly affecting Toy breed dogs that can result in sudden cardio-respiratory arrest. Surgical correction of atlantoaxial subluxation requires positioning of implants into the atlas and axis which is often perceived as a hazardous procedure and has been associated with unacceptably high perioperative mortality rates. This thesis investigates the most commonly reported ventral techniques of atlantoaxial stabilization attempting to improve currently available technical descriptions. The first part was aimed at developing a method of 3D analysis of vertebral bone corridors in order to generate precise definitions of optimal implant placement that could be used intraoperatively. We developed and validated a semi-automated method using free open-source version of OsiriXTM DICOM viewer and Microsoft® Excel software programs. This method was subsequently applied to a population of 27 dogs to generate objective definitions of atlantoaxial optimal safe implantation corridors. In the second part, we used these definitions to position implants in a population of 21 Beagle cadavers simulating intraoperative conditions of atlantoaxial stabilization. A 3D drill guide prototype was designed to allow positioning of the implants according to the previously generated definitions. Three commonly reported techniques of ventral atlantoaxial stabilization and 5 different implant sites were statistically compared. This study provided insights on technical limitations of the different methods of stabilization as well as biomechanical data that should be considered when performing these surgeries in clinical cases.