Atlantoaxial subluxation in dogs, literature review and 8 case reports

Abstract

Atlantoaxial subluxation (AAS) is a typical pathology of young toy breed dogs, such as Chihuahuas, Yorkshire Terries, Pomeranians, Pekingese and Poodles. Caused by a malformation in the odontoid process of the axis or dens of the axis, which can present congenital abnormalities in this structure such as aplasia, hypoplasia, dorsal angulation or degeneration of the odontoid process, or it also may be caused by a malformation, laxity or rupture of ligaments. These changes cause instability of the atlantoaxial joint. This instability allows the dorsal displacement of the dens of the axis and causes compression of the spinal cord. Apart from congenital causes, this pathology can be caused by trauma in both young toy dogs and older dogs of larger breeds. In these dogs, rupture of the axis, atlas and ligaments may occur, including ventral displacement of the axis, and clinical signs may be more acute. The general symptomatology varies greatly, from cervical pain, ataxia, lameness, ambulatory tetraparesis, non-ambulatory tetraparesis or even respiratory arrest and death. For its diagnosis the best option is to perform a radiographic study with a lateral and a ventrodorsal projection since in most cases is possible to diagnose with this technique. But there are also many diagnostic techniques that can provide greater accuracy to the cause of the pathology or can help to make an appropriate surgical approach such as CT or MRI scans. Conservative treatment is possible through the use of a cervical splint that immobilizes the neck and with the support of appropriate medication to control pain. But the most recommended and also most used treatment is the surgical stabilization which may be a dorsal or ventral fixation of the joint using lag screws; retractors; pins with or without the addition of bone cement; blocked butterfly plates; even application of implants designed with 3D technology. The objective of this review is to evaluate the different types of diagnosis and treatments and try to determine which one offers better results and fewer complications using 8 cases of Dr. Juan Pablo Zaera Polo and Dr. David Oliverio Rodríguez Lozano as an example, collected between the HCV of the University of Las Palmas de Gran Canaria and the Sierra de Madrid Veterinary Hospital